Materials for Cold Seals, Piston Seal and Displacer Seals for Cryopump

The biggest issue with this post is that there is no mention of the process fluid, its temperature and its pressure, all too common in CR4 threads these days.

The biggest issue with the suggestion is that this boss is steering away from a supplier's seal, with its attendant product guarantee, support and equipment warranty features, into a home-brew design that might affect the equipment's longevity and the process' safety without backup. Just why does this individual feel that in-house technicians, that have experience of just this one item of equipment, can come up with a better solution than the original equipment supplier, who has experience of hundreds-to-thousands <rhetorical question>?

The best way for the organisation to save money would be for that individual to leave.

Hi Betty,

It sounds like your Boss is being "Penny Wise and Pound Foolish".

I think it is highly unlikely that anyone can tell you the material of the seals from a black and white photo and a description.

If you get it wrong the loss of production and possibly new shafts or even a new pump would, I suggest, pay for several (many?) seal kits.

Your best option, if you intend to continue is to take a set of seals to a seal supplier and see if they can offer an alternative.

Best of luck,

John

You are inviting unforeseen /unsurmountable problems. Best option as has been suggested in two posts above , go for OEM kits.

Having the seals made in your mechanical workshop will insure the purchase of a new cryopump in the near future.

The use of the correct FACTORY seal kits will assure that the pump will give proper service for years to come, if used properly.

Compare the cost of a new pump to 50 factory seal kits and give that the the boss.

Ms. Yeung, You are talking to your doctor who has just informed you that you need a heart transplant, you ask the cost, he says $1,000,000, you say too much, are there any alternatives. He says sure we can use the heart of a horse, the price is only $100,000, similar tissue (mammal), similar function (pumps blood), similar size (may need to be trimmed to fit properly), similar life expectancy (except horses only live 25-30 years). Which one do you choose?

Same logic for a specialized piece of equipment such as a cryopump, when you consider the cost to replace the seals multiple times, loss of process fluid, loss of production, possible equipment damage, etc., do you really believe someone would want to purchase substitute a "similar to" set of seals?

I'm worried at where this thread might have intended to go.

A first time user, asking us how to make a cheap "copy" of reputable suppliers items (including obvious display of part numbers) and even asking what material it might be.

I sense a potential counterfeit operation starting.

If they truly own and operated a cryogenic pump for liquid Helium, then they probably have the smarts to arrange for an assay of the materials from a plastics supplier.

They then think that they could machine a component with similar behaviour to the original piece.

If I'm wrong, then all apologies to the original poster, but trying to manufacture replacement seals that are there in part to protect the expensive portions of the pump is folly. The time would be better invested finding how to extend the time between service intervals so fewer seals need to be replaced.

I agree with all of the other comments in general. Selecting the right material is not trivial and the manufacturer of the pump undoubtedly spent a lot of time and effort with the Tier 1 seal supplier to get it right. There is even a small chance that the material is reinforced with fiber or has metallic component like brass. I work with engineers who have been developing cryogenic pumps (300 bar, -160 C approx) for LNG (liquefied natural gas) and durability is highly dependent on base materials for seals, exact dimensions and tolerances, surface finish, filtration and cleanliness of assembly process. Paying for original parts is the best value. Good luck.