Flexible Wedge:

The flexible wedge gate valve described in below figure is a one-piece disk within a cut around the perimeter to improve the ability to match error or modify in the angle among the seats. The cut varies within shape, size, and depth. A shallow, narrow cut provides little flexibility but retains strength. A wider and deeper cut, or cast-in recess, leaves little material at the center that permits more flexibility but compromises strength. The correct profile of the disk half in the flexible wedge design could provide uniform deflection properties at the disk edge, so in which the wedging force applied within seating will force the disk seating surface uniformly and strongly against the seat.

Figure: Flexible Wedge Gate Valve

Gate valves used in steam systems have flexible wedges. The purpose for using a flexible gate is to avoid binding of the gate inside the valve while the valve is in the closed position. While steam lines are heated then they expand and cause a few distortions of valve bodies. When the system is heated and pipes elongate if a solid gate fits snugly among the seats of a valve within a cold steam system, the seats will compress against the gate and clamp the valve shut. This problem is overcome through using a flexible gate, whose design permits the gate to flex as the valve seat compresses it.

The main problem related along with flexible gates is in which water tends to collect within the body neck. Below certain conditions, an admission of steam might cause the valve body neck to rupture, the bonnet to lift off, or the seat ring to collapse. Subsequent correct warming process avoids these problems.