Genuine or equivalent spares: where the warranty actually sits

The price difference between OEM and aftermarket turbine parts is real, and so is the paperwork difference. Here is what each route actually buys you.

The argument over equivalent parts is usually framed as quality. In practice it is framed by two documents: the material certificate and the warranty clause. Get those right and a qualified aftermarket part is a defensible engineering decision. Get them wrong and the saving is a liability with a part number.

What a genuine part carries

• OEM part number traceable to the frame serial and the assembly drawing revision
• Material and heat-treat certificates from the OEM supply chain
• A warranty that is usually conditional on OEM-supervised installation and OEM consumables
• A documented design provenance, which matters if there is ever an insurance or litigation question

What a qualified equivalent carries

• A dimensional report against the OEM drawing, measured and signed
• Raw material certification to the same specification, from a named mill
• Coating and heat-treatment records if the part is a hot-section item
• A warranty on the part itself, and — this is the part to negotiate — on consequential damage

The decision in practice

We buy aftermarket for everything that cannot destroy the rotor. Above that line it is OEM or it does not go in.

Procurement director, independent power producer

Questions to ask before you accept a quote

• Which drawing revision was the part measured against, and can I see the report?
• Who is the mill, and can I see the certificate rather than a summary of it?
• What does the warranty exclude, in plain language?
• If the part fails and damages the machine, what is covered?
• Will you provide an exchange unit on the same lead time for the next outage?

A supplier who cannot answer these without a round of internal email is not a supplier for a hot-section component. The answers are either in the file or they do not exist.

• Spares
• Warranty
• Traceability