Following on from last week's article on Liquid Nitrogen, this week we take a quick look at the safe use of gas cylinders.
INTRODUCTION
Accidents involving gas
cylinders can cause serious injury or even death. HSE guidance provides simple
practical advice on eliminating or reducing the risks associated with using gas
cylinders.
The legal term that covers gas
cylinders is “pressure receptacle”. This is a generic term covering a number of
types of pressure receptacle: tube, pressure drum, cryogenic receptacle, bundle
of cylinders as well as cylinders themselves, plus the valve(s) fitted directly
to the receptacle. But for the purpose of this guidance, the term “gas
cylinder” shall be taken to mean all these various types of pressure
receptacle.
Gas cylinders used in adverse
or extreme conditions, such as for breathing apparatus, may require special precautions.
Although the advice in this guidance is valid for all uses of gas cylinders
these special precautions, such as different frequencies for periodic inspections,
are not covered.
As an employer or
self-employed person, you have a duty to provide a safe workplace and safe work
equipment. Designers, inspectors, manufacturers, suppliers, users and owners also
have duties.
Employers have a further duty
to consult any safety or employee representatives on health and safety matters.
Where none are appointed, employers should consult the workforce directly.
The main
hazards are:
Impact
from the blast of a gas cylinder explosion or rapid release of compressed gas;
Impact
from parts of gas cylinders or valves that fail, or any flying debris
Contact
with the released gas or fluid (such as chlorine);
Fire
resulting from the escape of flammable gases or fluids (such as liquefied
petroleum gas);
Impact
from falling cylinders;
Manual
handling injuries;
The main
causes of accidents are
Inadequate
training and supervision
Poor
installation;
Poor
examination and maintenance;
Faulty
equipment and / or design (eg badly fitted valves and regulators);
Poor
handling;
Poor
storage;
Inadequately
ventilated working conditions;
Incorrect
filling procedures;
Hidden
damage
HOW TO REDUCE THE RISKS
Anyone who examines,
refurbishes, fills or uses a gas cylinder should be suitably trained and have
the necessary skills to carry out their job safely. They should understand the risks
associated with the gas cylinder and its contents. In particular:
- New
employees should receive training and be supervised closely;
- Users
should be able to carry out an external visual inspection of the gas cylinder,
and any attachments (eg valves, flashback arresters, and regulators), to
determine whether they are damaged. Visible indicators may include dents,
bulges, evidence of fire damage (scorch marks) and severe grinding marks etc.
- Valves
should only be removed by trained personnel using procedures that ensure that
either the cylinder does not contain any pressure or that the valve is captured
during the removal process.
Handling and Use
Use gas
cylinders in a vertical position, unless specifically designed to be used
otherwise.
Securely
restrain cylinders to prevent them falling over.
Always
double check that the cylinder/gas is the right one for the intended use.
Before
connecting a gas cylinder to equipment or pipework make sure that the regulator
and pipework are suitable for the type of gas and pressure being used.
When
required, wear suitable safety shoes and other personal protective equipment
when handling gas cylinders.
Do not
use gas cylinders for any other purpose than the transport and storage of gas.
Do not
drop, roll or drag gas cylinders.
Close the
cylinder valve and replace dust caps, where provided, when a gas cylinder is
not in use.
Where
appropriate, fit cylinders with residual pressure valves (non-return valves) to
reduce the risk of back flow of water or other materials into the cylinder
during use that might corrode it (eg beer forced into an empty gas cylinder
during cylinder change-over).
Ensure
that the valve is protected by a valve cap or collar or that the valve has been
designed to withstand impact if the cylinder is dropped.
Lifting
Use
suitable cradles, slings, clamps or other effective means when lifting
cylinders with a hoist or crane.
Do not
use valves, shrouds and caps for lifting cylinders unless they have been
designed and manufactured for this purpose.
Gas
cylinders should not be raised or lowered on the forks of lift trucks unless
adequate precautions are taken to prevent them from falling.
Transport
Fit
suitable protective valve caps and covers to cylinders, when necessary, before
transporting. Caps and covers help prevent moisture and dirt from gathering in
the valve of the cylinder, in addition to providing protection during
transport.
Securely
stow gas cylinders to prevent them from moving or falling. This is normally in
the vertical position, unless instructions for transport state otherwise.
Disconnect
regulators and hoses from cylinders whenever practicable.
Do not
let gas cylinders project beyond the sides or end of a vehicle (eg fork-lift
trucks)
Ensure
gas cylinders are clearly marked to show their contents (including their UN Number) and the danger signs associated
with their contents.
It may be
necessary to take special measures with certain types and quantities of compressed
gases and fluids in order to ensure their safe carriage. If you have any doubts
seek further guidance (see Further Advice on page 11).
The
transport of gas cylinders is subject to carriage requirements. For example,
that:
i)
The
vehicle is suitable for the purpose;
ii)
The
vehicle is suitably marked to show that it is carrying dangerous goods;
iii)
The
driver is suitably trained; and
iv)
The driver carries the appropriate
documentation about the nature of the gases being carried.
Storage
Gas
cylinders should not be stored for excessive periods of time. Only purchase
sufficient quantities of gas to cover short-term needs.
Rotate
stocks of gas cylinders to ensure first in is first used.
Store gas
cylinders in a dry, safe place on a flat surface in the open air. If this is
not reasonably practicable, store in an adequately ventilated building or part
of a building specifically reserved for this purpose.
Gas
cylinders containing flammable gas should not be stored in part of a building
used for other purposes.
Protect
gas cylinders from external heat sources that may adversely affect their
mechanical integrity.
Gas
cylinders should be stored away from sources of ignition and other flammable
materials.
Avoid
storing gas cylinders so that they stand or lie in water.
Ensure
the valve is kept shut on empty cylinders to prevent contaminants getting in.
Store gas
cylinders securely when they are not in use. They should be properly
restrained, unless designed to be freestanding.
Gas
cylinders must be clearly marked to show what they contain and the hazards
associated with their contents.
Store
cylinders where they are not vulnerable to hazards caused by impact, eg from
vehicles such as fork-lift trucks.
While the cylinder label is
the primary means of identifying the properties of the gas in a cylinder, the
colour coding of the cylinder body provides a further guide.
Cylinder shoulder - European
standard colour coding
The colour applied to the
shoulder, or curved part at the top of the cylinder, signifies the European
standard colour coding.
The aim of the new standard
(EN 1089-3), which has replaced the old cylinder colour scheme (BS349), is to
help improve safety standards within the gases industry.
A number of gases have been
assigned a specific colour and some of these are shown below:
For
more detail you should refer to:
· The Carriage of Dangerous Goods
and Use of Transportable Pressure Equipment Regulations 2004 (SI 568/2004 The
Stationery Office 2004 ISBN 0 11 0490630).
· The Pressure Equipment
Regulations 1999 SI 1999/2001 The Stationery Office 1999 ISBN 0 11 082790 2
· European Agreement concerning the
international carriage of dangerous goods by road (ADR) and protocol of
signature done at Geneva on 30 September 1957 (www.unece.org/trans/danger/publi/adr/)
· Regulations concerning the
International Carriage of Dangerous Goods by Rail (RID)
· Guidelines on the appointment of
conformity assessment bodies for transportable pressure vessels in Great
Britain: The Carriage of Dangerous Goods and Use of Transportable Pressure
Equipment Regulations 2004 (copies available from HSE at 020 7717 6303 or from
HSE’s web site at http://www.hse.gov.uk/cdg/pressure.htm.
Approved construction standards are posted on
HSE’s web site http://www.hse.gov.uk/cdg/pressure.htm