Written Scheme of Examination
Pressure systems must be inspected in accordance with a written scheme of examination created (or certified) by a competent person.
The user (or owner) of the pressurised system must ensure that the competent person has the necessary knowledge, experience and independence to undertake the tasks required of them.
With respect to the written scheme of examination, the role of the competent person is either:
- to create and certify a written scheme of examination, or
- to certify a written scheme of examination created by somebody else
(such as the owner or user of the pressure system).
The level of expertise needed by the competent person depends on the size and complexity of the system.
The competent person should ensure the written scheme specifies:
- which parts of the pressure system need to be subject to examination
- what types of examination are necessary and the intervals between them.
The written scheme of examination is a document containing the relevant information about a pressure system.
The typical contents of a written scheme of examination include:
- the details of the owner or user of the pressure system
- the (usual) location of the pressure system
- identification of all of the items of plant or equipment within the pressure system
- identification of those parts of the system that are to be examined
- details of the nature of the examination required, including details of any inspection and testing to be carried out on any protective devices
- details of any preparatory work that is 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
- the date of certification
Typical equipment that is likely to require a written scheme of examination includes:
- compressed air receivers and associated pipework, where the capacity of the system is greater than 250 bar litres
- steam boilers and associated pipework and protective devices
- autoclaves and associated pipework and protective devices
- gas loaded hydraulic accumulators
- vapour compression refrigeration systems, where the installed power exceeds 25 kW
- narrow gauge steam locomotives
- the components of self-contained breathing apparatus sets, excluding the gas container
- fixed LPG storage systems workplace
Conversely, the following (pressurised) systems are unlikely to require a written scheme of examination:
- an office hot water urn (for tea making);
- a machine tool hydraulic system;
- portable gas welding sets; and
- an atmospheric oil storage tank
The HSE have taken the view that written schemes of examination are not required for the:
- regulators
- pressure gauges
- hoses
- torches
- and other components that form part of conventional gas welding sets (portable, twin cylinder, oxy-acetylene or oxy-propane sets used for welding, cutting and burning).
In most cases, it is the duty of the users of the pressure system, to define the items of plant which form a pressure system and to define within that system the items of plant and equipment that need to be included in the written scheme of examination. In the case of mobile pressure systems (such as hired pressure plant), this duty falls on to the owner of the equipment (such as the hire shop).
If there is more than one pressure, then there will usually be a requirement to have a corresponding number of written schemes of examination.
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- reproduce the scheme readily as a written copy
- be authenticated by the competent person
- be protected from unauthorised alteration.
If appropriate, the requirement for an examination before the system is first put into use should be specified in the written scheme of examination.
Review and Revision of the Written Scheme of Examination
The written scheme of examination must be ‘suitable’ throughout the lifetime of the plant or equipment. It should be reviewed and, when necessary, revised. As the plant and equipment involved ages, it may become necessary to carry out more frequent examinations or to change.
Frequency of Examinations
When deciding on length of periods between examinations, the aim should be to ensure sufficient examinations are carried out to identify at an early stage any deterioration or malfunction that is likely to affect the safe operation of the system. Different parts of the system may be examined at different intervals, depending on the degree of risk. Protective devices should be examined with at least the same frequency as the plant they are fitted to. Some protective devices may need to be examined at more frequent intervals. Each examination should include checks that the devices function correctly and are properly calibrated, or alternatively that they have been replaced by recently tested units.
Report Following Examination
The report must:
- detail the components examined, their condition and the examination results
- specify the repairs/modifications/changes to safe operating limits necessary to prevent danger, or to ensure continued effective operation of the protective devices, and the time limit for carrying out the repairs, etc
- specify the date after which the pressure system cannot be operated without a further examination (this may be postponed in some circumstances)
- state whether the competent person considers the written scheme to be suitable, or in need of modification, in which case the reasons must be given.
Summary
The written scheme of examination is a statutory requirement placed on the users (or owners) of pressure systems. The purpose of the written scheme of examination is to ensure that the pressure system is safe to use remains so. The nature and frequency of the examinations are determined by a competent person and consider the nature and use of the equipment and the effects of wear and tear on the pressure system. The pressure system must be inspected, again by a competent person, in accordance with the provisions f the written scheme of examination.
