PSSR Written Schemes of Examination: What Every Duty Holder Must Know
The Pressure Systems Safety Regulations 2000
The Pressure Systems Safety Regulations 2000 (PSSR) apply to all pressure systems used at work where there is a risk of serious injury from the uncontrolled release of stored energy. These regulations replaced the earlier 1989 regulations and introduced a more structured, risk-based approach to pressure system safety.
The consequences of pressure system failure can be catastrophic. Boiler explosions, ruptured vessels, and failing pipework can cause fatal injuries, severe burns, and extensive property damage. The PSSR framework is designed to prevent these outcomes through systematic planning, examination, and maintenance.
What Constitutes a Pressure System?
A pressure system under PSSR includes:
- Steam boilers and associated pipework
- Pressurised hot water systems above 0.5 bar
- Compressed air systems and receivers
- Autoclaves used in laboratories, hospitals, and manufacturing
- Hydraulic power systems
- Gas storage and distribution systems
- Refrigeration systems operating above specified pressure thresholds
- Pipework and fittings connecting these systems
The regulations apply to the system as a whole, not just individual components. This means that pipework, valves, gauges, and safety devices are all part of the pressure system and must be included in the examination scheme.
Transportable Pressure Equipment
Gas cylinders and other transportable pressure receptacles have specific requirements under separate regulations, but when connected and in use as part of a workplace pressure system, they fall within the scope of PSSR.
The Written Scheme of Examination
The centrepiece of PSSR compliance is the Written Scheme of Examination (WSE). This document specifies what parts of the pressure system must be examined, the nature of the examination required, and the maximum intervals between examinations.
The WSE must be drawn up or certified by a competent person -- typically an engineer from an inspection body such as a UKAS-accredited organisation. The scheme must cover:
- All protective devices (safety valves, pressure relief devices, and pressure gauges)
- Every pressure vessel within the system
- All pipework and fittings where deterioration could lead to danger
- The nature and frequency of each examination
- Any special measures or preparation required for examination
Reviewing and Updating the WSE
The Written Scheme is not a static document. It should be reviewed whenever there are significant changes to the system, when examination findings suggest that intervals should be shortened, or when operational conditions change materially. The competent person responsible for the scheme should be consulted on any modifications to the pressure system.
Examinations Under PSSR
Examinations must be carried out by a competent person in accordance with the Written Scheme. The competent person must be sufficiently independent from the operating organisation to make impartial judgements. In practice, this usually means an engineer employed by a specialist inspection body.
During an examination, the competent person will:
- Assess the condition of pressure-containing components through visual inspection and, where specified, non-destructive testing
- Verify the correct operation of all safety devices
- Check that operating parameters remain within design limits
- Review maintenance records and operational data
- Confirm that the system is being operated within the parameters assumed in the Written Scheme
- Produce a written report of findings within 28 days (or immediately for imminent danger defects)
Duty Holder Responsibilities
The user of a pressure system (the duty holder) has several key obligations under PSSR:
- Ensure a Written Scheme of Examination is in place before the system is operated
- Ensure examinations are carried out in accordance with the scheme
- Provide safe access for the competent person to carry out examinations
- Act on the findings and recommendations in examination reports
- Maintain the system in good repair so that it does not give rise to danger
- Keep adequate operating and maintenance records
- Ensure that persons operating the system are properly trained and informed of hazards
Safe Operating Limits
Every pressure system must have established safe operating limits. These limits define the maximum (and sometimes minimum) pressure, temperature, and flow rates at which the system can safely operate. The operating limits must be documented and communicated to all persons who operate or maintain the system.
Operating a pressure system beyond its safe operating limits is one of the most dangerous things a duty holder can do. Over-pressurisation can cause sudden catastrophic failure, and operating at temperatures beyond design parameters can weaken materials and compromise joint integrity.
Work Equipment Inspection
LDN Inspection Services provides thorough examinations and statutory inspections for lifting equipment, pressure systems, and work equipment across the UK. Our competent engineers deliver fast, reliable reports to keep your operations safe and compliant.
Book InspectionFrequently Asked Questions
A Written Scheme of Examination (WSE) is a document that specifies which parts of a pressure system must be examined, the nature of each examination, and the maximum intervals between examinations. It must be drawn up or certified by a competent person and must be in place before the pressure system is operated.
If your compressed air system includes a receiver (air tank) or operates above certain pressure thresholds, it almost certainly requires a Written Scheme of Examination under PSSR. Even relatively small systems can present significant hazards if they fail, so it is important to have a competent person assess your specific installation.
The examination intervals are specified in the Written Scheme of Examination and are determined by the competent person based on the type of equipment, its condition, operating parameters, and the consequences of failure. Typical intervals range from 12 to 26 months for pressure vessels, though safety devices such as relief valves are often examined more frequently.
Some equipment, such as hydraulic cranes, falls under both PSSR and LOLER. In these cases, both sets of regulations apply simultaneously. The lifting function is examined under LOLER, while the hydraulic pressure system is examined under PSSR. A competent person can often coordinate both examinations to minimise disruption.
As the user (duty holder), you must ensure a Written Scheme of Examination is in place, arrange examinations in accordance with the scheme, provide safe access for the examining engineer, act on defect findings within specified timeframes, maintain the system in good repair, keep operating and maintenance records, and ensure operators are properly trained.
LDN Inspection Services
We are a specialist inspection body delivering statutory examinations of lifting equipment, pressure systems, and work equipment to businesses across the United Kingdom. Our team of competent engineers is committed to helping duty holders meet their legal obligations efficiently and without disruption.