Not all encapsulated o-rings are of equal quality and performance abilities even though they may look alike!
Most manufacturers of encapsulated O-Rings use CYANOACRYLATE (quick glue) to join the ends of the Viton™ cord instead of vulcanizing with a fully curable fluorocarbon based adhesive. The glued joint is inferior to a vulcanized joint at elevated temperatures.
PROBLEM A: Introducing a foreign material, cyanoacrylate, may cause contamination thru permeation of the FEP or PFA jacket.
PROBLEM B: Certain chemicals, thru permeation, will attack and break down the glue, causing premature seal failure.
PROBLEM C: The quick glue bond is dramatically weakened during a rise in temperature and breaks down completely nearing 400°F; whereby the elastomer shrinks and the joint separates leaving a gap between the ends of the Viton™ cord.
PROBLEM D: When heating and stretching a glued O-Ring to fit over a shaft, the bond may break.
SOLUTION: Insist on ROW, INC. TFE-O-SIL® vulcanized encapsulated O-Rings! Ask your supplier what method they use to join the ends of their Viton™ encapsulated O-Rings...or simply run your own test by placing the O-Ring in an oven at 350°F for only 15 minutes. It will be clearly visible that the splice has completely separated, creating a gap or potential leak path.
Occasionally, encapsulated O-Rings will exhibit an AIR GAP of .005" - .010" between the elastomer core and the jacket.
PROBLEM A: The air gap allows considerably more compression set and reduces the resilience of the encapsulated O-Ring, resulting in premature leakage.
SOLUTION: Run compression tests to compare TFE-O-SIL® encapsulated O-Rings with other supplier O-Rings...or specify ROW TFE-O-SIL® O-Rings which have no air gap.