Valves are essential components of oil refining and petrochemical pipeline systems. Its primary function is to connect and cut off the logistics, and adjust the pressure, flow, emptying, and discharging, to ensure the safe operation of the device.
Gate valve refers to the opening and closing body for a gate plate, driven by the valve stem, along the sealing surface of the seat for lifting movement to connect or cut off the logistics.
- Gate valve structure characteristics
- Gate: usually WEDGE gate. There are single RAM and double RAM. The single DISC has a SOLID WADGE DISC VALVE and a FLEX.GATE valve.
The DISC of SOLID WADGE DISC VALVE is a wedge-shaped whole with a simple structure and small size. But the sealing surface is easy to scratch, and the ram is easy to get stuck when the temperature changes. Therefore, it is suitable for average temperature and medium temperature.
The FLEX. GATE VALVE’s ram shape, like two wheels connected to a very short shaft, and firmly into one, as shown in the figure, is characterized by allowing a small amount of elastic change in the wedge Angle of the two sealing surfaces of the ram to compensate for changes in the wedge Angle caused by pipeline distortion or thermal load deformation of the valve body. Therefore, the sealing is reliable and can prevent the ram from sticking. However, the closing torque should not be too large to avoid exceeding the elastic range of the ram. Suitable for small and medium-diameter valves.
The wedge plate of the wedge valve is composed of two round plates and is hinged into a wedge plate with a spherical top center. The wedge Angle of the sealing surface of the wedge plate can be automatically adjusted by the top center. When the temperature changes, the gate plate is not easy to be stuck and it is not easy to produce chafing of the seal surface. The disadvantage is that the structure is complex, the parts are more, and the ram is easy to fall off. Not suitable for viscous substances. Generally used for water and steam and other large-diameter pipelines.
The main components of the gate valve are the body; bonnet; and TRIM: including stem, gate, and seat ring.
From the point of view of operation, there are bright rods and dark rods. The open rod is also called the RISING rod, that is, when operating, the handwheel does not rise, and the rising stem valve. Dark rod is when the hand wheel is operated, the ram rises and the rod does not move.
The most commonly used is the lifting rod valve, its structure is BOLTED BONNET AND OUTSIDE SCREW AND YOKE.
Other structures include: INSIDE SCREW STEM, BOLTED BONNET; OS&Y UNION BONNET
- Application situation
Because the opening and closing of the gate are perpendicular to the direction of the fluid when the gate is partially opened, eddy currents will be generated on the back of the gate, which is easy to cause erosion and vibration of the gate, so the gate valve is suitable for full opening or full closing and is not suitable for throttling. And suitable for clean fluid and not suitable for too viscous logistics.