HSE guidance on written schemes of examination stresses that an appropriate scheme must be in place before a pressure system is operated and that examinations must be carried out in accordance with it. The scheme should cover protective devices, pressure vessels and any sections of pipework whose failure could be dangerous. For operators, this means the scope should not stop at the vessel shell alone.
The real value of a written scheme is that it defines in advance what should be examined, how often, by which method and under what preparation conditions. Its logic should be based on fluid characteristics, safe operating limits, historical damage mechanisms and service conditions, rather than copied from another plant.
HSE also makes clear that a statutory examination performed under a written scheme is not a substitute for routine maintenance. Users still need routine inspection, leak checks, gauge verification, valve maintenance and incident recording. Treating the written scheme as a replacement for everyday maintenance is a management error.