Gate Valve Disc Types: Solid, Flexible, and Split Wedge

Gate valve sealing performance and operating torque are strongly influenced by disc (wedge or gate) design. Choosing the right disc type for the service conditions prevents seat galling, stuck valves, and leakage at temperature extremes.

Solid Wedge

The solid wedge is the most common gate valve disc. Its rigidity provides good sealing at moderate temperatures. However, thermal distortion in high-temperature service can cause the solid wedge to lock in the seat, making the valve difficult or impossible to open after a high-temperature shutdown.

Flexible Wedge

A circumferential groove machined into the wedge periphery allows slight flexing as the disc seats. This flexibility accommodates minor seat misalignment and thermal distortion without locking the disc in the seat. Flexible wedge gate valves are standard for steam and hot water service.

Use flexible wedge for steam, condensate, and hot water serviceFlexible wedge provides better seat conformance than solid wedge after thermal cyclingNot suitable for abrasive slurry service where groove can trap solids

Split Wedge (Double Disc)

The split wedge design consists of two independent discs connected by a spreader mechanism. As the stem pushes down, the spreader forces the discs outward against both seats. This design compensates for seat misalignment and reduces the risk of thermal lock. It is used in refined product pipelines and power station isolation valves.

Slab Gate (Parallel Slides)

Pipeline slab gate valves use two parallel flat gates with a spring or stem-loaded mechanism to seal against the downstream seat only. This design provides a full-bore opening for pigging and inspection. Common in oil and gas pipeline service.

Specify flexible or split wedge for steam service above 260 °CUse slab gate for pipeline and pigging requirementsConfirm seat angle matches disc angle—contact vendor if replacing wear partsNever use gate valves for throttling service—disc erosion and seat damage will result