Application of butterfly valve and gate valve under different working conditions

Gate valve and butterfly valve both play the role of switching and regulating flow in pipeline use. But there are methods in the selection process of butterfly valves and gate valves.

    In the water supply network, in order to reduce the depth of the soil covering of the pipeline, the butterfly valve is generally selected for larger diameter pipelines. If it has little effect on the depth of the covering soil, try to choose a gate valve, but the price of the gate valve of the same specification is higher than that of the butterfly valve. As for the demarcation line of caliber, it should be considered according to the specific situation of each place. From the perspective of use in the past ten years, the failure rate of butterfly valves is higher than that of gate valves, so it is worthy of attention to expand the scope of use of gate valves when conditions permit.

    About gate valves In recent years, many valve manufacturers have developed and imitated soft-sealed gate valves. Compared with traditional wedge or parallel double gate valves, this gate valve has the following characteristics:

   1. The valve body and bonnet of the soft-sealed gate valve are cast by the precision casting method, which is formed at one time, basically does not need mechanical processing, does not use the sealing copper ring, and saves non-ferrous metals.

   2. There is no pit at the bottom of the soft-sealed gate valve, and no slag is accumulated, and the failure rate of the gate valve opening and closing is low.

   3. The soft seal rubber-lined valve plate has uniform size and strong interchangeability.

Therefore, the soft sealing gate valve will be a form that the water supply industry is willing to adopt. At present, the diameter of soft-sealed gate valves manufactured in China is up to 1500mm, but the diameter of most manufacturers is between 80-300mm. There are still many problems in the domestic manufacturing process. The key component of the soft sealing gate valve is the rubber-lined valve plate, and the technical requirements of the rubber-lined valve plate are relatively high, which not all foreign manufacturers can achieve, and are often purchased and assembled from manufacturers with reliable quality.

    The copper nut block of the domestic soft sealing gate valve is embedded above the rubber-lined valve plate, which is similar to the structure of the gate valve. Due to the movable friction of the nut block, the rubber lining of the valve plate is easily peeled off. Some foreign companies embed the copper nut block in the rubber-lined gate to form a whole, which overcomes the above shortcomings, but the concentricity of the combination of the valve cover and the valve body is relatively high.

    However, when opening and closing the soft sealing gate valve, it should not be closed too much, as long as the water stop effect is achieved, otherwise it is not easy to open or the rubber lining is peeled off. A valve manufacturer uses a torque wrench to control the degree of closing during the valve pressure test. As a valve operator of a water company, this opening and closing method should also be imitated.

The gate valve is an opening and closing gate, the movement direction of the gate is perpendicular to the direction of the fluid, and the gate valve can only be fully opened and fully closed. To improve its manufacturability and make up for the deviation of the sealing surface angle during processing, this gate 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, only 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 forcibly sealed, 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.

    Movement mode: The gate of the gate valve moves in a straight line with the valve stem, which is also called a rising stem 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 is determined according to the position of the gate (ie stroke). Some gate valve stem nut is set on the gate, and the rotation of the handwheel drives the valve stem to rotate, which makes the gate lift. This kind of valve is called a rotating stem gate valve or a dark stem gate valve.

    What is the difference between butterfly valve and gate valve?

    According to the function and use of gate valve and butterfly valve, the gate valve has small flow resistance and good sealing performance. Because the flow direction of the gate valve plate and the medium is at a vertical angle, if the gate valve is not switched in place on the valve plate, the scouring of the medium on the valve plate will make the valve plate vibrate. , It is easy to damage the seal of the gate valve.

    Butterfly valve, also known as flap valve, is a kind of regulating valve with simple structure. Butterfly valve that can be used for on-off control of low-pressure pipeline medium means that the closing member (disc or plate) is a disk, which rotates around the valve shaft to achieve opening and closing. A valve that can be used to control the flow of various types of fluids such as air, water, steam, various corrosive media, mud, oil, liquid metal and radioactive media. It mainly plays the role of cutting and throttling on the pipeline. The butterfly valve opening and closing part is a disc-shaped butterfly plate, which rotates around its own axis in the valve body to achieve the purpose of opening and closing or adjustment.

    The butterfly plate is driven by the valve stem. If it turns 90°, it can complete one opening and closing. By changing the deflection angle of the disc, the flow of the medium can be controlled.

Working conditions and media: Butterfly valves are suitable for conveying various corrosive and non-corrosive fluids in engineering systems such as producer, coal gas, natural gas, liquefied petroleum gas, city gas, hot and cold air, chemical smelting and power generation environmental protection, building water supply and drainage, etc. On the pipeline of the medium, it is used to adjust and cut off the flow of the medium.


Post time: Sep-28-2022