Cleanliness specification
Cleanliness specification
(OP)
Anybody know of an existing ISO/SAE/ASTM/etc. cleanliness specification for o-rings? I hate inventing my own if there is some industry standard I can reference.
Some background:
We normally buy o-ring direct from the manufacture, they come in sealed plastic bags and we take them straight into our clean room without washing. We have a couple of applications that use fluorosilicone o-rings which are somewhat delicate and rather easy to damage during installation so we have been having those o-rings shipped from the manufacture to another supplier who applies an anti-friction coating. These go back to the manufacture who repackages them and ships to us. Even though we 100% leak test the finished assemblies before shipping, we have had some field returns for leakage. When we test them we verify the leakage and on disassembly have found small fibers on the coated o-rings. We did a complete process walk of our clean room procedures and have determined that the fibers are on the coated o-rings when we receive them. We want to establish a cleanliness requirement for the incoming o-rings, hence my request.
I don't understand quite how these units pass initial testing and fail later but I'm pretty sure that won't happen if we don't have any fibers.
Some background:
We normally buy o-ring direct from the manufacture, they come in sealed plastic bags and we take them straight into our clean room without washing. We have a couple of applications that use fluorosilicone o-rings which are somewhat delicate and rather easy to damage during installation so we have been having those o-rings shipped from the manufacture to another supplier who applies an anti-friction coating. These go back to the manufacture who repackages them and ships to us. Even though we 100% leak test the finished assemblies before shipping, we have had some field returns for leakage. When we test them we verify the leakage and on disassembly have found small fibers on the coated o-rings. We did a complete process walk of our clean room procedures and have determined that the fibers are on the coated o-rings when we receive them. We want to establish a cleanliness requirement for the incoming o-rings, hence my request.
I don't understand quite how these units pass initial testing and fail later but I'm pretty sure that won't happen if we don't have any fibers.
----------------------------------------
The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.





RE: Cleanliness specification
Standards for allowed particle content of fluids (hydraulic oils, fuel oils) exists, and might be well adaptable in your case.
Not my area, but one of the links below might help you to search further. I got hits in Scandinavian and European standards.
http://www.sis.se/fluidsystem-och-delar/hydraulisk...
See page 10 in http://www.parkerhfde.com/pdf/conmon/dd015/DD00000...
RE: Cleanliness specification
----------------------------------------
The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
RE: Cleanliness specification
Cleanliness is vitally important to assure proper sealing
action and long O-ring life. Every precaution must be taken
to insure that all component parts are clean at time of
assembly. Foreign particles — dust, dirt, metal chips, grit,
etc.— in the gland may cause leakage and can damage the
O-ring, reducing its life.
I don't see anything saying how clean their o-rings are on delivery.
We have found that the problem o-rings are getting contaminated after they initially leave the manufacturer. It's happening either at the people applying the coating or when they are repackaged later. We are eliminating the repackaging and are running a trial eliminating the coater.
I'd still like to find a cleanliness spec for o-rings.
----------------------------------------
The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
RE: Cleanliness specification
The procedure was never used, as it was deemed easier to procure the o-rings to a vendor's standard packaging spec (believe it was Parker).
Why not use a little silicone grease on the o-ring at the time of application?
RE: Cleanliness specification
These are very small o-rings, it's difficult to pick them up (we use vacuum devices) and trying to lubricate them by hand would be a nightmare. Plus even in the clean room it's possible to get something on your gloves and then transfer it to the o-rings.
We have very tight leakage requirements on these products and even when the part passes initial testing we find some that fail later, usually because of a fiber on the o-ring. I can only surmise that the o-rings move in the glands enough during pressurization / de-pressurization cycles that a fiber that originally did not compromise the seal works it's way into a position where it does cause a leak.
----------------------------------------
The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.