Pressure System Written Scheme of Examination

A Written Scheme of Examination (WSE), is a legal document required prior to use of Pressure Systems. This is legislated by UK regulations detailed in Pressure System Safety Regulations (PSSR) 2000. It details items within a Pressure System that necessitate examination by a competent person.

As specified in Regulation 8.1 of PSSR “The user of an installed system and owner of a mobile system shall not operate the system or allow it to be operated unless he has a Written Scheme for the periodic examination, by a competent person”. 

HSE defines competency as the combination of training, skills, experience and knowledge that a person has and their ability to apply them”.

The Competent Person will identify which items of the pressure system fall within the scope of the WSE, such as pressure vessel, protective devices and pipework. Once these items have been established the frequency of examinations will be outlined.

The following types of pressurised systems are likely to require a WSE:

  • Compressed Air Systems where the vessel has a pressure volume product greater than 250 bar litres (This is calculated by multiplying the operating pressure of the vessel in bars by the size of the vessel in litres –  bars x litres );
  • Steam sterilising autoclaves;
  • Certain espresso type coffee machines with steam boilers;
  • Pressure cookers;
  • Gas-loaded hydraulic accumulators, if forming part of a pressure system;
  • Portable hot water/steam-cleaning unit fitted with a pressure vessel;
  • Vapour compression refrigeration system where the installed power exceeds 25 kW;
  • Steam boilers, including standard or narrow-gauge steam locomotives;
  • The components of self-contained breathing apparatus sets (excluding the transportable pressure receptacle);
  • Fixed LPG storage systems supplying fuel for heating in a workplace.
  • Protective devices such as Pressure gauges, safety valves, pipework, level indicators, pressure and temperature switches


The WSE must remain relevant to the Pressure System it relates to and therefore requires periodic reviews. Frequency of reviews may vary depending on the competent person.

Provision of WSE

Mandate Systems are equipped to provide Competent Person services up to and including Major Systems. Therefore we can fully complete all WSE, examinations and reviews. Mandate have technically qualified and experienced staff with knowledge of the law, codes of practice, examination and inspection techniques. We also have a thorough understanding of the effects of operation for the system concerned, all supported by a chartered engineer. This means we can assist with every requirement.   


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What is covered under a Written Scheme of Examination?

Pressure storage units: 

This includes air receivers, boilers, autoclaves, gas cylinders and pressure cookers

Protective devices:

This includes pressure gauges, safety valves, pipework, level indicators and pressure and temperature switches

This is NOT an exhaustive list and a competent person must be employed to certify and establish items for inclusion to a written scheme.

Access can be arranged so that the “End User” a “Group Owner” a “Service Provider” would be provided with different levels of access.

What is the purpose of a Written Scheme of Examination?

The written scheme of examination specifies items for examination, a frequency for examination (eg. 6, 12, 24 months) and contain detail as to how the equipment is to be examined. If any special measures are required to prepare the system for safe examination then these would be included.

Do I need a Written Scheme of Examination?

Under the Pressure Systems Safety Regulations you must have a WSE in place prior to the use of the system. This system would include a rigid vessel and a relevant fluid, mainly gas (Carbon Dioxide, Nitrogen, Argon, Steam among others), with a pressure at 0.5 Bar or above excluding steam, which is at any pressure, and any pressure vessel that has a pressure x volume product of 250 bar litres or more.