Use the actual bill of materials
The spare list should match the valve, actuator, instrument and control models on the supplied skid. Record part numbers, material grades, elastomers and revision details. A visually similar valve kit can be incompatible with the installed seat or product-contact requirement.
Rank by consequence and supply time
Consider which failures stop the whole system, which allow reduced-capacity operation and which can wait for planned service. Long-lead items deserve a different stocking decision from standard locally available parts. Include the plant location and import lead time in the assessment.
Separate consumables from strategic spares
Filter elements, seals and wear parts may be consumed on a service schedule. A spare instrument or controller is a different investment and may need configuration or backup files. Storage conditions and shelf life matter for some components. Ask what commissioning consumables are already included to avoid duplication.
Keep the list current
Update the spare register after an approved equipment change. Review actual usage after the first operating season and adjust quantities from evidence. The objective is faster restoration with the correct parts, not an unnecessarily large store. Include a clear supplier contact and the system serial number in the maintenance handover so that future requests can be resolved accurately.
General engineering guidance. Numerical examples are illustrative; project specifications and acceptance criteria are agreed for the actual duty.