Gas Con Gas Consultants
SAFETY with GASES
Delegates’ Guide
Contents Introduction
3
Compressed Gas Cylinders
4
Confined Spaces
7
Inert cryogens and liquefied nitrogen
11
Fuel gases
13
Primary pressure equipment
14
Welding Fumes Safety Alert
21
Manual Handling
23
Copyright exists on all Gas-Con publications. No part of this guide may be reproduced without prior consent, in writing, from Gas-Con Ltd Š Gas-Con Ltd 2014
2
Delegate’s Guide Introduction Gases and gas cylinders are inherently safe. The gas industry enjoys a very low incident rate. This is, in part, due to the nature of the gas cylinders used and the safety measures put in place to prevent accidents. Every day, thousands of gas cylinders are used in a wide variety of industries, from the factory to the home, and for a multitude of diverse applications. Many of these gases are stored and used at high pressure without incident. This guide is based on industry experience in the safe use and handling of gas cylinders and gas-related equipment. It is not possible to cover all aspects of gas safety in one booklet; however, from reading this booklet, you will have a better understanding of the hazards associated with the use of compressed gases - thus providing you with a better knowledge to undertake Risk Assessments. The information in this book is based on the current legislation, Codes of Practice and Guidance Notes. It is a requirement for all users of gases to have a understanding of the properties of the gases they use, as well as having a working knowledge of the equipment. Any gases and equipment used on site should have a corresponding Safety Data Sheet and a set of operating instructions to ensure the safety of the user. Safety Data Sheets are freely available from your gas supplier or downloaded free from the Internet. Equipment operating instructions are available from the equipment manufacturer or supplier. Safety is everyone’s responsibility. Through training and diligence we can seek to improve your safety and that of those around you. NOTE: All instructions and procedures are generically based and must only be used as a guide. It is important to fully understand the gases and equipment used prior to any procedure involving gases or associated equipment. Gas-Con Gas Consultants Ltd accepts no liability or responsibility in connection with any misuse of the information contained in this guide. 3
Compressed Gas Cylinders Compressed gas cylinders are inherently safe, with the design and construction in accordance with EU standards or ISO standards and specifications. The standards specify the material of construction, the method of construction, the test pressures the cylinders are subjected too, and the maximum allowable fill pressure. The standards also define the test period and procedure that all compressed gas cylinders are subject too.
Design and Type of construction The type of gas cylinder used is dependent on the gas and its pressure. Typically, high-pressure, compressed gas cylinders are a solid-drawn steel construction whilst low pressure cylinders, e.g. Propane, are a welded steel construction. Recently there has been an increase in the use of carbon-wrapped cylinders, due to the weight saving capabilities and, on occasions, Aluminium has also been used for lower pressure gases, e.g. CO2.
Cylinder valves There are a number of cylinder valve outlet fittings used, which vary depending on the gas inside the cylinder. British Standards offers us a wide variety of BS341-type valve outlets - examples of which are BS341 No 3 for inerts and oxygen, and BS341 No 4 for flammable gases. Your gas supplier will confirm which valve type is used for which gas, and it is imperative to know the correct gas valve in order to use the appropriate type of gas fitting on the primary gas equipment. Apart from the outlet fitting, the gas companies will also offer a choice of two main types of valve opening/closing mechanism. One type will have the outlet fitting in the top of the valve and use a spindle key to open and close the valve. The spindle key must always be left in the cylinder when in use. The other is a handwheel-operated valve that has the gas outlet on the side. These will typically employ a cylinder guard to protect the cylinder valve from damage. It is important to note that all gas cylinders MUST be opened slowly. If the cylinder valve is tight to turn, contact the gas supplier for a replacement.
4
NOTE: It is vital to ensure that the cylinder valve is clean prior to connecting the primary gas equipment. Use only a lint-free cloth to clean the valve before connecting the gas equipment. It was once common practice to undertake a valve clearance procedure by venting a small amount of the gas prior to connecting the equipment. In most cases this is NOT permissible and is now frowned upon; however, there is one gas for which this practice is accepted: Oxygen, when under high pressure, may cause ignition if there is debris in the cylinder valve. If it is necessary to carry out a valve clearance procedure you MUST follow the safety precautions. 1. 2. 3. 4. 5. 6. 7. 8.
Ensure a safe operating procedure is in place Ensure all operators have been trained in the standard operating procedures Wear PPE; the minimum being eye protection, gloves and ear defenders Conduct the procedure outdoors, or in a well ventilated area. Secure the cylinder in an upright position Ensure there is no risk of ignition from other sources Stand clear of the valve outlet Open the cylinder valve no more than Âź turn of the spindle key or handwheel and then close immediately.
Cylinder testing All industry-used compressed-gas cylinders are subject to inspection. The cylinders undergo a series of tests to ensure they are safe and suitable for use, then re marked and fitted with a new valve before being returned to service in the gas company. The “test due� dates are denoted by a series of 18 coloured shapes around the neck of the cylinder valve. The colour and shape will identify which year that particular cylinder needs to be retested. These are identified by the gas company and removed from service until the tests are complete.
5
Cylinder colour coding Colour classification by hazard property Bright green
Inert
Red
Flammable
Colour classification by specific gas Maroon
Acetylene
White
Oxygen
Dark green
Argon
Black
Nitrogen
Grey
Carbon dioxide
Brown
Helium
All gas companies must colour the gas cylinders in accordance with the current ISO standards. Each group of gases will have a specific colour to identify the gases: green for inert, red for flammable and yellow for toxic/corrosive. Apart from Acetylene, which is painted maroon all over, it is only the shoulder of the gas cylinder that needs to be painted. Contact your gas supplier for a colour chart.
Labelling and identification Gas cylinders are labelled with the gas type and fill pressure, UN along with its specific ISO 100 warning/Class diamond. 1 L There may be several Class 5 1 2 diamonds on the one label; DANGER EC 200-816-9 this indicates that the gas has multiple associated hazards. Usually these are part of a label around the neck/collar of the gas cylinder. Never use a gas AC ET
YL EN E, D
ISS
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Refer to SDS for further information
6
cylinder that is missing the gas label. Propane is labelled differently, with the gas name painted on the side; it is labelled in this manner because propane is also used by the public or for home use.
Pressure relief devices Typically, compressed gas cylinders do not have any form of pressure relief built in; however, certain gases do - such as low pressure liquefied gases, e.g. Propane and CO2. These consist of three main types: Pressure relief valve: Bursting disc: Fusible plug:
Re-sets once the pressure has dropped below a pre-set relief pressure. A pressure-sensitive device which will release the full contents. A temperature-sensitive device which will release the full contents.
Examples: ● Propane has a pressure relief device set at approximately 26bar. ● CO2 has a bursting disc on the cylinder valve which will vent at approximately 180bar.
Confined Spaces BCGA (British Compressed Gases Association) guidance note GN9 details the procedure for a Confined Spaces Risk Assessment. When using gases in any pipe, pit, sewer, trench, tank, confined space or any other location which, by virtue of its enclosed nature, constitutes a confined space, it is necessary to undertake a “Confined Spaces Risk Assessment” It need not be complicated but you must assume a worst-case scenario when considering the volume of gas that could escape or leak into that area. The gaseous volume of your respective compressed gas cylinder or liquefied gas tank will depend on the size of the cylinder or vessel; ask your gas supplier for this information. Once you have established the volume of gas, you must determine the free volume of air space by calculating the volume of the area minus the objects in that area. A simple calculation will determine the risk of saturation of the area by the gas or gases that are being used, piped or stored in that area. If in doubt, seek advice.
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References to a Confined Space:- (Legislation and/or guidance covering the control of gases in a Confined Space include:) BCGA GN9 BCGA TIS30 BCGA GN11 HSE L101 HSE INDG 258 It is generally recognised that air breath consists of nine gases - three of which make up the majority, with the remainder only amounting to 0.11%. The two largest, by volume, are nitrogen at 78.03% and oxygen at 20.93%. It is essential for life to have our oxygen level at the required 20.93% - oxygen enrichment will cause fires to burn more intensely. On the other hand, if our oxygen depletes, we suffer - as it affects us and our ability to stay alive.
Call service on: 07706 592814 Open doors to ventilate
In general, oxygen deficiency leads to a loss of mental alertness and a distortion of judgement and performance. THIS HAPPENS WITHIN A RELATIVELY SHORT TIME, WITHOUT THE PERSON'S KNOWLEDGE AND WITHOUT PRIOR WARNING. Oxygen levels depleted to the following percentages will produce the stated indicators: • • • • •
21 -14% - Increasing pulse rate, tiredness 14 - 11% - Physical movement and intellectual performance becomes difficult, unaware of surroundings and/or alarms. 11 - 8% - as above + Possibility of headaches, dizziness and fainting after a fairly short period of time 8 - 6% - Fainting within a few minutes, resuscitation possible if carried out immediately 6 - 0% - Fainting almost immediate, death or severe brain damage
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It can take as little as two or three breaths in an oxygen-depleted environment to render someone unconscious, and death will follow in a matter of minutes. If operators are working in a confined space or poorly ventilated area, then it is recommended to carry out a Confined Spaces Risk Assessment. It is strongly recommended to consider the use of portable oxygen depletion or specific gas monitors and adopt a “buddy” system. It is essential that all operators should be trained in emergency procedures. Inert gases Inert gases typically do not react with any other materials or substances, and they are used in industry to displace oxygen in order to maintain an inert atmosphere - e.g. an argon-filled tank when welding titanium. Industrial inert gases would be nitrogen, argon, helium and carbon dioxide, all of which can cause an oxygen-deficient atmosphere and, therefore, constitute a risk to life through asphyxiation. When working with inert gases, it is advisable to be in a well-ventilated area and to always leak-test all joints in the system. Any gas released into the area will quickly displace the air, thereby reducing the oxygen levels - leading to a potentially oxygendeficient atmosphere. Follow the guidelines above for “Confined Spaces” Oxygen and oxidising gases Oxygen and oxidising gases are not classed as flammable gases; however, they do support combustion and, if in an oxygen-enriched atmosphere, they will accelerate and promote combustion of materials that typically do not burn in a normal atmosphere. It is vital that all oxygen and oxidising gases are stored, and used, away from any source of ignition or energy that would not normally be considered sufficient to cause ignition. Smoking nearby is prohibited - as is the storage of oils and oil-based products. Suitable warning signs must be displayed. High-pressure oxygen reacts violently with oils, grease, tar and other oil based products. This includes soaps, hand creams, barrier creams and PTFE thread tape. When under high pressure, the oxygen reacts with the oily substance and ignites immediately, causing devastating consequences to equipment, processes and people. Never attempt to use PTFE thread tape on a cylinder fitting: if the metal to metal seal is leaking, you should follow the Standard Operating Procedure for checking and reconnecting gas cylinders; otherwise consider the equipment or cylinder valve to be defective.
9
When using oxygen equipment, it is imperative to use an oxygen-approved leak detection fluid when connecting any joint. Traditional soapy water contains oil and will react with high pressure oxygen, so use only a detergent-based fluid. e.g. Teepol Hazards associated with oxidants Oxygen enrichment from leaking equipment will create an oxygen-enriched atmosphere. Oils and oil-based materials violently react. Never use equipment that is not specified “for oxygen use” as this may not have been cleaned to “oil-free” status. Never use PTFE thread tape on any gas joints. Never purge a system with oxygen, as it may react with oils in the line. Always ensure equipment is free from dust, dirt and debris before connecting to oxygen. Always open the cylinder slowly to avoid shocking the equipment. Carbon Dioxide. Carbon Dioxide (CO2) is a compressed, liquefied gas, stored at 50.9bar in the gas cylinder. Under pressure it changes from a gaseous phase to the liquid phase. CO2 is filled and sold by weight, not pressure; it is, therefore, important to note that any primary pressure regulator’s pressure gauge will always remain at a constant 50.9 bar (at 15oC) and must not be used as an indication of the contents of the cylinder. CO2 is colourless, odourless, heavier than air and is an asphyxiate if sufficient quantity is released into a confined space. CO2 gas cylinders are fitted with a bursting disc-type pressure-relief device which operates when the pressure in the gas cylinders exceeds the pre-set level of approximately 180bar, and will evacuate the entire contents of the gas cylinder into the surrounding area. Under the EU directive 98-24-EC and 89-391-EEC, CO2 has a defined exposure limit. The effects of CO2 on a typical human being is set out below; please consider that, for those with a lung deficiency or suffering from asthma, the effects may occur sooner. The UK has assigned a 'workplace exposure limit' of 0.5% over 8 hours and 1.5% for 10 minutes. The following indicates the symptoms exhibited at various concentrations of CO2 present in the atmosphere: •
1% - Slight, and un-noticeable, increase in breathing rate.
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•
•
• •
•
2% - Breathing becomes deeper, rate increases to 50% above normal. Prolonged exposure (several hours) may cause headache and a feeling of exhaustion. 3% - Breathing becomes laboured, rate increases to 100% normal. Hearing ability reduced, headache experienced with increase in blood pressure and pulse rate. 4 - 5% - Symptoms as above, with signs of intoxication after 30 minutes exposure and a slight choking feeling. 5 - 10% - Characteristic pungent smell noticeable. Breathing very laboured, leading to physical exhaustion. Headache, visual disturbance, ringing in the ears, confusion probably leading to loss of consciousness within minutes. 10 - 100% - Loss of consciousness more rapid, with risk of death from respiratory failure. Hazard to life increased with concentration, even if there is no oxygen depletion. Concentrations of 20-30% and above are immediately hazardous to life.
Inert cryogens and liquefied nitrogen
G R A
C
O
2
O
N
EN O
XY G
M EL IU H
G O IT R N
GAS PROPERTIES (Stated temperature values are at mean sea level/Ordnance Datum)
EN
There are several liquefied cryogens, with nitrogen probably the most common. Liquid nitrogen can be stored, transported and used in a variety of vessel types such as cryogenic tanks, open dewars and dewar flasks. Each container has unique filling procedures and these must be followed to prevent spillages and accidents. Use only approved vessels for storage and transportation of liquefied gases. Always follow Standard Operating Procedures when decanting liquefied gases splashing of the liquid onto exposed skin can result in cold burns, frost bite and hypothermia. Operators must wear suitable PPE designed for use with cryogens - standard
Colour of gas
None
None
None
None
None
Normal boiling point at 15oc*
-196oc
-269oc
-183oc
-78.5oco
-186oc
Ratio of liquid to gas at 1.013bar at 15oc*
680.4
734.4
843.6
845
825.5
Specific gravity to air (air=1)
0.967
0.138
1.105
1.48
1.38
28
4
32
44
40
78.08
0.00052
20.946
0.04
0.934
Molecular weight g/mol Concentration in air vol% * ambient temperature
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“rigger�-type gloves will not offer suitable protection against the extreme low temperatures. Extreme caution must be used when handling and moving liquefied gas vessels. Never travel in a lift with any vessel, and you must ensure that you have control over the lifts to avoid anyone else entering on another level whilst the vessel is in transit. When moving a mobile cryogen tank, ensure that the pressure is no greater than 50% of the set relief pressure; if it requires venting, this must be done in a well-ventilated area - ensure all the valves are closed and the route is clear and free from objects that could block your path. A risk assessment must be carried out each time, prior to the vessels being moved. When possible, locate vessels outside; if this is not possible, ensure the vessels are in a well-ventilated area. It is recommended, if located indoors, that a Confined Spaces Risk Assessment is completed to identify the risks and to ensure that gas monitoring devices are installed. Hazards of liquid cryogens Cryogenic liquids are extremely cold and can freeze human tissue immediately - inflicting irreparable damage. Breathing of the cold vapours can provoke frostbite to the nose and mouth; this is often recognised by localised pain and a discolouration to the soft tissue. Never touch any un-insulated pipes or vessels with exposed skin as this can cause the skin to stick to the frozen surface resulting in soft tissue damage. If, at any point, your clothing is splashed by liquid cryogens and causes it to stick to the skin, NEVER try to pull the clothing away from the skin until it has completely thawed as this will result in soft tissue damage. Cold burns and frostbite should receive medical attention as soon as possible; immediate first aid can be given by running tepid water over the affected area to prevent further soft tissue damage. Never use warm or hot water, use tepid water only.
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Fuel gases There are many flammable gases, but in this section we are covering the top three flammable fuel gases : acetylene, propane and hydrogen only. Acetylene is highly flammable, and, when used in conjunction with oxygen, it is a very effective solution for cutting and welding applications. Acetylene or C2H2 , using the chemical formula, has a wide flammability range of 2.2% to 82% saturation in air; this means that it doesn’t need much to ignite it, and doesn’t require a great deal of oxygen in which to burn. Cylinders are maroon in colour and fitted with a left hand BS341 No4 connection. The cylinder is filled to a pressure or 15.5 bar at 15oC. The gas is colourless and has a distinctive smell of garlic. Acetylene is produced from a reaction between calcium carbide and water. Due to its explosive properties, acetylene is stored by means of dissolving the gas in acetone which is contained in a porous mass within the gas cylinder. If the cylinder has been laid down, it must not be used for a minimum of 1 hour after being placed upright. It is highly sensitive to external heat sources, and reacts with copper and silver to form acetylides which are highly sensitive to shock and, subsequently, become explosive. Only use equipment designed for use with acetylene, as other equipment may contain higher than permissible levels of copper or silver. When acetylene is subjected to excess heat, it can cause the molecular bond to break; this is known as thermal decomposition. The gas is extremely unstable and the slightest shock or movement will cause the cylinder to explode. If you believe heat may have affected the cylinder, check the temperature of the cylinder using the back of your hand; if you feel any heat, do not move the cylinder but contact the emergency services. Propane, a by-product of the petrochemical industry, comes under the family of Liquid Petroleum Gases(LPG). It is used in industry in conjunction with oxygen for cutting and heating, and is also used in domestic markets as an alternative to mains gas, as well as for leisure items such as BBQ’s and patio heaters. It is naturally colourless and odourless; however, due to its domestic usage, gas companies add a stench of rotting fish to aid with detection of leaks. Propane is stored at low pressure, approximately 7.5bar, in cylinders of welded construction, red in colour and also fitted with a BS341 No4 left hand connection. Propane is highly flammable, with a flammability range of 25% to 10% saturation in air; once again, not a lot is required for ignition but, unlike acetylene, it is hungry for oxygen, and greater than 10% saturation will not have sufficient oxygen to support combustion. It must only be used in a well-ventilated area and, as propane is 1½ 13
times heavier than air, it must not be kept or used over drains as it can enter the drain system and travel through the pipes. The gas is stored as a liquid under pressure and, when required, the operator opens the cylinder valve releasing the top pressure of gas in the cylinder. This causes the liquid to “boil off� more gas into the vapour space. Once the valve is closed, the pressure will build to approximately 7bar and then stabilise, preventing further gas to boil off. Propane must be transported, stored and used in an upright position unless the cylinder is of a specific design to be used on its side, such as for fork lift trucks; in this case, the cylinder is marked with an arrow indicating the correct orientation of the gas cylinder when in use. Never exceed the maximum propane take-off rate, as this can cause the flame to extinguish on the appliance in use and, as such, leak gas into the area. If greater takeoff rates are required, use multiple cylinders manifolded together to attain the necessary flow. Hydrogen, produced by steam reforming carbons, is highly flammable, with a flammability range of 4% to 75% saturation in air. It is odourless, colourless and burns clean - making it extremely difficult to see the flame. It also has a negative Joules Thompson effect, making it difficult to feel the ambient heat if it is burning. It is lighter than air, and any escape of gas can result in pockets forming in the roof space above - therefore it should be ensured that all lighting is intrinsically safe in order to avoid potential risks of combustion through electrical sparks. Never perform a valve clearance procedure on a hydrogen gas cylinder as this action can cause immediate combustion of the gas which is very difficult to extinguish; the only method is to shut the supply. Hydrogen will cause certain grades of steel to become brittle and it is essential to ensure all equipment used with hydrogen is suitable and approved for use.
Primary pressure equipment Pressure regulators As gas contained in cylinders can contain up to 300bar of pressure, the primary pressure gas equipment is the first safety device in ensuring that pressure is contained and controlled when in use. Primary gas management equipment can come in many forms: wall-mounted manifold, single stage cylinder-mounted regulator and two-stage - also called multi-stage cylinder-mounted regulators.
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All primary gas equipment is subject to regular inspections and testing and, each time you use a piece of gas equipment, it is vital to give the item a visual check prior to use to ensure that the item is suitable for use and not broken or faulty in any way. Refer to Regulator Inspections section in this guide. The BCGA (British Compressed Gases Association) produces a wide range of documents relating to compressed gases, one of which, CP7, is a Code of Practice detailing the safest and best operating practices for gas equipment. The document outlines the recommended time periods for the service or replacement of gas equipment. It recommends that primary gas regulators be serviced or exchanged every 5 years from date of manufacture; this is regardless of how often it has been used and whether or not the regulator in question has been sat on a shelf. The 5 year period starts from its manufactured date and not when it first came into use. Some manufactures will detail the exchange date clearly, some show the manufactured date and some manufacturers use a code to determine when it was manufactured or when it is due for exchange. For full details of gas equipment markings please refer to BCGA TIS 18
Importance of single-gas service Although several of the BS341 gas fittings are widely used for different gases, e.g. BS341-3 for Inert and Oxygen, and BS341-4 used for flammable gases including Hydrogen and Acetylene, it is vitally important that gas equipment is ordered specifically for single-gas service only and NEVER swapped from one gas type to another. If the requirement is, for example, Oxygen, the gas equipment MUST be oil-free and any equipment specified for Oxygen will be free from oil and grease; however, this cannot be guaranteed if the regulator has seen service with another gas using the same BS -3 fitting. (Oil contamination can cause at catastrophic reaction when in contact with compressed Oxygen.) The simple rule is to only use the regulator on the gas it is meant for.
Single-Stage Regulators In the single-stage regulator, a "force balance" is used on the diaphragm to control a poppet valve that regulates the pressure. With no inlet pressure, the spring above 15
the diaphragm pushes it down on the poppet valve, holding it open. Once inlet pressure is introduced, the open poppet valve allows gas flow to act on the diaphragm, and pressure in the upper chamber increases until the diaphragm is pushed upward against the spring, causing the poppet to reduce flow - stopping further increase of pressure. By adjusting the pressure adjustment handle, the downward pressure on the diaphragm can be increased, requiring more pressure in the upper chamber to maintain equilibrium. In this way, the outlet pressure of the regulator is controlled.
When the spindle of the cylinder is opened slowly, the high-pressure gas from the cylinder enters into the regulator through the inlet valve. The gas then enters the body of the regulator, which is controlled by the needle valve. The pressure inside the regulator rises, which, in turn, pushes the diaphragm and the attached valve, closing the valve and preventing any more gas from entering the regulator. The outlet side is fitted with a pressure gauge which indicates the working pressure on the process/outlet. With gas being drawn ‘’off’’ from outlet side, the pressure inside the regulator body falls. The diaphragm is pushed back by the spring and the valve opens, letting more gas in from the cylinder. The pressure in the body therefore depends on the spring's pressure, which can be adjusted by means of a regulator pressure adjustment handle.
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Two-stage or Multi-stage Regulators Two-stage regulators are nothing but two single regulators combined into one unit that operate to reduce the pressure progressively in two stages instead of one. The first stage, which is pre-set, reduces the pressure of the cylinder to an intermediate stage; gas at that pressure passes into the second stage. The gas now emerges at a pressure (working pressure) set by the pressure-adjusting control knob attached to the diaphragm. Two-stage regulators have safety valves, so that, if there is any excess pressure, there will be no explosion of the regulator. A major objection to the single-stage regulator is the need for frequent pressure adjustment in order to maintain a constant pressure on the outlet. When the cylinder pressure drops, the regulator pressure increases due to the reduced pressure on the inlet poppet valve - necessitating pressure adjustment in order to maintain a constant outlet pressure. In the two-stage regulator, this phenomenon occurs only in the first stage, so the resulting impact on the second stage is far less; as a result, this compensates for any drop in the cylinder pressure - ensuring a constant delivery pressure is maintained. If the need is for a constant outlet pressure to the process equipment, the gas system must be set as a two-stage version. Consult your equipment supplier for further advice.
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Regulator inspection prior to use The following is a guide to pre-use regulator checks. It is a generic overview of the steps to be taken to ensure that the primary regulator is suitable for use. This does not replace the operator’s instructions for individual primary pressure items. 1. 2. 3. 4.
5. 6. 7. 8. 9.
10. 11. 12. 13. 14. 15. 16.
Confirm the regulator type is compatible with that of the gas it is intended for. Check inlet pressure is equal to, or greater than, the gas cylinder fill pressure. Check the date is current. Never use out-of-date equipment. Confirm that you are using the correct orientation of the cylinder regulator to meet with that of the gas cylinder valve. Side outlet use a side inlet and top outlet use a bottom inlet. Check that the outlet pressure meets requirements. Check that the regulator is marked with the manufacturer or supplier's name. For regulators up to and including 20bar service, ensure they are marked with BS 2503. Check that the regulator HP inlet fitting is compatible with that on the cylinder outlet valve. Check the regulator HP inlet fitting for damage to the face seal, and that the appropriate sealing washer is in place and is in good, serviceable condition. Only replace with gas-specific seal. Check that the threads on the HP inlet fitting are not damaged. Check that the LP outlet fitting is not damaged. Ensure that the pressure control knob is captive when fully backed-off. Check that the regulator has not been tampered with or modified. Check that the gauges are not damaged. Confirm that the inlet stem is straight and not bent, as this could indicate it has been dropped. If a multi-ported regulator body is fitted, ensure that the body has the appropriate blanking plugs in place.
Never try to repair a regulator and never use PTFE tape on the threads. Never use oil on any gas equipment.
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The above steps can be used to check the suitability of any primary gas equipment whether it be wall or cylinder mounted with minor changes to include the HP hoses. These checks do not constitute an annual inspection or maintenance, but are intended to be used as a guide to ensure, visually, that the regulator is suitable for use. It does not include checks on the internal integrity or functionality of the primary regulator and, as such, can only be regarded as a visual inspection. Note: All gas equipment MUST be subject to regular maintenance inspections by a competent person, in line with the operator’s guidelines. For pipeline equipment, refer to instructions defined in the Written Scheme of Examination (WSE).
Fitting the Regulator and Gas Leak Procedure Once you are certain that the regulator is satisfactory, you can then fit it to the corresponding gas cylinder. The following steps are a guide to connecting regulators. It is a generic overview of the steps to ensure that the gas system is fitted correctly without leaks. This does not replace the operator’s instructions for individual primary pressure items.
1.
Using a piece of lint-free cloth over your finger, clean the gas face of the cylinder valve. 2. At the same time, feel for any burrs on the threads - as this could indicate a damaged valve. 3. Offer the appropriate regulator up and align with the cylinder valve. 4. Screw the regulator fitting onto the gas cylinder valve until secured in place. 5. Rotate the regulator to ensure that its position allows for the outlet fittings to be connected correctly and without hindering the spindle key operation. 6. Using a suitable gas spanner, tighten the nut accordingly. 7. Ensure the pressure control knob is fully backed off, then slowly open the gas valve to pressurise the HP side of the gas regulator. 8. Using an approved leak detection fluid or spray, check for leaks at the cylinder fitting and HP gauge fitting. When satisfied, turn off the gas supply before connecting the LP equipment. 9. Connect the process line to the LP regulator outlet. Slowly open the cylinder valve and pressurise the regulator. Apply a small amount of outlet pressure by means of the pressure adjusting knob. Check for leaks at the LP fittings and process fittings. 10. Once you are satisfied that there are no leaks you can proceed. 19
The above steps can be used to connect and check for leaks on any primary gas equipment whether it be wall or cylinder mounted with minor changes to include the HP hoses. This procedure does not constitute exact instructions but is a generic guide to ensuring the regulator/ HP hose is fitted correctly and gas-tight prior to use. Please refer to specific gas instructions from the gas supplier or equipment manufacturer.
Flashback Arrestors The flashback arrestor is a device design to capture a flame back-flowing up the hose. The flashback incorporates a cut-off device which automatically shuts-off the flow of gas when it detects the flame. All equipment used for fuel-gas and oxygen supply, when used in conjunction with one another, must be fitted with the appropriate flashback device. Ensure the flashback device is suitable for the fuel-gas and the correct pressure prior to use. Single-use or re-settable type Two types of flashback arrestors are available; the single-use type and the re-settable type. As described, the single-use type is just that; it will cut off the gas supply when it detects a flame back-flowing up the hose and cannot be re-used. The re-settable type can be reset to function multiple times as the flame arrestor.
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Common faults that cause a flashback 1. 2. 3. 4. 5. 6.
The most common cause for a flashback is failure to correctly purge the torch and hoses prior to lighting the torch. Incorrect gas pressure. Faulty or damaged torch end. Incorrect nozzle selection. Blocked torch. Kinked or trapped hose.
The following must be checked prior to use, and this information must be present in order to comply with the relevant BCGA Code of Practice: 1. 2. 3. 4. 5.
Always check that the flashback is in date. Suitability for the gas and gas pressure to be used. Direction of flow. Manufacture's/supplier's name or logo. BS/EN standards number.
NEVER use a flashback that shows signs of damage to its body, threads, inlet/outlet connections or has been repaired or modified.
Welding Fumes Safety Alert Workplace fumes and particulates kill thousands at work every year or cause the onset of long-latency pulmonary disease. Fumes: The content of fumes may be either asphyxiating or toxic. Asphyxiating fumes are mainly due to shielding gases and produce their effect by displacing oxygen from the surrounding air; excessive quantities can cause suffocation. These gases are most commonly argon (Ar), helium (He) and nitrogen (N2). This risk is well documented and is covered in BCGA Guidance Note GN11. Toxic fumes can be both gaseous and particulate. These fumes can present a serious threat to health and, ultimately, life in both the short and long term.
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Short-term risks are: Eye irritation. Shortness of breath and irritation to the respiratory tract. Metal Fume Fever. Poisoning by many metals e.g. zinc, barium, manganese, nickel, lead, copper, chromium, cadmium, aluminium. Fume containing these metals is toxic and can cause immediate risk of injury. Ozone, carbon monoxide and oxides of nitrogen are formed in some welding and cutting processes. These cannot be detected by the senses, but are toxic. Long-term risks: There is an increasing understanding that exposure to fume can lead to serious chronic health problems in the long term, perhaps many years later. Smoking is now well-known to cause serious health problems in later life, and exposure to fume must be treated as a similar risk. The risks include: Chronic Obstructive Pulmonary Disease (COPD): This is caused by many factors, such as exposure to dust, and is now linked to exposure to welding fume. Lung cancer: This can be caused by exposure to many substances, including heavy metal fume. The Health & Safety at Work Act places general duties on employers and employees. Employers, including self-employed persons, must: • Conduct a risk assessment of all activities which involve a risk to health and safety. This must be formally recorded. • Make available to employees, information about the risks identified and the control measures put in place to mitigate them. • Provide protective equipment as necessary. • Provide training to employees on procedures and safety. Employees must: Cooperate with their employer in relation to health and safety issues. This requires that they: • Follow instructions for safe working. • Participate in training. • Use the protective equipment provided. The BCGA has released a Technical Information Sheet, TIS 24 on welding fumes. Copies are available from the web site. www.bcga.co.uk
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Manual Handling More than a third of all "over 3 day" injuries at work are due to manual handling or, more to the point, a lack of it. It is your duty to undertake a risk assessment each time prior to commencing a manual handling operation. There are four key factors to consider before you start: 1. 2.
3. 4.
TASK – what is it I have to do? LOAD – what is it I have to move? Consider both the weight and size of an object - even a lightweight but large object may require more than one person to move it. INDIVIDUAL – am I able to undertake the task or do I need help, physical or mechanical? ENVIRONMENT – where do I need to go and what route should I take? What obstructions could cause issues - such as ramps, doors or stairs - and do I need to have control over lifts or automatic doors? When moving gas cylinders, always use a suitable trolley that is large enough to carry the gas cylinder safely. It is your responsibility to check that the trolley is in good working order, without defects, prior to use. When “churning” the gas cylinder, only do this for as short a distance as possible. Tip the cylinder just off the midpoint and slowly roll it on the edge of the base. The cylinder should be able to stand upright if released - if not, the angle is too great. NEVER try to do this with more than one cylinder at a time. Always wear the correct PPE.
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Connecting Regulators To ensure that your regulator is connected correctly and without leaks, it is important to follow a Standard Operating Procedure (SOP). The following information is a guide to establishing a SOP for the connection of individual gas regulators to a compressed gas cylinder. This is for reference only, as it is your responsibility to produce a SOP for your own specific equipment and gases. 1. Is the regulator in date? If it is older than 5 years from the date of manufacture, it is recommended to service or exchange the regulator in accordance with BCGA’s CP7. 2. Check that the regulator is for the gas you are using. Some regulators are labelled for a specific gas use, others may not be. It is vital that once a regulator has been used for a specific gas, it must remain in the service for that gas type only, and NOT be used for any other gas types. 3. Check that the maximum inlet pressure of the regulator is rated sufficiently for the cylinder pressure Refer to the cylinder label for the fill pressure and compare the data to the maximum working pressure of the gas regulator to ensure that the equipment is compatible. 4. Check when the regulator was last inspected It is good practice to visually inspect the gas equipment each time prior to use; it is also recommended that all gas equipment receives an annual inspection for functionality and that this is recorded. 5. Check that the maximum outlet pressure is suitable for your needs. If you require a high pressure outlet, it is vital that you ensure your equipment can supply the pressure you need. It is just as important that, when you only require a low pressure, the regulator scale is such that you can clearly see the set pressure you require. 6. Check that the regulator has the manufacturer's/supplier's name or logo visible This is required for traceability should the need arise to contact the supplier/manufacturer 7. Check that the pressure adjusting screw is captive on the regulator. The pressure adjusting screw must be captive and not able to be removed; if this can be removed, do not use the regulator until it has been checked by a competent per-
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son. The pressure adjusting screw must always be backed off by turning it anti-clockwise until it stops. 8. Check the cylinder fitting for damage to the sealing face Depending on the type of fitting, the seal can be a metal to metal bull nose, and any damage to this face will result in a leak. Fittings that use a sealing washer must also be in good order as well as the washer itself; never used any other type of “O� ring or washer, and only ever use sealing washers meant for that specific gas and connection. 9. Check the threads on the high-pressure connection. If the threads on the high-pressure nut are damaged, this may cause the regulator to leak if the operator is not able to secure the regulator to the cylinder effectively. 10. Check the hexagon face of the high-pressure nut for damage. Many regulators and high-pressure hoses suffer damage to the face on the hexagon nut. This is typically caused by the use of grips and similar tools to connect the regulator. Only ever use a good quality spanner to prevent damage to the face of the hexagon nut. 11. Check that the inlet stem is at 90o to the body of the regulator. If the regulator has been dropped at any time, the inlet stem may be bent - making it difficult to fit or get a gas-tight seal. 12. Check that the regulator has the appropriate standard displayed. Industrial gas equipment under 20bar outlet pressure must be marked with the BS/EN number. Spec gas equipment and high pressure outlet regulators may not be marked with any standards. 13. Check the regulator for damage to the body. If the regulator has been dropped, it could affect the calibration and safe working of the regulator. 14. Check the gauges for damage. The gauges may also break if the regulator is dropped and may show signs of over pressurisation if the backs are open or the needles are bent. 15. Check that the relief valve is not damaged. This is a safety device to prevent the regulator from being over pressurised. Never attempt to replace it. 16. Check the regulator for any unauthorised modifications. Regulators must only be serviced or repaired by authorised and approved bodies. 25
17. Check for an inlet filter in the end of the inlet stem. This is not always visible, and some manufacturers place the sintered filter on the end of the inlet stem and some at the body. This makes it difficult to check and, if you are unable to see the filter, you should consult the manufacturer to confirm its location. 18. Check that you using the correct orientation of regulator to suit the gas outlet on the cylinder. It is advisable to only use regulators designed for use with those specific gas cylinders; for example, a side-outlet gas cylinder should use a side-inlet gas regulator. This ensures that the operator can safely connect downstream equipment whilst still being able to see the gauges.
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NOTES
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Gas Con Gas Consultants
Contact: Gas-Con Ltd 63 Beckett Road Worle Weston-super-Mare Somerset BS22 7TN simon@gas-con.co.uk www.gas-con.co.uk
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