need help with vulcanizing autoclave

[marketz]

I am in desperate need of advice, as I don't know where to go from here.
We have six autoclaves, one which keeps blowing seals at the bottom. Seals used to last 2-3 weeks, now only 15-45 minutes.
This is a flat seal with a 'V' groove in it, not the standard o'ring seal.
We have used an angle grinder, then sandpaper to smooth the sealing surface, resulting in a temperary improvement to 1 week before blowing. After a week it back down to 15-45 minutes before blowing.
We have measured the door sealing surface to the autoclave body and shimmed about .080" to bring the bottom in line. This had no results.
The same seal works fine on the other autoclaves currently in use (last typically 2-4 weeks), so it is not a seal or material issue. Material is rated at 400F, autoclaves run at 340F (supplied up to 350F from steam generator).
This is definitely a autoclave sealing issue.
These are Industrial Metal Products autoclaves (company now defunct), so there is no help from them.
Included is a sketch of the seal and it's mating surfaces.
Any advice is greatly appreciated.

 

[Compositepro]

That is a somewhat odd seal design. Does the rubber stay in the groove when the door is opened? Does the door rotate to lock with the claws on the vessel? It appears that the door may be designed with a fairly large gap between it and the vessel during operation. Perhaps this gap has gotten too large due to wear.

If using an angle grinder on the sealing surface improved things, I would have to say that it must be in really bad shape. The sealing surface should be close to polished. This type of seal should last for months or years before needing replacement. I'm guessing that you are used to seeing a small amount of leakage on a brand new seal and it then gets progressively worse. Any leakage will cause erosion of the rubber which leads to rapid failure.

You might find that a standard O-ring might work better for you. The flat surface of your sealing ring does not provide the contact pressure amplification that you get with an o-ring. You also seem to have vent holes between the chamber and the backside of the ring. This provides pressure to push the seal against the door. Are these holes plugged with dirt and debris, perhaps?

Pictures of failed seals would be helpful.

 

[marketz]

Compositepro, thank you for your email.
You asked: Does the rubber stay in the groove when the door is opened?
When the autoclave was sealing, the 'V' of the seal does stay in the groove, until the seal has seen around two days of use, then the silicone has elongated too much to stay in, and the seal falls out when opened.

You asked: Does the door rotate to lock with the claws on the vessel?
Yes
With the door locked, the seal is not actually touching the door. The holes in behind the 'V' groove pressurize and push the seal against the door.

You commented: The sealing surface should be close to polished.
If material is missing, is there a way to add material and re-surface the sealing surface?

You commented: I'm guessing that you are used to seeing a small amount of leakage on a brand new seal and it then gets progressively worse.
It doesn't appear to leak when installed, after the seal is pushed against the door. I guess I am probably afraid of taking the shroud off and closely inspecting for leaks when it may blow anytime- I would be forced to clean out my pants.

You commented: You might find that a standard O-ring might work better for you.
I would consider that, but wouldn't the angled surface (highlighted green in picture) prevent the o'ring from staying in place?

You asked: Are these holes plugged with dirt and debris, perhaps?
The gasket seems to push against the door after a short steam leakage out all areas, so I assume the are open. The diagram shows a short tube, but any wire we stick in the hole goes on and on. Is there a 'safe' way we can determine if the two holes are open to let steam to push the gasket?

Included is a picture of a failed seal. This failed seal is still pliable, only ran about 10 minutes. The seals in the other autoclaves get brittle and rip when aged before failing.

Compositepro, thanks for you help.

 

[Compositepro]

Your link is not working.

 

[marketz]

Sorry, I can't seem to get the pictures to load correctly when editing.
Here is the blown seal picture (hopefully).

 

[marketz]

It looks like a shorter filename works, I'll try this.

 

[3DDave]

The file download failed due to the filename containing the "#" character. It can still be downloaded if the URL is copied, pasted, and the "#" replaced with %35 before hitting Return.

See

https://www.ascii-code.com/

for other character replacements.

The other character people like to use that does not work is "&" (%38)