Ring Joint gasket for FBE coated RTJ flange 1

[Mateeng]

Happy Holidays, folks!!!
Does anybody can help find a suitable ring joint gasket suitable for FBE coated RTJ flange?
We a have a FBE coated piping with Class 1500# rating and Ring Joint Flange. Metal ring gasket like Soft Iron ring gasket may damage the FBE coating of the groove and cause corrosion in service.
Any thoughts or suggestion for ring gasket could work for water services at max 80 C.
Thanks in advance.

 

[mk3223]

As you pointed out, the potential damaged FBE coating on the RTJ gasket may cause leaking on the flange joint. It's highly possible. Can the gasket material be changed for the service?

 

[cap1a79]

Based on my experience, FBE flange is susceptible to crevice corrosion by coating defect as epoxy coating has limited design life.(ex., from 5 to 10 years) I think you'd better check the suitability of FBE coated flange before selecting the gasket. You may consider bare metallic flange(ex., CRA) that is suitable against the fluid.





Lee SiHyoung,
WorleyParsons Oman Engineering,

 

[Mateeng]

Hi Lee,
Great!!!
Let me see other options.
Actually if we go with Solid CRA/CRA weld overlay flange then wonder which the type of ring gasket we to use. Soft Iron does not work. Same CRA material (Alloy 625) would work and may provide the necessary sealing?
Have you heard about rubber coated iron ring joint gasket for FBE coated RTJ flanges? Any help appreciated.

 

[cap1a79]

1) In case the CRA(ex. alloy 625) is confirmed as suitable against process condition, then same metallic material(ex., 625) for inner & centering ring with graphite sealing can be used for gasket. In a safer side, complete sealing shall be confirmed by gasket vendor, finally.

2) If you do not have any idea whether the CRA is suitable or not, just check the material selection for the connected valve body, assuming that the valve body material was suitably selected, exposed to same process fluid. (Generally, FBE coating is not recommended not only for flange(due to crevice) but also valve body(due to susceptibility of turbulent flow). Hence, flange & valve body can be classed in a same group to apply same CRA, once same fluid is exposed to.

3) Also, you can review chemical resistance table provided by the vendor as a double check. You can see the one of the examples as per the link below. (ex., graphite product is suitable against sea water from the example.)

https://www.sealingprojex.com/wp-content/uploads/2012/05/gasket-chemical-resistance-chart.pdf

4) I do not have any experience for FBE coated flange and the associated gasket. As stated before, due to the reason of crevice, I've never accepted it and won't consider it unless it is for temporary use.





Lee SiHyoung,
WorleyParsons Oman Engineering,