"Dowty" seals

[mwfanwy]

Hi All,
More slow progress on the Milner Hunslet! (I'll post some pics soon).
Has anyone successfully used stainless steel with viton rubber "dowty" seals for seating a safety valve body to the boiler on an engine?
I have just completed two 1/2 BSP safety valves to Gordon Smith's design which have now been set on air at 100 PSI.
My thoughts turned to how best to seal these safety valves as they may need to be removed later and it may be helpful for maintenance and even to fill the boiler. Hence the thought of using dowty seals without any other sealant, relying on the face to face seal with the dowty washer. The viton is good for over 200 deg C, so should be OK with steam at 160 deg C (100 PSI wet).
Any thoughts guys?

[GeorgeRay]

I just use copper washers no sealant required and they provide a steam tight seal. The face of the bush does need to be smooth and flat though.

George Ray

[ejparrott]

There's one engine is use at the club that has dowty seals and it's having problems, after two steamings they start bubbling and leaking. Not sure on the condition of the seal face though. Copper washer's for me.

I absolutely detest safety valves being removed frequently for any reason. Repeated fitting and removing of boiler fittings will cause unnecessary wear ultimately leading to possible scrapping of a boiler. RMES had to have a new Netta boiler for just this reason. Once boiler fittings are assembled on my engine they will not be removed unless required for a failed component. Filling will be via a connection on the blowdown valve, safeties will be clamped for pressure test.

[Shawki Shlemon]

I do the same as ejparrott .

[mwfanwy]

Thanks for the thoughts guys. I'll use copper washers then!

[ejparrott]

It's old sckool, I know its not moving with the times, but I'm convinced they can stand the environment, copper washers work I know!