Application of butterfly valve and gate valve under different working conditions
Gate valve and butterfly valve are used in the pipeline to regulate the flow. Of course, there are some methods in the selection of butterfly valve and gate valve.
In the water supply network, in order to reduce the soil depth of the pipeline, butterfly valve is generally selected for the larger diameter pipeline. If it has little effect on the soil depth, gate valve is selected. However, the price of gate valve with the same specification is higher than that of butterfly valve. As for the demarcation line of caliber, it should be considered according to the specific situation. In recent ten years, the failure of butterfly valve is higher than that of gate valve. Therefore, it is worthy of attention to expand the application scope of gate valve when conditions permit.
In recent years, many domestic valve manufacturers have developed and imitated soft seal gate valves. Compared with traditional wedge or parallel double gate plate gate valves, this kind of gate valve has the following characteristics:
The valve body and valve cover of soft seal gate valve are cast by precision casting method. They are formed at one time without mechanical processing or using copper sealing ring, so as to save non-ferrous metals.
There is no pit at the bottom of the soft seal gate valve, no slag deposit, and the failure rate of the gate valve is low.
Soft seal rubber lined valve plate has uniform size and strong interchangeability.
Therefore, the soft seal gate valve will be a form of water supply industry willing to adopt. At present, the diameter of soft seal gate valve manufactured in China is 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 soft seal gate valve is rubber lined valve plate, and the technical requirements of rubber lined valve plate are higher, which can not be achieved by all foreign manufacturers. They are often purchased and assembled from reliable manufacturers.
The copper nut block of domestic soft seal gate valve is embedded above the rubber lined valve plate, which is similar to the structure of gate valve. Due to the movable friction of the nut block, the rubber lined valve plate is easy to peel off. For the soft seal gate valve of a foreign company, the copper nut block is embedded 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 required to be higher.
However, when opening and closing the soft seal gate valve, it should not be closed too tightly, as long as the sealing effect is achieved, otherwise it is not easy to open or peel off the rubber lining. A valve manufacturer uses a torque wrench to control the closing degree during the pressure test of the valve. As a valve operator of a water supply company, he should also follow this method.
What is the difference between butterfly valve and gate valve?
According to the function and application of gate valve and butterfly valve, the gate valve has small flow resistance and good sealing performance. Because the flow direction of gate valve plate and medium is vertical, if the gate valve is not opened and closed in place on the valve plate, the erosion of medium on the valve plate will make the valve plate vibrate, and the seal of gate valve will be easily damaged.
Butterfly valve, also known as flap valve, is a simple structure control valve, which can be used for low-pressure pipeline medium on-off control. Butterfly valve refers to a kind of valve whose closing piece (disc or butterfly plate) is a disc and rotates around the valve shaft to open and close. The valve can be used to control air, water, steam, various corrosive media, mud, oil, liquid metal and radioactive media The flow of fluid. It is mainly used to cut off and throttle the pipeline. The opening and closing part of butterfly valve is a disc-shaped butterfly plate, which rotates around its own axis in the valve body, so as to achieve the purpose of opening and closing or adjustment.
The butterfly plate is driven by the valve stem, and can be opened and closed once if it is turned 90 degrees. The flow of medium can be controlled by changing the deflection angle of butterfly plate.
Working condition and medium: butterfly valve is applicable to the pipeline conveying various corrosive and non corrosive fluid medium in the engineering system of generator, gas, natural gas, liquefied petroleum gas, city gas, cold and hot air, chemical smelting and power generation environmental protection, building water supply and drainage, etc., to regulate and cut off the flow of medium.
Gate valve is a kind of gate, whose movement direction is perpendicular to the fluid direction. Gate valve can only be fully opened and fully closed, and the unsuitable parameters vary, usually 5 ° and 2 ° 52 “when the medium temperature is not high. This kind of gate is called elastic gate.
When the gate valve is closed, the sealing surface can only rely on the medium pressure to seal, that is, only rely on the medium pressure to press the sealing surface of the gate valve to the seat on the other side to ensure the sealing surface, which is self sealing. Most gate valves are forced to seal, that is, when the valve is closed, the gate should be forced to the valve seat by external force, so as to ensure the tightness of the sealing surface.
Movement mode: the gate valve gate along with the stem for linear movement, also known as rising stem gate valve. Generally, there are trapezoidal threads on the lifting rod. Through the nut on the top of the valve and the guide groove on the valve body, the rotary motion is changed into linear motion, that is, the operating torque is changed into operating thrust. When the valve is opened, when the lifting height of the ram is equal to 1:1 of the valve diameter, the fluid channel is completely unblocked, but in operation, this position cannot be monitored. In actual use, the apex of the valve stem is used as the mark, that is, the position that can not be opened is used as its full open position. In order to consider the lock phenomenon of temperature change, usually in the open to the top position, and then back 1 / 2-1 turn, as the position of the full open valve. Therefore, the full open position of the valve is determined by the position of the RAM (i.e. stroke). Some gate valve stem nut is set on the gate, the hand wheel rotation drives the stem to rotate, so that the gate is lifted. This kind of valve is called rotary stem gate valve or Non rising stem gate valve.
Source: China Valves Manufacturer – Yaang Pipe Industry Co., Limited (www.pipelinedubai.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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