High Pressure Seal

[jb1008]

Hello,

I have browsed your forum many times and found some helpful information but require some of your knowledge for one of my own problems.

I am having trouble finding/making a high pressure seal on one of our parts.

In short we have a pipe with a central pin though it, that needs a pressure seal capable of holding 200Bar indefinately. The seal will be used for a variety of chemicals from everyday fuel gasses to hydrogen sulphide, ammonia, chlorine etc.

The pipe ID is Ø11.1mm with the central pin Ø5mm. The pipe is welded and very rarely round so the seal must be adaptable (very very far from a machined finish). The seal must also pass over an M6 thread before gripping the 5mm pin inside the pipe. Other catches are that the seal must have very good dielectric strength as the pin could have a constant 690V through it. The working temperatures will be -40°C to +100°C.

Cost and manufacturability are obviously an issue, we have been looking at O-rings, but for 200bar with backing rings we cannot guarantee the minimum gap required with the weld and potential deformities(<0.3mm for 90+ Durometer).

Any advice even if it's just 'not possible' would be greatly appreciated.

If you have any questions please do not hesitate to ask more.

Thank you in advance,
James

 

[israelkk]

A drawing will be helpful.

 

[jb1008]

A very basic sketch of the part:

http://files.engineering.com/getfil...abf4-4d57-94c2-c4cdd9a920c9&file=Pressure.jpg

 

[flexibox]

do you have a better drawing? It does not seem to be very clear

 

[tr1ntx]

You don't explain why there can't be a post-welding machined bore on the pipe end where the seal would be. For 200 bar, I seriously doubt if you're going to be able to get consistent sealing on a pipe ID that is "very rarely round" and "very, very far from a machined finish". An elastomer pliant enough to conform will likely not be firm enough withstand that pressure.

Don't push the seal over the M6 thread. Construct a little mandrel, oh say 6.1mm ID and thin-walled, to slide over the thread and allow the seal to slip over it.

 

[DLite30]

Looks pretty sketchy to me...I'd steer away from this one guys.

I advise you that these forums are monitored.

 

[Hidromar]

Hi!

With such a high gap, for this pressure, an o-ring with back-up ring will do the work. Economy is not to be seen on how much a seal cost, but how much dismounting the hardware can be. If it's easy, consider an O-Ring, if the cost is high, refuse O-Ring.

By the way, back-up ring should be done according to real hardware.

The question here is why the gap has this size. The gap is defined by machining, of by the tube passing trougth?

By the way, as tribology is a "matter of each one", test must be held before using on productions, even with your ideas.

http://www.hidromar.es