A solid wedge is one rigid piece — strong, simple and standard for general service. A flexible wedge has a peripheral groove letting each face flex independently, preventing thermal binding in steam lines. A split wedge is two loose halves that self-align to worn or distorted seats. Choice depends on temperature cycling and seat condition.
The wedge is the gate valve's sealing element, and its internal architecture answers one question: what happens when the seats move? A valve body is not rigid — pipe loads bend it, and temperature swings distort the seat angle measurably.
The solid wedge ignores the problem with mass: a single casting or forging, guided in body rails, seating on both faces simultaneously. It is the strongest and cheapest option and handles turbulent flow and vibration best — the default below 150°C. Its weakness is thermal binding: close a solid-wedge valve on a hot steam line, let it cool, and the contracting body grips the wedge so hard the stem may break before it opens. The flexible wedge answers exactly that: a circumferential groove around the wedge perimeter lets each seating face deflect a millimetre or so independently, absorbing seat distortion and releasing after thermal cycles — which is why power-station practice specifies flexible wedges for steam. The split wedge goes further: two separate halves with a ball-and-socket interface, each free to find its own seat angle — forgiving on aged or field-refurbished seats, at the cost of more parts and vibration sensitivity.
VTXFLOW casts and forges all three patterns; flexible wedges are standard on our API 600 steam-class gate valves.