Compressed Gas Safety Training
These refer to cylinders in storage, i.e. not in use or attached to equipment or instrumentation.
Storage area should be:
- free from risk, away from sources of heat and ignition
- designated as a "no smoking" area (not necessary if building is smoke-free and posted as such)
- clearly marked as a gas storage area with appropriate hazard warning signs such as flammable, oxidizer, etc.
- kept clear with access restricted to authorized personnel
- provided with appropriate safety and emergency equipment, including a fire extinguisher, adequate ventilation, etc. Check the local fire code for compliance requirements
Compressed gas containers in storage should be:
- stood upright
- properly secured with approved cylinder support
- segregated according to their various categories, such as flammable, oxidant, etc., and providing 20' between incompatible gases
- segregated in the storage area according to whether cylinders are full or empty
- managed to ensure that the oldest stock is used first (individual labs may not store more than one each of any cylinders of flammable or toxic gases)
- checked periodically for general condition
Personnel in adjacent work areas should be:
- familiar with the operation and use of the safety and emergency equipment provided, e.g., fire extinguishers and alarms, main shut-offs, local exhaust ventilation, etc.
- familiar with the hazards of the products stored
- Aldrich Technical Bulletin AL-151 Gas Regulators, Selection and Installation
- Compressed Gas Association, numerous free pubs, also pamphlets for sale
- AirProducts Appendix - Safe Handling and Use
- BOC gases - a wide selection of gas MSDSs.
Usage area should be:
- well ventilated
- arranged so as to minimize fire risk in the vicinity of the gas containers. It may also be necessary to eliminate ignition sources, for example where flammable gases are used for non-combustion applications and where there is a risk of leakage
- provided with appropriate safety and emergency equipment, e.g., fire extinguishers, breathing apparatus, eye protection, etc. For a better understanding of the usage/storage area check with the local fire code for compliance
Compressed gas containers should be:
- standing upright (valve up, >45o from horizontal unless designed specially for use in horizontal position).
- properly secured with approved cylinder support, individually if not capped. No uncapped cylinder should be secured to a cart, and no cylinder cylinder secured to a cart should be uncapped.
- checked to contain the correct gas in the designated usage area and properly secured to prevent falling over or other movement which could fracture the connecting pipework
- leak tested around the valve and valve outlet connection
- fitted ONLY with the appropriate compatible regulator -- no adapters.
Personnel should be familiar with:
- the identification of the gas container contents and the potential hazards. They should also have access to the appropriate Material Safety Data Sheets.
- the operation and use of the safety and emergency equipment where provided, e.g., fire extinguishers, breathing apparatus, eye protection, ventilated gas cabinets, etc.
- the gas container and its valve, including the procedures for rectification of leakages at the valve gland (where appropriate) and outlet connection.
- the correct operation of the gas flow and control equipment including purging procedures
- the importance of ensuring that the gas container is not contaminated by a backfeed from the process
Handling and Control Information
It is important to observe all handling precautions, and to use the correct pressure and flow control equipment. The choice of suitable equipment is dependent on the gas supply pressure, the chemical and physical properties of the gas, the gas purity, and other users' requirements.
- Installations handling flammable gases should be grounded to minimize the risk of sparks due to static discharge. Flash arestors should be used where appropriate.
- Installations handling hygroscopic corrosive gases such as anhydrous hydrogen chloride must be provided with a means of purging. An adequate device or control to prevent the backfeed of liquids, gases or other contaminants into the container must also be incorporated.
- Before using the gas, read all label information and the data sheets associated with the use of that particular gas.
- Before attaching cylinders to a connection, be sure that the threads on the cylinder and the connection mate, and are of a type intended for gas service.
- The threads and mating surfaces of the regulator and hose connections should be cleaned before the regulator is attached. Wipe the outlet with a clean, dry, lint-free cloth. Particulate can clog the regulator filter (if so equipped) or cause the regulator to malfunction.
- Always use the proper regulator for the gas in the cylinder. Check that the CGA numbers match, and always ensure that the regulator appears sound before attaching it to a cylinder. If the connections do not fit together readily, the wrong regulator or a defective regulator is probably being used.
- Attach the regulator securely with the secondary valve closed and preferably with the regulator flow backed off (counterclockwise) before opening the cylinder valve wide.
- Do not permit oil or grease to come in contact with cylinders or their valves, or with regulators or flow controls. Oil or grease should especially be avoided with containers of oxidizing gases.
- Cylinders containing oxygen or oxidizing gases, e.g., chlorine, (empty or full) should be separated from cylinders containing flammable gases by a minimum distance of 20 feet or by a barrier at least 5 feet high having a fire-resistance rating of at least one-half hour, e.g., a concrete block wall. 3.Do not store oxidizing gases near flammable solvents, combustible materials or near unprotected electrical connections, gas flames or other sources of ignition.
- Always use a cylinder wrench or other tightly fitting wrench to tighten the regulator nut and tube connections. Use "backup" wrenches to minimize stress on tubing and fittings where appropriate.
- Teflon tape should never be used on cylinder connections or tube-fitting connections. Use Teflon tape only on pipe threads where the seal is made at the threads. All other connections have metal to metal face seals or gasket seals.
- Open cylinder valves SLOWLY. Point the valve opening away from yourself and other persons. Never use a wrench or hammer to open or close a hand wheel type cylinder valve. If the valve is frozen and cannot be operated by hand, return the cylinder to the vendor.
- Before a regulator is removed from a cylinder, close the cylinder valve and release all pressure from the regulator.
- Never completely empty a "rented" gas cylinder, rather discontinue use of the cylinder when it has at least 25 psi remaining. Mark the cylinder so that others know that it is nearly empty, e.g., write "approx 25 psig remaining -- MT" on a piece of tape and stick it on the cylinder. Close the valve and secure the cylinder valve protective cap and outlet cap or plug, if used.
CORRECT LABELING AND PROPER FITTINGS ON COMPRESSED GAS CONTAINERS
CGA Safety Bulletin 10-998
It is essential that any person handling a container of compressed gas or cryogenic liquid be certain of the contents before the container is connected to a system. Discharging a gas or cryogenic liquid into a system not intended for the material could cause a fire, explosion, equipment failure, gas leak, or other hazard resulting in a serious or fatal injury.
Before attempting to connect a container to a system, be certain of the following:
- Personnel using the container are trained and knowledgeable regarding the product, container, fittings, equipment, and proper connection procedures.
- The container is clearly and properly marked or labeled with the identification of the contents, and there are no conflicting markings, labels, or coloring. Do not rely solely on the color of the container to identify the contents. If there is any conflict or doubt about the contents, do not use the container.
- The labeled contents are the correct product for use in the system.
- The container has the proper outlet connection(s) for its contents according to ANSI/CGA V-1, American National, Compressed Gas Association Standard for Compressed Gas Cylinder Valve Outlet and Inlet Connections .
- The connection(s) on the container and the system fit together properly without being too loose or too tight. A proper connection will go together smoothly. Do not use adapters or excessive force.
See CGA P-1, Safe Handling of Compressed Gases in Containers, and CGA C-7, Guide to the Preparation of Precautionary Labeling and Marking of Compressed Gas Containers, for additional information [2, 3].
WARNING: Failure to follow these precautions has caused fatalities.
 ANSI/CGA V-1 American National, Compressed Gas Association Standard for Compressed Gas Cylinder Valve Outlet and Inlet Connections, Compressed Gas Association, Inc., 1725 Jefferson Davis Hwy., Suite 1004, Arlington, VA 22202. CGA P-1, Safe Handling of Compressed Gases in Containers, Compressed Gas Association, Inc., 1725 Jefferson Davis Hwy., Suite 1004, Arlington, VA 22202. CGA C-7, Guide to the Preparation of Precautionary Labeling and Marking of Compressed Gas Containers, Compressed Gas Association, Inc., 1725 Jefferson Davis Hwy., Suite 1004, Arlington, VA 22202
Equipment personnel who spend significant time moving or handling gas containers should be provided with:
- protective footwear, e.g. steel cap shoes
- heavy gloves
- hand cart or other suitably designed device for transporting containers and a chain or another method for securing the container while it is being moved
Most accidents and injuries involving compressed gases occur during the moving or handling of the gas container. Personnel should be instructed in the following key points:
- remember the mass of the container
- beware of trapping fingers between containers while they are being moved
- when it is necessary to lift heavy containers manually, seek help and to observe the correct lifting posture
- use a cylinder hand cart or other suitable device for transporting heavy containers, even for short distances, and ensure the container is secured
- ensure valve protection devices, e.g., caps, guards, etc., are fitted to containers while they are being moved
Empty containers are not really empty. They contain gas at atmospheric pressure, which of course does not cause deflection of the gauge needle because the gauge reports psig, the pressure greater than atmospheric. In abosolute terms the cylinder still contains approximately 15 psia (pounds per square inch absolute). Depending on cylinder size, this can be a substantial quantity of toxic or flammable substance.
It is important to ensure that gas containers are in a safe condition after use. Before returning empty gas containers, a check should be carried out to ensure that:
- the container valve is closed and not leaking
- the container valve outlet plug or cap nut, when supplied, has been securely refitted. This is particularly important if the contents of the container are toxic
- the container valve protection device is properly fitted
The most effective action in an emergency situation will result from careful prior planning. The following checklist identifies some of the key factors that should be considered:
- Is there a properly documented and practiced emergency procedure?
- Are personnel properly trained in the product properties and the use of emergency equipment?
- Has the Fire Department been advised of the products used on site and their location?
- Is there a properly trained team of technicians on site to deal with emergency situations?
- Have the local medical services been advised of the products handled on site and are any specialized medical requisites readily available?
- Is there adequate emergency equipment readily available, and are people trained in its use?
Emergencies involving compressed gases are unlikely, provided the recommendations are followed for their correct storage, handling, and use. When problems do arise they are usually due to:
- Fire threatening the cylinder: The compressed gas container is a high integrity package. However, if it comes in contact with excessive heat for prolonged periods, then there is a risk of rupture and explosions.
- Flammable gas leak: All flammable gases will form explosive mixtures with air. When ignited, significant explosive energy can be released from flammable gas-air mixtures.
- Toxic gas leak: Safe working limits are prescribed by the Material Safety Data Sheets. Where proper facilities and equipment are provided, personal injury from exposure to toxic gas is extremely unlikely.
- 'Inert' gas leak: This is usually considered to be harmless. However, if in a confined space, asphyxiation (oxygen starvation) of unprotected personnel can occur.
- Unplanned chemical or other reaction: This can arise when gas users allow process material back into the gas supply cylinder and can possibly result in rupture or explosion. It can also arise if the gas cylinder content is mistakenly identified. This type of emergency is extremely unlikely where operational procedures are properly controlled and staff are properly trained.
- General: If possible, isolate gas supplies into affected area, and safely release the gas pressure in affected pipelines and equipment.
- Fire threatening compressed gas containers: There is a risk of a rupture or explosion of cylinders subjected to prolonged heating (such as in a fire). Such cylinders should be moved to a safe place before they become too hot. If this is impossible, cool cylinders with water hosed from a safe distance. Any cylinder that has been involved in a fire must be clearly marked as such, and the supplier must be notified accordingly.
- Ignited flammable gas leak: If possible, isolate the gas supply. If this is impossible, try to ensure the flammable gas burns in as controlled a manner as possible, does not ignite anything else, and does not impinge on any pressurized gas containers, equipment, or pipelines.
- Never extinguish a flammable gas leak without stopping the flow of gas, because a potential explosion hazard would result.
- General: Assess the likely effects of the gas leakage and the affected area. This will determine the subsequent emergency action taken and the level of personnel protection needed.
- Leaking cylinder: Most leaks occur at the valve fitted into the top of the cylinder. Leakage areas that may be involved are:
- Valve outlet connection: Leakage here is frequently due to dirt in the connection, or damaged connections or washers where required. Such leaks are easily rectified.
- Valve stem (i.e., around valve operating spindle): Leakage from valves fitted with an adjustable gland can easily be cured by gently tightening the gland nut while the valve is partially open. A quarter turn is normally sufficient (maximum torque: 50 ft-lbs). All gland nuts have "right-hand" threads. Some gland nuts are backed with a lock-nut (which must be loosened before gland nut adjustment and tightened afterwards).
- Joint between cylinder valve and cylinder: Leakage here is extremely rare and where it does occur, is normally identified and rectified by the cylinder filler. No attempt should be made to tighten a cylinder valve into a full cylinder. Such cylinders must be set aside for the attention of the supplier.
- Valve closure: Leakage from a cylinder valve that will not readily shut off can usually be reduced by careful application of a greater closing torque (using a wrench or other means of greater leverage). All defective cylinders should be clearly labeled before being returned to the supplier.
- Leaking gas control equipment/pipelines, etc: Isolate the gas supply. Before attempting to repair leaking equipment, ensure that the pressure has been released and the equipment purged to remove all hazardous gases.