Double Acting Cap

Product Overview

A self-actuating, bi-directional, extrusion resistant seal that combines low breakout and running friction with minimal leakage.

The seal is constructed of a premium grade PTFE sealing element and an elastomer energiser.

The Double Acting Cap Seal is a reliable, compact design with a long service life and is available in both rod and piston type geometries to retro-fit into ISO7425-2.

Stick-slip is eliminated even after long periods of inactivity whether in a lubricated or non-lubricated environment, giving low breakout friction.

Double Acting Cap Seal

Double Acting Cap Seal Part Number Format

Standard Radial Sections

Radial Section CodeStandard Bore/Rod Diameter (mm)Piston Groove Diameter (mm)Rod Groove Diameter (mm)Groove Width (mm)
A = 1.78 8 - 16.9 Bore Ø -4.9 Rod Ø +4.9 2.20
B = 2.62 17 - 26.9 Bore Ø -7.3 Rod Ø +7.3 3.20
C = 3.53 27 - 59.9 Bore Ø -10.7 Rod Ø +10.7 4.20
D = 5.33 60 - 199.9 Bore Ø -15.1 Rod Ø +15.1 6.30
E = 6.99 200 - 255.9 Bore Ø -20.5 Rod Ø +20.5 8.10

Elastomeric Energiser Materials

ElastomerColourHardness (IRHD)Temperature RangeSelect for..Compound Reference
Silicone (VMQ) Red 70 -60 to +220oC

High and very low temperature; high eccentricity

Polyacrylate (ACM) Black 70 -10 to +150oC

High temperature capabilities; good compatibility with engine oils


Nitrile Rubber (NBR)

Black 70 -30 to +120oC General purpose 36624
Fluorocarbon (FKM, A-Type) Black 75 -20 to +200oC

High temperature performance; high speed applications; 514141 (Viton® GF type) for improved coolant and fuel resistance

Green 75 -20 to +200oC 51414G
Fluorocarbon (FKM, GF-Type) Black 75 -10 to +200oC 514141
Hydrogenated Nitrile (HNBR) Black 70 -30 to +180oC High temperatures, moderate fuel resistance 88625

PTFE Grade Codes

Material CompositionColourCoefficient of FrictionTemperature RangeSelect for..PTFE Reference
Virgin PTFE White 0.05/0.08

-240 to +200oC

Static or low duty cycles E400
Glass and MoS2 reinforced PTFE Grey/Black 0.06/0.10 -160 to +290oC

Dynamic or static, medium duty cycles, hardened metal running surfaces

Graphite reinforced PTFE Black 0.06/0.10 -200 to +250oC

Dynamic, medium duty cycles


Carbon and graphite reinforced PTFE

Black 0.08/0.12 -200 to +250oC Dynamic, medium duty cycles E462
Polyester reinforced PTFE Beige 0.08/0.12 -130 to +290oC

Dynamic or static, medium to high duty cycles, minimum 45 HRc running surface

Carbon, graphite and PPS reinforced PTFE Grey/Black 0.08/0.12 -130 to +290oC

Dynamic or static, high duty cycles, hardened metal running surfaces