Written Schemes Of Examination

Under the Pressure Systems Safety Regulations 2000, users and owners of pressure systems need to show that they understand the safe working limits (especially pressure and temperature) of their operations and that they are safe following these conditions.

They require that a suitable written scheme of examination is in position before the system is operated. They also need to ensure that the system is actually examined according to the written scheme of examination.

What is a written scheme of examination?

A written scheme of examination contains information about selected items of plant or equipment that form a pressure system, operate under pressure, and contain a ‘relevant fluid’.

The phrase relevant fluid is described in the Regulations and covers compressed or liquefied gas, including air, at a pressure greater than 0.5 bar (approximately 7 psi) above atmospheric pressure; pressurised hot water above 110 °C; and steam at any pressure. 

Common contents of a written scheme of examination involve:

• identification of the items of plant or equipment within the system
• those parts of the system which are to be examined
• the nature of the examination required, including the inspection and testing to be carried out on any protective devices
• the preparatory work needed for the item to be examined safely
• where appropriate, the nature of any examination needed before the system is first used
• the maximum interval between examinations
• the critical parts of the system which, if modified or repaired, should be examined by a competent person before the system is used again
• the name of the competent person certifying the written scheme of examination; and
• The date of certification. 
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How do I draft up a written scheme of examination?

First of all, study your workplace and determine which items of plant or equipment operate under pressure and make a pressure system.

Then, follow the actions outlined in the HSE leaflet Pressure systems.

Then, check the Regulations’ exceptions, as you may find your particular pressure system does not require a written scheme of examination at all. For example, you don’t normally need to include the compressor associated with an air receiver in the scheme of examination.

To understand if any of your plant or equipment is an exclusion under the Regulations, the most suitable place to look is the Safety of pressure systems. Pressure Systems Safety Regulations 2000. Approved Code of Practice.

Which items of plant should I incorporate in the written scheme of examination?

An item of plant from the pressure system should be incorporated in a written scheme of examination if its failure could unintentionally discharge pressure from the system, and the resulting discharge of collected energy could provoke injury.

All systems are likely to be different, but the subsequent questions might assist users in arriving at some decisions:

• Do the manufacturers of the plant or equipment creating the pressure system provide guidance, instruction and precautions to take for the safe handling of the system?
• Could the malfunction of any part of the pressure system cause someone in the environment to be injured by releasing pressure, fragments or steam?
• Does the pressure system include any protective devices? 
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If your answer to any of the above questions is “Yes”, then those particular plant items may require to be incorporated in the written scheme of examination.

What types of typical pressurised systems might need a written scheme of examination?

The following pressurised systems are possible to require a written scheme of examination:

• a compressed air receiver and the associated pipework, where the product of the pressure in bars multiplied by the internal capacity in litres of the receiver is equal to or greater than 250 bar litres
• a steam sterilising autoclave and associated pipework and protective devices
• a steam boiler and associated pipework and protective devices; 
• a pressure cooker
• a gas-loaded hydraulic accumulator
• a vapour compression refrigeration system where the installed power exceeds 25 kW
• a narrow-gauge steam locomotive
• the components of self-contained breathing apparatus sets (excluding the gas container); and
• a fixed liquefied petroleum gas (LPG) storage system, supplying fuel for heating in a workplace.

The following pressurised systems are excused from the Regulations and don’t need a written scheme of examination:

• a machine tool hydraulic system
• any pipeline and its protective devices in which the pressure does not exceed 2 bar above atmospheric pressure
• a portable fire extinguisher with a working pressure below 25 bar at 60 °C and having a total mass of no more than 23 kg; and
• a tyre used on a vehicle.

The following pressurised systems may not need a written scheme of examination:

• an office hot water urn (for making tea etc.)
• a pneumatic cylinder in a compressed air system
• a handheld tool
• a combustion engine cooling system
• a portable compressed air receiver and the associated pipework, where the product of the pressure in bars multiplied by the internal capacity in litres of the receiver is less than 250 bar litres; and
• a portable LPG cylinder. 

These are common examples of direction purposes only. It would help if you decided whether your pressurised system is covered by the Regulations in practice.

Do I require written schemes of examination for portable gas welding kits?

A written scheme of examination is not required for the following:

• regulators
• pressure gauges
• hoses
• torches; and
• other components that create part of conventional gas welding sets (portable, twin-cylinder, oxyacetylene or oxy propane kits used for welding, cutting and burning).

Who determines which items of plant are incorporated in the written scheme of examination?

Users of pressure equipment that isn’t mobile, or owners of mobile systems (e.g. hired pressure plant), become a legal obligation to define the items of plant that create a pressure system and, inside that system, the items of plant which require to be incorporated in the written scheme of examination.

To come to an accurately informed decision, users or owners may require to ask advice from other experts, such as in-house engineering staff, inspection bodies or consultants. But the legal obligation for determining the extent of the scheme holds with users or owners.

The written scheme should commonly include all items within a self-contained pressurised system, which may increase the danger. If you hold more than one self-contained pressure system, you will presumably require more than one written scheme, i.e. one system, one scheme.

What occurs when the extent of the written scheme has been decided?

The user or owner of the pressure system should:

• talk to a person with adequate information and expertise about the system,i.e. one who is competent in giving knowledgeable advice on the matter;
• review the extent of the written scheme with them; and 
• if required, adjust the extent, respectively. 

The written scheme of examination should then be presented to an accountable person (as defined in the Regulations), who may or may not be the same competent person who directed the user or owner on the extent of the written scheme.

The competent person will usually guide on the nature and frequency of examination and any specific safety measures required to prepare the system for examination. If asked by the user, the competent person may put together a suitable written scheme of examination, or they may certify a written scheme of examination provided by the user or owner as being suitable.