The Safe use of Gas Cylinders

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