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Backup seal for 8n hydraulic piston

R

Randy Hurt

Member
Got a backup seal part #87051231 and a new o ring for hydraulic lift piston thought it would b a neoprene ring but it is a cupped rubber one
My question is which way does the cupped side go? Next to the o ring or toward the back side. My guess would be next to the o ring.
 
IF you have the correct part and that's a big IF the cup always faces toward the pressure side. That way the pressure expands the cup and seals it against the cylinder.
 


87051231 is a continuous loop pliable back up washer (black) that will stretch over the piston and into the groove . The O-Ring touches the cupped side .

The PTFE (teflon) ring for these pistons (white) are solid and has a 45 degree cut where the ends meet so it may be installed in a groove .

With most things mechanical there can be made an argument for either side being "Better" But 94% or 96% is the argument when 75% will last 20 years .I have both types in stock and will be using the Black one piece cupped back up washer on all of mine .

The bigger factor would be the smoothness of the cylinder wall . Ideally ( 94 - 96% ) you would have a smooth perfect bore . But if I had to choose from a tight bore with small scratches or a slightly oversized bore that was very smooth I would choose the smooth bore for the O-Ring which has some compression built into the sizing (30% compression ? ) .

I plan on keeping one 8n at least until I can't drive it anymore . I will be installing a live hydraulic pump set up , mostly for the oil filtering capabilities .

YMMV - Ken(Ark)
 
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