8N Lift Piston

Dave S. · Aug 18, 2013

Bought new lift cylinder & single groove piston, where does the backing washer go, (in front of o-ring on the oil pressure side, in back of o-ring away from oil pressure or underneath the o-ring)? Shouldn't the piston with o-ring installed fit tight in cylinder?

Greg 2N (TX) · Aug 18, 2013

The leather backup washer goes in back of the o-ring away
from the fluid side.
The o-ring should make the tight seal and the leather backup
forms a backstop against the groove edge when under
pressure.

FYI
I had my cylinder honed as much as possible considering the
scratches.
Used CNH o-ring and CNH neoprene backup washer instead
of the leather one.

Greg

TheOldHokie · Aug 18, 2013

(quoted from post at 11:00:22 08/18/13) Bought new lift cylinder & single groove piston, where does the backing washer go, (in front of o-ring on the oil pressure side, in back of o-ring away from oil pressure or underneath the o-ring)? Shouldn't the piston with o-ring installed fit tight in cylinder?

The "backup" washer goes to the backside of the o-ring - e.g. the side away from the oil pressure. It supports the back of the o-ring and helps prevent o-ring extrusion. Extrusion occurs when the oil pressure deforms the o-ring into the gap between the cylinder wall and the edge of the o-ring groove in the piston damaging it - see image below. In a double acting cylinder you typically have backup rings on both sides of the o-ring since pressure is applied in both directions.

TOH

8N Lift Piston

Dave S.

Member

Greg 2N (TX)

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TheOldHokie

Well-known Member

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