pressure seal Gate Valve forged steel

pressure seal gate valves are generally used under high temperature and high pressure. Its working principle and function are similar to ordinary gate valves, but the sealing performance is better. In order to ensure the safety of the valve in extreme environments, it is necessary to ensure that the valve does not leak. Therefore, it is necessary to adopt a self-sealing Gate Valve with better sealing performance.
Forced sealing of the valve: Tighten the middle flange bolts, apply pressure to the gasket, the pre-tight gasket is compressed, and the uneven micro-gap on the sealing surface is filled. In this way, the initial sealing condition is formed to prevent the leakage of the medium, and the preload ratio is formed on the sealing surface. When the medium pressure rises and the valve is operated, the preload ratio on the sealing surface will drop, and the gasket will rebound. If the gasket has sufficient rebounding ability, the working sealing ratio on the sealing surface will always be greater than When the medium and operating pressure are compared, the sealing surface maintains a good sealing state. It can be seen that the necessary condition for forced sealing is that a certain residual pressing force can still be maintained on the sealing surface under the action of medium pressure and operating force. It should be emphasized that the medium pressure in forced sealing is always driven to reduce Preloaded seal ratio reduces sealing performance
Before the self-tightening seal of the valve increases the pressure, first tighten the bolts to make the bonnet rise, so that the initial sealing condition is formed between the bonnet and the wedge-shaped gasket, and between the valve body and the wedge-shaped gasket - preload on the sealing surface Compare pressure. When the medium pressure rises, the sealing ratio between the valve cover and the wedge-shaped gasket and between the valve body and the wedge-shaped gasket increases gradually with the increase of the pressure. In the self-tightening seal, the working seal ratio on the sealing surface is composed of two parts: one is the ratio of the tight seal, and the other is the ratio formed by the medium pressure. It should be emphasized that the pressure of the medium in the self-tightening seal always tends to increase the pre-tightening seal ratio and increase the sealing performance. The higher the medium pressure, the greater the working sealing ratio and the better the sealing performance. According to this feature, self-tightening sealing is a high-pressure sealing technology, which is often used in high-temperature and high-pressure large-diameter valves.

The opening and closing part of the gate valve is the disc, and the movement direction of the gate is perpendicular to the direction of the fluid. The gate valve can only be fully opened and fully closed, and cannot be adjusted or throttled. The wedge angle varies with the valve parameters, usually 50, and 2°52' when the medium temperature is not high. The gate of the wedge gate valve can be made into a whole, called a rigid gate; it can also be made into a gate that can produce a small amount of deformation to improve its manufacturability and make up for the deviation of the sealing surface angle during processing. The plate is called an elastic gate.

When the gate valve is closed, the sealing surface can only rely on the medium pressure to seal, that is, relying on the medium pressure to press the sealing surface of the gate to the valve seat on the other side to ensure the sealing of the sealing surface, which is self-sealing. Most gate valves are forced to seal, that is, when the valve is closed, the gate must be forced against the valve seat by external force to ensure the tightness of the sealing surface.
The gate of the gate valve moves linearly with the valve stem, which is called a lift-rod gate valve (also called an open-rod gate valve). Usually, there are trapezoidal threads on the lift rod. Through the nut at the top of the valve and the guide groove on the valve body, the rotary motion is changed into a linear motion, that is, the operating torque is changed into the operating thrust.
When the valve is opened, when the lift height of the gate is equal to 1:1 times the diameter of the valve, the fluid channel is completely unobstructed, but this position cannot be monitored during operation. In actual use, the apex of the valve stem is used as a sign, that is, the position where it cannot be opened, as its fully open position. In order to take into account the lock-up phenomenon due to temperature changes, it is usually opened to the top position, and then back to 1/2-1 turn, as the position of the fully open valve. Therefore, the fully open position of the valve, according to the position of the gate


Precautions:

The handwheel, handle and transmission mechanism are not allowed to be used for lifting, and collision is strictly prohibited.
Double-gate gate valves should be installed vertically (ie, the stem is in the vertical position and the handwheel is on top).
The gate valve with the bypass valve should open the bypass valve before opening (to balance the pressure difference between the inlet and outlet and reduce the opening force).
The gate valve with transmission mechanism shall be installed according to the provisions of the product instruction manual.
If the valve is used frequently, lubricate it at least once a month.

The advantages of gate valves are as follows:
1. The fluid resistance is small, and the sealing surface is less brushed and eroded by the medium.
2. It is more labor-saving to open and close.
3. The flow direction of the medium is not restricted, the flow is not disturbed, and the pressure is not reduced.
4. The shape is simple, the structure length is short, the manufacturing process is good, and the application range is wide.
The disadvantages of gate valves are as follows:
1. It is easy to cause erosion and scratches between the sealing surfaces, and it is difficult to maintain.
2. The overall size is large, a certain space is required to open, and the opening and closing time is long.

Application range of gate valve
Cast steel gate valve is suitable for the conversion method of nominal pressure 4.0 MPa ~ 10.0 MPa MPa (1 MPa = 10 kg), and the working temperature is minus 29 to 600 degrees Celsius in petroleum, chemical, pharmaceutical, fertilizer, power industries, etc. On the pipelines of various working conditions, the pipeline medium is cut off or connected, and adjustment and throttling cannot be performed. Applicable media are: water, oil, steam, acidic media, etc.



Installation
1. Check the valve cavity and sealing surface before installation, and no dirt or sand is allowed to adhere; 2. The bolts of each connecting part should be tightened evenly; 3. Check the packing parts and require compression, which not only ensures the tightness of the packing , but also to ensure that the gate can be opened flexibly; 4. Before installing the valve, the user must check the valve model, connection size and pay attention to the flow direction of the medium to ensure consistency with the valve requirements; 5. When installing the valve, the user must reserve the valve drive Necessary space; 6. The wiring of the drive device must be carried out according to the circuit diagram; 7. The gate valve must be maintained regularly, and must not be bumped and squeezed at will, so as not to affect the sealing.

technical parameter
Strength test: 2.4, 3.8, 6.0, 9.6, 15.0, 3.1, 7.8, 10.2, 15.3, 23.1, 3.1, 7.8
Sealing test: 1.8, 2.8, 4.0, 7.0, 11.0, 2.1, 5.6, 7.5, 11.2, 16.8, 2.1, 5.6,
Air tightness test: 0.5～0.7
Working temperature: PTFE≤150℃ PPL≤300℃ Carbon fiber≤350℃
Applicable medium: C: water, oil, steam P: nitric acid (temperature≤200℃) R: acetic acid (temperature≤200℃)
Design Parameters:
Design and manufacture: GB/T12237-2007
Flange connection: JB/T79-94, GB9113-2000
Structure length: GB12221-2005
Nominal diameter: DN15~DN150mm
Nominal pressure: PN1.6, 2.5, 4.0MPa.