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Valve Seals: Material Selection, Sizing, and Replacement Requirements
Quick Answer: A valve seal closes the clearance between a valve stem and the valve bonnet, guide, or seal housing. The correct valve seal is selected by stem diameter, seal cavity dimensions, fluid type, temperature, pressure, stem motion, and material compatibility. CORASEALS supplies replacement and custom valve seals in NBR, FKM, EPDM, PTFE, FFKM, polyurethane, and spring energized configurations.
Valve seals are also called valve stem seals or stem seals. A valve stem seal controls leakage along the stem while allowing rotary or reciprocating movement. Common applications include ball valves, gate valves, globe valves, control valves, solenoid valves, compressors, engines, pumps, and process equipment.
A valve seal is not the same as valve stem packing. Valve stem packing is a separate product category and is normally compressed inside a stuffing box. A valve seal is a preformed or machined sealing element installed in a specific seal cavity or groove.
Replacing a valve seal starts with the seal cavity, not the old seal alone. An old seal may be cracked, swollen, or worn. Those changes affect the measured dimensions. Record the stem diameter, seal cavity bore, groove width, groove depth, and valve model before ordering.
Valve Seal Types CORASEALS Can Supply
- Single lip rubber valve seals for rotary and reciprocating stems
- PTFE lip seals with elastomer or spring energizers for chemical and low friction service
- Spring energized PTFE valve seals for low temperature, high temperature, and high pressure applications
- U-cup and V-type valve stem seals for hydraulic and pneumatic valves
- O-ring type valve seals for static and low dynamic stem movement
- Custom machined valve seals based on customer drawings or sample sections
Metric and inch dimensions are available for many valve seal profiles. Do not rely only on type codes such as TC, UN, UHS, or UPH. These codes can have different section definitions in different catalogs. Always compare the seal cross section, material, hardness, and dimensions before ordering.
Valve Seal Material Selection
Material selection depends on the fluid, temperature range, pressure, and stem movement. The table below gives general comparison points. Final material selection must be checked against the specific process fluid and operating condition.
| Material | Typical Temperature Range | Typical Valve Seal Use | Main Limitation |
|---|---|---|---|
| NBR | -30 °C to 100 °C | Mineral oil, water, water glycol, and fuels | Avoid strong acids, ozone, and steam |
| FKM | -20 °C to 200 °C | Mineral oil, fuels, many chemicals, and high temperature | Avoid hot water and some polar solvents |
| EPDM | -40 °C to 150 °C | Hot water, steam, brake fluids, and outdoor exposure | Not suitable for most mineral oils and fuels |
| Silicone VMQ | -50 °C to 200 °C | Dry heat, ozone, and some food contact services | Poor mineral oil and abrasion resistance |
| PTFE | -200 °C to 260 °C | Broad chemical resistance and low friction | PTFE can creep under load and may need an energizer |
| FFKM | -20 °C to 300 °C | Aggressive chemicals and high temperature | Higher cost and less elastic than NBR or FKM |
| Polyurethane | -30 °C to 100 °C | Abrasive services and hydraulic oil | Avoid hot water, acids, and alkalis |
In industrial buying, FKM is often called Viton, PTFE is often called Teflon, and FFKM is often called Kalrez. These trade names belong to third-party owners. CORASEALS supplies FKM, PTFE, and FFKM valv