PEEK Back Up Rings - Considerations in Design скачать в хорошем качестве

PEEK Back Up Rings - Considerations in Design

(Poly-Ether-Ether-Ketone) back up rings can be an excellent solution to give O-Rings greater pressure capability. However, there are design considerations when using this engineered polymer. What is this material we call PEEK? The PEEK molecule is comprised mainly of interconnected carbon rings. Covalent Carbon-Carbon bonds are very strong and are part of what gives PEEK it’s high strength properties. Another interesting fact about PEEK is that it is a semi-crystalline material, which means that it has areas where the molecular chains line up in an orderly fashion. You can think of these crystalline areas as reinforcements, thereby increasing the strength and extrusion resistance of the base material. How do we make sure we design a back-up ring correctly? The main consideration is that PEEK is about 20 points harder on the shore D scale than PTFE. What that means for us is that we can’t use standard PTFE back up specifications and apply them to PEEK. Essentially, we have to design with PEEK like it is a metal component. We need to know the exact hardware dimensions and tolerances to make sure we have a clearance fit. PTFE is soft enough that it can be stretched or compressed in a gland, but PEEK is not. PEEK back up rings must also be split to install in solid glands. Another thing that must be considered when using a PEEK back-up ring is the pressure cycling of the system. Rapid pressure cycling can cause the hardware to expand and contract, which in turn causes the split in the PEEK back-up to open and close. This situation can lead to a phenomenon called “nibbling”. When nibbling occurs the PEEK surfaces chew away into the softer O-Ring. The solution to this is to put a PTFE back-up in between the O-Ring and the PEEK, thereby protecting the O-Ring from the hard edges of the PEEK. There are several other things to consider if you are looking into PEEK as an option and a discussion with our engineering team would be encouraged. To learn more about this topic by visit eclipseseal.com and following the link below. http://eclipseseal.com/blog/seals/gui...