Graphite containing gaskets for sea water application in SS/SDSS/Ni alloys

[Raghuram Bathula]

What is your experience with graphite containing gaskets used in sea water? Many gasket vendors recommended these for sea water application, but one of the NACE papers published is receommeded not to use..

The following is the extract from NACE paper 07262 : FACTORS AFFECTING GASKET SELECTION FOR STAINLESS STEELS IN SEAWATER  

Graphite is sometimes used as a filler in spiral wound gaskets. Provided it never contacts seawater, it should not cause a corrosion problem. If the windings are damaged prior to installation, so that the graphite is exposed to seawater, then there is a possibility of galvanic corrosion of the flange faces.

Strandmyr and Hagerup reported problems with graphite-containing gaskets on 6% Mo stainless steel flanges on several North Sea platforms13. The problems were solved by re-machining the flange face and changing to neoprene gaskets. Shrive14 reported a similar problem on the Rob

Roy/Ivanhoe platform, with super duplex stainless steel. Again the problem was solved by remachining the flange faces and changing, this time, to synthetic fibre gaskets.

[Devang Majithia]

True, graphite loaded gasket creates this kind of corrosion as graphite acts as a cathode against metal.

We are facing similar issue in our sea cooling water heat exchanger. For DSS/SDSS we are going with weld deposition with Alloy59 and gasket used is Inco625.

However, above mentioned approch is very costly and time consuming. We are thinking for using full Telfon gasket which will acts a barrier between different metals. 

Regards

Devang Majithia

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[Bagesh Kumar]

I faced this problem in one of the project of environmental importance located at the coast of Trinidad and Tobago, Client BP were categorically specified the use of Graphite as sealing agents for gaskets and valve packings, We utilized Peek gaskets instead of Graphite for moderate temperature services while Thermoculite was selected choice on High temp, 

Graphite when contacted with Sea Water tends to release chlorine which causes galvanic corrosion. 

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Bagesh Kumar
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[MW]

Dear Devang

what type of gasket it it? 

we have cam profile inco625 with graphite coating using in the subject case

[Devang Majithia]

Dear Raghuram,

It is spiral wound with/ without inner ring based on design. Gasket type was same, we just changed it to Inco625 in place of DSS/SDSS. I think full PTFE gasket from GORE/ TEADIT/ JAMES INMARCO can solve this issue. We are presently working on it and field trial in progress.

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