Concept:
Gate valve is a type of valve widely used in industry. Gate valve works by opening and closing the valve door in the up or down direction. When the gate valve is completely closed, the gate valve stops the flow of material. material, at this time the flow pressure is large. when the valve is fully open, their gate is not in the material flow, at this time the resistance is almost no, the pressure drop and energy consumption is limited to the minimum.
Valve structure:
The two valve ends are connected to the pipeline through flanges, between the valve flange and the pipeline are inserted a sealing ring to prevent material leakage, and finally fixed by Bolts.
There are two other types of connection between the valve body and the pipeline: + Threaded joints. + Connect key. + Connected by knee welding method.
In the valve cap there is a space that is equal to the valve gate to accommodate the valve gate when the valve is opened. Valve cover and valve body connect through flange and use sealing ring to prevent leakage, The method of connecting valve cap and valve body is the same as between valve body and pipeline
Structure of the valve rod (Sterm):
The valve gate is directly connected to the valve stem, the valve stem end has a spiral thread to convert the circular motion of the valve arm into the linear motion of the valve arm. There is a cap on the top of the valve stem to seal to prevent material leakage. This type of valve can be called a valve with a moving lever. When observing the protrusion of the valve rod, we can know the valve opening.
The picture above is a type of valve with a valve structure that only rotates around the shaft, the valve arm and the valve lever are separate, inside the handwheel has a threaded groove, when turning the handwheel, the spiral thread on the valve rod will slide on the groove and move in the direction stand up or down.
The above type of valve uses a dynamic connection, the valve arm and the valve lever are connected together, the inside of the valve cover has a spiral groove. When turning the handwheel, both the valve arm and the valve rod will move around the shaft and move up or down thanks to the valve. spiral groove.
When the valve gate moves down to block the flow, when the valve moves up and down, it will create friction between the valve and the two contact rooms in the valve body, causing abrasion at the contact, on the other hand, when the valve is partially open. In case A ), the flow under high pressure will cause erosion, the higher the pressure, the faster the wear (Case B), the valve gate in case B will be worn out faster than in case A If the valve gate and rings Contacts are too abrasive they will no longer be able to stop the flow completely. Due to uneven wear in the regulating position, it is not used for flow regulation purposes.
Gate valves also have many different types of regulation. The most common type of door is the solid door which is manufactured with only one panel.
Another type used to regulate the flow is to use 2 valve discs: With this type of valve, the valve gate is composed of 2 valve discs mounted on 2 sides of the valve wedge and fixed to the valve rod. 2 discs act as 2 parallel valves, so the pressure is only acting on one side of the valve, making the valve less worn.
When the lower wedge touches the closed valve position, it prevents the valve from moving any further. At this time, both Wedges will push the 2 valve discs to the 2 sides to contact the 2 sealing rings, thereby stopping the flow. The part of the disc that is in contact with the flow will be more abrasive, but the other side is still preserved, so it still ensures the required tightness. In some systems with large changes in temperature, the pipeline expansion affects the body and creates a large force on the valve gate, jamming the valve gate. Because the valve has 2 parallel gates using 2 wedges, When the upper wedge is pulled up, it will reduce the force on the two valves, making the valve easier to move. Because the gate structure of this valve consists of many components, it is easy to get stuck if impurities are attached, so it is often used to regulate flows with high purity.
Compiled by: Maintech Reference source: Vinamain industrial valve textbook #Gate_valve #Gate_valve Service: - Repair and maintenance of thermal power plants - Precision mechanical processing - Repair and maintenance of rotating equipment - Repair and maintenance of industrial valves Hotline: 096 285 39 36 Address: Km375 National Highway 1A, Khoa Truong Village, Tung Lam Commune, Nghi Son Town, Thanh Hoa Province, Vietnam