Material Options for Cryogenic Nitrogen Seal Faces 1

[mechengr12]

I am looking for some help and recommendations on cryogenic nitrogen service seal faces. I currently use a Tungsten Carbide to PPCF polymer faces as in the link below.

http://www.ppcmechanicalseals.com/PDFs/Cryogenic-Brochure.pdf

We have significant seal issues and typically get a few days to possibly a few weeks of seal life. The soft polymer seems to wear extremely quickly. We are working on operating issues to prevent dry running and cavitation but still would like to consider other seal types and materials to try ourselves. Has anyone tried to hard faces together in this type of service? Possibly Tungsten Carbide to Tungsten Carbide? Also, has anyone has experience with a John Crane non-contacting seal in a cryogenic service?

https://www.johncrane.com/products/mechanical-seals/non-contacting/type-285

Lastly, is it acceptable to have a machine shop machine your own seal face and lap the face?

Any help is greatly appreciated.

 

[flexibox]

Don't play with this. Go to a reputable seal company and ask for their support and I do recommend the 285 seal for this application. It's cost is high when compared to a local workshop but it's reliability will out weigh the cost and a local workshop does not understand mechanical seals in detail.

 

[Chpal1984]

Yeah you don't want to be using polymers on cryogenic applications, hence why the John Crane seal uses metal bellows. Save yourself some money and go straight to a seal company John Crane, eagle burgmann etc

 

[mechengr12]

flexibox,

Thanks for the response. I have ordered a John Crane seal, but was wondering if you had any recommendations on the rotating and non-rotating faces. Are there any good combinations for Tungsten Carbide paired with a harder material? Something like carbon or TC against TC?

 

[Chpal1984]

Whats your reason for wanting hard vs hard? I've used SiC vs SiC before, but never TC vs TC.

Generally on pump gas seals people prefer one of the faces to be carbon. Gas seals work using grooves on the face, if you have hard vs hard any contact risks damaging the grooves. Whereas if you grooves are in TC and there is any contact with a carbon face, you won'r damage the grooves. Simples