Soft-Seated vs Metal-Seated Butterfly Valves: Differences, Applications & Selection Guide

source： date：2026-09-29

Butterfly valves fall into two families by seat material — soft-seated and metal-seated — differing significantly in temperature, pressure, tightness class, wear resistance and price. Choosing the wrong seat type is a common cause of early valve failure. Drawing on industry sources, this article summarises the core differences, gives a duty-based selection table, and adds notes on actuator sizing for both types.

Core Differences

Item	Soft-seated	Metal-seated
Seat material	Rubber (EPDM/NBR), PTFE, fluorine-lined	Metal-to-metal (stainless steel, hardfaced alloy)
Sealing principle	Elastic seat conformity, deformation compensation	Metal sealing surfaces (mostly triple-eccentric)
Temperature	Generally ≤150℃ (EPDM ≈120℃, PTFE ≈150–180℃)	Up to 400–700℃ and beyond
Pressure class	Mainly PN10/PN16	Higher temperature and pressure capability
Tightness	Excellent — bubble-tight zero leakage achievable	Triple-eccentric designs also reach zero-leakage classes
Wear & media	Good corrosion resistance (lined), but vulnerable to particle scour and heat ageing	Resists scour, particles and heat; sealing faces vulnerable to corrosive media
Service life	Long in ambient water duty; ages at high temperature	More durable in severe hot duty
Price	Lower	Higher

Selection by Duty

Ambient water, HVAC, water supply/drainage (≤80℃): centre-line soft-seated butterfly valve (EPDM seat) — economical and tight
Corrosive media (acids, alkalis, chemicals): fluorine-lined soft-seated valve (PTFE/F46), noting the ≈≤150℃ limit
Steam, thermal oil, hot flue gas (>150–200℃): metal-seated butterfly valve (double- or triple-eccentric); above 200℃ metal seating is a must
Particle-laden, powder or abrasive media: metal-seated — soft seats are easily scratched and fail
Cryogenic media (below -40℃): low-temperature soft seats or special metal-seated constructions
Food and pharma: hygienic stainless body with soft seat, balancing cleanliness and tightness

In short: soft seats seal better, resist corrosion and cost less, but fear heat and particles — for clean media at ambient conditions; metal seats take heat, pressure and abrasion — for severe duties.

Notes on Actuator Sizing

The two seat types behave differently when fitted with electric or pneumatic actuators: soft-seated valves have smaller, smoother operating torque, while metal-seated (especially triple-eccentric) valves show a pronounced torque rise near the seated position. Therefore:

Size the actuator from the valve manufacturer's torque data at maximum differential pressure; allow ample margin for the seating torque of metal-seated valves
For soft-seated valves, avoid crushing the seat with excessive actuator torque — set torque-seating values per the valve manufacturer's data
For modulating duty (frequent starts), prioritise seat wear resistance and actuator positioning accuracy

This article is a synthesis of public industry sources; always confirm with the valve manufacturer's data and actual duty parameters before selection.