Install the energizer first
Place the O-ring or elastomer energizer in the clean groove without twisting it.
PTFE seal installation
How to Install an Energized PTFE Hydraulic Seal Without Overstretching It
Energized PTFE seals behave differently from flexible rubber or polyurethane U-cups. The PTFE ring has limited elastic recovery, so controlled expansion, clean tooling and post-installation sizing are especially important.
Energized PTFE seal visual sequence
PTFE has limited elastic recovery, so expansion and sizing need more control than a flexible U-cup.
Expand the PTFE ring evenly
Use the specified cone/tool to expand the PTFE ring only enough to pass over the piston or gland.
Seat over the energizer
Center the PTFE ring over the energizer and remove any visible twist or uneven bulge.
Size/calibrate the ring
Use the specified sizing sleeve or recovery procedure to bring the seal close to its working diameter.
Protect assembly edges
Cover threads, ports and sharp shoulders before the seal crosses them during final assembly.
Assemble without shaving
Enter the mating surface squarely and stop if the PTFE ring starts to shear or bunch.
Do not improvise heat, stretching distance or sizing time. PTFE seal installation limits depend strongly on the exact design.
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1. Clean and inspect the groove
PTFE can be damaged by sharp burrs and can permanently deform if forced. Deburr the groove, protect threads and cover adjacent grooves the ring must cross.
2. Install the energizer first
Where the design uses an O-ring energizer, place it in the groove without twisting it. Confirm material and size before fitting the PTFE ring over it.
3. Expand the PTFE ring gradually
Use a smooth tapered mandrel or expansion tool where recommended. Increase the diameter slowly and evenly; avoid localized stretching.
4. Move the ring into the groove
Guide the expanded ring over the protected component and into its groove. Confirm it is centered over the energizer and not trapped on an adjacent edge.
5. Size or calibrate the ring
After expansion, the PTFE ring may stay oversized. A sizing sleeve, calibration mandrel or burnishing shell restores the working dimension and helps prevent the ring from being shaved during final assembly.
6. Allow recovery time when the manufacturer specifies it
Some materials and profiles benefit from time after sizing before final assembly. Follow the seal maker’s instructions rather than forcing an oversized ring immediately into service.
7. Final assembly must be smooth
Use the designed lead-in chamfer and insert squarely. A PTFE ring that catches on a sharp edge can be sliced even though it appears visually robust.
Do not substitute improvised sharp tools. PTFE installation tools are primarily about controlling stretch and preventing edge damage.
See also hydraulic seal material compatibility.
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To connect this inspection with the next repair decision, see Skydrol & Phosphate-Ester Seal Compatibility: Guide and Checker.
Technical references
Always use the exact seal manufacturer and machine service instructions when they are available.
Not sure which seal you have?
Identify the seal and confirm the failure mode before installation.
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