The spring within the U-type spring energized seal provides sealing force under zero-pressure conditions; as system pressure enters the U-shaped cavity, it forces the sealing lips more tightly against the shaft, the higher the pressure, the tighter the seal.
Furthermore, the PTFE material offers excellent universal chemical resistance and a wide operating temperature range of -180°C to +200°C; it supports pressures up to 40 MPa (dynamic) / 60 MPa (static) and linear speeds up to 15 m/s, making it suitable for a broad range of operating conditions.
U-type spring energized seal is a PTFE U-shaped jacket with a metal spring inside. It is a unidirectional sealing element designed for rod (internal sealing) or piston (external sealing) applications.
How it works:
Zero pressure: Spring provides initial sealing force, seals even when system is not pressurized
Under pressure: System pressure enters U-cavity and pushes sealing lips harder against mating surface, pressure = tighter seal
Self-energizing: Spring compensates for wear, hardware tolerances, and thermal cycling, maintains seal force over time
|
Feature |
U-Type |
V-Type |
|
Sealing Direction |
Radial — piston rods, valve stems |
Axial — flanges, covers, end faces |
|
Best For |
Dynamic sealing (reciprocating/rotary) |
Static sealing |
|
Pressure Range |
Up to 40-60 MPa |
Up to 60 MPa |
|
Speed |
Up to 15 m/s (reciprocating) |
Lower — static or low-speed rotary |
|
Problem |
How U-Type Solves It |
|
O-rings leak at zero pressure |
Spring provides sealing force — no "starting leak" |
|
Rubber degrades in chemicals |
PTFE jacket is chemically inert — pH 0-14, universal resistance |
|
Elastomers fail above +150°C |
Handles -180°C to +200°C |
|
High friction — stick-slip |
PTFE has lowest friction — smooth motion, no stick-slip |
|
O-rings fail on moving shafts |
Designed for reciprocating and rotary motion — dynamic sealing |
|
Frequent replacement |
Spring compensates for wear — lasts years, not months |
|
Feature |
U-Type Spring Seal |
O-Ring |
V-Type Spring Seal |
|
Zero Pressure Sealing |
✅ Yes — spring provides force |
❌ No |
✅ Yes |
|
Pressure — Dynamic |
Up to 40 MPa |
Moderate |
Lower |
|
Pressure — Static |
Up to 60 MPa |
Moderate |
Up to 60 MPa |
|
Temperature |
-180°C to +200°C |
-180°C to +200°C |
-180°C to +200°C |
|
Chemical Resistance |
★★★★★ universal |
★★☆☆☆ |
★★★★★ |
|
Friction |
★★★★★ lowest |
★★★★☆ |
★★★★★ |
|
Shaft Movement |
Reciprocating & rotary |
Static only |
Static/low-speed |
|
Wear Compensation |
✅ Spring compensates |
❌ No |
✅ Yes |
|
Best For |
Piston rods, valve stems |
General static |
Flanges, covers |
|
Cost |
$$$ |
$ |
$$$ |
|
If Your Service Is... |
Choose... |
|
Piston rods, valve stems — reciprocating motion |
U-Type with helical/cantilever spring |
|
Rotary shafts — low speed rotation |
U-Type with cantilever spring |
|
Flanges, covers, end faces — static sealing |
V-Type |
|
General purpose, low cost, clean media |
O-Ring |
|
High pressure (up to 60 MPa) |
U-Type with back-up rings |
|
Extreme temperature (-180°C to +200°C) |
U-Type with Elgiloy/Hastelloy spring |
|
Food/pharma contact — FDA compliance |
U-Type with virgin PTFE jacket |
|
Industry |
Application |
|
Chemical Processing |
Piston pumps, valve stems, reactors — acids, solvents, aggressive chemicals |
|
Pharmaceutical |
Sterile processing, filling equipment — FDA/USP, CIP/SIP sterilization |
|
Food & Beverage |
Sanitary valves, filling machines — FDA compliance, CIP fluids |
|
Semiconductor |
High-purity gas and chemical seals, vacuum systems — ultra-purity |
|
Oil & Gas |
Wellhead equipment, control valves, pumps — high pressure, H₂S |
|
Aerospace |
Hydraulic systems, fuel systems — extreme temperature, high reliability |
Challenge: A chemical plant was replacing rubber O-rings on piston pumps handling solvents every 2-3 months due to swelling and hardening, causing production interruptions.
Solution: Installed U-type spring-energized seal with carbon-filled PTFE jacket and 316 stainless steel spring. Standard AS568A groove design maintained.
Result: Seals lasted over 9 months, 3x longer than rubber. Zero leakage. Maintenance intervals extended from weeks to seasons.
Challenge: A pharmaceutical filling machine required a seal for a rotary valve handling sterile product. Rubber O-rings could not pass FDA extractables testing.
Solution: Supplied U-type spring seal with virgin PTFE jacket and 316 stainless steel spring. FDA-compliant material. Full documentation provided.
Result: Passed FDA extractables testing. Seal survived repeated CIP/SIP sterilization cycles. No replacements in 18 months.
Note: Actual case results vary by application conditions. Contact us for application-specific recommendations.
|
Parameter |
Value |
|
Temperature Range |
-180°C to +200°C (grade dependent) |
|
Pressure — Dynamic |
Up to 40 MPa (with back-up rings: up to 60 MPa) |
|
Pressure — Static |
Up to 60 MPa |
|
Speed — Reciprocating |
Up to 15 m/s |
|
Speed — Rotary |
Up to 1-3 m/s |
|
Material |
PTFE jacket + Stainless Steel spring (301/316) |
|
Chemical Resistance |
pH 0-14 — virtually universal |
|
Sealing Type |
Radial sealing — rod or piston |
|
Grade |
Best For |
Key Benefit |
Chemical Limit |
|
Virgin PTFE |
Clean chemicals, FDA applications, general service |
Universal chemical resistance, lowest friction, FDA compliant |
Soft — lower wear resistance |
|
Carbon-Filled PTFE |
High speed, heat dissipation, anti-static |
Thermal conductivity, improved creep resistance |
Not for strong oxidizers |
|
Glass-Filled PTFE |
Abrasive media, high wear, slurries |
Increased mechanical strength, wear resistance |
Not for HF or strong alkali |
|
MoS₂-Filled PTFE |
Sticky media, low torque, enhanced lubricity |
Reduced friction, improved wear resistance |
Not for oxidizing acids |
|
Spring Material |
Best For |
|
301 SS / 316 SS |
General chemical service, moderate temperatures |
|
316L SS |
Improved corrosion resistance — aggressive chemicals, salt water |
|
Elgiloy® |
Excellent corrosion resistance, high temperature — aerospace, critical |
|
Hastelloy® C-276 |
Extreme corrosion resistance — highly aggressive chemicals, acids |
|
Inconel® |
High-temperature strength — extreme heat (+260°C+) |
|
Spring Type |
Best For |
Key Feature |
|
Helical Spring |
High pressure, static/low-speed dynamic |
Highest load, consistent pre-load |
|
Cantilever Spring |
Dynamic sealing, abrasive media |
Load at lip edge — scraping action |
|
V-Spring |
Reduced friction, moderate pressure |
Soft spring characteristic, low friction |
100% Virgin PTFE Resin — no regrind, no recycled material. Consistent quality, batch after batch.
Precision CNC Machined — No mold costs. Custom sizes from 5mm to 3300mm diameter.
Full Traceability — Every batch traceable from raw material to finished seal. Material certificates on request.
ISO 9001 Certified — Manufacturing processes certified under ISO quality management systems.
FDA-Compliant Grades Available — Virgin PTFE meets FDA 21 CFR 177.1550 and BfR requirements.
Spring Alloys Available — 301/316 SS standard; Elgiloy, Hastelloy, Inconel for extreme conditions.
Standard Groove Compatibility — Fits AS568A, DIN 3771 standard O-ring grooves.
A: A PTFE U-shaped jacket with a metal spring inside. Seals from zero pressure to high pressure (up to 60 MPa) on moving shafts.
Use it when O-rings or rubber lip seals fail, on piston rods, valve stems, and dynamic applications handling aggressive chemicals, extreme temperatures, or high pressure.
U-type vs V-type: U-type is radial sealing, for piston rods and valve stems. V-type is axial sealing, for flanges and covers.
If you are sealing a moving rod: choose U-type.
If sealing a flange or cover: choose V-type.
A: Cost depends on diameter, jacket material, spring alloy, spring type, and quantity. Standard sizes start at approximately X−X−Y. Custom sizes quoted per drawing.
Spring alloy impacts cost: 301/316 SS (standard, lowest cost) → Elgiloy/Hastelloy (extreme corrosion/high temperature, higher cost).
Spring type impacts cost: Helical (higher load) vs cantilever (dynamic scraping) vs V-spring (low friction).
A: Temperature: -180°C to +200°C (grade dependent).
Pressure: up to 40 MPa (dynamic) / 60 MPa (static).
Speed: up to 15 m/s (reciprocating), up to 1-3 m/s (rotary).
Chemical limits:
PTFE jacket: not for molten alkali metals or elemental fluorine.
Glass-filled: not for HF or strong alkali.
Carbon-filled: not for strong oxidizers.
Three common mistakes:
(1) Damaging the lip during installation: inspect before installation.
(2) Over-tightening or improper groove design: U-type seals fit standard AS568A O-ring grooves. Wrong dimensions damage the seal.
(3) Installing backward: U-type seals are directional. The U-opening must face the pressure side (where pressure enters the "U").
Address
No.1028, Qiersan Street, Andong Town, Cixi City, Zhejiang Province, China
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