Knowledge - 2026-07-03
What a Written Scheme of Examination Should Do
How a Written Scheme of Examination supports PSSR compliance and why it must reflect the actual pressure system.
Key takeaways
- A Written Scheme of Examination identifies what parts of a pressure system must be examined and when.
- A generic document can miss real installed components.
- Pressure examinations often need preparation, isolation and access planning.
The purpose of the written scheme
Under PSSR, many pressure systems need a Written Scheme of Examination before they are operated. The scheme is not just a certificate. It is a working document that defines the relevant parts of the system, the nature of the examination and the examination interval.
The scheme should make sense when compared with the installed system. If plant has been modified, moved, repaired or expanded, the written scheme should be reviewed so it still covers the real equipment.
- Pressure vessels
- Protective devices
- Relevant pipework
- Safe operating limits
- Examination intervals
Why generic schemes are risky
A pressure system can look simple from the outside while containing several relevant parts. A generic written scheme may fail to identify protective devices, receivers, connected vessels or sections of pipework that matter for safety.
The duty holder should be able to explain why each item is included or excluded. That does not mean every small component must be overcomplicated, but the scheme should be specific enough to be defensible.
- Compare the scheme with the plant on site
- Check whether repairs or modifications have been made
- Confirm safe operating limits are known
- Keep previous examination reports with the scheme
Planning the examination
Pressure-system examinations often need more planning than a visual walk-round. Some examinations require the system to be cooled, drained, isolated, depressurised or opened safely. That means the due date should not be the first time the site thinks about access.
Good planning avoids production disruption and gives the competent person the access needed to examine the system properly.
- Confirm shutdown windows early
- Arrange isolation where needed
- Have maintenance support available if covers or guards must be removed
- Keep repair evidence ready for review