Solid, flexible or split wedge: choosing the gate valve closure
The wedge design decides how a gate valve copes with heating, pipe loads and frequent cycling. A poor choice can leave a valve impossible to open after a steam line cools. Here are the three main types.
TAZ Engineering Team · · 6 min
Solid wedge
Simple and robust, cast or forged in one piece. It suits water, oil products and gas at steady temperature, and media with solids that could clog gaps. Its weakness is sensitivity to body distortion: as seats move with heating and cooling, a solid wedge can bind or lose tightness.
Flexible wedge
A flexible wedge has a groove around its perimeter or consists of two faces joined by a hub, so it can flex slightly to follow the seats. This reduces binding under thermal cycling and improves sealing. It is the usual choice for steam and hot water and is common in steel gate valve standards such as API 600. In services with deposits the groove can fill, so a solid wedge may be preferred.
Split wedge and parallel discs
Two independent discs with a spreading mechanism press against the seats on closing. The design tolerates misalignment and seals well on water and low-energy steam. Parallel double-disc valves, such as the cast-iron 30ch6br, spread the discs at the end of the stroke.
Practical guidance
Water and gas at constant temperature: solid wedge. Steam, hot water and frequent warm-up: flexible wedge. Low-pressure water and heating networks where simple repair matters: split wedge or parallel discs. Water up to 70 °C: resilient rubber-encapsulated wedge. State the medium, temperature range and duty in the RFQ and TAZ will propose the closure type.
Checklist
- medium
- maximum and minimum temperature
- warm-up frequency
- deposits
- PN
- required tightness
- maintainability