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TECHNICAL SELECTION GUIDE
How to Select Valve Body, Trim and Seat Materials
Correct valve materials are selected by reviewing fluid composition, concentration, temperature, pressure, solids and required shut-off together.
Direct answer
Correct valve materials are selected by reviewing fluid composition, concentration, temperature, pressure, solids and required shut-off together.
Technical review: MDES Engineering Technical TeamUpdated: 2026-10-25
Body material
Cast or ductile iron suits many water services; carbon steel supports more demanding pressure and temperature; stainless and high alloys are considered for corrosion. Confirm grade, standard and pressure-temperature limits.
Trim and internals
Stem, disc, ball, plug, seat ring and guides contact the process. Erosion, cavitation, particles and galling may require a different alloy or hard facing from the body.
Soft and metal seats
EPDM, NBR, FKM and PTFE have distinct chemical and temperature limits. Metal seats can suit high temperature, abrasive or fire-safe duty; leakage class remains a separate requirement.
Compatibility verification
Provide full composition, concentration, pH, chlorides, solids, cleaning chemicals and temperature range. Obtain written manufacturer confirmation for mixtures and uncertain duties.
Material-selection checks
| Part | Examples | Main check |
|---|---|---|
| Body | Ductile iron, carbon steel, stainless | Pressure, temperature, corrosion |
| Trim | Stainless, alloy, hard facing | Erosion, cavitation, galling |
| Seat | EPDM, NBR, FKM, PTFE, metal | Chemical and temperature compatibility |
| Packing | PTFE, graphite, combinations | Leakage and emissions |
Key points
- Provide full fluid composition and concentration.
- Separate normal and maximum temperature.
- State particles, cavitation and cleaning regime.
- Define leakage or emission class.
Frequently asked technical questions
Does stainless steel resist every chemical?
No. Alloy grade, concentration, temperature and components such as chlorides change performance.
Are EPDM and FKM interchangeable?
No. Their compatibility with water, steam, hydrocarbons and chemicals differs.
Is a metal seat always better?
No. It may suit heat or abrasion, but tight shut-off and torque must be checked.
What data supports material confirmation?
Composition, concentration, pH, temperature, pressure, solids and cleaning conditions.
Technical references
- Emerson/Fisher valve material documentation
- Manufacturer chemical-compatibility tables
- Project fluid analyses and process conditions
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