Selecting valve material based on pipe material doesn't always work.
A common example is 304 SS piping systems. While 304 pipe and fittings are readily available and less expensive than 316, the cast equivalent for 304 SS valves (CF8) is considered special, and is less available and more expensive than 316 SS valves (CF8M) - so - provided the application is compatible, it is quite common to specify 316 SS valves in a 304 SS system. PLEASE NOTE - 316 SS API Cast Steel Valves is not always an "upgrade" to 304 SS. Although rare, there are applications for which 316 SS is not suitable, but 304 SS is.
This is but one example. There are many others - so be sure to involve someone knowlegable in the field.
Pipe- material and pipe general layout are normally selected before valves in a project, as piping is (normally)the largest cost and determining for the total plant/project layout.

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