Safe use of gas cylinders

Overview

General rules and working practices

• Use the smallest cylinder size appropriate for the work activity. This is particularly important when using flammable or toxic gases.
• Eye protection should be worn when connecting regulators to cylinders
• Approval must be given by the Safety Advisor before the purchase and use of all flammable or toxic gases
• Cylinders of toxic, flammable, or reactive gases should, where practicable, be used in fume hoods
• Hydrogen: Use of a hydrogen generator should always be considered first where possible. If a generator is not appropriate, the cylinder must be fitted with a gas detector linked to an automatic shut-off valve.  If not, this must be fully justified in the risk assessment for the work activity involving the use of hydrogen.
• Do not expose cylinders to temperatures higher than 50°C. Some rupture devices on cylinders will release at about 65°C.
• Never use a cylinder that cannot be positively identified. Do not rely on the colour of the cylinder to identify its contents
• Never lubricate any part of the cylinder valve or equipment with oil or grease due to the risk of spontaneous combustion with high pressure gas
• Do not loosen or remove the safety plug or rupture disc
• Naked flames or other sources of ignition must are not permitted in the vicinity of a cylinder or pipeline outlet or in confined spaces where cylinders are used and stored
• Keep cylinders containing liquefied gases upright. Note that it is often difficult to determine the contents of a cylinder containing liquefied gas, except by weighing. As long as a liquid is present, the cylinder or vapour pressure will remain constant. The cylinder pressure for liquefied carbon dioxide does provide an indication of cylinder content
• 'Snifting' should not be carried out. This is when the valve is quickly opened and shut to remove dust and grit. To remove any material from the valve you should use a compressed air duster (whilst wearing eye protection), which can be purchased from Biology Stores
• Care should be exercised when compressed air or gas is used to blow away dust or dirt, since the resultant flying particles are dangerous
• If you store your cylinders outside you should wear gloves when you intend to move them during cold weather
• Rapid release of a compressed gas will cause an unsecured gas hose to whip dangerously and also may build up a static charge which could ignite a combustible gas
• Do not extinguish a flame involving a highly combustible gas until the source of gas has been shut off as it can re-ignite causing an explosion
• When not in use, cylinder and bench valves should be closed tightly. Remove the regulators from empty cylinders and replace the protective caps
• Do not keep cylinders filled with corrosive, explosive, or highly toxic gases for more than 6 months; do not keep cylinders with oxygen or liquids or flammable gases for more than 3 years

Emergencies

Emergency procedure

The following procedure should be followed in the event of a sudden and unexpected leak of gas e.g. as a result of a burst cylinder disc:

• evacuate the area immediately
• where possible:
  • check that the cylinder valve is closed
  • move cylinder outside
    OR, if this is not practical, or safe,
    open any windows to maximise ventilation
• do not enter an area unless it is safe to do so; confined spaces are particularly hazardous when asphyxiant gases (such as CO₂ and nitrogen) are released
• in a medical emergency, any casualty should only be removed to an uncontaminated area if it is safe to do so, before contacting the emergency services (see below) and a local first aider
• contact:
  • Normal working hours:
    • David Nelson (Health & Safety Advisor, 8524)
    • Lucy Hudson (Operations Manager, 8745)
  • Outside normal working hours:
    • Emergency University Number: 3333
    • BOC 24 hr emergency number: 0800 111333
  • In the event of a fire immediately contact:
    • Emergency University Number: 3333
      OR
      Fire & Rescue Service: 999

Leaks

Testing for leaks

Leaks on pressurised systems can be monitored by:

• using an approved leak test detection spray (available on YEP)
• 'pressure drop' test: pressurising the system, turning off the cylinder stem valve and looking for a drop in the discharge pressure. The location of leaks can be identified by test detection spray

Transport

Transport of gas cylinders within the Department

• Cylinder trolleys should be used to transport cylinders between locations and should only be manually handled when loading/unloading onto the trolley.
• Suitable closed-toe shoes must be worn to prevent crushing when moving cylinders.
• When moving cylinders, they should be strapped to a properly designed cylinder trolley to ensure stability.
• Cylinders must not be accompanied in lifts
• Move cylinder with the cap securely in place to protect the valve stem.
• Due to the way the cylinder is handled it is recommended that the individual is at least as tall as the cylinder if you are intending to manually handle it.
• When moving a cylinder manually you should use the 'churning' method. This involves placing one hand at the top of the cylinder and rolling it with the other. It should only be done under the following conditions:
  • Over short distances
  • Even ground
  • Dry conditions
  • Well lit areas
• Following transportation of cylinders to the laboratory area the cylinders should be immediately secured in position and a gas regulator attached.

Transport of gas cylinders by vehicles

• The following requirements only cover the road transport of inert non-flammable gases (e.g. nitrogen, air, oxygen)
• To be exempt from the full requirements of the Carriage of Dangerous Goods Regulations, the quantity of compressed gas must be below the threshold quantity; for non-flammable gases (transport category 3, UN division 2.2/5.1) the limit is equivalent to 500 Litres water capacity in cylinders.

Key Requirements

• Use an open vehicle (ideally) or one that has good ventilation. If this is not possible and a closed vehicle is used, the cargo doors must be labelled in letters not less than 25mm high: 'WARNING NO VENTILATION, OPEN WITH CAUTION'. Note: the drivers cabin must be isolated from the cargo carrying area if the cargo area is not open / ventilated.
• A 2 kg or larger dry powder fire extinguisher must be carried. The extinguisher must be readily accessible in the driver compartment, and should carry and inspection label indicating that is has been checked within the last 12 months. The purpose of the extinguisher is to put out an engine or brake fire.
• Cylinders must be properly secured so they do not shift during transport, and should not project from the sides or ends of the vehicle.
• Check the gas cylinders before loading:
  • cylinder valves must be closed and not leaking whilst in transit, and any equipment disconnected
  • make sure the cylinders are in good condition and properly labelled
• A Class 2.2 green diamond hazard label / placard (non-flammable, non-toxic compressed gas) must be displayed on the rear of the vehicle. These must be removed from the vehicle once the cylinders are unloaded.
• Ensure the driver has read these requirements and is trained in:
  • how to handle and transport cylinders safely
  • use of fire extinguishers
  • emergency procedures (see below)
  • aware of properties and potential hazards associated with the gases to be transported
• The driver does not need to carry documents (e.g. safety data sheets) detailing the load they carry. However, this information would be useful in the event of an accident.
• If a leak is suspected during transport park the vehicle in a safe place and contact the gas supplier. The area should be kept clear until assistance arrives.
• If you are involved in an accident advise the emergency services:
  • what cylinders are being carried, their capacity and how how many

Fittings

Fittings

Hoses

• Use only, correct, pressure-rated tubing
• The correct hosing should be used according to the type of gas:
  • Flammables (except LPG) RED
  • Oxygen BLUE
  • CO2, Air, Nitrogen, Argon BLACK
  • LPG ORANGE
• Protect hoses from excess heat
• Keep hoses as short as is tractable
• Do not allow hoses to become greasy
• It is preferable to connect hoses to equipment with 'O' clips
• Hoses should be periodically checked for cuts, tears, burns etc.

Regulators

• Use the appropriate regulator on each gas cylinder. Adapters or home-made modifications can be dangerous.
• A regulator should be replaced after 5 years, regardless of the frequency of use. New regulator orders can be placed via Biology Stores.
• Safety glasses or face shield should be worn when locating or removing the pressure regulator and when opening the spindle valve.
• Regulators must be checked before and after use- broken or damaged regulators must be replaced immediately.
• It is imperative that you use the correct regulator for the gas you are using. The bar (pressure) level and name of the gas should match the information label on the cylinder.
• You should regularly check your regulator and connections for leaks.  This can be done with leak detection spray, which can be purchased on YEP.

See also Check procedures for gas cylinders (PDF , 15kb) for more information on connecting regulators to cylinders

Storage

Storage

• Store cylinders with the cap securely in place to protect the valve stem.
• Cylinders of all sizes must be restrained by firmly located straps, chains, or a suitable stand to prevent them from falling. Never leave cylinders standing unsupported.
• Cylinders of flammable gases must not be sited on the same rank as cylinders of oxygen.
• As far as possible, cylinders of flammable gases, e.g. hydrogen, should not be sited on emergency escape routes.