Stainless steel pipes with carbon steel flange and valves

[abba7114]

I came across some 4" stainless steel pipes with carbon steel flanges and valves(butterfly), I first thought it was a mistake but further cheking revealed that all the flanges and valves are carbon steel as listed on the isometric.

But the piping material spec. sheet quite ok has s/s flanges but no butterfly valve.
I have since written to client for clarification.

Has any one come across such a thing and what could be the rationale.
thanks
Abba7114

 

[NozzleTwister]

Lap Joint (Van Stone) C.S. flanges are commonly used with stainless pipe. And many butterfly valves are lined.

Otherwise, I'd say the service wasn't that critical and someone tried to save some money or it's what was available on short notice.

NozzleTwister
Houston, Texas