Gate Valve Wedge Types and Selection

Role of the Wedge

The gate (wedge) is the closure element in a gate valve. Its geometry determines sealing performance, operating torque, susceptibility to thermal binding, and ease of disassembly after long service periods.

Solid Wedge

• Most common type—simple, robust, and low cost

• Rigid design may cause thermal binding in high-temperature steam service

• Excellent for water, oil, and gas at moderate temperatures

• Both-sides seating provides bidirectional shut-off

Flexible Wedge

The flexible wedge has a groove cut into the gate, allowing slight deflection to compensate for seat misalignment and thermal distortion. This design prevents the thermal binding common with solid wedges in steam service and is standard in power plant gate valves.

Split Wedge (Double Disc)

• Two separate disc halves with a spreader mechanism between them

• Self-aligning to seat faces under operating pressure

• Good for non-uniform seat wear or misaligned seats

• Preferred in vacuum service and clean fluid applications

Selection Summary

Use solid wedge for standard water and petroleum service. Choose flexible wedge for steam lines where thermal cycling causes binding. Use split wedge where seat alignment is critical or for vacuum applications. Always match wedge and seat materials for corrosion compatibility with the process fluid.