What is PSSR?

PSSR regulates how pressure systems are designed, inspected and operated around the UK. Ensuring your pressure systems are compliant with PSSR is important to prevent unwanted injury or loss of life.

PSSR stands for pressure system safety regulations.


This Approved Code of Practice (ACOP) and guidance, produced in support of the Pressure Systems Safety Regulations 2000 (SI 2000/128) (PSSR), was reviewed in 2014. It is aimed at duty holders under the Regulations, which includes users, owners, competent persons, designers, manufacturers, importers, suppliers and installers. To work out whether PSSR applies to your pressure system.

Although only the courts can give an authoritative interpretation of law, in considering the application of these Regulations and guidance to people working under another’s direction, the following should be considered:

If people working under the control and direction of others are treated as self employed for tax and national insurance purposes, they are nevertheless treated as their employees for health and safety purposes. It may therefore be necessary to take appropriate action to protect them. If any doubt exists about who is responsible for the health and safety of a worker, this could be clarified and included in the terms of a contract. However, remember, a legal duty under section 3 of the Health and Safety at Work etc Act 1974 (the HSW Act)1 cannot be passed on by means of a contract and there will still be duties towards others under section 3 of the HSW Act. If such workers are employed on the basis that they are responsible for their own health and safety, legal advice should be sought before doing so.

Each section of this ACOP gives practical guidance on a specific regulation, the number, title and content of which appear at the head of each section.

Words and expressions which are defined in the HSW Act or in PSSR have the same meaning in this ACOP and guidance unless the context requires otherwise. Where the expression ‘user/owner’ is used in the ACOP and guidance, it should be read as an abbreviated form of ‘user of an installed system or owner of a mobile systems.

The aim of PSSR is to prevent serious injury from the hazard of stored energy, as a result of the failure of a pressure system or one of its component parts.

The Regulations are concerned with steam at any pressure, gases which exert a pressure in excess of 0.5 bar above atmospheric pressure and fluids which may be mixtures of liquids, gases and vapours where the gas or vapour phase may exert a pressure in excess of 0.5 bar above atmospheric pressure. A list of equivalent measurements to 1 bar is given in Appendix 2 of this ACOP.

With the exception of the scalding effects of steam, the Regulations do not consider the hazardous properties of the contents released following system failure. PSSR does not deal with all the hazards arising from the operation of such a system. The contents may be toxic, or the plant may be part of a major hazard site. These aspects are the subject of separate legislative requirements and duty holders.

Safety of pressure systems must consider these other risks when deciding on the precautions required. In PSSR, the stored contents’ properties are of concern only to the extent that they may be liable to cause a more rapid deterioration in the condition of the system, so leading to an increased risk of failure. The risk from steam includes not only any possible deterioration in the condition of the system, which could increase the risk of failure, but also its scalding effect in the event of release.

In the case of some storage systems where gas is kept in liquid form at very low temperatures in a tank, the pressure above the liquid is below 0.5 bar (gauge) and PSSR would not apply unless the pressure rises above 0.5 bar (gauge). The Regulations do not apply simply as a result of pressure exerted by a head of liquid. Also, the Regulations do not aim to deal with vacuum conditions.

The amount of stored energy in a vessel is generally considered to be directly related to the volume of the vessel and the pressure of the contents. The measure of the stored energy has been expressed by multiplying the pressure by the internal volume (P x V), ie the pressure-volume product. If the values used are bar for pressure and litres for volume, the measure (or product) is given in bar litres


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