Insulation gasket between dissimilar metals in instrument air service
Insulation gasket between dissimilar metals in instrument air service
(OP)
Hello,
Our Client has asked for an insulation gasket where we have dissimilar material for the piping flange connection. In our case the flange connection is between SS instrument flange and galvanized pipe, while as per our drawings we have a graphite gasket.
Is it required to provide insulation gasket in such a case when the service is instrument air (i.e. dry service)? My understanding is that in such a case, galvanic corrosion is not an issue in the absence of an electrolyte.
Thanks,
Maen
Our Client has asked for an insulation gasket where we have dissimilar material for the piping flange connection. In our case the flange connection is between SS instrument flange and galvanized pipe, while as per our drawings we have a graphite gasket.
Is it required to provide insulation gasket in such a case when the service is instrument air (i.e. dry service)? My understanding is that in such a case, galvanic corrosion is not an issue in the absence of an electrolyte.
Thanks,
Maen





RE: Insulation gasket between dissimilar metals in instrument air service
If so, just do it.
Perhaps they are concerned about potential upset conditions. Or external corrosion due to moisture intrusion. Whatever it is, if the insulating gasket is not detrimental and the client is paying for it - do what they want.
RE: Insulation gasket between dissimilar metals in instrument air service
There is no clear requirement apparently and thus we arent payed for it (we would have done it if the client payed for it). This was listed as a punch point and as you are aware we try discourage the client from making unjustified demands here and there.
What do you mean by upset conditions? Is there a probable risk of onset of galvanic corrosion due to moisture intrusion?
RE: Insulation gasket between dissimilar metals in instrument air service
In a personal example, our "house" compressed air is supposed to be clean and dry here. In the 8 years I've been here, we have had 2 occasions where we had gallons of rusty liquid water come through. This was later followed by enough powdered rust to clog our filter traps.
RE: Insulation gasket between dissimilar metals in instrument air service
I asked earlier if there a probable risk of onset of galvanic corrosion due to moisture intrusion. Would corrosion be exacerbated by the attack of zinc from the galvanized flange on stainless steel as do zinc rich coatings?
Appreciate everyone's feedback.
Thanks,
RE: Insulation gasket between dissimilar metals in instrument air service
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: Insulation gasket between dissimilar metals in instrument air service
RE: Insulation gasket between dissimilar metals in instrument air service