Flat Gate Valve Characteristics, Structure and Application

The flat gate valve is a sliding valve with a closing element of a parallel gate. The closing element can be a single gate or a double gate with a supporting mechanism in between.

The clamping force of the gate against the valve seat is controlled by the pressure of the medium acting on the floating gate or floating valve seat. In the case of a double gate flat gate valve, the supporting mechanism between the two gates can supplement this clamping force.

I. Characteristics of the Flat Gate Valve

1. The valve seat adopts an O-shaped sealing ring for sealing and a floating valve seat structure with applied pre-tightening force, ensuring bidirectional sealing of the flat gate valve. The opening and closing torque of this structure is only half that of ordinary valves, making it easy to open and close the gate valve.
2. When fully open, the passage is smooth and straight, with extremely low flow resistance and no pressure loss. It can be used for cleaning the pipeline with a pig.
3. It adopts a self-sealing packing structure that does not require frequent adjustment, making it extremely easy to open and close, with reliable sealing performance. The packing box is equipped with an auxiliary sealing grease injection structure, ensuring absolute sealing reliability and achieving zero leakage. This solves the common problem of packing leakage in general valves.
4. The flat gate valve automatically relieves the high pressure inside the cavity when closed, ensuring safe use.
5. It has a fully enclosed structure with good protective performance, suitable for all-weather requirements.

II. Applications of the Flat Gate Valve

1. (Class 150~900LB/PN1.0~16.0MPa, operating temperature -29~121℃) Petroleum and natural gas transmission pipelines. Flat gate valves with flow guide holes are also convenient for cleaning pipelines.
2. Finished oil transportation pipelines and storage equipment.
3. Oil and gas wellhead devices, also known as valves for Christmas trees.
4. Pipelines with suspended particles.
5. Urban gas transmission pipelines.
6. Municipal water projects.

III. Advantages of the Flat Gate Valve

It has low flow resistance, comparable to the flow resistance of short pipes without contraction. Flat gate valves with flow guide holes can be directly cleaned with a pig on the pipeline. Because the gate slides on two valve seat surfaces, slide gate valves are suitable for media with suspended particles. The sealing surface of the flat gate valve is automatically positioned. The valve seat sealing surface is not damaged by the thermal deformation of the valve body. Even when the valve is closed in a cold state, the thermal expansion of the valve stem will not overload the sealing surface. At the same time, when the valve is closed, a flat gate valve without a flow guide hole does not require a high precision in the gate’s closed position, so an electric flat valve can use the stroke to control the opening and closing position.

IV. Disadvantages of the Flat Gate Valve

When the medium pressure is low, the sealing force of the metal sealing surface may not be sufficient for satisfactory sealing. Conversely, when the medium pressure is high, frequent opening and closing may cause excessive wear on the sealing surface if the surface is not lubricated with system medium or external medium. Another drawback is that a circular gate moving laterally in a circular flow path is only sensitive to flow control when it is at 50% of the valve’s closed position. Moreover, when the gate obstructs high-speed and high-density media flow, it will generate severe vibration. If the valve seat is made with a V-shaped passageway and closely guided with the gate, it can also be used for throttling.

V. Selection Principles of the Flat Gate Valve

1. For petroleum and natural gas transmission pipelines, choose a flat gate valve with a single gate or double gate. If cleaning the pipeline is required, choose a flat gate valve with a single gate or double gate with flow guide holes.
2. For finished oil transportation pipelines and storage equipment, choose a flat gate valve with a single gate or double gate without flow guide holes.
3. For oil and gas wellhead devices, choose a flat gate valve with a hidden stem floating valve seat and flow guide holes, mostly in accordance with API16A standards, with pressure ratings of API2000, API3000, API5000, API10000, API15000, and API20000.
4. For pipelines with suspended particle media, choose a knife-type flat gate valve.
5. For urban gas transmission pipelines, choose a flat gate valve with a single gate or double gate, and a soft-sealed exposed stem.
6. For urban municipal water projects, choose a flat gate valve with a single gate or double gate, and an exposed stem without flow guide holes.