Valve Basics - Soft-Seated or Metal-Seated? The Key Decision in Butterfly & Ball Valve Selection

When requesting a quote for butterfly or ball valves, one question always comes up: soft-seated or metal-seated? Choose wrong, and you risk a short sealing life — or a leak. Here is the three-minute explanation.

Soft-seated valves use non-metallic seat or sealing materials such as rubber, PTFE, or PPL. The advantages: excellent conformity and sealing — bubble-tight or even zero-leakage at ambient temperature and pressure — plus low operating torque and a friendlier cost. The limits are temperature and media: NBR up to about 80°C, EPDM about 120°C, PTFE about 180–200°C, and PPL about 250°C. Soft seats are also easily scored by media containing solid particles.

Metal-seated valves seal metal-to-metal, typically with hardfacing alloy welded onto stainless steel. They withstand high temperatures (400°C+ depending on material), resist wear and particle erosion, and suit steam, solids-laden media, and frequent cycling. The trade-offs: tighter machining tolerance, higher cost, and — under identical conditions — sealing class usually slightly below a high-quality soft seat.

In one line: for ambient-temperature water and gas where zero leakage matters, choose soft-seated; for high-temperature steam, particle-laden media, and frequent operation, choose metal-seated.

Real-world selection also depends on pressure class, media corrosivity, and operating frequency. Unsure about your conditions? Send your parameters to the JOLA engineering team for free selection advice.