INSULATION GASKETS REQUIREMENT

[IMSUT]

I have a question regarding the insulation gasket between dissimilar material.
In nozzle on a Carbon steel vessel I fit a Stainless steel Thermowell. Since they are dissimilar material, is the insulation gasket mandatory or can be used a convetional spiral wound gasket?
Some client ask for it only on piping, i.e. when a carbon steel line is connected to a st. steel line, others ask for all flanges, even for thermowells or blind flanges.
what is your opinion?
Is there any specification that indicate such requirements?

Any answer will be highly appreciated.

 

[XL83NL]

Looking for similar topics on this forum is easy.

Here are some examples of similar threads;

http://www.eng-tips.com/viewthread.cfm?qid=357250

http://www.eng-tips.com/viewthread.cfm?qid=277128

 

[LittleInch]

Also see this one which is almost identical.

http://www.eng-tips.com/viewthread.cfm?qid=358323

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