Inside Mining October 2016

Page 1

www.miningne.ws

af r ic an u pdates on th e

g ro un d a n d un d e rg ro un d

AVK Valves

Investing in more than valves

Boikarabelo Mining large coal deposits

BouNdiali

Exploration revealing great possibilities

Exxaro

Changes making the difference

ISSN 1999-8872 • R50.00 (incl. VAT) • Vol. 09 • No. 10 • October 2016


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contents

afr ic an up dates on the g round a nd underg round

08

22

Showing off mechanical and MARKET NEWS BHS AeroMaXX technology for turbo parallel-shaft gear units reduces power loss and oil consumption by 30%.

32 Editor’s Comment 3

One more chance

Mine water & wastewater management

Cover Story

25

Nitrate contamination in mine water

4

26

Using tailings for brickmaking

Africa Round-up

28

Variety of analytical solutions

6

Legal

Electrical Instrumentation & control

8

29

Investing in more than valves

News from around the continent

Safety first, zero tolerance

OCTOBER

2016

ON THE COVER p4 www.miningne.ws

Upgrading trolley assist technology AFR IC AN UPDATES ON THE

Commodity: Coal & Uranium 10

Mining large deposits in Waterberg

12

Changes making the difference

transformers

32

Processing fine and ultra-fine coal

14

35

Trip down memory lane

Comminution

36

Ensuring the quality of raw materials

16

Defining mineral sizers

Industry News

18

In-pit crushing, sizing and conveying

39 The latest news from the African

21

Fundamentals of rock breakers

mining industry

Pipes, pumps & valves

Events

22

40

The science of pumps and pumping

AVK Valves

Investing in more than valves

Minerals Processing

Focus on Africa: Ivory Coast Exploration revealing great possibilities

GROUND AND UNDERGROUND

31 Importance of maintaining

Open mining conversations

BOIKARABELO Mining large coal deposits

BOUNDIALI

Exploration revealing great possibilities

EXXARO

Changes making the difference

ISSN 1999-8872 • R50.00 (incl. VAT) • Vol. 09 • No. 10 • October 2016

AVK Holdings Southern Africa just invested R200 million in a new manufacturing plant and training centre in South Africa.

@mining_news www.facebook.com/pages/ Mining-News

Endorsed by In sid e M in in g 1 0 | 2016

1


UNEARTH

your brand’s potential using our print and digital solutions

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• Digimags • Newsletters • Website page views • Social media

Inside Mining, www.miningne.ws and the newsletter feature topical information on mining, exploration and minerals processing with a special focus on the mining value chain. Our readers are key decision-makers in the industry. Advertise with us and boost your products and services by receiving multi-platform exposure to your target market.

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editor's comment

Publisher Elizabeth Shorten Editor Mientjie Kleinhans Journalist Phila Mzamo Head of design Beren Bauermeister Designer Ramon Chinian Chief sub-editor Tristan Snijders Sub-editor Morgan Carter Contributors Casper Booyse, Johan de Korte, Jim Jones, Hugo Pienaar, Elizabeth Sonnekus, Dave Thompson, Ian Venter, Martin Vorster Client services & production manager Antois-Leigh Botma Production coordinator Jacqueline Modise Marketing manager Mpinane Senkhane Financial manager Andrew Lobban Administration Tonya Hebenton Distribution manager Nomsa Masina Distribution coordinator Asha Pursotham

One more chance October brings with it a sort of reality check. It marks the start of the last quarter of the calendar year, leaving just three months to finalise projects and bring ideas to fruition.

I

t also offers one more opportunity to change things around this year. The recent mining slump hasn’t been all bad

– it has offered mining companies the opportunity to do things differently.

Printers United Litho Johannesburg

Now, with mining seemingly on the

Tel: +27 (0)11 402 0571 ___________________________________

rebound – with an 11.8% growth rate in

Advertising Sales

mining and quarrying for Q2 2016 – it’s hoped that the industry will continue

Annemarie Prins Tel: +27 (0)11 233 2600 annemarie@3smedia.co.za ___________________________________

its upwards trend, buoyed by recent lessons learned. One such company that decided to

No. 9 3rd Avenue, Rivonia 2191

do things differently is Exxaro. Due to the

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growth of the company and the effects

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of the mining slump, its management

Fax: +27 (0)11 234 7274/5

team realised that business is about

www.3smedia.co.za ___________________________________

more than ticking boxes in order to

Annual subscription:

South Africa: R550.00 (incl vat & postage) African countries: US$80

comply with legislation and regulations. By introducing new practices, the company was able to save 20% in costs through effective risk management and

Foreign: US$100

better resource allocations. Read more

Email: subs@3smedia.co.za

on page 12.

ISSN 1999-8872 Inside Mining Copyright 2016. All rights reserved. ___________________________________ All material in Inside Mining is copyright protected and may not be reproduced either in whole or in part without the prior written permission of the publisher. The views of contributors do not necessarily reflect those of the publishers.

It is no secret that the next big region for coal mining is in the Waterberg. Inside Mining takes a look at the new Boikarabelo Project – an open-cut surface mine, which will start full production in Q1 2019. It will be a longterm project, with an expected life of mine of 70 years, possibly extending up to 200 years.

To our avid readers, be sure to sign up and get the latest updates and inside scoops from the mining industry. Check out what we are talking about on our website and Facebook page, or follow us on Twitter and have your say.

@mining_news www.facebook.com/pages/ Mining-News

Read how the mine is claimed to be the most advanced new mine in the Waterberg on page 10. A greenfield project that is still at the beginning of the exploration process is the Boundiali Project by Predictive Discovery in the Ivory Coast. This recent discovery of gold employed modern geochemical methods and the early exploration results indicate encouraging surveys. Read more about this fascinating project, which has no people living on or near the site, on page 14. If you’re more interested in mechanical matters, veteran Jim Jones, who has been in the pumping industry for more than 50 years, takes a look at pumps and explains how pumps are measured, and more. Inside Mining also looks at how mineral sizers compare to double-roll crushers, and how they work. Further, in-pit crushing and sizing and in-pit crushing and conveying are compared to the economics of truck haulage of material. To ensure that future generations are aware of current and historic coal processing methods, the Southern African Coal Processing Society is assisting the Geology Museum in Johannesburg with the set-up of a display. There will also be other, nondisplay items available to researchers. To augment the display, the curator of the museum requires donations of any objects related to coal mining. Read more about this initiative on page 35.

Mientjie Kleinhans FOLLOW THE LINK For updated news: www.miningne.ws

In sid e M in in g 1 0 | 2016

3


cover story

Investing in more than valves Investing R200 million in a new plant and complying with the DTi’s local content rules are testament that AVK Holdings Southern Africa believes in the country. The company combines this with the true passion of the employees to offer unique product solutions.

T

HE DEPARTMENT of Trade and

Complying with the rules means that

weeks, or manufacture according to

Industry’s (DTi) designation rules

the company is proudly South African; it

specifications. “This means that compa-

stipulate that state-owned entities

manufactures in South Africa and exports

nies don’t have to wait for their products

must procure locally manufac-

to other countries, and can assist with job

to be shipped from overseas, which

tured products with 70% local content.

creation and transfer of skills. “Apart from

could take anything between 10 weeks -

AVK Holdings Southern Africa realised

the 70% local designation, 40% needs

24 weeks. It also excludes various shipping

what that would mean for the local

to come from SMMEs. Therefore, we are

problems such as storms at sea, or cus-

economy and took the lead in complying

making use of many SMMEs to assist us

toms clearance issues,” explains Kloppers.

with the designation rules, even though

in the manufacturing process of various

they are not yet compulsory.

components,” says Kloppers.

“When considering the new mining

during the manufacturing process, or

charter that is coming out soon, local

R200 million plant

designation and local manufacturing are

Kloppers is very excited about the new

“Normally, companies would have to get

going to play a key part in the future of

manufacturing plant in Alrode, Johannes-

international employees or international

the mining charter. Together with all the

burg. The new facility includes a

branches to inspect the goods prior to

other important aspects like BBBEE, which

1 200 m training facility, 2 500 m office

is also changing with the new scoring

area and 2 000 m2 logistics and ware-

2

prior to delivery to their plants and sites.

2

leaving the factory. “This offers peace of mind with the

systems, it made sense for the company

house space. With the new manufactur-

products being manufactured local-

to comply with the rules,” says Riaan

ing plant in South Africa, the company

ly, which is unique to our company,”

Kloppers, manager: Industrial Division,

can either supply directly off the factory

says Kloppers. The company also involves

AVK Valves Southern Africa.

floor and save companies six to eight

the mining industry with its research and

The new AVK manufacturing plant in Alrode, South Africa

4

He adds that South African companies can now inspect the ordered goods

Ins i de Mi n i n g 1 0 | 2 0 1 6


cover story development (R&D) in developing different types of products specific to local conditions. Kloppers says that the company does just about everything in-house regarding the R&D, which means having a local manufacturer that can assist with extra development. “When mines want to introduce new technology, they can join us while we design or manufacture products for them. We can also install it for them and they can give us their feedback; it is a total value-add.” Kloppers adds that many AVK products

Left to right: Lars Kudsk, Tjaart Van der Walt, Paul Hubbard, Trine Rask Thygesen, Malebo Mabitje Thompson, Niels A Kjaer, Peter Thomson and Brian McGugan

in the meaning of cost of ownership. Our products might be 2% more expensive, but they will save an immense amount of money in installation and reduced downtime. We offer products that last

are unique to the South African market. “All the patented products specific to

valve-related products globally. “We

for the lifetime that the plant was initially

South Africa that used to be manufac-

obviously looked at which products are

designed on,” claims Kloppers.

tured elsewhere in the world will now be

in high demand in Southern Africa and

manufactured locally.”

will manufacture those in huge quantities.

Training centre

These include products with SABS certifi-

The company identified a need for train-

cations, and products for

ing in the market. First and foremost, the

specific contracts.

new training centre will assist with skills

New technologies The new plant includes a brand-new, state-of-the-art powder-coating plant that is unique to South Africa. The new

“We will also manufacture gate valves, resilient seated valves, valves used for

transfer and will offer a variety of courses, from beginner to more advanced

testing equipment as

drilling shafts and valves

programmes. The idea is to keep it neu-

well as the new num-

used to find water

tral and generic. Kloppers explains that

pockets or gas pockets.

new engineers, as well as people who

Furthermore, we man-

order products, need to understand the

ufacture gas detection

different valves available. “For instance,

systems for different

we struggle to get the correct informa-

types of applications

tion from clients ordering valves. With

and ball valves for the

the training centre, we assist the market

nuclear industry. We are

by laying out the foundation from a nov-

bering system, with full traceability, are new technologies as well. “We have a fool-proof system in place to eliminate the human

Companies don’t have to wait for their products to be shipped from overseas

error that one normally finds in a manufacturing plant, thereby

currently reviving the entire range of IPV

reducing possible delays,” says Kloppers.

valves, which are used in harsher types of

Products

applications,” says Kloppers. He adds that another unique aspect

ice person to engineers.” The training centre will look at various topics and courses such as plant evaluations, to identify three elements that

Every single one of AVK’s products has

to the company is that the majority of its

could prolong the life of valves by at

some or other unique patented feature,

products are maintenance-free. Where

least five to ten times, namely:

according to Kloppers. AVK manufac-

maintenance is required, it is a simple,

• Are the valves installed in

tures just over 60 000 different valves and

fast procedure where one doesn’t have to drain the entire system. The replacement of the product might take up to 10 or 15 minutes, before restarting the process and resuming production. This adds up to a product with unique tech-

the correct position? • Is it the right valve for the specific application? • Is the valve manufactured for the material passing through?

nologies that can save the end user time,

Conclusion

money, and effort. “We believe strongly

Kloppers explains that the company sees itself expanding even more in South Afri-

Malebo Mabitje Thompson, deputy director general of the Department of Trade and Industry, and Niels A Kjaer, owner of AVK Holdings A/S, at the opening of the new premises

ca. “We still have about R250 million on the cards to invest in South Africa, specifically regarding new technology.”

www.avkvalves.co.za

In sid e M in in g 1 0 | 2016

5


Mining news

from around the continent Burkina Faso Gold rush prompted by high deposits

busy with the feasibility study of the mine, to make sure the mine is still viable; this obviously needs money. Up until now, the number of illegal miners has gone from several hundred into the thousands, and we have asked the government to reinstate the security they had previously assisted with to try and rectify the situation. “We’ve had to withdraw all non-critical workers on the mine, and leave those who are providing critical services to the mine and the community at large, because it is now a safety issue, but there has been limited intervention by government,” he continued.

IVORY COAST

Processing facilities at the Essakane Mine in Burkina Faso

BURKINA FASO

Mining exchange for exploration and operation West Africa’s regional stock exchange – the Bourse Regionale des Valeurs Mobilieres (BRVM) – plans to start a

on the mining company’s production or

separate section for mining stocks and

costs, as the mine wasn’t forecast to be

have a dedicated mining platform in

operating this year, but the prolonged

place by 2018, general manager Edoh

The West African nation of Burkina Faso

occupation of illegal miners on the

Kossi Amenounve said in an interview.

has increased its gold output by more

mine threatens the long-term viability

than 20 times in the last decade. In a

of the mine. In February, the military

for resources companies to raise funds

review of its geological records, it was

protection unit that was posted on the

in the local Communauté financière

noted that the country has more gold

mine withdrew its protection, leaving

d’Afrique franc currency, the head of the

waiting to be discovered.

the mine vulnerable, and it was overrun

BRVM said. The mining exchange will be

by illegal miners.

open for companies exploring or operat-

High gold deposits prompt rush

Mining Minister Alfa Omar Dissa said, in

The move is aimed at making it easier

an interview, that the government wants

Steward Bailey, senior vice-president:

to help companies that are already op-

Investor Relations & Group Communica-

The BRVM is in talks with the Toronto

erating in the African nation to lengthen

tions, AngloGold Ashanti, said, “The mine

Stock Exchange to set up a “technical

the lives of their mines and make it eas-

was placed on care and maintenance.

partnership” between the two bourses

ier for new investors to get information

We had the intention of modernising the

inspired by the Canadian mining-ex-

about deposits.

mine in order to convert it. We were also

change model. “Mining companies

ing mines in the region, he added.

“We’ve reviewed the eastern, western and southern regions, and we found some very interesting information,” he said. Deposits previously unknown include gold, lithium, nickel, a bit of uranium, and even traces of oil. The country has seen a gold rush in recent years because of the high grades found in some deposits, which hold as much as 17 grams per tonne, compared with the global average of 1.5 grams per tonne, Dissa explained.

GHANA

Tightened security hoped to repel illegal miners Disruptions by illegal miners at AngloGold’s Obuasi mine have not impacted

6

Ins i de Mi ni ng 1 0 | 2 0 1 6

Ghana Locked gates to keep illegal miners out


SOUTH AFRICA

Edoh Kossi Amenounve, general manager, Bourse Regionale des Valeurs Mobilieres

Survey suggests executives investing in technology A survey reflected in KPMG International’s 2016 Global Metals & Mining Outlook noted that less than half of the executives responding depicted low levels of confidence in the prospects of the global economy over the next

The future of mining lies in advanced technology and robotics

two years, albeit the tight relationship operating in the region only raise funds in

between the fortunes of the global econ-

different than in the past, particularly

foreign currencies,” the GM said. “Some

omy and that of the global metals and

given the structural changes taking place

of them have approached us to see how

mining industry.

and the environmental regulations cur-

they could raise the resources they need in local currency.

The KPMG survey taken by senior metals

rently being tabled around the world.”

executives suggests that most metals ex-

To alleviate the tensions in the market,

Some have even asked us for a dual

ecutives are confident that there will be

tapping into technology is one aid they

listing with the Toronto stock exchange,

growth in the next two years, citing two

intend on using. The survey shows that

but the regulating framework isn’t com-

main strategies – growing their existing

metals executives plan to channel signifi-

patible at the moment.” Companies

market share and entering into new mar-

cant investment towards developing and

that want to sell shares on the bourse are

kets. Jacques Erasmus, global head: Min-

implementing new manufacturing tech-

currently required to provide certified

ing, KPMG, says, “When growth does re-

nologies aimed at driving efficiency and

accounts for at least two years.

turn, the market will likely be significantly

improving performance.

In sid e M in in g 1 0 | 2016

7


legal

Safety first, zero tolerance Mines have implemented a variety of policies and procedures to keep workers as safe as possible. One such preventative measure is testing for alcohol at the security entrances of mines. By Hugo Pienaar and Elizabeth Sonnekus, Cliffe Dekker Hofmeyr

Y

ET, WITH ALL these precau-

Act (No. 66 of 1995) (LRA) recognises

tions in place, people under

misconduct by an employee as a fair

the influence of alcohol are

reason for dismissal.

found on-site during working

the employee is under the influence of

ger, whether they are driving heavy ve-

Two scenarios in which an employee may be charged for alcohol use at the workplace

hicles or operating potentially danger-

In the first scenario, the employee’s

to work has been impaired.

ous machinery. Even if people under

drunkenness can be proven by sight,

the influence are just walking on-site, it

smell and/or the conduct of the em-

that a positive test result is sufficient

can put their lives in danger.

ployee. Aggressive behaviour from

proof to charge the employee for be-

the employee, slurred speech and

ing under the influence of alcohol.

hours. These people place their lives and those of their colleagues in dan-

Due to all the policies and proce-

alcohol or that the employee’s ability Employers often mistakenly believe

dures in place, one would expect that

bloodshot eyes are some of the factors

people under the influence at work

indicating drunkenness. The degree

a positive test result is not necessarily

could be dismissed immediately. This

of drunkenness has to be to such an

sufficient to dismiss an employee. In

has been proven not to be the case.

extent that it impairs the employee’s

Tosca Labs v CCMA 2012 33 ILJ 1738

Often, employers are under the im-

ability to work. The onus is on the em-

(LC), the Labour Court found that a

pression that when an employee tests

ployer to prove this. No expert witness

positive test result on a breathalyser

positive for alcohol, the person is ac-

is required for such purposes.

test is not sufficient proof to indicate

tually under the influence of alcohol.

8

People under the influence of alcohol are a potential safety hazard to co-workers and machinery

The second scenario is where an em-

Recent case law has confirmed that

that the employee was under the

Alcohol and drug abuse is a form of

ployee tests positive for alcohol on a

influence of alcohol. The court

misconduct. Schedule 8 of the Code of

breathalyser apparatus. A positive out-

referred to Tanker Services (Pty) Ltd v

Good Practice of the Labour Relations

come does not necessarily prove that

Magudulela 1997 12 BLLR 1552 (LAC),

Ins i de Mi n i n g 1 0 | 2 0 1 6


legal which stated that the real test is

summarily dismissed irrespective of

whether the employee’s competence

whether his/her ability to work is im-

to perform their work has been

paired or not. To adopt such a policy

impaired. In this case, the employee

depends on the status thereof, and

was able to perform his tasks and the

may sometimes simply require consult-

court held that the dismissal was substantively unfair.

What should an employer do? The employer should adopt a zero-tolerance

ing with the employees be-

The degree of drunkenness has to be to such an extent that it impairs the employee’s ability to work

policy in terms of

fore its implementation. The employer should always ensure that all employees are aware that there is a zero-tolerance policy, and that if they test positive for any usage of alcohol, they will be in breach of the policy and

alcohol in the workplace. Such a

may be subjected to disciplinary ac-

policy should be specific and also

tion and possible dismissal.

provide for a summary dismissal, even

In addition to the above, the breath-

when the employee has only been

alyser apparatus should be properly

tested positive for the use of alcohol

calibrated and the person administer-

or drugs. The rationale for such a policy should be based on the safety considerations of the employer. This means that an employee may be

People under the influence of alcohol can create a danger on-site, regardless of what they may be doing preferably be obtained to show that the employee’s ability to work was impaired – if that was indeed the case. If it emerges that an employee is

ing the test should be trained to do so

dependent on alcohol, the employer

correctly. The test should also always

has an obligation to consider

be done in the presence of a witness.

providing counselling and assisting

However, where possible and applicable, evidence should

the employee as set out in item 10 of Schedule 8 of the LRA.

In sid e M in in g 1 0 | 2016

9


Commodity: Coal & Uranium

Mining large deposits in Waterberg T

HE BOIKARABELO Coal Project

Sedgman has a strong track record in

more consistent and will increase our

will be a long-term project with

terms of design and construction, and

yield,” explains Van der Bank.

an expected 70-year life of mine,

coal handling, as well as a strong bal-

with a possibility to extend up to

The washing plant has a 2 100 t/h duel-

ance sheet. The second strategy that

integrated module design (each unit

200 years. This is unsurprising, taking into

the company adopted to save costs is to

with with a 1 050 t/h capacity) with a

consideration that the Boikarabelo coal

base contracts on fixed-price lump sums.

two-stage concept: high-cut/low-cut

seam is between 120 m and 130 m thick,

“In other words, the EPC undertakes

and between 20 m and 30 m below the

to provide the services for a fixed price.

both a high-grade product and a

surface. The zones contain varying quali-

Any cost overrun will be for their ac-

secondary lower-grade product.

ty thermal and soft coking coal.

count, rather than ours. The benefit of

Resource Generation (ResGen)

implementing these two aspects is that

acquired 16 000 hectares of land in

the risk is now moved from our balance

the Waterberg and reported probable

sheet to the balance sheet of the con-

reserves of 744.8 million tonnes of coal on

tractor,” says Lowe.

35% of the tenements. Mobilisation of the processing plant

Processing plant

construction crew will occur from January

Zirk van der Bank, COO, ResGen, explains

2017 and the plant should be commis-

that the processing plant will process

sioned from July 2018 and operational by

2 100 t/h (tonnes per hour), starting off

the end of Q4 2018. The open-cut surface

with 700 tonnes run of mine ore. From

mine will start full production Q1 2019.

there, the material will go to the crushing circuit that has a capacity to process

Contractor

2 500 t/h.

To ensure that the mine yields the best

“The three-stage size reduction system

results at the lowest possible cost, Res-

crushes ore down from 1 000 mm to

Gen adopted a new execution strategy,

50 mm. The first stage is beneath the run

based on using a limited number of en-

of mine bin that crushes the material to

gineering procurement and construction

300 mm, followed by duel slow-speed

(EPC) contractors with a good track re-

roll sliders that will reduce the material

cord and a strong balance sheet. They will also have the right to recall a contract in case of failure or delay. “With these requirements in mind, we went

The project is located 40 km from an existing rail system, which will mean access to the ports of Maputo, Richards Bay and Durban

into an agree-

10

Waterberg is said to be the next coal resource in South Africa, with approximately 40% of the country’s remaining coal reserves. This is exactly where ASX- and JSE-listed, South Africa-based company Resource Generation has started to develop the Boikarabelo Project. By Mientjie Kleinhans

down to 50 mm,” explains Van der Bank. From the run of mine and crushing circuit, the coal will go on to the run of mine stockpile facility with a 150 000 tonne capacity. A coal linear stacker with

ment with Sedgman Limited, a member

a full-face-bridge-type bucket wheel

of the CIMIC Group, for a fixed lump

reclaimer ensures that it fully blends the

sum contract of US$141 million, subject

stacked raw coal for smooth feeding

to exchange rate fluctuations,” says

into the coal processing plant. “This is

Rob Lowe, CEO, ResGen. He adds that

to make the raw coal plant feed much

Ins i de Mi n i n g 1 0 | 2 0 1 6

washing stage designed to produce

The entrance gate to the Boikarabelo project


Commodity: Coal & Uranium

The Boikarabelo project is located in Waterberg in Limpopo province

sustainable water resource underground that is within the mining rights area. The plant has been optimised to ensure that “The key process circuits include two-

be an open-pit mine with a strip ratio

we use the minimum amount of water,”

stage dense medium cyclones for coarse

of less than 1, which is extraordinary in

says Van der Bank.

coal processing and a two-stage reflux

mining terms.” Further to that, ResGen

classifier system for fine coal processing,”

has developed a logistics solution that is

the local municipality’s sewerage plant

says Van der Bank. The fines will be

competitive and Lowe hopes that this will

in the future for use at the mine. “There

dewatered through belt press filtration.

encourage other mines to follow suite.

are a couple of options we have re-

The project is located 40 km from an

He adds that they will treat water from

garding water, but our main source will

Unique

existing rail system, which will mean ac-

According to Lowe, the Boikarabelo

cess to the ports of Maputo, Richards

Project will be the most advanced new

Bay and Durban – opening up domestic

Energy

mine in the Waterberg. “The Waterberg

and export routes. “When we receive

The project will make use of 30 MWa

have been identified as the next viable

funding, we will proceed to develop the

power from Eskom and the substation

coal reserve for South Africa. We see

railway link,” says Lowe.

has been constructed. “That will pro-

ourselves as the key that will unlock

be underground water.”

vide sufficient electricity to the mine.

the Waterberg and an essential part

Water management

of SIP1, which is unlocking the northern

A detailed water management plant

day now, which will be in time for when

mineral belt with Waterberg as the cat-

has been developed for the water man-

construction commences,” concludes

alyst. Adding to that, Boikarabelo will

agement on the project. “We have a

Van der Bank.

Eskom will connect to our system any

In sid e M in in g 1 0 | 2016

11


Commodity: Coal & Uranium

Changes making the difference

A combination of tough economic times and a strategic realignment required Exxaro to change its governance, risk and compliance (GRC) management system. These changes brought about cost savings through effective risk management and better resource allocation. By Mientjie Kleinhans

A

S THE SECOND LARGEST coal

challenging themselves to as to why it is in

producer in South Africa, Exxa-

the Act itself. “For example, if one looks at

ro implemented a new strate-

the Act, it assists in creating a safe work-

gy that goes beyond the the-

ing environment. Instead of looking at the

ory and tick-box approach, moving staff

objective of a safe working environment,

approach, and is expanding on to a

to understand GRC management and ask

people are walking around with check-

sixth capital, namely intellectual capital.

why things are done in a specific way.

lists and doing inspections because they

The other five are:

“What I have seen, in general, is that min-

think it is going to create a safe working

• natural capital

ing companies often introduce a GRC

environment. But, instead, they are simply

• human capital

system for compliance’s sake. It is as if

proving that they comply with the differ-

• social capital

they are losing the practical perspective

ent laws and regulations,” explains Van

• manufactured capital

because they are so inundated with var-

Loggerenberg.

• financial capital. “With this inclusion, we have done well

ious laws and regulations they need to

The same applies to risk management

comply with that they tend to forget to

at an operational level. By really under-

by marrying our sustainability goals

consider why they need to comply with

standing the reasons of the Act and

with the overall company goals. We no

the different pieces of legislation. This is

complying therewith, the Act will help

longer talk about the sustainability goals

especially the case in the operations en-

businesses achieve their objectives,

separate to the general company goals

vironment with regard to complying with

of which one is safety. Simply asking

– something that companies did wrong

the Mine Health and Safety Act

why the company has to comply will

in the past,” explains Van Loggerenberg.

(No. 29 of 1996). People need to under-

change the perspective on compliance

stand why they should be doing certain

risk management.

tasks,” says Saret van Loggerenberg,

12

Dust management has been elevated to a higher risk level due to especially dry conditions in South Africa

A successful solution lies in marrying the GRC system to what the company wants to achieve in business, and over-

manager: Risk & Compliance, Exxaro. She

Sustainability goals

laying that with the overall strategy. “For

explains that people often have a strin-

Exxaro introduced the five capitals

us, it was really all about identifying the

gent tick-box approach, without really

model as part of its triple bottom-line

overall GRC approach and then looking

Ins i de Mi n i n g 1 0 | 2 0 1 6


Commodity: Coal & Uranium

dust risk at one level, and challenge the strategic risk at the very top. This means explaining to people how to adopt

Effective risk management and better resource allocation brought about cost savings for Exxaro

the same risk management process at different layers of the organisation,

extracting water, and the quality of

replicated in different layers but for

water that is discharged again. Mines

different purposes.

need to be cognisant of the water

“People now need to understand that

less with their water usage, lest they

apply it to different objectives. You can

exacerbate the problem.”

apply the same process in different are-

Saret van Loggerenberg, manager: Risk & Compliance, Exxaro

availability challenges and not be reck-

they must follow the same logic, but just

as, such as technology, engineering and

Challenges

mining, by using different sets of facts,”

Van Loggerenberg says that another

says Van Loggerenberg.

challenge Exxaro is facing is to alter its

The same goes for another cru-

compliance-driven tick-box approach

cial element of water conservation

to accommodate changes to the sus-

and management.

tainable business objectives; one of

Van Loggerenberg explains that, generally, businesses should employ a

which is operational safety. “The other challenge that I have seen

strategy that aligns with their objectives

is that people are operating in silos

at how the business can support that. I

while also ensuring sustainability. “The

and there is not much cross-functional

think, if one does that, then much of the

reason for this is that most companies

collaboration happening within the

gap can be filled with business imple-

believe in GRC and in being sustainable,

company – especially concerning safe-

mentation and negotiation.

but it often stops at

“It is also important to understand

the strategic level,

ty. Some people think

“We have done well by marrying our sustainability goals with the overall company goals.”

that safety is solely safety

the culture of the organisation that

and sustainable KPIs

one works in to ensure that the systems

are never pushed

support the goals in terms of thought or

through to the oper-

compliance management processes. It

ation. They will pro-

is really critical to understand the goal

vide the necessary

you are chasing and then to implement

measures on these

a system that mirrors that. It is all about

things, but they

adjusting the system to suit the compa-

don’t always know

Loggerenberg.

ny’s needs,” says Van Loggerenberg.

why they have

She believes that anoth-

specialists’ problem, so they push that obligation away from themselves and their respective departments. Everybody should become proactive,” says Van

measures on the sustainable KPIs.” She

er challenge is the reluctance to adapt

adds that the sustainability KPIs are used

and enhance technology to achieve

One of the risk areas recently discussed

to improve social licence to operate.

an integrated proactive approach –

within the company is dust manage-

For this reason, it is essential that they be

to change behaviours and traditional

ment, which has been elevated to a

measured, although companies are not

ways of thought.

higher level due to the dry season that

being told why they are measured.

Dust management

South Africa has been experiencing late-

“To me, it is more of an add-on to

“We still have a long way to go there, but at least we have started. We have

ly. Another focus area for the company

the operations’ objectives. With water

a very proactive CEO in Mxolisi Mgojo,

is integration and, with the integrated

being a definite challenge, we are

who believes that we need to change

system process, the company uses the

carefully monitoring our water perfor-

the way we do business,” concludes

same process to unpack elements of the

mance and how people are using and

Van Loggerenberg.

In sid e M in in g 1 0 | 2016

13


Focus on Africa: Ivory Coast

Exploration revealing great possibilities Using modern geochemical methods, new gold resources have been discovered and explored in the Ivory Coast. Mientjie Kleinhans finds out what makes Predictive Discovery’s Boundiali Project so interesting, besides being located in a favourable gold mining investment destination.

A

S A GREENFIELD development

suggest that the gold mineralised system

“This new set of results confirms that the

without pre-existing artisanal

persists over most of that length, suggest-

newly discovered Nyangboue gold

miners or people living on

ing the potential for large tonnages of

mineralised system persists both at

or near the site, with initial

gold mineralisation.

depth and along strike. We are espe-

drill results indicating visible gold in the

cially encouraged by the high grade of

higher-grade sections, the project is truly

so far are in the unweathered zone,

the first of the deepened holes on the

worth investing in.

which suggests that there is potential for

first section drilled, possibly indicating

mineable grades to substantial depth,”

an additional mineralised zone. These

explains Roberts.

new assays tell us that the gold system

“The project is still at the beginning of the exploration process and we have received results from only two of the eight

extends at least 320 m to the next line

drill lines. In the event that we define a

Drill results

potential gold deposit and after com-

The latest drill highlights from Boundiali’s

sults covering a 2 km strike length yet to

pletion of a definitive feasibility study, a

Nyangboue prospect include:

come,” says Roberts.

decision to start a mine would be some

• 9 m at 7.9 g/t gold from 99 m,

years in the making,” says Paul Roberts, managing director, Predictive Discovery. He explains that initial drilled gold

including 1 m at 44.7 g/t gold

to the north, with the majority of drill re-

He adds that the assay results have been returned a little more slowly than

• 7 m at 3.8 g/t gold from 33 m,

hoped, due to some delays at the ana-

including 1 m at 11.3 g/t gold

lytical laboratory. “We now expect that

grades and widths are both very impres-

• 8 m at 1.5 g/t gold from 38 m

the rest of the results will arrive soon. We

sive and the gold value starts from the

• 9 m at 1.2 g/t gold from 20 m.

will release these assays as soon as they

surface. “There is visible gold in the high-

The multiple mineralised zones on the

come to hand.”

grade sections, suggesting that the gold

second drill line, 320 m north of the first,

is unlikely to be refractory and may be

indicate that the mineralised package

mit is located within a very well mineral-

partly, or even largely, treatable by rela-

extends for at least 320 m along strike,

ised greenstone belt. “This area contains

tively low-cost gravity methods.”

and is open to the north and south and

the two gold mines in the Ivory Coast

at depth, according to the latest results

and Mali, namely Tongon and Syama.

interesting is that the coherent gold-

report. To get the results, 92 holes were

There has been little exploration in this

in-soil geochemical anomaly is large

drilled, totalling 5 496 m. Six drill sections

area and, hopefully, there will be more

– 2 km long – and the more recent results

with 69 holes are still outstanding.

gold to be discovered.”

What makes the project even more

The exploration team at work on-site

14

“The highest-grade intercepts obtained

Ins i de Mi n i n g 1 0 | 2 0 1 6

Roberts explains that the Boundiali per-


RELIABLE SIZER PERFORMANCE In 1978 we developed and introduced the Twin Shaft MINERAL SIZER™ to help underground coal mines break coal more efficiently and effectively whilst also increasing productivity. Today we have progressed the Twin Shaft MINERAL SIZER™ to provide a unique range of trusted solutions and systems for both underground and open pit mining operations. With over 3000 installations worldwide, MMD have the knowledge and expertise to deliver reliable systems that maximise production, improve safety and increase efficiency. MMD remains a group of committed and experienced professionals who have the skills and knowledge to provide reliable after-sales service and technical support via a network of local offices.

+27 11 608 4801

sizers@mmdafrica.co.za

For more information please visit WWW.MMDSIZERS.COM


COMMINUTION

Defining mineral sizers Understanding what defines the MMD Twin Shaft Mineral Sizer, how it compares to a double-roll crusher, and the role it plays in comminution, can make all the difference. Martin Vorster* discusses the role of mineral sizers in comminution.

A

LTHOUGH MINERAL sizers are

are the three-stage breaking action,

These subject the rock to multiple-point

manufactured in various

the rotating screen effect, and the

loading, inducing stress into the material

sizes, the principle remains

deep-scroll tooth pattern.” Mineral sizers

to exploit any natural weakness and

the same. The definition of a

exploit the already inherent weakness in

fracture planes – fundamentally utilising

mineral sizer is best described by MMD

rocks. The patented tooth geometry and

tensile rather than compressive forces to

Mineral Sizing (Africa): “The basic con-

configuration subjects the material to

break material.

cept of the MMD sizer is the use of two

stress, bending, tension and shear forces

rotors with large teeth, on small-diameter

in an effective and quick three-stage

Stage 2

shafts, driven at a low speed by a direct,

breaking action.

At the second stage, material is broken

high-torque drive system. This design

in tension by being subjected to three-

produces three major principles that all

Stage 1

interact when breaking materials using

Initially, the material is gripped by the

tooth faces on one rotor and rear tooth

sizer technology. The unique principles

leading faces of opposed rotor teeth.

faces on the other rotor.

point loading, applied between the front

A typical example of a double-roll crusher

16

Ins i de Mi n i n g 1 0 | 2 0 1 6


COMMINUTION table 1 Characteristics of good mineral sizer utilisation

Primary mineral sizer

Secondary mineral sizer

Double-roll crusher

Highest possible reduction ratio to be used

Driven toward final product size “finishing”

Ideal for tertiary crushing application where small product size is required (<30 mm)

Sizing effort a maximum at primary stage

Typically lower reduction ratios

Typically even lower reduction ratios

Larger wear components translate to extended operating throughput

“Hard work” to be done by primary sizer

Care must be taken to match feed material to nip void

Smaller wear components require more frequent changing Minimises fines generation

Stage 3

a rotating screen effect, and typically

A breaker bar, located beneath and

features large teeth on relatively small

between the twin shafts, provides a third

shafts. At the same time, it allows lower

stage of breaking in the centre of the

power demand due to scrolled engage-

machine, for maximum three-dimension-

ment. Typically, a reduction ratio of ~5:1

al control of the finished product size.

and above can be achieved. A mineral

Deep-scroll tooth pattern The deep-scroll pattern conveys larger

sizer can be designed for primary, secondary or tertiary sizing applications. A double-roll crusher has the potential

material to one end of the machine

for “slabby” product to pass through the

and distributes the feed of raw material

machine, due to the parallel-teeth ar-

along the length of the rotors. This unique

rangement. With the double-roll crusher,

action offers a large reduction in energy

fines generation becomes an issue if the

requirements to size material when com-

material feed is mismatched with the

pared with multiple-tooth engagement.

nip void, which causes a grinding effect.

The pattern also allows for the rejection

Indirectly, this results in higher wear rates.

of oversized material, if required. Without a deep-scroll pattern, the material feed must be well matched to the drum diameter or else material

The material is broken in tension by being subjected to three-point loading

There is a higher power demand due to the multiple-tooth engagement, and

Any lumps of material that still remain oversized are broken, as the rotor chops through the fixed teeth of the breaker bar

the typical reduction ratio is ~2:1.

hang-up and the grinding of oversized

Good mineral sizer utilisation

materials are likely. This causes excessive

When a mineral sizer is used in a primary

wear and fines generation, due to the

application, the highest possible reduc-

grinding action. If the material is too

tion ratio is used to get the material as

big, it will be grinded – which creates

small as possible, as quickly as possible;

unnecessary fines.

therefore, the sizing effort needs to

Furthermore, double-roll crushers

The material is gripped by the leading faces of opposed rotor teeth

be at its maximum at the first stage,

typically demand higher power con-

where a mineral sizer’s larger wear

on the application and requirements

sumption, due to increased crushing

components translate into extended

of the client. The machine’s compact

effort, with multiple-point simultaneous

operating throughput.

dimensions make it ideal for mobile in-

engagement along the rollers.

The rotating screen effect

When a mineral sizer is used in the

stallations or retrofitting in underground

secondary crushing stage, the sizer is

operations where space is limited.

geared towards final product size, or

Finally, a key design benefit is that all

A mineral sizer creates a rotating screen

“finishing”. This, typi-

effect from the interlaced rotor design

cally, allows for lower

that allows undersized material to pass

reduction ratios with

through with minimal degradation. The

minimal wear and the

continuously changing gaps around

hardest work to be

the rotor minimise fines generation and

done by the primary

reduce power consumption. In turn, this

sizer. A double-roll

means the MMD sizer negates the need

crusher is ideal for tertiary crushing ap-

ability to process wet, sticky material or

for pre-screening.

plications where a small product size, of

hard, dry rock, or a combination of the

<30 mm, is required. A double-roll crush-

two, and has proved to be the ideal

er typically offers even lower reduction

sizing solution for over 80 different

A machine is a mineral sizer when it de-

ratios. With this type of crusher, care

minerals worldwide.

livers a 3D cubical product controlled

must be taken to match feed material

in all three principal directions. The ma-

to the nip void. A full range of MMD

*Martin Vorster is the managing director

chine also minimises fines generation via

mineral sizers is available, depending

of MMD Mineral Sizing (Africa).

Characteristics

the breaking forces

A machine is not a sizer if it does not scroll the material

are fully contained within the frame, requiring minimal support structure. MMD’s Twin Shaft Mineral Sizer has the

In sid e M in in g 1 0 | 2016

17


COMMINUTION

In-pit crushing,

sizing and conveying In-pit crushing and sizing (IPCS) and in-pit crushing and conveying (IPCC) are not new technologies, yet applications thereof should be seriously reconsidered in these challenging financial times. The potential savings can be significant. By Dave Thompson*

T

he majority of development of coal in South Africa, over the last

poor hauling conditions.

Benefits The benefits of an IPCC/IPCS system

century, has been in the Emalahl-

All of the above options require roads,

surpass the initial layout costs in the long

eni and Middelburg areas in the

but in the soft rock mining industry, we

run, as it increases the run of mine pro-

Mpumalanga province. Now, all eyes

tend to fall flat. We end up having large,

duction by between 10% and 20%. It can

are on the Waterberg region as the next

heavy trucks travelling on poor roads,

also increase the plant yield, as the coal

potential coal fields to expand to. This

which damages the trucks. We get nei-

fed into the plant is void of rubbish. This,

region will predominantly be opencast

ther the availabilities nor the productiv-

in turn, means less maintenance costs,

mining due to the shallow line of coal

ities – all because we are mining a bulk

with less wear and tear due to the ab-

in the area.

commodity and the bulk is crucial to

sence of hard material.

When considering new mines, it is important to consider the crucial design

keeping the costs down. Further than having

stages of any project and to keep inno-

to build and maintain

vation in mind. Obviously, capital, oper-

roads, the trucks are driv-

ations, services and marketing are key

ing up costs due to:

drivers to any business venture.

• high maintenance and

Challenges The challenges that are all very pertinent

repair costs • poor road-building practices

to the coal mining industry at the mo-

• poor safety records

ment include:

• regulatory constraints

• low commodity prices • increasing strip ratios

There are quite a few

An IPCC/IPCS system discards the rock and mud stones, sending only products to the processing plant

options to consider over big trucks hauling material between the pits and the processing plant. A truck is an inefficient mode of transport. Implementation of in-pit crushing and conveying, or in-pit crushing, sizing and conveying is not a new concept. A

now being imposed that make operat-

semi-mobile IPCC/IPCS system brings the

ing trucks even more costly

run of mine closer to the working phases,

• decreasing saleable product yields

• long haul routes

and, therefore, half the number of trucks

• global demand for cleaner energy

• poor equipment utilisation.

are required for the operation.

• pressure to reduce carbon footprints

The question that keeps coming up is

• project financing challenges

why do we want to take low-quality run

cient method to remove the run of mine

• high costs of labour

of mine feeds, which have mud stone

product or overburden in a more cost-ef-

• productivity challenges.

bands and sand stone bands, all the

fective way.

With that, the current open-pit mining

way to a centralised crushing facility

method options include:

to remove all the waste material and

of the truck is always going to be 50% to

• draglines, which have high capital cost

upgrade them there, and then have to

55% of the load. A point to consider is all

bring all the waste material back to the

the energy spent to move the 50 tonne

in-pit regions to backfill and rehabilitate?

to 200 tonne per unit truck around, even

This is especially pertinent when one

when it is empty. Then, it gets loaded

could quite easily introduce a system of

with an equivalent mass. This is an ineffi-

selective mining, crushing and screening

cient means of materials handling com-

directly in the pit. An IPCC/IPCS system

pared to a conveyor.

and limited flexibility • extra-large shovel and truck, which require high-quality road conditions • large shovel and truck, which, in turn, require medium-quality road conditions • medium shovel and truck, which requires lower-quality road conditions • small shovel and truck, which is suitable to soft rock, with good roads

18

• excavator and truck, which is good in

Ins i de Mi n i n g 1 0 | 2 0 1 6

discards the rock and mud stones,

Conveyor belting is a much more effi-

The big consideration is that the weight

Other than the fact that there is one

sending only useable products to the

operator per truck, in my personal expe-

processing plant.

rience, there are never enough trucks


COMMINUTION

Dump truck

Belt conveyor

Gradeability (°)

6-8

18

Payload (%)

50 - 55

90 - 95

No. of operators

1 per truck

none

Power draw (kW/tkm)

0.5 - 1.0

0.1 - 0.15

Cost/tonne($/tkm)

0.35 - 0.50

0.10 - 0.15

Max particle size(inches)

No practical limit

16

GRAPH 1 Total costs and categories

US$/tonne

Table 1 Belt conveying offers lower operation costs and in-pit crushing

DT-system

LT-system

behind the digger to fully utilise it. Time

without considering recapitalisation

means that the backfill areas are much

and time again, the excavator will be

of trucks every five or six years, or re-

closer to the working phases, and dis-

waiting for trucks, meaning lost produc-

placement of trucks being written off

tances of waste material haulage can

tivity at the end of the day.

or destroyed.

be drastically reduced. This means that

The alternative to truck haulage is

A rule of thumb is that, if the trucking

transport distances can be halved.

conveyor belting, which has one-third

cycle times are more than 30 minutes,

There are various options and combi-

of the costs. There might be slightly

then some form of IPCC system needs

nations of IPCC/IPCS systems available

higher capital outlay costs, but the

to be looked at, because the opera-

– it all depends on the requirements

energy costs are lower, and so are the

tion runs at the lower ends of produc-

of the mine. An IPCC/IPCS system can

labour and maintenance costs.

tivity and higher ends of cost.

typically mean up to 90% availability,

The additional capital spent initially

with no stopping or standing times for

years’ time. The life cycleof the crushing

In-pit crushing and conveying concept

conveying systems is so much longer

Conveyor belts can easily work on an

*Dave Thompson is a mining consultant

than the 60 0000 hours of a truck,

incline of between 12° and 15°, which

at DRA Global.

becomes insignificant in a couple of

trucks. It just all makes sense.

In sid e M in in g 1 0 | 2016

19


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COMMINUTION

Fundamentals

of rock breakers

With so many rock breakers and rock breaking systems available on the market, acquiring new equipment can be a challenge in itself. Casper Booyse* sheds more light on these machines.

Casper Booyse, product sales manager, BTi Equipment: Osborn

T

here are typically four options for rock breakers in the mining market and it depends on what the mine’s requirements are as to which op-

tion will be best suited. The first option is a stationary rock

break down to from the maximum sup-

important operational spares. And the

plied oversize.

company also interacts closely with all

There are a few important factors to keep

customers to pre-empt long deliveries on

in mind when acquiring rock breakers or

any long lead items that will be needed

rock breaking systems, and one has to ask

on its products. As an added benefit to

the following questions:

the customer, airfreight of parts is often

• What is the correct system or breaker for

conducted to reduce lead times.

the specific application and duty? • What is the required quality?

*Casper Booyse is the product sales

• What is the technical backup service

manager at BTi Equipment: Osborn.

offered by the company? • How available are the parts and backup service? nicians, trainers, a Parts Division and technical sales staff to support customers

breaker system where the complete unit

with any aspect of aftersales assistance

is fixed next to a static grizzly or crusher,

required. Some of the aftersales services

and assists with the continuous flow and

provided include 24-hour backup services

breaking of oversize material. The second

in the Parts Division, maintenance and

option is breakers, fitted to excavators

operational training, preventative mainte-

for breaking oversize boulders in-pit or, in

nance and machine audits, and routine

some cases, also on a static grizzly.

and emergency service backup.

Third, mobile rock breakers are wheeled,

er systems different is the robust design

ly used for underground applications to

that caters for tough applications where

break rock on ore passes and at the blast-

a lot of raking and clearing of big, over-

ing face. The last option is a semi-mobile

size material is needed. They also match

unit that is a trailer-mounted system.

the systems with a powerpack that can supply more than the required power output to handle the booms and breaker

Rock breaker systems are sized according

fitted to the unit. The company increased

to specific guidelines. These guidelines

the efficiency of the breakers with finer

assist companies, like Osborn, in supplying

tolerances between the internal surfaces

the correct system for the application and

to increase the output of the breakers.

duty. Typically, the guidelines address

This allows a lighter-weight breaker to sup-

the following:

ply the same or more output energy as a

• type of material

heavier competitor breaker, which means

• hardness of material, determined by the

that more powerful breakers can be fitted

specific gravity (SG), bulk density and unconfined compressive strength (UCS) of the ore

A rock breaker mounted on a Hitachi machine

What makes the company’s rock break-

dedicated rock breakers that are typical-

Guidelines

An example of a mobile rock breaker

Osborn has dedicated service tech-

Site needs to determine the choice of rock breaker

to smaller carriers.

Spare parts

• reach required

The company carries adequate stock

• maximum throughput required

at all times, covering all machines sold

• maximum oversize expected

into the market. Daily checks are done

• product required – the required size to

on stock holding to limit any shortfalls on

In sid e M in in g 1 0 | 2016

21


Pipes, Pumps & Valves

The science of pumps and pumping Pumps are among the oldest and most misunderstood machines known to man. Mechanically, they are quite simple, but often very complicated hydraulically. Whether pumping slurry or water, it is rarely the pump’s fault when things go wrong. By Jim Jones*

A

pumping system is about moving liquid from one point to the other and everything in-between. When one plac-

es a pump into a system, it can become very complicated, and often the problem lies in the system within which it operates. Nobody is in the business to make a bad pump. When pumping slurry or water, the liquid to be moved is generally above the pump, but can also be below. Pumps do not suck – a vacuum has to be created, so that atmosphere pushes the liquid up into the pump.

Centrifugal pumps Centrifugal pumps are relatively cheap, mechanically compact and generally the first choice for many applications. These pumps are available as horizontals or verticals, and the pumps vary in hydraulic design using different materials of construction. While there are many different designs used in mining, the most common is the centrifugal slurry pump. Centrifugal pumps represent only 5% of the pumps in industry, but when it comes to cost, these pumps represent 80%

transmission. Slurry pump casings are

• closed with three or more vanes

of the running cost. Note that centrif-

either lined or unlined (single or double

• induced flow (vortex) with

ugals are significantly cheaper than

case) and use a variety of abrasion-

reciprocating pumps.

resistant alloys or elastomers. Water

Centrifugal slurry pumps are much heavier than their water or process

variety of materials, typically cast iron

Closed-impeller pumps

pump counterparts, and are always

for water.

Closed-impeller design allows for the

manufactured using abrasion-resistant

highest efficiency in slurry applica-

materials. A water or process pump

Impeller design

manufactured in the same abrasion-

Centrifugal pump impellers have a va-

It offers good suction performance

resistant materials is not a slurry pump,

riety of designs relating to vane shape,

and is essential for heavy and abra-

and can never be robust enough.

vane angles and flow direction. The

sive slurries. Closed-impeller pumps

three basic designs that are in general

can be sensitive to air locking and

use for slurry applications are:

are particularly sensitive to air.

The casings are generally radially split, thereby gaining access to impeller and

22

and process pumps also use a wide

multiple vanes • semi-open with multiple vanes.

Ins i de Mi n i n g 1 0 | 2 0 1 6

tions and has the lowest rate of wear.


pipes, pumps & valves

Figure 1 Characteristic curve shapes

RISING CURVE

UNSTABLE CURVE

STEEP CURVE

FLAT CURVE

“Lubricants are specifically designed to work in specific types of applications, and mines use very complex and sophisticated equipment that costs lots of money.”

Figure 2 A full set of characteristic curves

HEAD

Jim Jones, director: EMEA Region, Mining Flow Control, Metso

HEAD

SPEED

POWER

CAPACITY

given speed or speeds in terms of head

CAPACITY

(pressure), capacity (flow), efficiency, power and net positive suction head

HEAD

HEAD

required (NPSHR). Without this family of curves, it is impos-

EFFICIENCY

NPSHR

sible to accurately apply any pump to a particular system installation. All the data originates from test work, although

Induced and semi-open impeller

will always be a consequence. Pump

changes in speed and/or impeller diam-

Induced and semi-open impeller pumps

selection is, therefore, often a com-

eter are usually extrapolated. Individual

used in slurry applications are not sen-

promise, to accommodate a variety

curves are:

sitive to air locking and are ideal for

of parameters set by others. Therefore,

• head capacity curve

stringy and fibrous material. They cause

careful thought beforehand is a must

• efficiency curve

less damage to delicate solids, and are

– the more information provided at the

• power curve

good for large solids and viscous slurries.

inquiry stage, the greater the chances of

• NPSHR curve.

However, they offer relatively low effi-

getting the ideal solution.

The shape of the head/capacity (H/Q)

ciency, poor suction performance and

To make even a basic water pump

curve depends on the design of the im-

can suffer some impact damage with

selection, it is essential to be provided

peller, or more accurately the “specific

large solids.

with (as a minimum) the required flow

speed” of the design. The various shapes

rate and the head against which the

and their names are shown in Figure 1.

Impeller size

pump must produce the flow. Even with

Pump performance from a single

The diameter of an impeller governs

a given capacity and head, numerous

speed test is simply plotted on X and Y

head produced at any speed; the width

other data is needed for a trouble-free

axes, as illustrated in Figure 2.

of an impeller governs the flow rate.

installation. This data should relate to

Most, but not all, impellers have addi-

both the liquid handled and the system

Head, not pressure

tional vanes (pump-out vanes) on one or

under which the pump operates.

Centrifugal pumps generate head,

both sides of the impeller.

For slurries, additional data relating to

not pressure.

the solids present is required. Typically,

• 51.0 m head on water is 5.0 bar

vanes are designed to reduce internal

this includes:

• 51.0 m head on slurry of specific

recirculation and provide hydraulic bal-

• density of solid

ance. Compared to water and process

• average particle size

pumps, slurry pumps have impellers that

• maximum particle size and

These additional (expeller or pump-out)

are both larger and wider. Newton’s Third Law states that every

concentration.

gravity (SG) 1.5 is 7.5 bar • 51.0 m on a light oil duty of SG 0.75 is 3.75 bar • m to bar = metres/10.2 x SG • bar to m = bar x 10.2/SG.

action has an equal and opposite reac-

Centrifugal pump curves

tion. In our world, whatever we do when

Pump, or characteristic, curves repre-

measure pressure, even if marked to

designing and or specifying plant, there

sent the capabilities of the pump at a

show metres head.

Something to remember is that gauges

In sid e M in in g 1 0 | 2016

23


Pipes, Pumps & Valves Power absorbed

Table 1 Friction losses across a range of flow rate

Power absorbed by a pump at a given duty point is calculated as:

KW=

M3/HXMXS.G 3.68X Efficiency

m3/h

Friction (m)

Static (m)

Total head (m)

25

2.0

10.0

12.0

50

6.0

10.0

16.0

75

12.0

10.0

22.0

100

20.0

10.0

30.0

125

31.0

10.0

41.0

Friction (head loss) calculations In the absence of a computer, the fol-

curve, select an appropriate method

lowing formula may be used to assess

for estimating friction losses and stick

losses on water and settling slurries at

with it, whether it is tables, charts or

Seven deadly sins

higher velocities, where:

using a computer. Calculate the total

The seven absolutely deadly sins in a

• HF = m loss/100 m

equivalent length of straight pipe, using

pump system are:

• Q = m3/h flow rate

a given pipe size or range.

• off-design operation – the pump may

Next, tabulate friction losses for a

• D = pipe diameter in m

range of flows both below and just

• C = friction factor. 1.85

HF=

Q X C

1

D

4.87

X 3625

• polyurethane lined and plastic = 150 • seamless steel and spun

the pump’s fault • misapplied design

size, or range. Wherever a terminal pres-

• cavitation is vapour, not air in a pump

sure is required (spray bars or cyclones),

• excess nozzle loads

this can be added to the static, or listed

• poor lubrication – make sure that the

in a separate column for inclusion into

Pumps in series Two or more pumps can be operated

pump is correctly lubricated • misalignment means an unfair load on the bearings, which will cause collapse • neglect – it is important to physically

in series to generate more head or min-

attend to pumps to ensure effec-

• spiral welded steel and cast iron = 130

imise wear. While a single-stage water

tive operation.

• rippled bore rubber hose = 110.

pump may generate some 150 m, the

There are numerous charts and tables

resulting rate of wear on slurry necessi-

*Jim Jones is the director: EMEA Region

also available for quick calculations.

tates series pumping.

at Mining Flow Control, Metso

cast iron = 140

Pumps can be operated in parallel

Settling with slurries

where the required flow is not achiev-

Quite simply, if the average velocity in

able with a single pump; two or more

any given line drops below the critical

pumps can be operated in parallel. The

(minimum) velocity, then the coarse

discharge from all pumps is connected

solids start to deposit on the bottom of

to a common delivery line to increase

the pipe. If this situation is allowed to

the flow.

continue, then the pipe will block soon-

As increased friction affects output,

er or later, requiring cleaning, pigging or

the flow does not double when using

a very expensive renewal. Some guide-

the same size pipe. Should the pipe be

lines for pipes to remember are:

too small, only a marginal increase in

• increased velocities result in increased

flow will be achieved – at a consider-

power consumption • increased velocity with slurry brings a greater rate of wear

ably higher cost. In order to achieve a reasonable increase in flow, the pipe diameter should, in general, be increased

• the higher the velocity, the more a slurry behaves like water • the lower the velocity, the greater the risk of any solids settling out • for slurries, vertical pipes are better than inclined • never overestimate losses; always use best estimate • for slurries, obtain maximum data at the inquiry stage. The more information available, the better the pipe selection and estimate of friction. The golden rule is: if in doubt, seek professional help. To calculate a system

24

vibrate or fall to pieces, but it is not

above the required flow in a given pipe

the total head figure. Typical values for c include:

to keep friction losses down.

Ins i de Mi n i n g 1 0 | 2 0 1 6

Operating multiple pumps in series improves efficiencies


Mine water & wastewater management

Nitrate contamination in mine water One of the challenges that mines have to deal with is nitrate contamination in mine water. With water being scarce and mines environmentally regulated, nitrate contamination leaking through underground mine workings can be a threat.

U

underground mine workings during a

New technology

blasting campaign, according to recent

BME has evolved cold emulsion explo-

international studies, says Neil Alberts,

sives technology to new levels over the

operations manager, BME.

past three decades to help keep nitrates

P TO 28% of nitrates from tradi-

the overall quality of recycled water

tional ammonium nitrate fuel oil

and increase its applications on and off

(ANFO) explosives can leach

the mine site.”

into water draining through

High levels of ANFO wastage suggest

out of mine water. This technology assists

that it may be a contributor to nitrate

mines in preventing possible groundwater

levels in water passing through mine

contamination and allows for the optimal

workings, although the mining sector typ-

recycling of water on-site.

ically accepts that about 30% of ANFO

Neil Alberts, operations manager, BME

“Among the characteristics of our emul-

No oil Another advantage of emulsions

delivered to a blast site is not consumed

sions range is excellent water resistance,

highlighted by the tests was that no

in blasting. As mines work to prevent or

which means that the explosive material

oil was released, ensuring that water

mitigate environmental damage, pollu-

does not dissolve readily in water,” he

contamination by oil is also prevented;

tion or ecological degradation, the levels

says. “This reduces the amount of nitrate

both the nitrate and the fuel phases

of nitrate in water are usually monitored

leaching to negligible levels.”

of the mixture are bonded tightly by

– as high nitrate levels can render water unsafe for drinking. But, there is some

Tests conducted by the company indicated that, after being immersed in wa-

the emulsifier. “BME has already contributed to

good news. “These levels can be re-

ter for a month, its emulsion released only

environmental sustainability on mines

duced to as little as 2% by applying best

about 0.7% of its nitrate content.

by incorporating and consuming pre-

practice, but the long-term solution lies in

Alberts says that the key factor here is

explosives that do not release nitrates into

the effectiveness with which the oil in the

helping mines to dispose of these

water sources,” says Alberts.

emulsion surrounds and isolates the small

liquids safely and cost-effectively,” he

“By removing the possibility of nitrate

viously used oil in its emulsion products,

droplets of saturated oxi-

leaching from blasting chemicals un-

diser salt, preventing them

derground, mines can reduce the risk of

from dissolving in water.

groundwater contamination as water

“On the other hand, our

drains out of working areas,” says Alberts.

tests confirmed that ANFO

“At the same time, where mines are mak-

dissolves completely

ing efforts to recycle water from under-

when it comes into con-

ground, lower nitrate levels will enhance

tact with water.”

says. “The way we

“By removing the possibility of nitrate leaching from blasting chemicals underground, mines can reduce the risk of groundwater contamination.”

have evolved the matrix also ensures that no oil is released when our emulsion comes into contact with water at the stope face.”

In sid e M in in g 1 0 | 2016

25


Mine water & wastewater management

Using tailings for brickmaking The Witwatersrand Basin, in the economic heart of South Africa, has two main problems. One is the significant amount of mine tailings from gold mines in the area. The other is the need for building materials.

I

N A TECHNICAL paper titled ‘The

environmental legislations, has caused

viability of using the Witwatersrand

the scientific community to focus on

gold mine tailings for brickmaking’,

finding innovative methods of utilising

the authors, M Malatse and S Nd-

mine tailings. Even though some appli-

lovu, examine the possibility of using gold mine tailings in the production of bricks. By doing this, mines will be able to save costs on tailings, as disposal costs are very high, and save the environment and ecological systems. At the same time, it will lessen the pres-

There is a significant need to develop other longterm, commercially viable uses for mine tailings in order to minimise the disposal costs and the impact on the environment

particle size, and quantitative chemical

erated tailings have

analysis. The particle size analysis was

been exploited, such

done by physically screening the sam-

as in the building

ples using test sieves of various screen

of slimes dams and

sizes up to 212 µm.

backfill in under-

The authors add that the phase min-

ground mines, these

eralogy analysis was carried out using

uses do not take up

an X-ray diffractometer operated with

more than a fraction

Co-K radiation generated at 40 kV and

of the total amount

50 mA. The chemical analysis was car-

of tailings in the

ried out using wavelength dispersive

Witwatersrand region.

X-Ray fluorescence (SRF) spectrometry

There is, therefore,

operated with a rhodium tube excita-

a significant need to term, commercially

natural construction

tion source.

Brickmaking process

viable uses for mine tailings in order

The authors write that different mixing

to minimise the disposal costs and the

ratios of tailings, cement, and water

authors write that gold mining and pro-

impact on the environment,” write

were used in the brickmaking process.

cessing wastes contain large amounts

the authors.

From each mixture, a number of bricks

material of traditional building materials. In the introduction of the paper, the

of sulfide minerals such as pyrite, which generate acid mine drainage (AMD).

Materials and methods

were cast and dried. “The three feed material (tailings,

The materials used in the test work were

cement, and water) were mixed in the

challenges resulting from AMD and the

gold mine tailings, tap water and ce-

appropriate ratios in a commercial

government and mining companies are

ment as a binding material. Represent-

mixing machine. Dry mixing was done

under pressure to find viable solutions

ative samples used in all experiments

first and then a controlled amount of

to this problem. “This, coupled with the

were prepared using a riffle splitter.

water was added while continuing to

South Africa is currently faced with the

increasing landfill costs, and stricter implementation and enforcement of

26

cations of the gen-

develop other long-

sure on quarrying for

A recent study looked at the possibility of using tailings dams for brickmaking materials

Ins i de Mi n i n g 1 0 | 2 0 1 6

The gold tailings were characterised

mix thoroughly. The total mixing time

by investigating the phase mineralogy,

was 15 minutes. The mixture was then


Mine water & wastewater management table 1 Different mixtures used in brickmaking

Mixture number

Tailings (kg)

Cement (kg)

Water (ℓ)

1

2

1

0.6

2

14

2

2.65

3

9

6

3.0

4

7

8

2.5

5

10

5

2.5

6

12

3

2.5

7

5

10

3.3

8

10

5

3

table 2 Average compressive strength of bricks cured differently

Mixture

Average compressive strength (kN/m2) Water

Oven

Ambient

water absorption tests showed that

1

141

165

157

water absorption is higher in neutral

2

20

25

29

solutions compared to acidic solutions.

3

325

359

318

4

440

439

323

5

262

261

234

ble at 0.06%,” write the authors. The

6

215

235

230

authors recommend that more tests

7

530

479

454

should be done on a wider range of

8

149

98

127

The rate of absorption is high in the first day, but then stabilises. The weight loss over a seven-day period was negligi-

tailings to cement ratios to manufacture a stronger brick. “In addition, the size of the tailings

cast into the brick moulds. The brick

human exposure to tailings, conse-

used as aggregate should be varied to

moulds were then placed on a vibrat-

quently reducing the effect that mine

a wider range. This can be achieved

ing machine for five minutes in order to

waste has on the health of inhabitants

by adding overburden to the fine

fill the voids in mixture comprehensively

in the mining area. The use

and, thus, prevent the formation of

of gold mine tailings

The test revealed that more

air pockets.

for brickmaking also

cement was used in the

“The brick were then labelled and al-

constitutes an ad-

tailings material.”

manufacture of the tailings bricks than in commercial

lowed to cure for 24 hours. Three curing

ditional source

methods were used – sun dried, oven

of revenue for

bricks, which can be a

dried at 360°C, and cured in water for

the gold mining

disadvantage, as ce-

24 hours. After curing, the bricks were

companies and,

ment is more expensive.

de-moulded using an air compressor,

in the process,

weighted, and tested for compressive

creates jobs,”

strength,” write the authors.

write the authors.

“Looking at the bigger picture, the use of tailings as brickmaking material would have great advan-

Strength testing

Conclusion

The bricks were tested and, in the

In the paper’s conclusion, the

conservation and reduction of waste

process, force was applied on the

authors write that the results from X-ray

management costs.

brick until the brick failed. The force

powder diffraction (XRD) and XRF

measured at failure was documented.

showed that the chemical composition

uranium is present in Witwatersrand

The mixture ratio that gave the highest

of the Witwatersrand gold mine tailings

gold tailings, extensive research with

compressive strength was then em-

is similar to that of the clay materials

regard to the chemical properties and

ployed for further tests.

used for commercial brickmaking.

the chemical stability of the bricks

“It was then concluded that it would

Cost implications

be technically viable to use the tailings

“Since the use of tailings for brick-

for brickmaking. Following the South

making conserves natural resources,

African masonry standards for brick-

one could say that the benefit to

making and testing, it was found that

the environment outweighs mere

the commercial brick has an average

economic considerations.

compressive strength of 750 kN and

tages in terms of environmental

“Since the XRD analysis showed that

produced from gold mill tailings is required,” conclude the authors.

follow the link

that the strongest bricks made from

For the complete technical paper published in the SAIMM Journal, go to:

companies have to spend less on

the tailings have an average compres-

waste management, while reducing

sive strength of 530 kN. “Results from

http://bit.ly/2bG9bRA

“The use of tailings would mean that

In sid e M in in g 1 0 | 2016

27


Mine water & wastewater management

Variety of

analytical solutions

The current drought situation around the world emphasises the need to take care of all water resources. Combine that with environmental legislation and having to save costs wherever possible, and the need for a practical solution in organics monitoring arises.

O

NE SUCH PRACTICAL solution

of organic carbon (TOC),” says Galliford.

is the range of monitoring

When it comes to compliance reporting,

tools from SMM Instruments

the tools typically used are oxygen de-

for analytical and laboratory

mand parameters (based on historical

applications. As an international agent,

practice); however, the time required for

the company supplies sub-Saharan

BOD testing (days) or COD (hours) makes

web browser interface allows users to

Africa with, among others, GE Power

it impractical for the real-time deci-

remotely monitor and control operations

Water & Process Technologies’ analytical

sion-making required for process control.

and results using a web-based interface via the instrument’s Ethernet port.

instruments. The instruments are aimed

“TOC analysers installed for discharge

to assist companies to prevent product

monitoring tend to include a correlation

loss, lower waste treatment costs, and

to the oxygen demand test and report

Accessories

reduce system maintenance and energy

in mg/ℓ BOD or COD. When used for

“To enhance the analysers, there are a

consumption through organics monitoring

process control, output is typically in

range of accessories to choose from.

in wastewater treatment.

C. TOC enables online, near real-time

These include an air purifier that removes

reporting of organic contamination,”

CO2 from the air and a filter panel that

Monica Galliford, national sales manager, SMM Instruments, explains that process and wastewater

explains Galliford.

filters one sample stream and is auto-

matically cleaned by back-flushing with

contamination includes organic and

Models

inorganic components. “Sources of

The range of GE instruments

organic contamination include process

developed for process water and

rate of each sample stream stops or

chemicals, heat transfer fluids, and food

wastewater include:

when consumables need replenishing.

products, as well as naturally occurring

• M9 Laboratory and Autosampler

Other accessories include a mounting

organics in surface- and groundwater.”

• M9 On-Line

stand, a sample peristaltic pump and

• M9 Portable

multistream configurations.

To analyse the water, laboratory personnel make use of a variety of

• M5310 C On-Line

monitoring tools to prevent corrosion

• InnovOx Laboratory and On-Line.

and equipment damage, and optimise

The Sievers InnovOx Laboratory and

treatment processes.

On-Line TOC analysers offer a variety of

“The tools used for organics monitoring

28

“Sources of organic contamination include process chemicals, heat transfer fluids and food products, as well as naturally occurring organics in surface- and groundwater.”

Fail-safe sensors detect when the flow

features and benefits, and measure up

include oxygen demand testing, an in-

to 50 000 ppm of TOC. The instruments

direct measurement of organic carbon

are easy to operate and offer preset

(BOD or COD), and direct measurement

protocols for easy start-up. The Ethernet

Ins i de Mi n i n g 1 0 | 2 0 1 6

compressed air,” says Galliford.

www.smmafrica.com


Electrical Instrumentation & Control

Upgrading trolley

assist technology

Although trolley technology was first introduced in 1981 in South African mines, it is still used by various mines to assist trucks uphill. The latest upgrade in trolley assist technology sees the launch of fully automated 11 MW DC containerised substations.

T

ROLLEY ASSIST solutions are

in the mining industry.

The company offers full

normally installed on an uphill

An interesting fact of

assembly, installation,

stretch where mineral-ore-carrying

this new order is that

testing and commis-

haulage trucks struggle with the

90% of components in

sioning of these fully

gradient of the incline due to the diesel

the containerised sub-

automated facilities.

engine’s horsepower limitations.

stations are entirely

The trolley assist solutions supply electric

The container includes

manufactured by Siemens, compared to

the 1.8 kV DC switchgear, rectifiers, 33

power to the wheel motors of the haul-

past units that contained approximately

kV ring main unit, Siprotec AC protec-

age trucks, which enables the vehicles to

30% Siemens components.

tion device and Sitras Pro DC Feeder

move faster uphill. This results in quicker turnaround times and higher productivity.

“Consistent innovation has kept us at the forefront of mining technology, and

protection device. The control and protection of the entire

sourcing nearly all of our components

substation is automated with a Siemens

provide electric power to the overhead

internally means greater quality control,

PLC and distributed I/O units connected

DC power lines, which, in turn, provide

improved functionality, and greater

via Profibus, significantly reducing the

DC power to the adapted diesel-elec-

capacity,” says Phiwa Thindaw, project

number of interface cables between

tric haulage trucks. One of the three

manager, Siemens SA.

equipment and allowing for the ef-

The new 11 MW Siemens substations

launched units will be used to power a

Siemens’ DC containerised substations

fleet of Komatsu 960E trucks, which are

are manufactured in Pretoria, with com-

substation and equipment via a touch

among the industry’s biggest and highest

ponents currently imported from Germa-

panel. Cooling of this unit is provided by

capacity mine haulage vehicles, with a

ny. “The company aims to manufacture

two inverter air conditioners, keeping the

load capacity of 214 m3 or 327 tonnes.

components such as switchgears and

inside temperatures between 18°C to

control panels locally in future,” says Joey

22°C under normal load conditions.

Each 11 MW containerised substation boasts 1.8 kV of DC voltage and up to

Govindasamy, lead: Rail Electrification

10 000 amps to ensure that it can run

Business Unit, Siemens SA.

two trucks continuously, three trucks for

fective control and monitoring of the

“Our experience gained over the past 20 years of providing DC mobile substations for trolley assist projects at various

10 minutes, or four trucks for one minute

Specifications

along the overhead power lines. This

Each substation is housed in a 6 m x 3.3 m

cess of this project,” concludes Karl van

combination of substation and overhead

x 3 m container that weighs approximate-

Rensburg, Siemens’ lead engineer who

line is known as trolley assist technology

ly 8.5 tonnes when fully commissioned.

designed the substation.

mines has greatly contributed to the suc-

At the launch of the latest fully automated DC containerised substation are Siemens SA’s Sabine Dall’Omo, CEO, and Clifford Klaas, executive director: Corporate Affairs, HR and Sustainability

In sid e M in in g 1 0 | 2016

29



Electrical instrumentation & control

Importance of maintaining transformers Just because there are limited moving parts in transformers, it doesn’t mean they are maintenance-free. Labelled as among the most efficient pieces of equipment developed by man, transformers require preventative maintenance for optimum performance.

T

WO OF THE main benefits

“We are able to provide verifiable

the transformer to replacing gaskets

achieved from transformers, when

reporting on the condition of the

and cone rubbers right up to major on-

a comprehensive preventative

transformer using oil sampling, analysis

site repairs including replacing offload

maintenance and service strategy

and thermal graphics surveys, all of which

tap changers.

is in place, are optimum performance

meet international quality standards

and a long functional life.

reporting requirements and are accepted

offer this level of support to industry and

by most insurance,” says Mans.

ongoing training ensures that our team

“Preventative maintenance of transformers is critical, not only from an

“We are one of few OEMs that can

is kept abreast of technology as well

operational reliability perspective, but also

On-site

because a well-structured maintenance

As part of on-site preventative

height, firefighting and HV regulations,”

programme will significantly extend the

maintenance, skilled individuals will

says Mans. Other maintenance activities

life of the transformer. In most cases, it is

conduct transformer oil sampling to

done on-site deal primarily with the

not inconceivable for a well-maintained

ensure accuracy and reliability. The way

condition of the transformer and could

transformer installation to have a lifetime

in which the sample is taken is crucial to

entail purification and regeneration as

that outstrips that of an average human,”

the result; therefore, sampling tins are only

well as vacuum treatment being done to

says Andre Mans, COO, WEG Transformers

used once to avoid cross contamination.

eliminate entrapped air.

Africa (WTA), a division of Zest WEG Manufacturing. “This could between

In addition to the visual assessment and oil sampling and analysis, the WTA team undertakes thermal

40 to 50 years.” To assist customers with maintaining transformers in ideal conditions, WTA offers a suite

as operational skills such as working at

“Preventative maintenance of transformers is critical.”

of support services

graphic surveys to determine areas where excessive heat may be present in the transformer and other electrical equipment. Samples are brought back

for its transformers customer base.

to the oil-sampling laboratory at WTA's

These services include preventative

facility in Heidelberg to analyse the oil.

maintenance programmes that can be

The oil sample is compared to a base

structured to accommodate customer

line, which enables the technicians

needs and/or budgets. According to

in the laboratory to identify potential

Mans, it is most important for customers to

problems that cause transformer failure.

do an initial assessment of the transformer

Other tests include kV or dielectric

installation as this will allow a base line to

strength testing to determine the

be verified and, following any corrective

insulating properties and DGA (dissolved

action, a customised support programme

gas analysis), which provides a clear

can be implemented to ensure the

indication of internal failure conditions.

optimum reliability of the transformer.

Acid levels are also checked against

A team of skilled technicians will rate the transformer according to the application

Andre Mans, COO, WEG Transformers Africa

acceptable standards.

in which it is being used during a

Follow-up interventions

preventative maintenance assessment.

Following the comprehensive oil analysis,

Then, the team will implement a needs-

WTA’s mobile field service teams are able

based maintenance strategy with the

to implement interventions to address

objective of reducing the probability of

identified issues. These interventions could

transformer failure.

include anything as basic as re-torqueing

In sid e M in in g 1 0 | 2016

31


Minerals processing

Processing fine

and ultra-fine coal Fine and ultra-fine coal beneficiation is not a new science in the coal industry but an important part of coal processing. Johan de Korte* takes a look at processing options available in the market and how they have been performing in the mining industry.

T

HERE SEEMS to be much confu-

which is -6 mm, was just screened out of

raw fines were dewatered using dewa-

sion between the terms fine coal

the plant feed and discarded. Roddeck

tering screens and added to the PSS

and ultra-fine coal. To shed more

screens were used to remove the duff

raw. This made a positive contribution. In

light on the difference: normally,

from the plant feed. In later years, when

the mid-1980s, spirals were introduced in

coal processing plants start with a feed

most of the plants in KwaZulu-Natal pro-

the coal industry and proved very bene-

that is crushed to 50 mm top-size and

duced coking coal, flotation became a

ficial for that specific market, increasing

then de-slimed at 1 mm size by using

standard part of the process. The coal

the PSS yield by between 1% and 1.5%.

vibrating screens. The -1 mm material

was amenable to flotation and typically

goes to hydro-cyclones for classification

resulted in product yields of about 80%,

Coal processing today

and the underflow from the cyclones is

with 10% to 12% of ash product, so flota-

Currently, the main fine coal processing

the size fraction between 1 mm and 150

tion worked very well there.

equipment is spirals, which are still the

μm. The Australians call it sand-sized – in

During the 1970s and early-1980s, there was an agreement with Japanese steel

industry. A few teetered bed separators

The overflow from the cyclones, which is

mills to supply them with a 7% ash coal

(TBS), and reflux classifiers (RC) are com-

the really fine material of -150 μm, is the

and the coal mines in the Witbank area

ing into the local market, and two of the

ultra-fines.

did a double-stage wash of the coal

mines also use dense-medium cyclones

to produce the low-ash coal, as well as

to process the fine coal. Froth flotation

there was no such thing as fine coal

power station smalls (PSS) with a speci-

is the only process that really works on

beneficiation, or very little of it. Duff coal,

fication of 27 MJ/kg. In those days, the

ultra-fine coal.

In the early years of the coal industry,

Wescoal’s coal processing plant

32

fine coal processing workhorses in the

South Africa, it is referred to as fine coal.

Ins i de Mi n i n g 1 0 | 2 0 1 6


Minerals processing Spirals

~0.120 are typical for a TBS. One of the

problem and typically runs at about

Spirals are well proven in South Africa

big advantages is that it can cut at low

~1.4 kg/feed tonne. The main reason

– they have been in use for 30 years

density – ~1.50 is quite feasible.

for that is the efficiency of the new

at least. The typical Ecart Probable Moyen (EPM) value for spirals is >0.150, and the cut density is normally higher than 1.70. Spirals are simple-to-operate, low-cost units and are really good at removing pyrite from fine coal. One of the drawbacks is that spirals

Spirals are currently the main fine coal processing equipment and serve as the industry's workhorses

have a low capacity

Reflux classifier

generation of magnetic separators. A typical fine coal dense-medium

A relatively new tech-

circuit looks exactly like a conventional

nology in South Africa is

dense-medium circuit, with the only

the reflux classifier. There

difference being that it has magnetic

are full-scale installations

separators instead of drain and

at two mines in Mozam-

rinse screens.

bique and at one mine in Limpopo. Typically, a

Froth flotation

RC 2020 unit which has

Froth flotation is the only viable

a capacity of ~100 t/h is

process for ultra-fines. There is limited

used. It is very similar to

application in South Africa at present,

a TBS – the principle of

with only two or three plants using

per unit, so a plant usually requires a

operation is, for all practical purposes,

froth flotation, while it is becoming

large number of them.

the same. The control is the same, the

a standard feature for the plants

EPM is the same, and it can also cut at

in Mozambique.

Another problem with spirals is that because they are so easy to operate, they don’t ask for attention and, as a result,

low densities.

Once serious coal mining starts in the Limpopo, especially in the Musina area,

they don’t get any attention. Therefore,

Dense-medium cyclones

we unfortunately see much neglect

Dense medium is not a new process.

be a very important part of processing

of spirals in the industry. Spiral circuits

The first dense-medium plant to process

Limpopo coal.

are normally simple in design. Hydrocy-

fine coal was built in Belgium in 1957.

clones also feature quite prominently

Since then, several plants have been

but also an expensive process.

in a spiral circuit and are used to both

built around the world, including

Something that is important to

thicken and de-slime at the same time.

Europe, the USA, Australia, and South

remember is that flotation will not work

Africa. There are currently two fine coal

on weathered or oxidised coal.

Teetered bed separator (TBS) TBS units are in use at a few plants in South Africa. The advantage with the

dense-medium plants in South Africa both are in successful operation. Dense medium is the more efficient

froth flotation will be required, as it will

Froth flotation is an effective process,

Dewatering and drying When it comes to fine coal, benefici-

TBS is that it has a high capacity: 100

process compared to the previous

ation is only half of the problem when

t/h for a 3.65 m diameter unit. It is also

mentioned processes. Typically, the EPM

producing thermal coal. One has to

simple to operate: basically controlling

value is around ~0.08. One thing that

also dewater the product in order

of bed density and fluidising water.

everyone was worried about with dense

to reach the target calorific value

TBSs are really effective at removing

medium is the magnetite consumption,

(CV). Keep in mind that, when using

high-density fines. EPM values of about

but this has since proven not to be a

dewatering screens, the product is

Dense-medium cyclones in the fine coal processing plant

figure 1 Spiral circuits

In sid e M in in g 1 0 | 2016

33


table 1 TBS processing results by size fraction

Aury Africa provides customized solutions for the coal industry. We manufacture a comprehensive range of fine and coarse coal centrifuges. Aury products are manufactured from high quality raw materials to exacting standards, ensuring efficient, reliable and cost effective products to all of our customers.

Size

Feed

Product

Discard

Yield by ash balance

Feed ash/ Product ash

+1.0 mm

27.6

9.1

46.4

50.4

3.03

1.0 mm x 0.5 mm

31.8

13.4

58.7

59.4

2.37

0.5 mm x 212 μm

29.9

21.0

86.7

86.5

1.42

212 μm x 100 μm

38.8

35.7

90.5

94.3

1.09

-100 μm

52.8

51.5

77.3

95.0

1.03

Mass % Cumulative

Ash % Fractional

Ash% Cumulative

table 2 Influence of slimes on spiral product ash

Screen size(μm)

Contact us for more information on our centrifuges and centrifuge components.

Mass % Fractional

+1 000

0.5

0.5

10.4

10.4

-1 000 + 500

19.1

19.5

10.5

10.5

-500 + 250

26.7

46.2

11.3

11.0

-250 + 150

10.4

56.6

11.9

11.1

-150 + 106

14.0

70.6

15.3

12.0

-106 + 90

5.1

75.7

21.9

12.6

-90 + 75

4.8

80.6

25.1

13.4

-75 + 45

4.8

85.4

38.3

14.8

-45 + 25

5.1

90.5

40.2

16.2

-25 + 0

9.5

100.0

44.2

18.9

Reflux classifiers in coal processing plant

Conclusions The fine coal process chosen

dewatered but still has up to 25% surface moisture. Centrifuges are more expensive, but one can get down to about 14% to 16% surface moisture. Thermal drying can get down to 0% surface moisture, but thermal drying

Aury Africa - Pushing the limits, setting the standards 19 Graniet Road, Jet Park, Boksburg 011 026 6642 info@auryafrica.co.za

is more complicated. However, if one does the economics, it does prove to

depends on the specific requirement. The cheap option is not always the most economic one. De-sliming of the feed and product needs to be done well to produce good-quality product, and dewatering is as important as beneficiation of coal.

be viable, although it is not used in

*Johan de Korte is a senior

South Africa at the moment.

researcher at the CSIR.

34

I n s id e M in in g 1 0 | 2 0 1 6


Minerals processing

Down memory lane Taking a trip into the history of coal processing will soon be a reality when the Geology Museum, based in Museum Africa, Johannesburg, completes its display on coal. Initiated by the Southern African Coal Processing Society (SACPS), the exhibit will offer a variety of educational information. T THE MOMENT, the Geology

A

The initiative started last year and Kath-

later, the first double-stage Chance plant

Museum presents various ge-

erine James, curator: Geology Museum,

came into production. This plant was ca-

ological items, with opportuni-

City of Johannesburg, is still in the process

pable of processing some 100 000 tonnes

ties to touch a variety of rocks.

of getting everything together, hoping to

of raw coal per month. Dense-medium

But there has never been a coal display,

finalise the display at the end of the year.

processing using magnetite as the me-

and Mark Cresswell, committee member,

“The exhibit is estimated to cost about

dium came into use after about 1951,”

SACPS, noticed this absence.

R40 000 and will display 95 specimens of

“I have always been in awe of the fact

coal, the geology of coal, images and

writes De Korte. He goes into more detail about the

that Johannesburg is in within 100 km of

literature depicting the history of coal in

accepted standard for high-grade coal

many major coal, diamond, platinum

South Africa as well as coal processing

produced prior to 1922 and how coal

and gold mines, which is quite unique in

throughout the decades, to name a

preparation has progressed since then.

the world. The museum showcases many

few,” says James.

De Korte also details coal institutes and

facets of our country’s economy and

how they came about.

history. So I spoke to my colleagues on

History

the committee and said it would be nice

Cresswell points out an interesting fact

Memorabilia

to have a display of coal, especially since

about how mines are now looking at the

“We have a lack of mining equipment

there is already a display of the minerals,”

old mines of the 1930s to do pillar extrac-

to assist us in depicting the history of

says Cresswell.

tion. These old mines were relatively shal-

coal and coal mining in South Africa.

He adds that the SACPS wants to further

low underground mines and have now

Any memorabilia will do to add to the

the interests of coal processing and edu-

opened up as surface mines. “People are

coal collection, as long as it doesn’t fall

cation in the country, so the organisation

now finding items that were left in the old

apart,” says James. She adds that do-

readily agreed to sponsor a display unit

mines, from funny old mining hats to horse

nors’ names will be attached to the items

with items and information depicting

shoes, showing that they used pit ponies,”

and whatever is not displayed will go into

coal, mining, and coal processing.

says Cresswell.

storage where researchers can research

According to the technical paper

Katherine James, curator, Geology Museum, and Mark Cresswell of the SACPS

the items.

‘Coal preparation research in South Africa’ by GJ de Korte*, the first colliery

*The technical paper was first published

opened in 1864 near the town of Molteno

in The Journal of The Southern African

in the Eastern Cape. De Korte writes

Institute of Mining and Metallurgy.

that the earliest record of coal washing goes back to 1905, when the first of five jig plants was installed in the then Natal province. “In 1934, a 90 000 tonne per month Rheolaveur plant was commissioned in the then Transvaal province and, a year

follow the link To read more about coal preparation research in South Africa, go to: www.scielo.org.za/pdf/jsaimm/ v110n7/05.pdf

In sid e M in in g 1 0 | 2016

35


EDUCATION & training

Ensuring the quality of raw materials In the manufacture of polyethylene pipes, controlling the quality of the raw material used is as important as controlling the quality of the final installation. A fundamental part of ensuring dependable, high-quality pipe production is rigorous testing. By Ian Venter*

T

• Commissioning and testing of the prod-

economic consequences.

The designer needs to validate that all

When it comes to designing a pipe

the aspects related to these assumptions

system, certain design assumptions

are valid and true. For that reason, test-

are made:

ing the various aspects or properties of

• The product installed in the system will

the product at different stages is critical.

ESTING IS ESPECIALLY important when it comes to mining applications, where the stakes are high. Failure to detect faulty

pipes can have severe safety and

be compliant to a set of standards. • Storage and handling will be

uct/system will follow a set standard. • Usage of the system will be accordance with the set standard.

End users, specifiers and designers need

Ian Venter, product specialist, Marley Pipe Systems

standard (usually a SANS standard),

to understand the roles and responsibil-

which generally covers aspects such as

carried out in line with the

ities of various role players influencing

raw material, the pipe and its geometry,

component’s capabilities.

the life expectancy of their system. The

fittings, and the overall system. If these

product is manufactured to a specific

requirements are met, a certain life

• Installation and jointing will be

36

executed according to a set standard.

Ins i de Mi n i n g 1 0 | 2 0 1 6

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EDUCATION & training Failure to detect faulty pipes can have severe safety and economic consequences expectancy can be assumed. The SABS and other testing bodies are responsible for the initial standard testing in its entirety. With this, they also issue a set of permit conditions, which stipulate factors such as the standard, testing samples, secondary sampling, audit frequency and further onsite responsibilities of the manufacturer. Only if all permit conditions are met, may the manufacturer continue marking their product in compliance with the standard. This is important to understand because,

End users, specifiers and designers need to understand the roles and responsibilities of various role players influencing the life expectancy of their system

in the past, when somebody saw a prod-

Test results After determining the vitals, it’s crucial to determine vital components of the system and allocate specific property tests. It will also be important to draw up a QC plan, which shows the various dates, tests, test procedures, responsibilities and pass/fail criteria. From the test results, it’s possible to deduce whether the product complies with a standard and the required properties of that standard and, therefore, make a conclusion that the product will perform as expected and designed for.

Considerations There is a natural progression in all product development. The raw material, being an important component, determines the majority of properties that the

uct with an SABS mark on it, they were assured that the product

resulting product exhibits. It is, therefore, no surprise that the most

was compliant. With this new understanding

development goes into optimising the properties of raw materials.

of permit conditions, however, we now see that the responsibili-

One such example is the progression of PE63 to PE80 to PE100.

ty is placed squarely on the manufacturer – and not the testing

This is a natural progression and allows for better product prop-

body – to perform all tests necessary to prove compliance.

erties, like increased bore capacity, better resistance to environ-

Most important component The QC (quality control) testing of raw materials is probably the

mental stress cracking and better thermal stability. This natural progression has taken place entirely without compromising on the product’s overall performance.

most crucial test that needs to take place, as it accounts for 80% of the product cost. Why is this important? Manufacturers

*Ian Venter is a product specialist at Marley Pipe Systems.

often look to raw materials as the best opportunity for cutting costs, which sometimes results in inferior-quality materials making their way into pipe production. The addition of inferior regrind materials can cause weak points, which may lead to major failure of the entire system, jeopardising the safety and health of the community.

Good testing frequency A good testing frequency would be per product type, product size, product class (pressure or stiffness), raw material batch, machine and per manufacturer – all in line with the specific standard and with the specific permit conditions mentioned previously. Raw material testing should occur: • prior to production • after production • prior to delivery • after delivery (prior to installation).

Vital signs All products have specific failure modes linked to material and product properties. From these, we need to determine the failure modes critical to an application. In human terms, these would be things like temperature, heart rate, blood pressure, etc. For polyethylene, we look at three vital failure modes: • Material stress: the risk of joints failing or pipes cracking as a result of internal hoop pressure or ground axial or bending stress from expansion or contraction, or ground movement. • Environmental stress cracking: external or internal cracks in a plastic caused by localised stresses through contact with the pipe wall internally and/or externally. • Thermo-oxidative failure: degradation and embrittlement of the plastic due to thermo-oxidation over time, as a result of temperature and/or UV exposure.

In sid e M in in g 1 0 | 2016

37


Hear from the most influential executives active in investing and developing mining projects on the African continent: Featured Speakers ROGER BAXTER Chief Executive Officer Chamber of Mines of SA

NICK HOLLAND Chief Executive Officer Gold Fields Limited

MASHALE PHUMAPHI Managing Director Shumba Energy

MARK BRISTOW Chief Executive Officer Randgold Resources

CLIVE JOHNSON President and Chief Executive Officer B2Gold

ALWYN PRETORIUS Regional Senior Vice President Newmont Mining

TOM BUTLER Chief Executive Officer ICMM

GRAHAM KERR Chief Executive Officer and Managing Director South32

RICK RULE President and CEO Sprott U.S. Holdings Inc.

MARK CUTIFANI Chief Executive Officer Anglo American

SHEILA KHAMA Director African Natural Resources Center (AfDB)

ANTÓNIO CARLOS SUMBULA Chairman and Chief Executive Officer Endiama

ALAN DAVIES Chief Executive Officer Energy & Minerals Rio Tinto

BEN MAGARA Chief Executive Officer Lonmin

MIKE TEKE President Chamber of Mines of SA

ROBERT FRIEDLAND Executive Chairman and founder Ivanhoe Mines

DR. DAMBISA MOYO Macroeconomist

JOHN WELBORN Managing Director and Chief Executive Officer Resolute Mining

BRAD GORDON Chief Executive Officer Acacia

ANDREW PARDEY Chief Executive Officer Centamin

NIKOLAI ZELENSKI Chief Executive Officer NordGold

6-9 FEB 2017 CAPE TOWN | SOUTH AFRICA

REGISTER NOW

SAVE AN ADDITIONAL 10% on your delegate registration. Mention the required offer code PAIM2 for discount.

STAY CONNECTED

#miningindaba | www.miningindaba.com


MARKET news

from around the continent Bearing all for gears Reducing power loss and oil consumption of gear units by 30% is what Voith has achieved with the new BHS AeroMaXX technology for turbo parallel-shaft gear units. The company has also been able to increase the gear unit efficiency by up to 0.5%. Reducing the power loss and oil consumption of gear units means far better operating behaviour and reliability of engine and gear units. Due to high-pitch line velocities of up to 200 m/s, oil swirling and oil squeezing in the gear mesh accounts for a substantial part of the power loss of high-speed turbo gear units. An inner housing in the direct vicinity of the gear set absorbs heat and dissipates it into the bottom area on the external surface of the inner housing via cooling oil. This means that a substantially smaller volume of oil is required for the actual lubrication of the teeth contact surfaces, while the swirling oil/air mixture

Kansanshi has opted to renew its fleet of blast hole drill rigs with Sandvik drill rigs

itself is minimised. In addition to the inner housing, the technology also includes new BHS EcoMax sleeve bearings on the pinion shaft. These hydrodynamic bearings are optimised specifically for the application, and guarantee high energy efficiency along with significant oil savings. The technology reduces losses by separating lubrication and cooling, with a solution that has passive mechanical characteristics and does not require any additional accessories or components such as pumps or seals.

The new BHS AeroMaXX technology for turbo parallel-shaft gear units

Opening new doors Due to its ability to meet the pricing and delivery requirements of a customer, DCD Ringrollers is expanding into new market segments with its recent forging of a large nozzle component weighing over three tonnes. The company is also expected to now be able to participate more assertively in the local markets for these and similar components. “With a height of 850 mm, this forging is the largest of 43 components ordered by a South African customer for a pressure vessel application,” says Dion Booyens, executive director, DCD Ringrollers. “With this exciting achievement under our belt, we now look forward to the prospect of forging other components – such as even larger and heavier nozzles, bushes, rolls and pinions,” he says. “In particular, we are in a

position to manufacture a larger range for markets where pressure vessels are in use and heavy section nozzles are required.” The company’s manufacturing facility at Vereeniging, in Gauteng province, boasts a 35 000 tonne annual production capacity and is equipped with the latest automated forging equipment from leading German and Italian suppliers. Plants on-site include three forge presses, two ring mills, CNC vertical borers, and heat treatment facilities for austenising, normalising, tempering, annealing and polymer quenching. The strongest 3 500 tonne press is capable of both open and semi-closed forging, and the ring mills’ capacity ranges from 200 mm to 4 500 mm outside diameter. DCD also has automated hardness and ultrasonic testing machines.

One large nozzle component weighs over three tonnes

Copper miner renews drill fleet Zambian copper mine Kansanshi has opted to renew its fleet of blast hole drill rigs, even though it’s facing tough times in the country. The new fleet will consist of Sandvik D25KS and DP1500i drill rigs. Rob McMaster, key account manager, First Quantum Minerals Sandvik Zambia, says that the mining contractor, First Quantum Mining & Operations (FQMO), has taken the decision to renew the DR500 fleet with new drills that are easier to maintain and operate on-site. “We work closely with our customers to ensure operations are run optimally at all times. When circumstances change and a mine’s requirements are altered along with it, we do our utmost to restructure equipment and fleets in such a way that the customer’s new needs are met. This is precisely what we have done at Kansanshi, where we are proud to deliver a solution that is tailored to Kansanshi’s current and changing future requirements. The new drill rigs are machines that will require less maintenance and specialised care than their predecessors.” Thanks to its compact size, proven design and durable power groups, the Sandvik D25KS blast hole drill is a very stable and highly manoeuvrable surface drill for surface mining and large-scale quarrying. The D25KS is a down-the-hole (DTH) hammer drill with a high-pressure air compressor, air-line lubricator and fine feed control. It is commonly used in large mining operations globally with a choice of hole sizes from 127 mm to 172 mm. The DP1500i is an intelligent, self-propelled, self-contained, crawler-based surface drilling rig equipped with a cabin, movable boom and a rod changer. It is ideal for production drilling in large quarries or open-pit mines and construction work sites. It is also well suited for wall control (pre-split drilling) and development works. The rig can be customised to meet special customer requirements.

In sid e M in in g 1 0 | 2016

39


events

Open mining conversations

T

HIS YEAR’S Joburg Indaba will

This year’s speakers include: • Trevor Manuel, former Minister of Finance • Neal Froneman, CEO, Sibanye Gold • J oseph Mathunjwa, president, AMCU •M ike Teke, president, Chamber of Mines SA • J acques Erasmus, global head: Mining, KPMG •P iet Viljoen, chairman, Regarding Capital Management •P eter Steenkamp, CEO, Harmony Gold •H RH Kgosi Pilane, king of the Bakgatla-ba-Kgafela nation •A ndile Sangqu, executive head, Anglo American SA

once again bring the mining industry together to have bold and frank discussions.

It provides an opportunity to cover various topics and challenges with both government and investors. Local and international speakers, fund managers, analysts and captains of industry will gather in Johannesburg to outline the way forward. The indaba also presents the chance to share insights into global commodity market prospects and investment opportunities.

Some of the conversation topics will include: •H ow will the South African mining industry become internationally competitive and attract the right investment to secure its future? •W hat should the mining industry be doing to make itself a key driver of the economy? •C ommentary on the challenges and solutions outlined above •W hat are CEOs actually doing to attract investment into the future of their companies and the industry? • S afety: how good (or bad) are we really? •T he mining industry: taking charge of its future

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