hEX_20_07 by Modiconlv

hazardexonthenet.net

July 2020

the journal for hazardous area environments

Risk assessment Plant maintenance in the digital age

Explosion science Explosion prediction methodologies overview

Standards

Instrumentation

Asset management

Coronavirus: the end, or a new beginning?

An alternative approach to Zone 1 display instrumentation

Potential effects of the economic climate on asset integrity

the journal for hazardous area environments

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contents July 2020 On June 3, Russian President Vladimir Putin declared a state of emergency after 20,000 tonnes of diesel fuel leaked from a power plant belonging to a subsidiary of Norilsk Nickel (page 9). The leak occurred after a fuel tank became depressurised due to the subsidence of its support pillars. In a televised government meeting, President Putin criticised the local government for its response to the incident after it emerged that officials first heard about the leak on social media, two days after it had happened. During the meeting, Putin asked: “What, are we to learn about emergency situations from social networks? Are you alright healthwise over there?” The question could also have been asked of Norilsk Nickel when the company explained how the impacted fuel tank’s support pillars had held it in place for 30 years without difficulty. This explanation is a prime example of how complacency can lead to process safety incidents. As has been discussed countless times in Hazardex, including within this issue, risk assessments and asset maintenance are vital to ensuring potential incidents are identified and dealt with before accidents can occur.

14 12

perfect working order, but undetected corrosion could be occurring due to poor asset maintenance or simply because it hasn’t even been looked for. The issue of complacency has been amplified by the coronavirus pandemic as companies change their methods and operations to account for lockdown restrictions and social distancing measures. These changes have meant many maintenance tasks were postponed or cancelled during the pandemic, or some tasks would have been prioritised over others. However, as mentioned this could lead to a complacent attitude regarding products, systems and equipment which have been operating without issue. These assets may have been deemed low priority, exacerbating any undetected problems. It could therefore be argued that maintenance is now more important than ever and should play a key role in the ramping up of post-pandemic operations – regardless of an asset’s past performance. As can be seen by the incident in Russia, where the clean-up could cost up to 100bn roubles (£1.2bn; $1.5bn) and take up to ten years, if companies simply rely on the past as evidence for a safe and reliable asset, then the results can be catastrophic.

Just because a process is working without issue does not mean all is well. Corrosion is one such example where a false sense of security can lead to incidents. A pipeline may seem to be in

The issue with deferred maintenance is that it only grows in scope – and cost – the longer it is prolonged

20 14

This alternative design uses multiple well-established explosion protection techniques to produce a viable alternative for a flameproof Ex d instrument

…Alistair Hookway, Editor, Hazardex alistair.hookway@imlgroup.co.uk

in this issue 4 News Extra

• Global oil & gas decommissioning to total $42 billion through 2024 • UK approves plans for country’s largest solar park • World’s first 100% green hydrogen project set for east coast of Scotland • Two US chemical companies fined $1 million each for 2016 leak • US chemical manufacturer cited for 2019 explosion and fire which injured three • Russia declares state of emergency after 20,000 tonne oil spill • Indian chemical plant explosion kills eight, injures 50

Risk assessment software applications combine technology advantages with organisational experience and best practices to create improved safety solutions

11 Standards: Coronavirus: the end, or a new beginning?

12 Potential effects of the economic climate on asset integrity 14 An alternative approach to Zone 1 display instrumentation 17 Risk assessment for plant maintenance in the digital age 20 Explosion prediction methodologies overview

30 36Risk assessment

the journal for hazardous area environments

hazardexonthenet.net

July 2020

26 Datafiles

This article aims to review different explosion scenarios and describe one representative model within each category of methodology and explosion scenario.

Hazardex is a controlled circulation journal published monthly. Completed print or online registration forms will be considered for free supply of printed issues, web site access and online services. Annual subscription for non-qualifying readers is: UK £147; EU £215.25; Airmail £315 and single copy price is £23.10 plus P&P.

Hazardex content is the property of the publishers or relevant content providers. The publishers and sponsors of this magazine are not responsible for the results of any actions or omissions taken on the basis of information in this publication. In particular, no liability can be accepted in respect of any claim based on or in relation to material provided for inclusion.

Editor Alistair Hookway alistair.hookway@imlgroup.co.uk

Group Publisher Russell Goater russell.goater@imlgroup.co.uk

Sales Executive Kathryn Startin kathryn.startin@imlgroup.co.uk

Circulation subscriptions@imlgroup.co.uk Tel: +44 (0)1732 359990

IML Group Blair House, High Street, Tonbridge, Kent TN9 1BQ, UK Tel: +44 1732 359990 Email: events@imlgroup.co.uk ISSN 1476-7376

Production and Events Holly Reed holly.reed@imlgroup.co.uk

Design Graham Rich Design www.grahamrichdesign.co.uk

Plant maintenance in the digital age

Explosion science Explosion prediction methodologies overview

Standards

Instrumentation

Asset management

Coronavirus: the end, or a new beginning?

An alternative approach to Zone 1 display instrumentation

Potential effects of the economic climate on asset integrity

News Extra

The increased spending on decommissioning may limit the room for

Image: Shutterstock

operators to invest in other segments such as exploration, development and enhanced oil recovery projects. Leading players such as Shell, Total, Repsol and Premier Oil are expected to assign 10% or more of their North Sea spending in the next five years to decommissioning activities.

Global oil & gas decommissioning to total $42 billion through 2024, dominated by UK North Sea

ndependent energy research company Rystad Energy has

decommissioning costs in the US for the same period are estimated at $5.7 billion.

Plugging and abandonment (P&A) of wells is expected to make up about 45% of decommissioning costs for the period, followed by platform removals, which account for nearly 20% of the total costs. Platform wells are set to be the dominant segment for well P&A activity, making up about 65% of the total wells to be abandoned, while the rest are subsea wells. However, in terms of costs, subsea wells will take the lead as they cost on average $11 million each to abandon,

estimated that the total global value of decommissioning projects that will accumulate through 2024 could

“A protracted low price environment can potentially motivate operators to leverage

reach $42 billion. The prediction is a result of energy companies looking to increase spending in decommissioning work due to a shortage in profitable

low contract prices and commit to their asset retirement obligations, thus spurring decommissioning activity in the Northwest Europe region. This will also provide welcome

The low oil prices could play a pivotal role in boosting decommissioning spending in the UK if they persist beyond the end of this year. Nearly 10% of all UK offshore

investment alternatives caused by the coronavirus pandemic.

opportunities for contractors in an otherwise gloomy oilfield services market,” says Sumit Yadev, energy service analyst at Rystad

assets have lifting costs above $25 per barrel, which will hamper their life extension prospects and make decommissioning a

Rystad says that with an average asset age of 25 years, the Northwest European decommissioning market could grow 20%

Energy.

better financial option if low prices persist.

The high market share of the UK can be

Operators implemented strong cost

in annual commitments through 2022 if the current low oil prices don’t show signs of substantial recovery soon. In addition

largely attributed to its rapidly maturing production levels, as almost 80% of the country’s oil and gas assets have produced

optimisation measures after the oil price crash of 2014 and therefore have little room for further cost and efficiency

to a rapidly maturing asset base and low oil prices that erode commercial viability and potential life extensions, the North Sea

more than 75% of their available resources. Additionally, lacklustre exploration results, growing regulatory stringency and a prolonged

gains now, which may also expedite decommissioning spending.

decommissioning market will also be helped by favourable service contract prices.

low oil price environment may lead operators to fulfil their asset retirement obligations in the absence of any lucrative competing investments. Some of the leading assets that will drive the decommissioning market in the region include the Brent, Ninian and Thistle fields in the UK

Overall, more than 2,500 oil and gas wells are expected to be decommissioned across the North Sea in the coming decade, of which 1,500 are in the UK. The UKCS will also witness the removal of nearly 300,000 tonnes of topsides in the next five years, with nearly 50 topsides set to be decommissioned, representing an

way with nearly 80% of total estimated expenditure on Northwest European decommissioning in the next five years, followed by Norway with 14% and Denmark with 4%. The pool of removal projects in the region for that period is estimated

and Gyda in Norway. Shell’s Brent project would emerge as the single largest asset ever decommissioned globally, representing an outlay of nearly $3 billion alone over the coming decade. Ninian and Gyda would collectively present contracting opportunities

average topside removal cost of $5,300 per tonne. Additionally, almost 100,000 tonnes of substructures are expected to be removed in UK waters. In line with the broader North Sea trends, platform wells are expected to account for the bulk of the

at about $17 billion. By comparison,

worth nearly $2 billion.

well P&A activity with nearly 70%.

Only about 15% of North Sea assets have been decommissioned to date, but in the coming five years Rystad expects an average of 23 assets to cease production annually. The UK is poised to lead the

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compared with $5 million for an average platform well.

News Extra

UK approves plans for country’s largest solar park

he UK approved plans for the proposed £450 million ($554 million) Cleve Hill Solar Park Project on May 28 which could include one of the largest energy storage

of projects that may affect them. Local people, the local authority and other interested parties were able to participate in a 6-month long examination. The Examining Authority listened

The Cleve Hill Solar Park will generate up to 350MW of renewable electricity to power around 91,000 homes. According to Hive Energy, the project will reduce the UK’s dependence on

systems in the world. A 25-acre battery facility will be part of a 900-acre site near Faversham, southeast England which will include 880,000 solar panels generating 350 megawatts of power.

and gave full consideration to local views before making their recommendation.”

fossil fuels and lower CO2 emissions by 68,000 tonnes a year. The project won’t require any Government subsidies and aims to be one of the lowest cost generators of electricity in the UK.

Secretary of State for Business, Energy and Industrial Strategy Alok Sharma approved the plans which were first announced in 2017 but were met with opposition from locals who say

of the project, planning powers were taken away from local authorities as it is considered a Nationally Significant Infrastructure Project (NSIP). Construction of the site is expected

2017, we have worked alongside stakeholders and the community to listen to their feedback and to design a solar park that benefits the local environment whilst delivering a significant

the project will damage the environment, ruin the countryside and cause the loss of farmland.

to start next year with the facility becoming operational in 2022.

Announcing the government’s decision, the

Campaigners who have been fighting against

amount of renewable, affordable and secure energy generation. We are proud to lead the way, together with our partners at Wirsol, to deliver the UK’s largest solar park. Due to be

Planning Inspectorate’s Chief Executive Sarah Richards said: “The Planning Inspectorate is committed to giving local communities the

the project say that the large battery facility would be a significant safety hazard capable of devastating the local area should an

operational by 2022, the Cleve Hill Solar Park offers a real solution to our urgent climate needs and showcases the potential for the UK to lead

opportunity of being involved in the examination

explosion occur.

the green recovery.”

The project is a joint venture between Hive Energy and Wirsol Energy. Local website KentOnline reports that due to the large size

Giles Redpath, CEO of Hive Energy said: “Since

EDF submits planning application for Sizewell C nuclear power plant

DF announced on May 27 that it had submitted a development consent

order (DCO) for Sizewell C to the UK’s Planning Inspectorate after the process was delayed by the coronavirus pandemic in March. If plans are approved, Sizewell C will power around 6 million homes and create around 25,000 jobs during construction.

opportunities and long-term employment for people living in Suffolk and it will strengthen

An artist’s impression of Sizewell C – Image: EDF

will be introduced to make it easier for the final proposals to be scrutinised.

the nuclear supply chain across the country. On top of the economic benefits, Sizewell C will avoid 9 million tonnes of CO2 being pumped into the atmosphere each year. The project will play a key role in lowering emissions while helping the UK keep control of its low carbon future.”

Located on the coast of Suffolk in the east of England, Sizewell C will employ 900 people once fully operational. Up to 70% of the construction value will be spent with firms across the UK. To lower costs, Sizewell C

EDF plans to fund the Sizewell C project through a method that would see the company paid during construction of the plant. The method would see costs of construction

More than 10,000 locals and organisations

will re-use the designs for Hinkley Point C in Somerset, south west England. Using the same design means Sizewell C will benefit from significantly reduced construction costs and lower risk.

added to energy bills as the project went along, possibly decreasing development risk and lowering the final cost for consumers. However, critics believe that if the project was to be delayed or over-run, as the Hinckley

have so far contributed views and helped shape the proposals, however some residents

Humphrey Cadoux-Hudson CBE, Managing

Point C project has, then the taxpayer would be left with paying the extra cost.

raised concerns after EDF submitted the DCO while lockdown measures were in place, preventing any public gatherings for locals to discuss the plans. EDF said extra measures

Director, Sizewell C said: “Sizewell C is a net zero infrastructure project ready to kick-start the economy following the Coronavirus crisis. It will offer thousands of high-quality job

EDF hopes to complete the Development Consent Order process for the 3.2GW project within the next 18 months.

EDF had intended to submit a DCO in March, however the decision was taken to defer it by two months due to the uncertainty created by coronavirus, the energy company said in a statement. The application for a DCO follows four rounds of public consultation which began in 2012.

www.hazardexonthenet.net

News Extra

to realise its potential, both governments and industry will need to make bold decisions,”

Image: DNV GL

said Liv A. Hovem, CEO, DNV GL – Oil & Gas. “The challenge now is not in the ambition, but in changing the timeline: from hydrogen on the horizon, to hydrogen in our homes, businesses, and transport systems.” More than half of respondents to DNV GL’s research in Asia-Pacific (56%), the Middle East & North Africa (54%) and Europe (53%) agree that hydrogen will be a significant part of the energy mix within 10 years. North America (40%) and Latin America (37%) are only a little behind. The success of a hydrogen energy economy is closely aligned with the future of natural gas, renewable energy, and carbon capture and storage (CCS) technology, according to Heading for Hydrogen.

Study shows hydrogen is central to oil & gas industry decarbonisation as market growth expectations surge

new report reveals that hydrogen

While hydrogen gas produced from renewable energy (green hydrogen) is the industry’s ultimate destination, analysis shows that the sector can only realistically scale up to large volumes and infrastructure with carbon-free hydrogen produced from fossil fuels combined with CCS technology (blue hydrogen). DNV GL’s 2019 Energy Transition Outlook,

has surged up the priority list of many oil and gas organisations, taking a primary position in the sector’s

a forecast of world energy demand and supply, predicts that natural gas will become the world’s largest energy source in the

decarbonisation efforts. A fifth (21%) of senior oil and gas industry

mid-2020s, accounting for nearly 30% of the global energy supply in 2050. Natural gas and hydrogen can play similar roles

professionals say their organisation is already actively entering the hydrogen market, according to a new report published by

within the global energy system, and the synergies between them – in application and infrastructure – will drive the hydrogen

DNV GL. The proportion intending to invest in the hydrogen economy doubled from 20% to 42% in the year leading up to the Coronavirus-induced oil price crash.

economy.

The ‘Heading for Hydrogen’ report draws on a survey of more than 1,000 senior oil and gas professionals and in-depth interviews

reporting that their organisation is actively adapting to a less carbon-intensive energy mix – up from 44% for 2018 to 60% for

However, Heading for Hydrogen points to political, economic, and technical complexity in scaling the hydrogen economy. “To progress to the stage where societies and industry can enjoy the benefits of hydrogen at scale, all stakeholders will need

with industry executives. The report suggests that recent shifts in the industry’s investment priorities are unlikely to affect the sector’s long-term efforts to reduce carbon emissions.

2020. Carbon-free hydrogen production, transmission and distribution is now widely recognised as a central component to the oil and gas industry’s decarbonisation efforts.

immediate focus on proving safety, enabling infrastructure, scaling carbon capture and storage technology and incentivising value chains through policy,” said Hovem.

“Hydrogen is in the spotlight as the energy

Download Heading for Hydrogen at: dnvgl.

transition moves at pace – and rightly so. But

com/headingforhydrogen

DNV GL found a significant rise in those

www.hazardex-event.co.uk

News Extra

ensure at least the same safety and reliability standards expected from the current gas

Fife Energy Park – Image: Flickr / Sludge G

system. An on-site storage unit will hold enough hydrogen to ensure supply won’t be disrupted during even the coldest weather conditions. H100 Fife is part of the national Gas Goes Green initiative, a collaborative series of

World’s first 100% green hydrogen project set for east coast of Scotland

projects to prove the viability of hydrogen for heat. They share an objective to demonstrate how the UK’s world class gas network, comprising of over 280,000 km of pipes connected to 23 million homes and businesses, can provide a clear and cost-effective pathway to decarbonise heat through hydrogen at low cost, at pace and at scale. Decarbonisation of the gas networks

ife on the east coast of Scotland has been chosen as the location for the world’s first 100% green hydrogen project if approved by UK energy regulator Ofgem. Gas distribution company SGN

Innovation Competition. If successful, a 100% zero-carbon hydrogen network will be built later this year at the Fife Energy Park in Methil, around 17 miles (28km) north of Edinburgh across the Firth of Forth estuary.

has asked Ofgem to approve its plans for the H100 Fife project which will see the production of green hydrogen to replace

The plans would see hydrogen produced via an electrolysis plant powered by the

hydrogen demand and supply management, security of supply and ‘real world’ asset operation. As well as testing technical and

In a statement, SGN said that H100 Fife

Offshore Renewable Energy Catapult’s nearby offshore wind turbine. The proposed hydrogen production and storage system and heating

engineering capabilities, the project will provide insights into customer appetite and interest for hydrogen. Customers can

would provide critical evidence for a potential zero carbon energy source, helping to inform the UK’s long-term policy decisions

network will run alongside the current natural gas system, demonstrating every aspect of an end-to-end hydrogen-to-homes system

participate on an opt-in basis, meaning they will have the choice to switch to hydrogen, or remain with their existing natural gas supply.

for decarbonisation. SGN will bid for £2.8 million of funding from Ofgem this summer after passing an initial screening submission

to support plans for large scale roll-out in the future.

A demonstration facility within the project is proposed to allow customers to interact with hydrogen appliances in a home-like setting

process for Ofgem’s annual Network

The system will be designed and built to

prior to opting-in.

natural gas for an initial 300 homes.

The World’s #1 Issuer of Hazardous Location Certificates Let’s work together csagroup.org/hazloc

is necessary in order to achieve the Scottish Government and UK Government carbon netzero targets by 2045 and 2050 respectively. The project aims to provide critical insight into

News Extra

Image: CSB - Still image taken from CSB safety video

Topeka on May 27. The incident in October 2016 occurred when a delivery truck, owned and operated by Harcros Chemicals, carrying 4,000 gallons of sulphuric acid was mistakenly connected to a tank containing 5,800 gallons of sodium hypochlorite at MGP’s plant in Atchison, around 50 miles (80 kilometres) northwest of Kansas City. The chemical reaction formed a chlorine gas cloud which spread across the city for around 45 minutes. Local authorities ordered local communities to shelter-inplace while some residents were forced

Two US chemical companies fined $1 million each for 2016 leak

wo companies were fined $1 million

each on May 27 after they pleaded guilty to violating clean air laws in relation to a 2016 chlorine gas leak in Atchison, Kansas. Harcros Chemicals and MGP Ingredients violated the Clean

Air Act after they caused the gas leak which resulted in a large toxic cloud covering the city. Both companies pleaded guilty and paid their respective fine following sentencing in

to evacuate the area. In all, around 140 people required medical attention, including residents and employees of both companies. According to its website, MGP is a supplier of premium distilled spirits, and specialty wheat proteins and starches. The US Chemical Safety and Hazard Investigation Board (CSB) released its final report on the incident in March 2018, details of which can be found here: https://www.csb.gov/mgpiprocessing-inc-toxic-chemical-release-/

US chemical manufacturer cited for 2019 explosion and fire which injured three

he US Department of Labor’s Occupational Safety and Health

Administration (OSHA) has cited TPC Group LLC for exposing employees to workplace safety and health hazards after a fire and explosion at the Port Neches plant in November 2019. The company is facing fines totalling $514,692 for the blast which injured three workers at the plant in east Texas. Homes and businesses were evacuated, and a shelter-in-place order was issued after the large early morning explosion. The blast blew out the windows of homes

caused several explosions and fires. OSHA cited TPC for three wilful violations

Labor for Occupational Safety and Health Loren Sweatt. “OSHA has extensive

for failing to develop and implement procedures for emergency shutdown and failing to inspect and test process vessel and piping components.

resources available to help employers and workers understand requirements for process safety management.”

“Employers are required to conduct regular inspections and address potential hazardous conditions associated with chemical processes to prevent

The company has 15 business days from receipt of the citation and penalties to comply, request an informal conference with OSHA’s area director, or contest the findings before the independent

catastrophic events from occurring,” said Principal Deputy Assistant Secretary of

Occupational Safety and Health Review Commission

in neighbourhoods miles away and sent a chemical plume over the area. OSHA opened an investigation after vapour which formed at the base of a butadiene finishing tower ignited and Port Neches explosion - Image: Shutterstock

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News Extra

President Putin holds meeting about spill response - Image: Kremlin

In a televised government meeting, President Putin criticised the local

Norilsk, located around 190 miles (300km) inside the Arctic Circle, has a population

government for its response to the incident after it emerged that officials first heard about the leak on social media, two days after it had happened.

of around 175,000 and is built around the Norilsk Nickel plant. The nickel and palladium producer released a statement saying it was doing all it could to clear up the spill and that the incident was reported in a timely and proper way.

Rosprirodnadzor, Russia’s state environment watchdog, says that around

The spill is thought to have contaminated around 135 square miles (350 sq. km) and

On June 5, Russia’s Prosecutor General’s office ordered a review of all hazardous objects built on permafrost in the country. President Putin held a second online meeting with officials where he asked them to amend Russian law to help prevent

turned large parts of the Ambarnaya river a crimson red. The state of emergency was decalred to enable extra resources and

similar incidents from occurring in the future. Putin was also critical of Norilsk Nickel’s President, Vladimir Potanin, for not

ussian President Vladimir Putin declared a state of emergency on June 3 after 20,000 tonnes of diesel fuel leaked from a power plant near the Siberian city of Norilsk on May

manpower to be sent to the area to help clean-up efforts.

replacing the impacted fuel tank sooner.

29. A “considerable amount” of the spilled petrochemicals seeped into the Ambarnaya River, the Kremlin said.

and Natural Disaster Relief Yevgeny Zinichev said that measures are being taken to localise the spread of the spill,

River which eventually leads to the Arctic Ocean.

The spill originated from a power plant belonging to a subsidiary of Norilsk Nickel,

oil booms have been installed, and work is underway to collect oil products, contaminated water and soil. Specialists

The BBC quotes a former deputy head of Rosprirodnadzor who said the clean-up could cost up to 100bn roubles (£1.2bn;

the world’s leading nickel and palladium producer. The leak occurred after a fuel tank became depressurised due to the

from Moscow were flown to the area to help section off parts of the river.

$1.5bn) and take up to ten years.

subsidence of its support pillars. The spill consisted of fuel and lubricants and much of it flowed into the nearby Daldykan and

An investigation into the incident is ongoing while three employees at the plant have been detained for breaching environmental

an oil leak before, notably in 2016 when it admitted responsibility for a spill which turned parts of a nearby river crimson

Ambarnaya rivers.

protection rules.

red.

Russia declares state of emergency after 20,000 tonne oil spill

15,000 tonnes of oil products leaked into river systems while around 6,000 tonnes seeped into the subsoil.

In the conference call with President Putin, Minister for Civil Defence, Emergencies

Officials said that on June 9, the leak had reached Lake Pyasino. The lake is around 70km long and feeds into the Pyasina

Norilsk Nickel has been accountable for

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10 News Extra Representative image: Shutterstock

Indian chemical plant explosion kills eight, injures 50

n explosion on June 3 killed eight workers and injured 50 others at a

chemical plant in the state of Gujarat on the western coast of India. The cause of

the blast is unknown, with some local media reporting that it was a boiler explosion, while others suggested it

operation to begin. Six bodies were found on the site while two workers died in hospital.

occurred in a storage tank housing chemicals.

According to a local official, methanol and xylene were stored in tanks close to where the blast occurred.

Around 200 workers were on the site when the incident happened at the plant belonging

On June 8, a tribunal ordered Yashashvi Rasayan to make an interim deposit of

to chemical manufacturer Yashashvi Rasayan. A preliminary report by local authorities said the explosion happened in a chemical storage tank and caused a fire that spread across the plant. The report added that some workers who were near the

around Rs 25 crore (around £2.6 million) while an investigation into the incident continues. The National Green Tribunal, a body set up in 2010 to handle environmental disputes and issues, said it held Yashashvi Rasayan liable for the damage caused to

storage tank at the time were killed instantly after being covered in highly concentrated chemicals.

both human lives and the environment. The six-person panel comprising retired judges and former officials is expected to publish an investigative report within a month.

The injured workers were taken to local hospitals while around 5,000 local villagers were evacuated as a precaution. Footage posted on social media following the blast

The Rs 25 crore is in addition to the compensation which Yashashvi Rasayan has already been ordered to pay, including Rs 15

shows a large plume of smoke rising from the factory as workers run from the factory.

lakh (£15,694) to the families of those killed, Rs 5 lakh (£5,232) to those seriously injured, Rs 2.5 lakh (£2,616) to anyone injured, and

The fire was brought under control after a few hours, allowing a search and rescue

Rs 25,000 (£261) each to anyone displaced from their home as a result of incident.

Standards 11

Representative image: Shutterstock

Coronavirus: the end, or a new beginning? The quality of some of the links for the recent

pandemic and deals with how the schemes

UK Downing Street press conferences demonstrated that, even for those prepared to pay a premium for their service, latency and lip-sync can still be a major problem.

can continue to operate during the crisis, but in a way that still provides adequate confidence in the system.

So, will remote working replace our international

The current interim version of the document is available to view on the IECEx website and

face-to-face meetings after we have emerged from the current situation? There are clearly advantages in being able to hold short meetings for the discussion and resolution of

the final version should get formal approval in September. This includes the protocols for when surveillance visits can be delayed and how they can be conducted remotely. This is

am writing this on June 1, the day that the UK government set for the start of easing lockdown restrictions.

particular matters, but I am concerned that we will miss out on many of the advantages of being in the same room. And it is not just being able to judge reactions in the actual meetings,

not just for the certification bodies and their manufacturing clients, but also for the IECEx System’s supervision of certification bodies.

Except that we are now not a totally United Kingdom, with England, Wales, Scotland and Northern Ireland making

it is the side meetings, during the coffee breaks, that can be just as important. Many a discussion point, where two people seem to

In contrast to IECEx, IEC TC31 postponed its March standards meetings until the end of October, in the hope that two weeks of

their own slightly different rules on how to progress. So, even at the UK level we are seeing fragmentation, but it becomes more obvious the bigger the

hold opposing views during the meeting, can be resolved in a group of two or three in the break-out area. An interchange of emails, after the remote meeting has finished, is not really

meetings will still be able to take place. Over 100 people would normally gather in a series of separate one-, two- or three-day meetings, spread across the fortnight. A maximum of four

group you consider. How is this going to affect the standardisation process and certification worldwide?

effective in the same way. IECEx held the May meetings remotely

meetings will be held simultaneously. There can be conflicts, with a few people trying to be in more than one meeting at a time, but as the

Electronic meetings are now becoming the normal way of working. But internationally, this

and will do the same for those previously scheduled for Niagara in late September. This will certainly be a new innovation for me, as I

meeting rooms are all co-located this usually works. That would be more difficult with remote meetings, unless they are spread out across

brings problems of timing. IECEx has decided on a 12:00 UTC (13:00 BST) start. This suits Europe and the east coast of America, but

have not yet sat through meetings with over 150 remote participants. These are the formal annual meetings for the organisation, also

a much longer period, with only one meeting being held at any one time. However, this then removes the ability to have short “corridor”

anyone in California has to get up very early, and anyone in Australia gets to bed very late. We are yet to have any participants from New

attracting many observers into the various national delegations. The rule book provides for just three delegates per country, with only

meetings for those that are based in different meeting rooms.

Zealand!

the lead delegate allowed to vote. This is normally done by the lead delegate holding up the country identification card from the table. It will be interesting to see how we manage this process online. Provisionally, it has been decided that any observers beyond the official three delegates will have their microphones and cameras muted by the secretary of

Not all work is being postponed until October, with some of the smaller Maintenance Teams being able to work electronically, so although some revised standards will be delayed, others are keeping on target.

Every two months, SGS Baseefa Technical Manager Ron Sinclair MBE gives his perspective on the latest developments in the world of standards.

The IECEx meetings in May ran very smoothly, in part because most participants had met each other at previous meetings and could recognise voices. The secretariat imposed good “mute” discipline on microphones and, apart from the secretary who was sharing his screen showing the documents, cameras were off, in order to minimise bandwidth problems. We were unaware of latency issues in the sound and, because video was off, we were not put off by lip-sync issues or other glitches in the video stream.

the meeting, so they will truly be just that, observers. One of the major decisions, taken at the May meetings, was to finalise a version of the new Operational Document OD 060, which was drafted in response to the coronavirus

About the author SGS Baseefa’s Technical Manager Ron Sinclair MBE is a vice-chair of the European Notified Bodies Group for ATEX (ExNBG), as well as Chair of the IECEx Service Facility Certification Committee and a member of the IECEx Executive. He is chair of both the UK and European Standards Bodies operating in this area.

www.hazardexonthenet.net

12 Asset management

Caribbean Petroleum Corporation Disaster – Image: CSB

Potential effects of the economic climate on asset integrity D

uring the current economic climate, when it comes to budgets,

allowing employees to work up to 86 hours a week compared to the 72 hours currently

of the changing economic factors currently present in the industry.

practically every facility owner and manager has the same dilemma: doing more with less. When faced

permitted. In addition to allowing changes to shift

Shortfalls in maintenance and asset integrity related activities are often highlighted in

with shrinking budgets, it’s tempting to delay general maintenance, repairs, inspections and other operating costs to

patterns, the US Nuclear Regulatory Commission also allowed US nuclear plants to delay some inspections. Hence, when

investigation reports as a leading cause of process safety incidents. Some contemporary examples are:

a future point where the budget available may be more favourable – or even postponing the tasks indefinitely.

there is a challenge to an operating budget, maintenance and integrity related tasks are often reviewed as an option for cost cutting.

Similarities can be drawn between the current economic climate with the economic crisis of 2008/2009 which saw budgetary constraints across the energy industry.

The major hazards for energy facilities are ever present – fire, explosion and the release of hazardous materials. All these hazards have the potential to cause a major process

• On 23 October 2009, a large explosion at the Caribbean Petroleum Refinery in Puerto Rico caused extensive damage to numerous petroleum storage tanks as well as damage beyond the refinery’s boundary. The incident occurred during the offloading of gasoline from a tanker ship to the tank farm. The tank being filled overflowed,

The COVID-19 pandemic has doubtlessly challenged operating budgets, but it has also had a direct impact on human resources. There have been reports of worker’s shifts being extended due to the pandemic, which in some cases have been extended to as

safety incident. The energy industry is a dynamic and rapidly changing industry but one with ageing infrastructure and increasing cost pressures as the available revenue from oil and gas sales declines. There is a risk that the dedication of resources towards asset

resulting in a vapor cloud release and subsequent explosion. One maintenancerelated cause was identified in the investigation report – a malfunctioning tank fuel gauge. The faulty equipment prevented workers from noticing that one of the tanks

long as 12 hours a day for two weeks,

integrity will be allowed to decline as a result

was overflowing before the fuel vapours

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Asset management 13

ignited. It was reported at the time that the level transmitters were often out of service,

impact. The bigger the deferred maintenance number becomes, the potentially harder it

ensure that the necessary skills base is always retained within an organisation, particularly

may become to maintain the facility at an acceptable level of safety management. However, facilities that have implemented comprehensive preventive maintenance programmes have found that the operation of their systems is more reliable, and those

during an economic crisis.

treated for breathing problems and 20 people were admitted to hospital. The pipe was found to have been damaged by sulphidation corrosion. The key activity designed to combat this kind of failure is the implementation of routine inspections

systems also last longer.

make the case that prevention is a far more cost-effective option. Decisions based within short term budgetary challenges should consider this fact.

as part of a preventative maintenance strategy. In this case, recommendations for improvements were not followed-up.

These factors could be because of the equipment not being made available for maintenance due to plant configurations or a turnaround being postponed for a year or

awaiting maintenance tasks. • Pipe rupture on the Crude Unit of the Chevron Refinery in Richmond, California on 6 August 2012, resulted in a vapour release and explosion. Around 15,000 people from the surrounding area were

Deferral of maintenance tasks for energy facilities is not a new concept and there are often situations where tasks become postponed due to operating constraints.

Within the energy industry, there has been sizeable investment within asset integrity. This has resulted in improvements to physical integrity, progress in effective asset integrity

more due to commercial drivers or increased confidence in the equipment. The key to safe management of postponing these tasks is for the use of risk-based tools for

management, awareness and performance. Many operators have found that by applying best practices in maintenance and reliability

work prioritisation which has a defined clear responsibility for tracking overdue tasks to completion. An effective risk assessment

they can optimise asset integrity and reduce total maintenance cost.

may also provide the required evaluation of the effects of prolonging shutdowns and the effects on safety critical devices (such as pressure safety valve calibrations) must be

The key to effective decision making when revising maintenance plans is to review the criticality of the systems. The definition of critical equipment may vary from organisation

considered.

to organisation and if it is not formalised, there may be several interpretations of equipment criticality within a single

challenges to provide the skills, training and competencies required to deliver the high standards of asset integrity necessary in major

organisation. If the assumptions used to assess what equipment is critical are not technically based, then different individuals

hazard industries. The economic cycles in the global oil and gas industry have significant influence on recruitment and preservation

will identify different pieces of equipment as being critical as the selections will be based on individual opinions and lacking

of necessary competence. This needs to be recognised and effectively managed to

Across the industry, there is a current trend of

When the costs of process safety related incidents in the energy industry can be in the hundreds of millions, or even in the billions of dollars, it ought to be relatively simple to

About the author

Dr Jason Shirley is an experienced risk engineering manager within the high hazard process industries. He has had the privilege to view the operating practices across multiple energy installations throughout the Middle East and globally. Jason has 10 years of operations management experience within the energy industry. He has a strong background in sharing knowledge and best practice within the industry.

consensus. As a result, the potential for equipment failure having significant safety, environmental or economic consequences may be overlooked. The greater issue with deferred maintenance is that it only grows in scope – and cost – the longer it is prolonged. When repairs are delayed they can quickly become replacements. The longer that maintenance is deferred, the more components that are affected and the more costly that maintenance becomes. Run-to-failure is only a viable tactic in situations when there is little economic and no safety or environmental

Image: Shutterstock

www.hazardexonthenet.net

14 Instrumentation

An alternative approach to Zone 1 display instrumentation a large toughened glass window. If required, an elastomeric keypad to activate internal switches for the control and calibration of the instrument while it is in the hazardous area can be incorporated. To ensure that safety is maintained in an industrial environment during the lifetime of the product, the IEC increased safety standard IEC 60079-7:2015 requires non-metallic Ex eb and Ex ec enclosures to be subjected to both lengthy thermal endurance at high temperature and high humidity and to a period at a very low temperature. This is followed by subjecting the enclosure to 7J impacts at above the maximum and below the minimum operating temperature before measuring the

Figure 1 – Alternative Zone 1 instrument design

lameproof instruments are fairly simple to understand and apply, do not require Zener barriers or galvanic isolators and they do not involve users with the

It has traditionally been used for protecting Zone 1 and 2 electrical machines, luminaires, trace heating and is widely used for protecting terminal enclosures. Until recently, Ex e has

water and dust ingress protection provided by the enclosure. Although the standard only requires a modest IP54, most certified GRP Ex eb enclosures satisfy IP66 requirements and

perceived complexity of entity and cable parameters. Worldwide, flameproof Ex d explosion protection probably remains the

rarely been used for protecting low power instrumentation.

provide similar impact protection as a metal flameproof enclosure.

predominant means of preventing Zone 1 and 2 field mounting instrumentation igniting a flammable gas atmosphere.

The latest edition of the IEC increased safety standard IEC 60079-7:2015 introduced two levels of increased safety Ex e protection:

Alternative Zone 1 design

However, for hazardous area instruments incorporating a display such as indicating

Ex ec (Equipment Protection Level EPL ‘Gc’) For applications in Zone 2

shown in Figure 1. To allow installation in Zone 1, the electronic assembly within the Ex eb enclosure requires protecting by an additional

transmitters and loop displays, small flameproof enclosures do not lend themselves to accommodating large windows through

Intended as replacement for Ex nA protection. Electronic components such as semiconductors and capacitors may be used.

method of explosion protection. Although any protection technique suitable for use in Zone 1 could be used, the low voltage and power

Ex eb (Equipment Protection Level EPL ‘Gb’) For applications in Zone 1 and 2 Excludes the use of electronic components such as semiconductors and capacitors.

consumption of modern electronics make intrinsic safety Ex ib and encapsulation Ex mb particularly attractive. To provide maximum flexibility, this new alternative instrument design employs both Ex mb and Ex ib explosion protection techniques.

which displays can be easily seen. A new alternative design based on increased safety Ex e protection overcomes this limitation, allows tactile push buttons to be used and reduces the instrument cost. The resulting instrument may be installed in a Zone 1 or 2 hazardous area and used in the same way as an Ex d explosion proof instrument.

This alternative Zone 1 instrument design, which is housed in an Ex eb enclosure, is

Ex e increased safety relies heavily on the integrity of the equipment enclosure to protect

Energy limiting components are mounted

Increased safety Ex e is an explosion protection technique which when applied to electrical equipment, provides increased security against the possibility of excessive temperatures and

the electrical equipment within the enclosure, although the explosive atmosphere is not excluded from the enclosure. Unlike most flameproof enclosures which are manufactured from aluminium or steel, an increased safety Ex eb enclosure can be compression moulded in

within an encapsulated Ex mb assembly with an intrinsically safe Ex ib output. The encapsulation prevents a potentially flammable gas atmosphere accessing the energy limiting components and the intrinsically safe output is nonincendive allowing a wide range of

against the occurrence of arcs and sparks.

glass reinforced plastic (GRP) with provision for

electronic components including a display

Increased safety Ex e

www.hazardex-event.co.uk

Instrumentation 15

by a Zener barrier or galvanic isolator. They may be installed in Zones 1 or 2 and may be connected to almost any other certified instruments having flameproof Ex d, increased safety Ex e or pressurised Ex p protection, but they cannot be used with intrinsically safe instruments or systems.

First new models The new design technique has led to the production of two IECEx and ATEX certified Ex eb loop powered 4-20mA indicators which are a lower cost alternative for flameproof Ex d indicators. The new models are housed in a

Figure 2 – Ex eb instrument can be safely connected to instruments with other types of explosion protection.

robust IP66 GRP enclosure, have a large easy to read display, tactile push buttons and do not require flameproof cable glands.

to be connected to it. The capacitance and inductance of the instrument display, associated electronics and the push button

techniques to produce a lower cost, drop-in alternative for a flameproof Ex d instrument. Providing a much larger display and tactile

These new Ex eb models may also be used in place of Ex nA indicators for Zone 2 applications in anticipation of Ex nA non-sparking protection being replaced by

switches comply with hydrogen IIC intrinsic safety limits, and power is limited to prevent excessive surface temperatures, ensuring

push buttons the technique is suitable for many types of hazardous area instruments including fieldbus indicators, indicating transmitters and

Ex ec increased safety protection. This will happen when BS EN IEC 60079-15:2015, which defines Ex nA non-sparking explosion

that the circuits remain safe even under fault conditions.

loop powered indicators. The new design has the additional advantage that only Ex eb field wiring glands or conduit fittings are required, eliminating the need for Ex d glands.

protection, is de-harmonised in April 2022.

Advantages of the alternative design This alternative instrument design uses multiple well-established explosion protection

About the author

Like the explosion proof Ex d instrument they replace, instruments employing the new alternative design do not require protection

Figure 3 – BA304SG Ex eb loop powered indicator.

Olivier Lebreton CEng, MIET, is the newly appointed Managing Director of BEKA associates. Olivier joined BEKA in 2013 and became Technical Director in 2018 before becoming MD in June 2020. As Managing Director, Olivier will be responsible for all company operations, but will initially retain his Technical Director responsibilities. He is a chartered engineer and has 20 years’ experience managing design projects for many different applications including, oceanographic equipment, safety critical products and hazardous area instrumentation in France, Canada and the UK.

www.hazardexonthenet.net

Humidity & Temperature Monitoring in ATEX Environments A new generation of Intrinsically Safe humidity and temperature sensors for ATEX rated dust and gas environments is available. Conforming to the latest international standards, the HygroFlex5-EX transmitter from Rotronic uses interchangeable ATEX certified probes suitable for all applications. Rotronic developed the HygroFlex5-EX for the pharmaceutical, biotechnology, grain & sugar, petrochemical and oil & gas industries. HygroFlex5-EX • Stainless steel probes certified for operation in Zone 0/20 • HygroFlex5-EX measurement transmitter certified for Zone 1/21 • ATEX certified ranges -40...85 ºC, 0...100 %rh • Intrinsically Safe (secondary side); two-channel transmitter • Robust aluminium transmitter housing; IP66 protection • LC display with trend indicators and keypad

Visit www.rotronic.co.uk for more information or call 01293 571000

ROTRONIC Instruments (UK) Ltd Crompton Fields, Crompton Way, Crawley, West Sussex, RH10 9EE T: 01293 571000, F: 01293 571008, E: instruments@rotronic.co.uk

A PST Company (www.processsensing.com)

Figure 1 – Experience working in industrial plants and facilities is helpful when performing risk assessments, but it varies greatly from one person to the next. Image: Yokogawa

Risk assessment 17

Risk assessment for plant maintenance in the digital age R

isk assessment software applications

fully entrust their own well-being or the safety

legislation, best practices and good old

help industrial plants and facilities combine technology advantages with organisational experience and best

of personnel they supervise to an algorithm, and not many companies would stake their reputation as a responsible employer

common sense play a part also – but plant personnel possess different levels of experience and yes, common sense. These

practices to create improved safety solutions.

completely in the hands of a software program, however well designed. On the other hand, there is plenty we can do digitally to

types of variations often result in unacceptable levels of consistency or accuracy.

We live in an era where many of our day-today activities are carried out digitally – and many industrial plants and facilities also commonly perform tasks digitally – such as real-time machine and process control, work planning, and performance optimisation. Is it therefore a reasonable assumption that the same can be true for risk assessment?

help ensure the safety of personnel working in industrial plants and facilities.

It is difficult to imagine a completely digital solution where a risk assessment software program trawls safety and other operating records and spits out a comprehensive solution. The risk assessment software would undoubtedly find instances of things going wrong, and it could possibly identify some learnings from these incidents. However, what

Can we say that the electrons required in any digital evaluation of risk can replace the neurons required for the thought processes we currently use to perform these tasks?

selection of mitigating factors. These types of assessments rely on several sources for information.

Issues with risk assessment Let’s start by looking at the current methodology of risk assessment, where one evaluates the likelihood and potential of something going wrong before and after the

most people consider experience is also made up of things that don’t go wrong, as when long periods with no incidents are used as evidence of safe work practices.

Like many questions in life, the answer is a

Experience leads the way for many, with years of work in industrial settings (Figure

Times when things don’t go wrong probably

bit yes and some no. Few individuals would

1) informing many decisions. Standards,

by definition would not make it into any

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18 Risk assessment creating these knowledge bases, guiding users through the required procedures step by step. Users first select the icon elements for each task in the risk assessment software (Figure 2). The information contained within each element then expands to inform of

Figure 2 – Risk assessment software guides users through the steps required to identify and mitigate risks. Image: Yokogawa

the necessary controls and authorisations required, in this manner dictating the necessary workflow.

recordkeeping system, and these would

future risks, is not practical. The solution

Selections within the risk assessment software are then used to identify any

therefore not be found by any digital system. So, are digital solutions therefore of no use for risk assessment? And apart from digital solutions, how does one reconcile differences

is to instead break down the maintenance workplace into all its discrete elements using risk assessment software. These elements include all work conditions, activities and

exacerbating factors within the job, with the appropriate controls identified. This is carried out by selecting a series of ‘Considerations’ associated with the work element. These

among plant personnel to create consistent results?

tools – and all materials a worker might come into contact within the course of their prescribed duties.

considerations lead the user into identifying any additional potential hazards, and ultimately to identifying suitable controls.

and other issues by combining digital systems with human experience to produce better risk assessments.

Each of these elements includes a description of the source of risk and how it might be mitigated. Combining all these

For instance, when working on a roof, the consideration might prompt the user to consider if there may be skylights present. If

Risk management software solves problems Analysing every single maintenance task

elements completely characterises the risks inherent in the workplace and presents a means for dealing with each, creating a digital knowledge base of risks and

there are, the user will investigate further to establish what the consequences might be of working in the vicinity of these potential hazards. In this case, falling through a

that could ever happen in a plant to identify not only past incidents, but all possible

mitigation factors. Risk assessment software solutions are now available to assist with

skylight would be a reasonable, if not desirable, outcome.

Fortunately, it is possible to address these

Figure 3 – Work in potentially dangerous areas can be classified as such using risk assessment software. Image: Yokogawa

www.hazardex-event.co.uk

Risk assessment 19

If the user then selects this consideration, they will be presented with a variety of controls

People’s skills and attributes differ, including perception of risk, so two people assessing

trained a larger number of low-risk assessors, freeing up time for higher-risk assessors to

they could put in place to prevent the fall from happening. These controls could range from the erection of barriers, perhaps different types, to creating exclusion zones, or just a simple warning to keep clear. This element of the knowledge base is where the bulk of site

the same job often come up with different findings. Although companies can provide guidelines to improve consistency, it can often be difficult for an individual to choose between outcomes, for example the possibility of causing mild or serious injury.

concentrate on their tasks. This proved to be very successful, delivering their safest turnaround ever for this particular plant.

and company experience is located. The risk assessment software also ensures the risks identified aren’t too prescriptive, and all importantly, encourages the users to think and add helpful input. There is a free

To address this issue, risk assessment software can prescribe a risk level to each element contained within a task, thus guiding users to help them reach a consistent and accurate conclusion. The risk levels of these

Conclusion In the foreseeable future, industrial plants and facilities will probably not reach a stage where risk assessment can be completely carried out using only digital methods, but one can certainly anticipate how risk assessment software can be used to augment experience, incorporate learnings, and provide consistency

text area where users can add elements not present in the knowledge base, each of which can then be reviewed and added back to the knowledge base, thus strengthening and

elements can be adjusted at any point to reflect continuous learning from actual workplace experience.

and accuracy when assessing risk. The knowledge bases contained within these types of software applications will naturally grow and improve through use, eventually transforming

expanding it.

to add wisdom by representing the desired safety culture of the organisation.

In addition, when accidents and incidents do occur, learning from these can be quickly and

Another benefit concerns the competency of the individual carrying out the assessment. Most sites will have a recognised group of people who can perform risk assessments,

easily added to the knowledge base for all to share going forward. The same is true for changes in legislation and identification of best

and they will have the systems and methodologies in place to both train and support them. However, these people can

knowledge?

practices.

become overloaded at times – especially during turnarounds and capital projects. In these situations, it is difficult to allow other people to share the workload as each of them

With the proper risk assessment software, these knowledge bases can be translated into different languages. This means that every worker can follow the same standards and consistency, wherever they may be located

should first undergo full training and have the necessary experience.

worldwide. It also means best practices identified at one site in one language can be quickly assimilated at other sites, so a plant

But if the knowledge base software is organised in terms of discrete job elements, plants can make use of the allocated risk

need not experience an incident to capture learnings from others.

levels to allow certain people to carry out some assessments but not others. For instance, a less experienced worker can be

This specific functionality has been used to great effect by one multinational energy company. They have been able to set

used to assess a simple cleaning operation in a non-hazardous area, but not repair work in a potentially dangerous environment (Figure 3).

standards and adopt learning across all of their 20+ locations across the globe. What’s more, each site can now view what anyone is doing with the risk assessment software at any other site, translated to their own local language. This affords each site the opportunity to reinforce best practices and gain early warning of any sub-standard ways of working, before things go wrong.

By dividing tasks in this manner, more personnel with wider levels of experience can work on a project, thereby taking some of the load away from the typically limited supply of more experienced personnel. This technique was used to great effect by

Risk assessment software helps deliver consistency. Manual use of standard risk assessment techniques typically produces

one operator. They had analysed the inherent risks associated with their up-and-coming turnaround and identified the majority of tasks as relatively low risk, helped by the fact that during a turnaround there is likely to be a battery limit isolation in place to keep certain

very different results among different people.

areas certified as gas free. Therefore, the plant

Risk reduction results

For after all, is not wisdom the best use of

About the author

Mark Carter has had a varied career. As well as 12 years as a plant engineer with BP, he has also spent years sailing the Great Lakes and developing onboard ship devices, and he spent lots of time carrying out research into alternative energies and managing laboratory/quality facilities. For the 25 years following these endeavours, Mark has been the Managing Director of RAP International, the risk assessment company that he founded and sold to Yokogawa in September 2019. Latterly, he has been working as a Consulting Business Development Director for Yokogawa.

www.hazardexonthenet.net

20 Risk assessment

Explosion prediction metho 1. Introduction

This article aims to review different explosion scenarios and describe one representative model within each category of methodology and explosion scenario, with a focus on empirical

theoretical model is the key to the success of the project. Computationally expensive CFD methods are getting more popular but are deemed only necessary in this article when detailed analysis is required. There are also

various infrastructures such as buildings, stations, petrochemical plants, mines, gas utilities, etc. Predicting the possible consequences of these explosions has involved efforts through experiments, theoretical models and computational

models.

limitations of computational simulations for many industry applications due to the actual cost to run the simulations (numerous inputs that are both error prone and sensitivity prone, sophisticated usage, long simulation time, etc.).

simulations.

the model. Therefore, applying the correct

xplosion risk assessment usually involves high explosives or large gases/vapour cloud explosion, which represents a considerable hazard for

www.hazardex-event.co.uk

In most engineering applications, simple empirical models are sufficient for the project purpose as long as the engineer knows what they are doing and the applicability range of

Hazardex – July – p20-26

Risk assessment 21

Representative image: Shutterstock

[eyebrow] Risk assessment

[head] Explosion prediction methodologies overview

produced heat of detonation of some common explosives. It’s worth mentioning that approximately one third of the total

[G, this may be a tricky article to lay out as there a explosive few equations, special chara chemical energyare of the is released by etc. throughout. The figures may not detonation. be good enough qualityateither, The rest is released a slower so ratelet me kno don’t work and I’ll do my best to get better ones!] as heat ofquality combustion through burning of the explosive products mix with the surrounding air.

Table 1 – Explosive heat of detonation (Ref. )

[Insert image Patrick Mann Main Image and caption:] [1] Representative image: Shutt

[lead] 1. Introduction

Name of explosive

Heat of detonation [MJ/kg]

TNT

4.10-4.55

5.86

RDX

5.13-6.19

PETN

6.69

Explosion risk assessment usually involves high explosives or large gases/vapour clou PENTOLITE 50/50 5.86 6.30 which represent a considerable hazard NITROGLYCERIN for various infrastructures such as buildings, NITROMETHANE 6.40 petrochemical plants, mines, gas utilities, etc. Predicting the possible consequences NITROCELLULOSE 10.60 explosions has involved efforts throughAMON./NIT.(AN) experiments, theoretical models and compu 1.59 simulations. The impact of explosive munitions can be

broken down into the principal damage one representa This article aims to review different explosion scenarios and describe mechanisms and their primary effects, within each category of methodology and explosion scenario, with aand focus on empiri the secondary and tertiary effects induced

[body]

by these (Ref. [2]). Primary effects of explosive weapons are defined as those caused In most engineering applications, simple empirical modelseffects are sufficient directly by the destructive that radiate for the proje long as the engineer knows what they from are adoing theand applicability point ofand initiation include blast range of the m

heat of andthe light.project. Comp applying the correct theoretical modeloverpressure, is the key fragmentation, to the success The term ‘blast’ but refersistodeemed a high-pressure expensive CFD methods are getting more popular onlyblast necessary in th wave moving at supersonic speed, referred to detailed analysis is required. There are also limitations of computation simulations fo as the shockwave, which is followed by blast applications due to the actual cost to run the simulations (numerous input that are b winds. An ideal blast wave’s pressure time and sensitivity prone, sophisticated usage, long simulation time, etc.). history is provided in Figure 1. The value of

2. Unconfined explosion

odologies overview 2.1. High explosive explosion

2. Unconfined explosion 2.1. High explosive explosion The wide variety of explosives has led to the adoption of a universal quantity, which is used for all necessary computations of blast

the peak overpressure Pso and the velocity of propagation of the shock wave decrease with increasing distance from the detonation centre.

The wide variety of explosives has led When to thecharacterising adoption of universal quantity, which theablast loading on structures,TNT there(Trinitrotoluene) are three explosion types necessary computations of blast parameters. was chosen as its that need to be distinguished: characteristics resemble those of most solid type explosives. An equivalent TNT weig 1) Free-air bursts: the explosive charge according to following equation that links the weight of the chosen design explosive is detonated in the air, the blast waves equivalent weight of TNT by using the ratio of the heat produced during detonation:

during detonation:

𝑊𝑊 = 𝑊𝑊!"#

$ $!"# $ $%&%

[1]

where W is the weight of the explosive in

parameters. TNT (Trinitrotoluene) was chosen as its blast characteristics resemble those of most solid type explosives. An equivalent TNT weight is computed according to following equation that links the weight of the chosen design explosive to the equivalent weight of

terms of TNT equivalence [kg], Wexp is the weight of the actual explosive [kg], H dexp is the heat of detonation of the actual explosive d [MJ/kg], and HTNT is the heat of detonation of the TNT [MJ/kg].

TNT by using the ratio of the heat produced

Table 1 gives some examples of the

propagate spherically outwards and impinge directly onto the structure without prior interaction with other obstacles or the ground; 2) Air bursts: the explosive charge is detonated in the air, the blast waves propagate spherically outwards and impinge onto the structure after having interacted first with the ground; a Mach wave front is created; 3) Surface bursts: the explosive charge is detonated almost at ground surface, the

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22 Risk assessment

Figure 3 – Difference on Pressure Curve Characteristics: VCE vs. HE Detonation

2.2.1. TNT equivalency model In a TNT model, the energy of the material released is converted into TNT equivalency (as per section 2.1), based on which the local explosion overpressure is determined based on TNT blast charts. It is self-evident that the blast waves produced by a TNT explosion

Figure 1 – Ideal blast wave’s pressure time history

blast waves immediately interact locally with the ground and they next propagate hemi-spherically outwards and impinge

source to the point of interest [m], and W is the weight of the explosive in terms of TNT equivalence [kg].

onto the surface.

2.2. Vapour cloud explosion

and gas explosion are quite different: TNT blast is characterised by a shock wave of higher overpressure and shorter duration, while a gas explosion blast features lower overpressure and longer duration. Therefore, using a TNT method to model gas explosion is not strictly valid and is usually not

Figure 2 illustrates the three types of burst.

Vapour cloud explosion features a different

A blast assessment will firstly need to determine the location of the charge, then blast loading is decided based on the burst type. For outputs of blast prediction, Pso

loading pattern from the HE explosion, as demonstrated in Figure 3. Different vapour cloud explosion prediction methodologies exist, varying from simple empirical models

recommended to be used for vapour cloud explosion scenarios.

and the positive impulse are the most often required output from such blast prediction. The Kingery-Bulmash curve in section 4.1

to more sophisticated models. The more sophisticated methods are usually very complex, since these methods try to solve

TNO Multi-Energy Method (MEM)[5-7] is based on the premise that a vapour cloud explosion can occur only within that portion of a

provides a direct look up for the outputs. On the free-air burst, the free-field blast load can also simply be decided using many empirical

the governing equations for the intrinsic physical phenomena. These include phenomenological models (SCOPE, CLICHÉ,

flammable vapour that is partially confined, i.e. recognising that turbulence is the major cause of explosive, blast generating

2.2.2. TNO Multi-Energy Method

formulas. The Kinney equation is one of the etc) and CFD models (CFX, AutoReaGas, combustion. Thus, the amount of energy The Kinney Kinney equation is one onewell of with the formulas formulas (see Eq.[2])etc). which agrees well with withreleased the widely widely accepted The equation is of the Eq.[2]) which agrees well the formulas (see Eq.[2]) which agrees EXISM(see and FLACS, One of the major duringaccepted a VCE is limited by the Kinney equation is one of the formulas (see Eq.[2]) which agrees well with the widely accepted Kingery-Bulmash curve. the widely accepted Kingery-Bulmash curve. drawbacks of the sophisticated models is volume of the partially confined portion of Kingery-Bulmash curve.

gery-Bulmash curve.

= 𝑃𝑃(

! % )*)+,-. / 0 '( ( '( (".$

𝑃𝑃 = = 𝑃𝑃 𝑃𝑃 𝑃𝑃

! % %

)*)+,-. ! // 00 )*)+,-. ".$ ".$

&.$ % % ! ! ! % % % &.$ ! ! /% 0+,-. ! / 0+,-. 02 1+,-. &.$ &.(% / 0+,-.).($// 02 % % &.&"' ! ! 1+,-. ! / %0+,-.&.(% &.&"' ).($ 1+,-.&.&"'/ 0+,-.&.(%/ 0+,-.).($/ 02

[2]

the large amount of inputs and running time for one calculation [2] case.

[2]

the flammable vapour cloud. The MEM is a blast curve-based method. The blast curves are pressure-distance and duration-distance

There are several simplified models such as plots divided into 10 curves, with each curve where Zscaled is scaled scaled distance and is isas: defined as: where Z isZ distance and is defined theas: TNT-equivalent method, TNO multibeing called a severity level ranging from 1 where is distance and defined ere Z is scaled distance and is defined as: energy method, Baker-Strehlow-Tang model to 10. ( ( 𝑍𝑍 = = ∛* [3] (BST) and Congestion Assessment Method ( 𝑍𝑍 [3] [3] ∛* (CAM), etc. All require the determination TNO has further published formulating ∛* where R is the distance from the detonation source to the point of interest [m], and the weight where R is the distance from the detonation of amount of flammable material released, Guidance where R is the distance from the detonation source to the point of interest [m], and W Wforis isthe theApplication weight of the Multiere R is the distance from the detonation source to the point of interest [m], and W is theEnergy weight [8,9] cloud size and energy method (GAME). The GAME of of the the explosive explosive in in terms terms of of TNT TNT equivalence equivalence [kg]. [kg]. he explosive in terms of TNT equivalence [kg]. release upon ignition. project aimed to improve the Multi-Energy

These models feature method, on reducing conservativeness when simplified physics and determining the charge strength and charge [Insert [Insert Figure Figure 1 1 and and 2 2 with with captions:] captions:] are useful for quick size. Through designed experiment, formulas ert Figure 1 and 2 with captions:] calculations and screening were developed to relate the explosion Figure Figure 1 1 –– Ideal Ideal blast blast wave's wave's pressure pressure time time history history purposes for later detailed overpressure to explosion parameters. For ure 1 – Ideal blast wave's pressure time history Figure 2 – Three types of unconfined blast - a) free-air burst; b) air analysis with complex an open 3D configuration (low ignition energy Figure 2 – Three types of unconfined blast - a) free-air burst; b) air burst; c) surface burst.

Figurec)2surface – Three bursttypes of unconfined blast - a) free-air burst; b) air burst; c) surface burst. ure 2 – Threeburst; types of unconfined blast - a) free-air burst; b) air burst; models.c) surface burst. and no confinement): www.hazardex-event.co.uk

2.2. 2.2. Vapour Vapour cloud cloud explosion explosion Vapour cloud explosion Vapour Vapour cloud cloud explosion explosion features features aa different different loading loading pattern pattern from from the the HE HE explosion, explosion, see see aa

e MEM is a blast curve-based method. The blast curves are pressure-distance andof the Multi-Energy method TNO has further published formulating Guidance the Application ‘shock for pressure’. In addition, the effects of the high temperatures and accumulation of gase 110tocurves, 10. with 3.2. Vented explosion pressure. For the design of most fully vented cubic e plots dividedfrom into each curve being called a severity level ranging [8,9] (GAME). The GAME project aimed to improve the Multi-Energy method, on reducing products produced by the chemical process involved in the explosion will exert an additiona published formulating Guidance for the Application of the Multi-Energy method be neglected. TNO has further formulating for For thethe Application theThrough Multi-Energy method conservativeness when determining theGuidance charge anddesign charge size. designed Various formulas exist to predict the of peak Risk pressure. of of most fully vented cubicle typeassessment structures, the effects gas over pres 23 GAME project aimed to[8,9] improvepublished the Multi-Energy method, onstrength reducing (GAME). The GAME project aimed to improve the Multi-Energy method, on reducing experiment, formulas were developed to relate the explosion overpressure to explosion parameters. document on vapour explosion enclosure desig be neglected. For confined gas explosion, the simplest method to when determining theGuidance charge strength charge size. Through designed published formulating for the and Application of the Multi-Energy method [15] conservativeness when determining the charge strength and charge size. Through designed For an open 3D configuration (low ignition energy and no confinement): the minimum venting areasystem. required for a low-s conservation in an adiabatic mulas developed relate the overpressure toconfined explosion GAMEwere project aimed totoimprove theexplosion Multi-Energy method, reducing Foron gas parameters. explosion, the simplest methodparameters. to calculate the pressure rise is via the ene experiment, formulas were developed toboiling relate theatexplosion overpressure to explosion point the moment of its failure, onfiguration (low ignition energy and noand confinement): 3∙5 when determining the charge strength charge size. conservation Through designed ,# ..01 in confinement): an adiabatic system.[15] 3.2. +.0 𝐴𝐴2 Vented = 5/73 explosion [6] For an0.84 open∙ ,𝑉𝑉𝑉𝑉𝑉𝑉 3D configuration (low energy and no which results in rapidly expanding vapour 𝑃𝑃+ = ∙ - explosion 0 ∙ 𝑆𝑆,..0 ∙ 𝐷𝐷ignition [4] 64!$ mulas were developed to relate the overpressure to explosion parameters. ,# ..01 and flashing liquid. Overpressure and +.0 3.2. Vented explosion Various formulas exist to predict ..01 𝑉𝑉onfiguration ∙ -0 ∙ 𝑆𝑆,..0 ∙ 𝐷𝐷ignition [4],and 2 the peak overpres (low energy no confinement): # (low For a 2D configuration energy and confinement between parallel 2 where Avthe is the area ), C is venting para fragments are the usual consequence of such plates): where Av is vent vent area (m ), C (m is venting 𝑃𝑃 ∙ ignition 𝑆𝑆,..0 ∙ 𝐷𝐷+.0 [4] + = 0.84 ∙ ,𝑉𝑉𝑉𝑉𝑉𝑉 ∙ - 0 document on vapour explosion enclosure is 2 [16,17] designpre 1/2 in ), P is the maximum enclosure (m red Various formulas exist to predict the peak overpressure vented explosions. A widely ..01 For aenergy 2D configuration (low ignition energy explosions, although if the vessel contains parameter (barg ), As is internal surface area venting ,# (low ignition ation and confinement between parallel plates): ,# ...1 ..0 +.0 the minimum venting area required for a low-stren ..0 +.0 [18] a certain venting condition 𝑉𝑉 ∙ 0 ∙ 𝑆𝑆, For ∙ 𝐷𝐷 [4] a confinement 2D configuration and confinement between parallel plates): given 𝑃𝑃+and = 3.38 ∙ ,𝑉𝑉𝑉𝑉𝑉𝑉 ∙ 0(low ∙ignition 𝑆𝑆plates): ∙ 𝐷𝐷 energy [5] between flammable material, a fireball is another ofdetermine enclosure (mP2),redP68. maximum document on vapour explosion enclosure design is NFPA The following equation dete red is the - parallel , ,# ...1 3∙5 usually discussed consequence. venting pressure (barg). The equation can 3 ..0 +.0 the minimum venting area required for a low-strength enclosure (NFPA 68 Eq. 7.2.2).by the ...1 parameter C is determined 𝐴𝐴 = venting [6] 𝑉𝑉ation ∙ 0 (low∙ ignition 𝑆𝑆, P0∙ is 𝐷𝐷 energy andExplosion [5], confinement between parallel plates): 2Length 5/7 of Flame isThe 64!$ 𝑃𝑃+ =Maximum 3.38 ∙ ,𝑉𝑉𝑉𝑉𝑉𝑉 ∙ #0 Overpressure ∙ 𝑆𝑆,..0 ∙ 𝐷𝐷+.0 (bar), VBR [5]is Volume Blockage Ratio (-), Lp reversely be used to determine P given a 68 Eq. 7.2. red velocity, Mixture Su, less than 60 cm/s (NFPA - Obstacle Diameter (m), S 3∙5 Path (m), D is Average Burning Velocity of Flammable 3 L is Laminar Blast parameters of PVB explosion or certain venting condition. 𝐴𝐴 = [6] 2 ,# ...1 xplosion Overpressure (bar), VBR is Volume Blockage Ratio (-), L is Length of Flame 2 5/7 p where Av isofthe vent (m ), C is venting parame +.0 71 area Explosion Overpressure (bar), VBR64!$ isbeVolume Blockage Ratio (-), Lp is 𝑉𝑉 ∙ - 0 ∙ 𝑆𝑆,..0P(m/s). 𝐷𝐷Maximum [5] 0∙is 𝐶𝐶Length = 1.57 ×Flame ∙ (𝑆𝑆8 ). + 1.57 × 1079 ∙ (𝑆𝑆8 ) BLEVEsofcan calculated using the CCPS 2 10 erage Obstacle Diameter (m), SL is Laminar Burning Velocity Flammable Mixture ), P is the maximum venting pressu enclosure (m red Path (m), D is Average Obstacle Diameterguideline (m), SL[11]isA Laminar Burning Velocity of Flammable 2 1/2 , while efforts onarea modelling Theparameter ventingMixture parameter C),isAdetermined bysurface the where vent (m ),BLEVE C is venting (barg area of v is the s is internal 2.2.3. CFD method determine P given a certain venting condition. red xplosion Overpressure (bar), VBR is Volume Blockage Ratio (-), Lp is Length of Flame (m/s). 2 ), P is the maximum venting pressure (barg). The equation can reversely be enclosure (m P is Maximum Explosion Overpressure using CFD has also demonstrated feasibility. following equation for a fundamental burning red 0 erage ObstacleComputational Diameter (m), fluid SL is Laminar Burning Velocity ofofFlammable Mixture d 3.3. Dust explosion [12] dynamics (CFD) is a branch fluid mechanics that solves fluid flow problems by The venting parameter C is determined by the follo p (bar), VBR is Volume Blockage Ratio (-), L Other work includes Geng’s directional velocity, S , less than 60 cm/s (NFPA 68 Eq. determine P given a certain venting condition. red u 2.2.3. CFD method velocity, Su, less than 60 cm/s (NFPA 68 Eq. 7.2.2.1a numerical methods andDalgorithms. is aeffects widely used for gaseous7.2.2.1a). and vapour cloud is Length of Flame Path (m), is Average FLACS blast study fromCFD PVBsolver explosion. Dust explosions and gasforcloud explosionsburnin share The venting parameter C that isby determined by flow the following equation a fundamental uid dynamics (CFD) is a branch of fluid mechanics that solves fluid flow problems [10] [13] Computational fluid dynamics (CFD) is a branch of fluid mechanics solves fluid problems explosion. Other include AutoReaGas, EXSIM, OpenFOAM, etc., its own L is Laminar Obstacle Diameter (m), Ssolvers Burning PVB from cylindrical vessels needs to each having 71 by(𝑆𝑆 ). 79 (𝑆𝑆 ) od 𝐶𝐶combustion =7.2.2.1a). 1.57 × 10properties, ∙ 8 +and 1.57this × 10 ∙ could section velocity, Sand than 60 cm/s (NFPA 68 Eq. 8 + 0h u, less ds and algorithms. FLACS is a widely CFD solver for gaseous vapour cloud numerical methods andused algorithms. FLACS a widely used CFDnear solver Velocity of Flammable Mixture (m/s). beis treated carefully. In the field, for the gaseous and vapour cloud features and limitations. not found. ‘unconfined explosion’. However, as 71 er include AutoReaGas, EXSIM, OpenFOAM, etc., having its own [10] uidsolvers dynamics (CFD) is a branch of fluid mechanics that solves fluid problems 𝐶𝐶each = 1.57 ×flow 10 ∙ (𝑆𝑆8of).symmetry +by 1.57 each × 1079 ∙ (𝑆𝑆8 )its+own 0.0109 [7] overpressure along the axis (0 explosion. Other solvers include AutoReaGas, EXSIM, OpenFOAM, etc., having dustaccount, accumulated With FLACS CFD methods, factors effects can be thoroughly such indoor, it is usually discussed tations. ds and algorithms. islimitations. a widely usedcontrolling CFD solverexplosion for gaseous andhigher vapour cloud 2.2.3. CFD method degrees) remains for the cylindrical taken into features and 3.3. Dust explosion as fuel type,fluid configuration, containment vessel size, volume, of congestion andexplosion Computational dynamics is PVB thannature, for the spherical case. Aslevel distance 3.3. Dust er solvers include AutoReaGas, EXSIM,(CFD) OpenFOAM, etc., each having its own Dust may occur from agricultural products, carb ds, factors controlling explosion effects can besource thoroughly taken into account, such Dust explosions and cloud explosions share ma With CFD methods, factors controlling explosion effects can be thoroughly taken into account, such 3.3. Dust explosion a branch of fluid mechanics that solves increases, however, overpressure from Dust explosions and gasgas cloud explosions obstacles within vessel, ignition location and magnitude, venting, etc. The CFD approach tations. metals, plastic, wood, etc. Apart from NFPA 68 iguration, containment vessel nature, size, volume, level of congestion and combustion properties, when and this section could have as fuel configuration, containment vessel volume, level and fluid flowtype, problems by numerical methods the cylindrical PVBsize, drops to a value thatadvantage isof congestion share many characteristics it comes to should allow a higher accuracy for the explosion analysis; however, this is also often another widely used document Europe EN Dustnature, explosions and gas cloud explosions share many characteristics when itincomes toisigniti vessel, ignition source location and magnitude, venting, etc. The CFD approach not found. ‘unconfined explosion’. However, as mo ds, factors controlling explosion effects can be thoroughly taken into account, such and algorithms. FLACS is a widely used less than the sphere. Along the 45-degree ignition and combustion properties, and this obstacles within vessel, ignitioncost source and magnitude, venting, etc. The CFD approach complicated by the numerical and location other cost such as the efforts of tuning the model, model and combustion properties, and this section could have been placed in Section Error! Reference dust accumulated indoor, it inis Section usually discussed tog gher accuracy for the explosion analysis; however, advantage also often CFD solver for gaseous and vapour direction, overpressure is similar tothis thatadvantage for gained section could have been placed iguration, containment vessel nature, size, volume, level of congestion and should allow a higher accuracy for thethis explosion analysis; however, isinalso often parameter selection, grid sensitivities, etc., which canis‘unconfined offset the advantages some cases. not found. explosion’. However, as most often the dust explosion hazard is rela [10] cloud explosion. Other solvers the sphere, in CFD particular the farand field (R >1). the2 model, ‘unconfined explosion’. However, as most he numerical cost and other such asinclude thecost efforts tuning the model, model vessel, ignition source location and magnitude, venting, etc. The complicated bycost the numerical andof other cost such asapproach thein efforts tuning model and dust accumulated indoor, itof is usually discussed together with hazard ventedis explosion. Dust the may occur from agricultural products, carbona AutoReaGas, EXSIM, OpenFOAM, etc., each often dust explosion related 2.3. Pressure Vessel Burst explosion ion, grid sensitivities, etc., which can offset the advantages gained in some cases. gher accuracy parameter for the explosion analysis; however, this also often selection, grid sensitivities, etc.,advantage which canisoffset the advantages gained in some cases. metals, plastic, wood, etc. Apart from NFPA 68[18] f having its own features and limitations. 3.tuning Confined explosion to dust accumulatedmaterials, indoor, it is chemicals, usually Dust may occur from agricultural products, carbonaceous dyes, pigme he numerical cost and other cost such as the efforts of the model, model and another widely used document in Europe is EN 144 Unlike the high explosive vapour cloud3.1. explosion, which isexplosion a chemical explosion, the [18] Pressure sel Burst explosion Fully plastic, confined discussed together with vented explosion. 2.3. Pressure Vessel Burstor explosion metals, wood, etc. Apart from NFPA 68 for dust explosion enclosure design guida ion, grid sensitivities, etc., which can offset the advantages gained in some cases. Vessel (PVB) explosion is a mechanical explosion from purely physical reaction. It is usually With CFDBurst methods, factors controlling When an explosion occurs a cubicle another widely used within document in Europe is EN 14491.[19] The following equation determine xplosive or vapour cloud explosion, which istaken aLiquid chemical explosion, the Pressure Unlike the high explosive or vapour cloud explosion, which is a chemical explosion, themay Pressure discussed together with Boiling Expanding Vapour Explosion (BLEVE), although the different explosion effects can be thoroughly or containment-type structure, the peak Dust occur from agricultural products, sel Burst explosion B) explosion is ainto mechanical explosion physical reaction. It is Vessel Burstsuch (PVB) explosion ispurely a mechanical explosion purely reaction. Itcan is usually account, aspoint fuel type, configuration, pressures asdifferent well from as theusually impulse physical associated carbonaceous materials, chemicals, dyes, terminology can tofrom similar phenomena from perspective, more details be found er with Boiling Liquid Expanding Vapour Explosion (BLEVE), although the different discussed together with Boiling Liquid Expanding Vapour Explosion (BLEVE), although the different xplosive or vapour cloud explosion, which is a chemical explosion, the Pressure containment vessel nature, size, with theloss shock will be extremely pigments, gas metals, plastic, wood, etc. Apart in CCPS 2010 [11]. Here wevolume, see it level as a sudden of front containment of a pressure-liquefied existing congestion and obstacles within vessel, high will be amplified the confining from NFPA 68[18] for dust explosion enclosure point to similar phenomena from different perspective, more details beby terminology can point to similar phenomena from different perspective, more details can be found B) explosion is of aabove mechanical explosion from purely physical reaction. Itcan is of usually its normal atmospheric boiling point atand the moment itsfound failure, which results in rapidly location and magnitude, structure. The pressures reflected and design guidance, in CCPS 2010 [11]. Here weExplosion see liquid. it as of a(BLEVE), sudden loss ofand containment ofare a pressure-liquefied gas existing ].erHere seeignition itLiquid as asource sudden lossand of containment a pressure-liquefied gas existing with we Boiling Expanding Vapour although the different expanding vapour flashing Overpressure fragments the usual consequence ofanother widely used [19] venting, etc. The CFD approach should reinforced within the structure are termed document in Europe above its normal atmospheric boiling pointwhich at theresults moment ofbeitsfound failure, which results in rapidly is EN 14491. The atmospheric boiling point atfrom the moment its failure, in point to similar phenomena differentofperspective, more details canrapidly allow a higher accuracy for the explosion interior ‘shock pressure’. In addition, following equation determines the minimum vapour flashing liquid.of Overpressure and fragments r and liquid. fragments are the usual consequence of are the usual consequence of ]. Hereflashing we seeexpanding it as a Overpressure sudden lossand ofand containment a pressure-liquefied gas existing analysis; however, this advantage is also the effects of the high temperatures and venting area required for dust in a lowatmospheric boiling point at the moment of its failure,accumulation which results in rapidly often complicated by the numerical cost of gaseous products produced strength enclosure (NFPA 68 Eq. 8.2.2). The minimum venting area required for dust in a low-s r and flashing and liquid. fragments thetheusual consequence of in the otherOverpressure cost such as theand efforts of tuning are by chemical process involved equation can reversely be used to determine equation can reversely be used to determine Pred g the model, model and parameter selection, explosion will exert an additional ‘gas’ Pred given a certain venting condition. minimum venting area required for dust in a low-strength enclosure (NFPA 68 Eq. 8.2. grid sensitivities, etc., which can offset the pressure. For the design of most fully vented 6 9/> 79 >/9 equation can reversely be used to determine condition. red given 𝐴𝐴2+ = 1 ∙ P10 ∙ ,1 a+certain 1.54 ∙ 𝑃𝑃venting ∙A :;<; 0 ∙ 𝐾𝐾:; ∙ 𝑉𝑉 advantages gained in some cases. cubicle type structures, the effects of gas 2.3. Pressure Vessel Burst explosion

Unlike the high explosive or vapour cloud explosion, which is a chemical explosion, the Pressure Vessel Burst (PVB) explosion is a mechanical explosion from purely physical reaction. It is usually discussed together with

pressure may be neglected. 79

𝐴𝐴2+ = 1 ∙ 10

9/>

∙ ,1 + 1.54 ∙ 𝑃𝑃:;<; 0 ∙ 𝐾𝐾:; ∙ 𝑉𝑉 >/9 ∙ A 689" − 1 4!$

[8]

For confined gas explosion, the simplest where is the nominal static static burst pressure is the nominal burst pressure of t wherePstat Pstat method to calculate the pressure rise is ofdeflagration the vent (bar),index V is enclosure volumePmax (m3),is maximum p (bar-m/sec), static burst of the vent (bar), V is enclosure volume where Pstat is theinnominal via the energy conservation an adiabatic Kmaximum is the deflagration index (bar-m/sec), Pmax st pressure venting pressure (bar). maximum pressure the deflagration (bar), Pre system.[15]deflagration index (bar-m/sec), Pmaxisismaximum pressure of theofdeflagration (bar), phenomenological models(bar). of vented dust ex is the maximum venting pressure maximum venting pressure (bar). PAredfew

Boiling Liquid Expanding Vapour Explosion (BLEVE), although the different terminology can point to similar phenomena from different perspective, more details can be found in CCPS 2010 [11]. Here we see it as a sudden loss of containment of a pressure-liquefied

EFFEX from INERIS, to solve a set of coupled time d A few phenomenological models of vented dust explosions, ISOVEX fromGexco FM G pressuremodels as such a function of time. Various formulas exist to predict the peak Adeflagration few phenomenological ofas vented EFFEX from INERIS, to solve a set of coupled time dependent differential equations to [16,17] Explosion Simulation Code) to simulate dust explo overpressure in vented explosions. dust explosions, such as ISOVEX from FM deflagration pressure as a function of time. Gexcon has also developed a CFD code cal facilities. The code alsotobeen with FLA A widely accepted document on vapour Global and EFFEX fromhas INERIS, solvebundled a Simulation Code) explosions including explosions in comple explosionExplosion enclosure design is NFPA 68.[18]to simulate set ofdust coupled time dependent differential [10] facilities. The code hasthe also been bundled with FLACStheasdeflagration FLACS-DustEx. The following equation determines equations to obtain pressure 4.aBlast-structure interaction minimum venting area required for a lowas function of time. Gexcon has also

gas existing above its normal atmospheric

strength enclosure (NFPA 68 Eq. 7.2.2).

3.2. Vented explosion

4. Blast-structure interaction

developed a CFDmethod code called DESC (Dust 4.1. Empirical

Empirical formulas and charts are normally adopte www.hazardexonthenet.net the effects of accidental explosion.[3] Empirical formulas and charts are normally adopted when designing protective structu [Insert Figure 4 and caption:] the effects of accidental explosion.[3]

4.1. Empirical method

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maximummaximum venting pressure venting (bar). pressure (bar).

Riskand assessment 25 A few phenomenological models ofmodels ventedof dust explosions, such as ISOVEX FM Global and A few phenomenological vented dust explosions, such asfrom ISOVEX from FM Global EFFEX from INERIS, toINERIS, solve ato setsolve of coupled dependent differential equationsequations to obtain to theobtain the EFFEX from a set oftime coupled time dependent differential deflagration pressure as a function time. Gexcon also developed a CFD code called DESC (Dust deflagration pressure as aof function of time.has Gexcon has also developed a CFD code called DESC (Dust ExplosionExplosion Simulation Code)Code) to simulate including including explosionsexplosions in complex Simulation Code) to dust simulate dust explosions in industrial complex industrial Explosion Simulation to simulate dustexplosions [10] [10] facilities. The code including has also been bundled FLACS as FLACS-DustEx. explosions explosions in complex facilities. The code has also beenwith bundled with FLACS as FLACS-DustEx. industrial facilities. The code has also been bundled with FLACS as FLACS-DustEx.[10]

4. Blast-structure interaction 4. Blast-structure interaction 4. Blast-structure interaction 4.1. Empirical method method 4.1. Empirical 4.1. Empirical method Empirical and charts are normally Empirical Empirical formulasformulas and charts arecharts normally designing protectiveprotective structuresstructures to resist to resist formulas and are adopted normallywhen adopted when designing [3] [3] adopted whenof designing protective the effectsthe of effects accidental explosion. accidental explosion. structures to resist the effects of accidental

[Insert Figure 4 and [3] caption:] [Insert Figure caption:] explosion. Figure44and illustrates a graph

known as ‘Kingery-Bulmash curve’, usually Figure 1 illustrates a graph known asknown ‘Kingery-Bulmash curve’, usually used to determine pressure pressure Figure 1 illustrates a graph as ‘Kingery-Bulmash curve’, usually used to determine used to determine pressure and impulse and impulse loading on structures based on the scaled distance. The reflected pressure is usually is a usually a and impulse loading on structures based on the scaled distance. The reflected pressure loading on structures based on the scaled lot higherlot than incident which is awhich key question the blast design. The reflected higher thanpressure, incident pressure, is a key in question in structural the blast structural design. The reflected distance. The reflected pressure is usually a pressure can also be described in Eq.[9]. Reflected pressure corresponds to when blast pressure pressure can also be described in Eq.[9]. Reflected pressure corresponds to when blast pressure lot higher than incident pressure, which is a front hits front objecthits andobject compression occurs. Onoccurs. the other hand, when onewhen region is compressed, there and compression On the other hand, one region is compressed, there key question in the blast structural design. are other are regions which arewhich decompressed. This region features negative pressure and is known as other regions are decompressed. This region features negative pressure and is known as The reflected pressure can also be described rarefraction wave, which can be another concern to some structures depending on the mitigation rarefraction wave, which can be another concern to some structures depending on the mitigation in Eq. [9]. Reflected pressure corresponds objective.objective. to when blast pressure front hits object and compression occurs. On the other hand, when one region is compressed, there are

[Insert Figure and caption:] [Insert Figure 4 and caption:] other 4 regions which are decompressed.

This region features negative pressure andshock spherical wave of TNT charges from free-air bursts Figure 1 –Figure Parameters of positive of 1 – Parameters ofphase positive phase of shock spherical wave of TNT charges from free-air bursts is known as rarefraction wave, which can [3] [3] be another concern to some structures depending on the mitigation objective. 96 A06

: 96 A06 𝑃𝑃? = 2𝑃𝑃:@𝑃𝑃?6 3: =A06 2𝑃𝑃:@ 3: : 3:

63: A06:

[9]

where P0 is the ambient pressure, Pso is the incident pressure, and Pr is the reflected

is the ambient Pso is the incident and Pr is the pressure. pressure. where P0 where ambient pressure, Pso is thepressure, incident pressure, andreflected Pr is the reflected P0 is thepressure, pressure.

Figure 4 – Parameters of positive phase of shock spherical wave of TNT charges from free-air bursts [3]

4.2. CFD method 4.2. CFD method

4.2. CFD method

CFD modelling is oftenisalso used to assist blast structural design and weapon mitigation. CFD modelling is often also to assist blast structural design andeffects weapon effects mitigation. CFD modelling often also used toused assist [20, 21] There areThere a variety of CFD tools for HE blast simulations, among them there are ProSAir from[20, 21] from blast structural design and weapon effects are a variety of CFD tools for HE blast simulations, among them there are ProSAir [22] [23] [24] [22] [23] [24] mitigation. There are a variety of CFD tools Cranfield Cranfield University, BWTI from EAGLE EAGLE from QinetiQ, from Synthetik University, BWTIBakerRisk, from BakerRisk, fromBlastFOAM QinetiQ, BlastFOAM from Synthetik for HEetc. blast simulations, among them there Technologies, Technologies, etc. [20, 21] are ProSAir from Cranfield University, BWTI[22] from BakerRisk, EAGLE[23] from QinetiQ, BlastFOAM[24] from Synthetik Technologies, etc. The equations governing the HE blast CFD solvers take a different form from those governing the VCE CFD solvers, in that shockwaves are a consequence of the hyperbolicity of the systems of Euler equations governing inviscid flows, hence the HE blast solvers adopt Euler numerical scheme typically for high explosive purpose. The Euler numerical scheme for the hyperbolicity equations has been proven to be more efficient than solving traditional CFD governing equation, as mixing process

Figure 5 – CFD modelling of blast wave propagating against buildings (ProSAir[8,9])

www.hazardexonthenet.net

26 Risk assessment is not considered important for this type of explosion and therefore diffusion process is

5. Conclusion A review of existing models for predicting

engineer knows what they are doing and the applicability range of the model, therefore

not required to be modelled. For a tailored package such as ProSAir, an additional feature is the 1D and 2D phase modelling results can be mapped to 3D configuration before the blast wave hit relevant obstacles, so to greatly enhance the efficiency of

different explosion scenarios has been performed. The aim is to provide guidance and point to at least one representative model for usage at different types of explosion scenario. In most engineering applications, a simple empirical model is

applying the correct theoretical model is the key to the success of the project. In some cases, detailed analysis may be required, which is when computationally expensive CFD methods are applied. In this case, more expertise knowledge is usually

modelling process.

sufficient for the purpose as long as the

required.

Norway, 2012.

22. Geng, J.H., Thomas, K., Simulation

References 1. Karlos, V., Solomos, G., Calculation of Blast Loads for Application to Structural

11. Guidelines for Evaluating the

and Application of Blast Wave-Target

Components, JRC 87200, EUR 26456

Characteristics of Vapor Cloud

Interaction, Baker Engineering and Risk

EN, 2013.

Explosions, Flash Fires, and BLEVEs,

Consultants, LPS 2007.

2. Explosive weapon effects – final report, GICHD, Geneva, February 2017. 3. Unified Facilities Criteria (2008), “UFC 3-340-02 Structures to Resist the Effects

ISBN 978-0-470-93814-0, Centre for

23. Cullis, I.G., etc., 2016, Simulating

Chemical Process Safety of the American

geometrically complex blast scenarios,

Institute of Chemical Engineers, 2010.

Defence Technology, 12, 134-146.

12. Hutama, A., “Simulation of BLEVEs in

24. Heylmun, J., Vonk, P., Brewer, T.,

of Accidental Explosions”, U.S. Army

Unconfined and Confined Areas Using

blastFoam Theory and User Guide

Corps of Engineers, Naval Facilities

FLACS”, Universitetet I Stavanger Master

Version 2.0.0, 2019.

Engineering Command, Air Force Civil

Thesis, 2017.

Engineer Support Agency. 4. Structures to resist the effects of

13. Geng, J.H., “Pressure Vessels Burst Directional Blast Effects”, Spring Meeting

accidental explosions, Army TM 5-1300

& 5th Global Congress on Process

/ Navy Navfac P-397 / Air Force AFR 88-

Safety, 2009.

22, USA, 1990. 5. Mercx, W.P., Van der Berg, A.C.,

14. Hansen, O.R., Davis, S., Gavelli, F., Middha, P., “Onshore Explosion Studies

Hayhurst, C.J., Robertson, C.J., Moran,

– Benefits of CFD-Modelling”, Chemical

K.C., 2000, Developments in vapour

Engineering Transactions, 31, 2013.

cloud explosion blast modelling, Journal of Hazardous Materials, 71, 301-319. 6. Van der Berg, A.C., 1985, The Multi-

15. Lautkaski, R., Pressure Rise in Confined Gas Explosions, VTT, 2005. 16. Blanchard, R., etc., “Sizing of Explosion

Energy Method: A framework for vapour

Pressure Relief using the Efflux Function”,

cloud explosion blast prediction, Journal

Chemical Engineering Transactions, 48,

of Hazardous Materials, 12, 1-10.

2016.

7. TNO “Yellow Book”, CPR 14E, methods

17. Fakandu, B.M., “Gas Explosion Venting:

for the Calculation of Physical Effects,

External Explosion Turbulent Flame

3rd Edition, 1997.

Speeds that Control the Overpressure”,

8. TNO Research Project 202/1998. GAME: Development of Guidance for the Application of the Multi-Energy Method, TNO, the Netherlands. 9. TNO Report 1998-C53. Application of correlations to quantify the source strength of vapour cloud explosions in realistic situations. Final report for the project: ‘GAMES’, TNO, the Netherlands. 10. GexCon AS, “FLACS v10.0 User’s Manual”, GexCon Internal Report,

www.hazardex-event.co.uk

Chemical Engineering Transactions, 53, 2016. 18. NFPA 68, Standard on Explosion Protection by Deflagration Venting, 2007 Edition. 19. UNI EN 14491, Dust Explosion Venting Protective Systems, 2012. 20. ProSAir 2018.4 User Guide. 21. A Computational Tool for Airblast Calculations, Air3d version 9 user’s guide, Feb 2006.

About the authors Zhixin Hu is a Fire and Explosion Consultant at Patrick Mann & Associates. He has over fifteen years of experience in fire and explosion research, consulting and technical development. He did his PhD at University of Maryland on fire and explosion modelling and has been involved in several research programs on combustion related topics since then. He is currently with Patrick Mann & Associates, working as a safety and risk consultant focusing on fire and explosion hazards mitigation. Email: zhu@pmaaltd.co.uk Patrick Mann, Director at Patrick Mann & Associates, is a chartered engineer, a member of the Institute of Risk Management (IRM) and a Principal Member of the Register Security Engineers and Specialists (RSES). He has 30 years of experience of working within the areas of natural and man-made hazards, including blast, fire and security hazards, across numerous industries including the insurance, defence, nuclear, oil & gas and commercial sectors. Email: pmann@pmaaltd.co.uk

26 Intrinsic safety

Data Files/Buyers Guide 27

Explosion Proof ATEX Zone 2 iPhone 11 (Pro Max) – Increased Intrinsically Safe Apple Smartphone

Institute of Measurement and Control – Ex Special Interest Group

All new from Atexxo Manufacturing, the Netherlands. The Apple iPhone 11 (Pro Max) now suitable for use in hazardous locations. The explosion proof iPhones are originally manufactured by Apple than converted and certified according to the ATEX directives by Atexxo Manufacturing. makes Ex-SIG the TheThis InstMC won the Best User ATEX iPhones suited for safe use in gas /vapor zone 2 hazardous areas. (zone 22 on request) Sim-card can be installed by the end-userApplication themselves. award at the Hazardex 2020

Features: • Explosion safety level: II 3G ; Ex ec ic IIC T4 Gc • Charger 110-240VAC • Charger engagement at a50/60Hz professional level.

Awards for Excellence, which took Compliance with ATEX / EX regulations is achieved by modification of the casing together with the intrinsically safe electrical circuit, which makes the Hazardex Conference & place at the phones suitable for safe use in hazardous locations. All features of the original in Harrogate, UK on February product are preserved. Even the face scanner can be usedExhibition safely at hazardous locations. 26. The Hazardex awards are designed

The qualifi cation is based on peer review in Atexxo Manufacturing is market leading in the field of usermanner friendly and to install explosion proof the same as easy IEng/CEng, with a similar equipment. application process, and is overseen by the For more information or custom solutions Institute’s Professional Registration Committee. please contact our sales department or visit

The ATEX iPhone 11 (pro or pro max) comes with a black finish and is to case recognise excellence in the hazardous available in 64, 128 or 256gb versions. Beside safe use as a phone all versions he Institute of Measurement and area sector and has become the are excellent for use as intrinsically safe camera or RFID scanner.

Applications: Hazardous material storage, petro chemical plants and oil and gas extraction sites.

our website www.atexxo.com

Control Explosive Atmospheres Special Interest Group (Ex-SIG) aims to promote good practice and support continuing professional development in the Ex discipline through a range of activities

The Institute has a range of Special Interest benchmark for those supplying products, Groups, which members of the Institute can join services and systems. More details can be for free as a membership benefit, including: The EVL series lighting fixtures innovated and enhanced found at www.hazardex-event.co.uk. • Explosive Atmospheres The EVL series of LED lighting fixtures, launched • Functional Safety by Cortem Group in 2015 and available in four sizes, The Institute of Measurement andhas Control also and enhanced • Flow to offer an even been innovated

and publications. The group is producing a series of briefing notes to help inform members on key topics. These are first released to members of the SIG before being made publicly available. An example

safer and more performing• product. offers a professional level qualification in Ex Cybersecurity • New “Ex op is” certificate matters: ‘Registered Explosive Atmospheres • Digital Transformation • New multi-LED plate • Newmembers range of the ambient temperature to -40°C + 60°C and temperature Engineer’. This is available to InstMC • Measurement classes colder (T5) with gas group IIB+H2 and IIC who are registered with the Engineering Council • Standards • New supply voltages range from 12 to 277V as IEng/CEng, and who can demonstrate • New powers available start from 20W up to 220W, with steps of 10W and 20W

of one such briefing note is included on the page opposite.

• Different lumen outputs ranging from amay minimum of 1,700lm to Institute’s a maximum appropriate ‘competence & commitment’ Further details be found at the of 21,000lm in the Ex discipline, together with•ongoing www.instmc.org Transportable versionwebsite with electronic driver and a model specifically designed for

Do Do YOU YOU use use Twitter? Twitter? Follow Data files

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EEMUA Publication 186 - A Practitioner’s Handbook for potentially explosive atmospheres Data files Control Panels EEMUA 186 offers guidance for safe installation, inspection and maintenance work in potentially explosive atmospheres. EEMUA 186 focuses on ignition caused by electrical and mechanical sources and interprets relevantCONTROL parts AUTOMATION & TECHNOLOGY of international and European standards, directives and regulations. Your Total Solutions Provider EEMUA 186 covers application design engineering and in design and custom build of a wide range of duties of the Responsible Specialists Person (IEC standards). It includes Areahazardous Equipmentareas in separate chapters on fuel Hazardous filling stations, water and waste water, and mechanical ignition sources. OEM for and Technor Marechal Closely associated withRegistered the CompEx® training competency assessment scheme, this easily navigable resource is available to purchase at: Southampton https://www.eemua.org/Products/Publications/Print/EEMUASO40 9AH Publication-186.aspx +44 (0) 2380 665544 enquiries@trant.co.uk trant.co.uk

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