Guidance Note 38 – Pressure systems safety

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Pressure systems safety

Modern pressure systems have a good safety record; however, they present particular hazards because pressure vessels can release large amounts of stored thermal and kinetic energy following leaks or explosion of gases, fluids, vapours or steam.

Due to the complexity of the legislation, with its varying exceptions, it is strongly recommended that if you have a pressure system of any type to seek advice from a competent person. Your insurance company should be able to put you in touch with an appropriate engineer. You must identify a responsible person to run the pressure system on a day-to-day basis.

Responsibilities and duties

There is a split of responsibilities and duties, which is dependent on whether the system is a fixed installation or mobile. Differentiation is also made between owner and user.


The duties for the owner are assessed on whether they have control over the operation of the system or if they are leasing or hiring out the equipment. This applies if the system is:


Once it is installed, the user has primary responsibility for the pressure system, in particular:

The user has also to ensure that before the system is used by him or his employees the following is completed:

Where the owner or his agent do not have a place of business in Great Britain, the user assumes all the responsibility for compliance with the Regulations.

Pressure system

A pressure system is defined as:

Equipment types

A pressure system covers anything that contains a ‘relevant fluid’. Typical examples of this type of equipment are:

Relevant fluid

This is steam at any pressure, or any fluid or mixture of fluids that may exert a pressure in excess of 0.5 bar (7 lbf/in2 ). Fluids include gases, liquids or vapours – for example compressed air, nitrogen, oxygen, acetylene, pressurised hot water, etc.

General safety requirements for pressure systems

Principal causes of incidents

The principal causes of incidents include:

Hazards of pressure systems

Typical hazards associated with failure of pressure systems are:

Reducing the risk of pressure system failure

The degree of risk from pressure-system failure depends on these factors:

Daily checks

All checks should be in accordance with the manufacturer’s recommendations. These may include:

These regular checks should form part of a safe system of work.

What are the operating conditions?

Fit suitable protective devices

Protective devices include pressure relief valves and electronic gear which close the system down in case of malfunction. You should ensure:

The flowchart overleaf will help you decide if the Regulations apply to your pressure system.

Written scheme of examinations for pressure systems

All pressure systems that contain steam or any other relevant fluid above a 250 bar litre capacity must not be used unless they are subject to an individual written scheme of examination. The scheme enables a periodic and systematic inspection of the main safety hazards of the specific equipment – it is a maintenance handbook for the system concerned.

The written scheme will identify which parts are to be examined, what is required and how often it is required. It will deal with the first examination before being put into service, and subsequent examinations throughout the system’s working life.

The user/owner is responsible for ensuring the suitability of the scope of the written scheme and that it covers all the pressure vessels, protective devices and pipework.

Frequency of examinations

Examination periods will vary depending on the type of system, its age and its use. Periods can vary between 12 and 144 months.

Examination in accordance with the written scheme

The owner/user must ensure that the equipment is periodically examined by a competent person in accordance with the written scheme. They must also ensure the safety of the examiner by performing the required preparatory work.

Examination report details

The report obtained from an examination should include:

Keep documentary records

The owner/user should keep the following documents readily available:

Where a system is sold or changes hands the previous owner has a duty to pass over all documents held under this regulation to the new owner/user.

Competent person

The scheme must be drawn up by a competent person with the necessary knowledge and experience and independence to undertake the functions required of them. They should be able to demonstrate that they have practical and theoretical knowledge and actual experience of the relevant systems.

They may be:

Bodies holding United Kingdom Accreditation Service (UKAS) accreditation to BS EN 17020:2004 for the scope of in-service inspection of pressure equipment, can provide competent persons meeting the appropriate criteria. For more details of accredited companies UKAS can be contacted as follows:

United Kingdom Accreditation Service (UKAS)
21-47 High Street
TW13 4UN
Tel: 0208 917 8400


If ‘yes’,

If ‘yes’,

Further Guidance