Nottingham University, Physical Chemistry Safety Protocol

Compressed Gas Cylinders

Last revised:16/10/18 Restrictions? generic Author(s): RM

Transport, Storage And Use Of Compressed Gas Cylinders

Hazards
 Pressurised gas cylinders are very heavy and unstable objects and as such can present
considerable danger to those handling them.
 They contain gas which may be toxic, asphyxiating or flammable and at high
pressure.
 The pressure of cylinders is almost always too high to be of direct use and needs to be
reduced to more convenient levels by a pressure regulator; on small lecture bottles a
simple control valve is sometimes used instead. These fittings have to be supplied and
in good working order.
 Apart from the chemical risk from these gases, serious physical damage can be caused
by exposure to the full force of escaping gas.
 Gas cylinder valves are very robust but a broken valve can turn a cylinder into a lethal
projectile.
 Gas pressure regulators are much less robust and if damaged may allow the escape of
gas. Improperly fitted regulator/valves can be 'ejected' by the high pressures and
propelled from the cylinder at high velocity.
A falling cylinder or exposure to high pressure gas is likely to injure only the user of the
cylinder; however if equipment is blown apart by excessive pressure or toxic or asphyxiating
gases escape the damage may be widespread within a laboratory or beyond. Most accidents
with cylinders arise from maltreatment.

Transport and Storage

 Cylinder trolleys are to be used for transporting large cylinders and moved by pushing
and not by pulling. If the trolley shows signs of wear or damage, it must be taken to
the Mechanical Workshop where it may be repaired or replaced.
 It can be dangerous to move a cylinder with the regulator still attached, for if it should
fall over the gauge may shear off releasing the full pressure with explosive force.
Valves must be closed and it is recommended that regulators are removed before
transporting.
 Within labs cylinders should be located in secure racks or, secured in cylinder
trolleys. CYLINDERS MUST NEVER BE LEFT FREESTANDING.
 Cylinders are to be kept in the outside cylinder store until required. Smaller lecture
bottles may be stored in well-ventilated locations, having regard to the potential
hazards created by accidental leakage (COSHH !!).
 The number of gas cylinders at any site must be kept to a minimum.
 Flammable/fuel gases such as Hydrogen or Methane must never be stored in the
same rack/site as Oxygen: a separation of 3 metres or fire-resistant wall is required.

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Physical Chemistry: Safety Protocol

Operating Precautions
 The cylinder should be checked to ensure that it contains the expected gas by
checking the label and (less reliable) the colour code.
 The Pressure Regulator should be checked. Is it designed for the gas you are using?
(Corrosive gases require specialised regulators, made of compatible materials). Are
the pressure ratings correct? Is the inlet pressure capable of coping with the pressure
in the cylinder? Is the range of regulated outlet pressure appropriate for the gas line to
which it will be connected? Is the regulator marked with a red line to indicate the
maximum pressure to be applied to the experimental apparatus? Is it damaged?
Damaged regulators should be returned to Neil Barnes for repair/exchange.
 A bewildering array of fittings are in use with compressed gases. Some seal on metal-
metal surfaces, some on tapered pipe threads, some on gaskets; some are metric, some
imperial; some left hand threads, some right handed. Often this is to ensure that
incompatible process gases cannot be inadvertently interchanged. Take care to
identify and use matching fittings, and do not attempt to force incompatible fittings
together. Only use proper adapters and only after ensuring that this is appropriate.
Make certain that correct undamaged gaskets or PTFE sealing tape are used, but only
with fittings intended to seal this way. Consult if you are unsure about fittings!
 Correctly fitting tools/spanners should be used when fitting regulators to avoid
damage to the screw fittings.
 Blow foreign matter from the outlet before attaching a regulator valve.
 Oil or grease must never be used, especially on an Oxygen cylinder: - the oil or
grease may ignite - and PTFE tape or jointing compound should never be used to
attempt do-it-yourself sealing of leaks. N.B. Flammable gas cylinders have a left hand
thread.
 Gas line installation may be undertaken only by trained personnel. Lines to be should
be designed for the intended pressure and leak tested before commissioning. They
should be inspected/tested at suitable intervals thereafter.
 A Teepol/water solution may be used to check for leaks in lines and around the
regulator.
 The regulator should be turned to zero before opening the valve at the spindle and
when finished, the valve closed at the spindle. It is advisable to vent excess pressure
from the regulator and release the regulator diaphragm when the cylinder is not in use.
 It should be possible to open cylinder valves by hand using the standard key. Stiff or
seized valves should be treated cautiously. Do not use hammers bricks or excessive
force to free, but tap with a piece of wood.
 Do not empty cylinders completely but leave with a slight positive pressure and the
valve closed to prevent back diffusion of air, especially with flammable gases.
 COSHH assessments may be required for the gases in the cylinder!
Emergency Procedures
 Escape of gas: If the gas escape is large, evacuate the area - remember even an inert
gas can kill by asphyxiation. For small non-toxic leaks, a member of Staff should be
informed, and the room ventilated, evacuated, sealed and secured. In other cases more
detailed actions should be identified by COSHH assessments for the gases concerned.
Breathing apparatus is available for use by authorised personnel only. Warning:
Hydrogen leaks from a high-pressure cylinder may ignite spontaneously.
 Falling Cylinder: If a cylinder falls over, no one should EVER attempt to catch it. It
is much too heavy and will cause serious injury.
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