PSSR: Frequently asked questions about PSSR examinations

What does the term ‘relevant fluid’ mean as far as PSSR is concerned?

A PSSR examination or inspection is a statutory requirement. PSSR is designed to prevent serious injury from the hazard of stored energy. The term ‘fluids’ includes gases and liquids which are capable of exerting a vapour pressure. They do not include hydraulic oils. Hydraulic systems, while using high pressures, do not store energy in the system and so are not covered by PSSR. Under PSSR a relevant fluid is:

  • steam at any pressure
  • any fluid or mixture of fluids which is at a pressure >0.5 bar above atmospheric
  • a gas dissolved under pressure in a solvent (eg acetylene)

PSSR refers to an ‘installed’ system and ‘a mobile’ system. What is the difference?

A mobile system is one that can be easily moved from place to place, e.g. an air compressor that is taken from site to site. An installed system is one that is not a mobile system, e.g. a steam boiler.

Note: A steam locomotive is considered to be an installed system despite its obvious mobility. Similarly, a steam boiler fitted with skids (‘package boiler’) may be installed temporarily to maintain steam supply to a site during the replacement of an existing boiler, but this should also be treated as an installed system (see Safety of Pressure Systems, the ACoP for PSSR paragraph 46).

What is a written scheme of examination (WSE)?

A WSE is a document containing information about items of plant or equipment that form a pressure system, operate under pressure and contain a ‘relevant fluid’.

PSSR regulation 8 places a duty on the user of an installed system and the owner of a mobile system not to allow pressure systems to be used until they have a WSE covering:

  • all protective devices
  • every pressure vessel
  • every pipeline and pipework in which a defect might give rise to danger

An identification of the item of plant or equipment. Unique identification numbers or descriptions may be used.

The nature of the PSSR examination required, including the inspection and testing to be carried out on any protective devices.

The preparatory work needed to allow the item(s) to be examined safely, e.g.:

  • cooling down periods
  • isolation procedures
  • the maximum interval allowed between examinations

The critical parts of the system which, if modified or repaired, should be examined before the system (or part) is used again.

The name of the competent person certifying the WSE.

The date of the certificate.

PSSR regulation 9 requires an ‘examination in accordance with the written scheme’. What does this mean?

This means a careful and critical scrutiny of a pressure system, in or out of service as appropriate, using suitable techniques, including testing where appropriate, to assess both its actual condition, and whether it will not cause danger up until the next examination (subject to routine maintenance).

A competent person (CP), who will be appointed by the user/owner, will carry out the examination. The role and attributes of the CP are outlined in paragraphs 35 to 43 and 104 to 108 of Safety of Pressure Systems, the PSSR Approved Code of Practice.

No specific guidance is given on what should be in the report of examination as the size and complexity of systems differ greatly but paragraph 144 of Safety of pressure systems provides suggestions as to what should be included.

Must every pressure system comply with PSSR?

Not all pressure systems need to comply with PSSR. Schedule 1 of the ACoP provides a list of systems that are either excepted from all regulations or from certain regulations. Additionally, Appendix 1 to the ACoP has an easy-to-follow flow chart that specifies which systems must comply.

If the system does not contain a ‘relevant fluid’ then PSSR does not apply.

Note however that if the pressure vessel contains steam at any pressure then PSSR does apply, irrespective of the pressure x volume product value.

I operate a coffee machine which generates steam at pressure. Do the Pressure Systems Safety Regulations 2000 (PSSR) apply?

Commercial coffee boilers incorporating a pressure vessel (e.g. cappuccino makers) generate steam and therefore come under the requirements of PSSR. Regulation 8 requires the drafting and completion of a written scheme of examination (WSE), and regulation 9 requires that this examination be carried out by a competent person. Please see other FAQs for further details of the WSE, the examination in accordance with the written scheme, and the role and attributes of the competent person.

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