Sticky O-ring

[Rubicon500]

Excuse my lack of O-ring design experience, but we are currently using an EPDM o-ring on a Polyester (PBT) housing, in which either a Polycarbonate (PC) or PBT lid gets screwed onto. The O-ring is a radial seal and is designed to have between 8-25% compression. I should also add that we are using a Molycote #44 lubricant that is compatible with EPFDM. The problem comes when the lids are screwed down on the housing, they go on very nice, but when left for a day or two they are very difficult (Sticky) to remove the lids.

Has anyone else experienced something similar and had a successful resolution?

 

[btrueblood]

Any sign of any of the materials softening/getting tacky? I wouldn't expect it, as all of those are compatible with silicone.

Radial seal to me means the o-ring is trapped between two cylinders. That can be a tricky part to disassemble at any time. We have added a thread in our covers to allow a pull ring to be threaded in to aid disassembly. I've also seen push threads (through threads in the cover) that allow a screw to be threaded in and bear on the mating flange to push the cover out. Even a screwdriver pry slot or two might help.

 

[Hidromar]

Hi!

Sorry to be so late!

Standard EPDM O-Rings' compound tend to be more stickier than other standard rubber o-ring material. This can be the reason why it works fine at mounting but after a time (enough to get off the grease on the contact area) it becomes more difficult.

On the other hand, you are using a compression range that is too much under the point of view of sealing. A penumatic O-Ring seal needs about 10% and 20% on hydraulics

My proposal. If your system will be for a large quantity, try to get a EPDM compound that is less stickier, otherwise use a Plastic ring on the contact surface, so less friction will be applied.

http://www.hidromar.es