Spring Energized Seals & Spring-Energized PTFE Seals

PTFE jacketed seals for aggressive chemicals, vacuum, cryogenic service and low-friction dynamic sealing.

Overview

Spring energized seals combine a precision-machined PTFE or filled-PTFE jacket with a metallic energizer spring. The spring maintains sealing force when standard elastomer O-rings or pure PTFE seals cannot. This makes them the preferred solution for aggressive media, extreme temperature cycling, high vacuum, ultra-clean process systems and low-friction reciprocating motion. They are often specified as spring-energized PTFE seals, Variseal-style seals, canted-coil spring seals or U-cup spring seals depending on the profile and the OEM naming convention. In practice, all of these products solve the same engineering problem: they provide elastic preload to a chemically resistant sealing jacket.

Why Engineers Specify Them

Chemical Resistance Beyond Elastomers

PTFE jackets handle acids, solvents, ketones, CIP chemicals and ultra-pure media that attack FKM, EPDM or NBR.

Best for: Chemical processing, semiconductor wet benches, pharma skids

Works in Cryogenic and High Heat

Spring preload compensates for PTFE's lack of elastic memory across extreme temperature swings.

Best for: LNG, cryogenic valves, thermal cycling duty

Low Friction Dynamic Sealing

PTFE sealing lips reduce friction and stick-slip compared with rubber O-rings in precision motion systems.

Best for: Reciprocating rods, valve stems, servo equipment

Vacuum and Low-Pressure Sealing

The energizer spring maintains contact force even when system pressure is low or absent.

Best for: Vacuum chambers, analytical equipment, aseptic filling lines

Spring Types

Spring Type	Description	Best For
Cantilever Spring	A light-load spring profile with low friction and fast response. Suitable for dynamic seals and moderate pressure.	Reciprocating motion, rotary shafts, vacuum service
Helical Coil Spring	Provides a more uniform preload over a wider deflection range and handles thermal cycling well.	Static sealing, cryogenic service, thermal expansion mismatch
Canted-Coil Spring	High recovery force with excellent resilience under wear. Often used in premium Variseal-style dynamic seals.	High-cycle dynamic duty, demanding valve stems, aerospace and semiconductor

Jacket Materials

Material	Properties	Best For
Virgin PTFE	Lowest friction, universal chemical resistance, clean and non-contaminating	Food, pharma, analytical instruments, general chemical duty
Carbon-Filled PTFE	Improved wear resistance, reduced creep, better dry-running performance	Dynamic motion, compressors, pumps, valve stems
Glass-Filled PTFE	Higher compressive strength and improved extrusion resistance	High pressure static and reciprocating service
PEEK / Specialty Polymers	Higher rigidity and temperature capability for specific premium seal designs	Aerospace, high-load seats, specialized OEM systems

Common Profiles

Rod Seal

For external pressure sealing on reciprocating rods and shafts.

Typical use: Cylinder rods, actuator shafts, valve stems

Piston Seal

For internal pressure sealing in bores with low friction and long cycle life.

Typical use: Hydraulic pistons, dosing pumps, precision actuators

Face Seal

For axial static joints where aggressive chemicals or vacuum are present.

Typical use: Flanges, reactor lids, semiconductor chamber seals

Internal / External Seal

Profile selected by pressure direction, groove layout and installation constraints.

Typical use: Custom manifolds, valves, pumps, instrumentation

Selection Guide

Factor	Guidance
Media	Use spring energized seals when the chemistry is too aggressive for elastomers or when contamination must be minimized.
Temperature	Consider them when the system cycles between cryogenic, ambient and high-temperature conditions.
Motion	They are ideal for low-friction reciprocating or slow rotary motion where rubber O-rings wear too quickly.
Pressure	Profile and spring selection depend on pressure direction and whether low-pressure sealing or high-pressure extrusion resistance is the priority.
Surface Finish	Seal performance depends heavily on shaft/bore finish, lead-in geometry and gland tolerances. They are less forgiving than standard O-rings.

Typical Applications

Semiconductor

Wet benches, UPW skids, chemical dosing valves and aggressive process media

Pharmaceutical

CIP/SIP systems, aseptic fillers, high-purity pumps and mixers

Oil & Gas / LNG

Cryogenic valves, gas handling systems, aggressive hydrocarbon media

Aerospace

Fuel systems, actuation hardware, lightweight low-friction sealing

Industrial Valves & Pumps

Stem seals, reciprocating pumps, high-cycle low-leakage duty

Frequently Asked Questions

What is a spring energized seal?

It is a PTFE or filled-PTFE jacketed seal with a metallic spring inside. The spring provides the preload that PTFE alone cannot, enabling sealing at low pressure, in vacuum, and through temperature cycling.

Is a Variseal the same as a spring-energized PTFE seal?

Variseal is commonly used as a style name for spring energized seals. In practice, engineers use terms such as spring energized seal, spring-energized PTFE seal, Variseal-style seal and canted-coil PTFE seal to describe the same family of products.

When should I choose a spring energized seal over an O-ring?

Choose it when the media is too aggressive for elastomers, when friction must be lower than a rubber seal can provide, when vacuum sealing is required, or when cryogenic or high-temperature cycling makes standard O-rings unreliable.

Can spring energized seals run dynamically?

Yes. They are frequently used on reciprocating rods, valve stems and some slow rotary shafts. The exact spring and jacket combination must match the motion, pressure and surface finish.

Do you make custom sizes and profiles?

Yes. We support custom gland dimensions, spring options, PTFE compounds and profile geometry for OEM sealing programs.