Gate valves and butterfly valves are used as switches to regulate the flow rate in pipeline use. Of course, there are still methods in the selection process of butterfly valves and gate valves.
In the water supply pipe network, in order to reduce the depth of pipeline soil covering, the general diameter of the larger pipe is equipped with butterfly valve, and if the depth of soil coverage is not significant, strive to select the gate valve, but the price of the gate valve of the same specification is higher than the price of the butterfly valve. As for the demarcation line of caliber, each locality should be considered on a case-by-case basis. From the perspective of the use of the past ten years, the failure of the butterfly valve is higher than that of the gate valve, so it is worth paying attention to expand the use range of the gate valve if the conditions permit.
In recent years, many domestic valve manufacturers have developed and imitated soft seal gate valves, which have the following characteristics than traditional wedge or parallel double gate valves:
The valve body and bonnet of the soft seal gate valve are cast by precision casting method, which is formed at one time, basically not machined, and does not use sealing copper rings, saving non-ferrous metals.
There is no pit at the bottom of the soft seal gate valve, no accumulation of slag, and the failure rate of the gate valve opening and closing is low.
The soft seal lined valve plate is uniform in size and highly interchangeable.
Therefore, the soft seal gate valve will be a form that the water supply industry is happy to adopt. At present, the diameter of the soft seal gate valve manufactured in China is 1500mm, but the diameter of most manufacturers is between 80-300mm, and there are still many problems in the domestic manufacturing process. The key component of the soft seal gate valve is the rubber lined valve plate, and the technical requirements of the rubber lined valve plate are high, and not all foreign manufacturers can achieve it, and it is often purchased and assembled from the factory with reliable quality.
The copper nut block of the domestic soft seal gate valve is embedded and hung above the rubber lining valve plate, similar to the structure of the gate valve, and the rubber lining of the valve plate is easy to peel off due to the active friction of the nut block. For the soft seal gate valve of a foreign company, the copper nut block is embedded in the rubber-lined ram to form a whole, which overcomes the above shortcomings, but the concentricity of the combination of the valve cover and the valve body is higher.
However, when opening and closing the soft seal gate valve, it should not be closed too much, as long as the water-stopping effect is achieved, otherwise it is not easy to open or peel off the rubber lining. A valve manufacturer, in the valve pressure test test, the use of torque wrench to control the degree of closing, as a water company valve operators should also follow this method of opening and closing.
What is the difference between the use of butterfly valves and gate valves?
According to the function and use of gate valve and butterfly valve, the flow resistance of the gate valve is small, the sealing performance is good, because the flow direction of the gate valve plate and the medium is a vertical angle, if the gate valve is not in place in the valve plate switch, the medium scouring the valve plate makes the valve plate vibrate, and it is easy to damage the gate valve seal.
Butterfly valve, also known as flap valve, is a simple structure of the regulating valve, which can be used for the on/off control of low-pressure pipeline medium butterfly valve refers to the shut-off part (disc or butterfly plate) as a disc, rotating around the valve shaft to achieve opening and closing of a kind of valve, the valve 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, so as to achieve the purpose of opening and closing or adjusting.
The butterfly plate is driven by the valve stem, and if it turns 90°, it can complete a opening and closing. By changing the deflection angle of the butterfly, the flow rate of the medium can be controlled.
Working conditions and medium: Butterfly valve is suitable for transporting various corrosive and non-corrosive fluid media pipelines in engineering systems such as furnaces, 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., and is used to regulate and cut off the flow of media.
Gate valve (gate valve) is an opening and closing part of the gate, the direction of movement of the gate is perpendicular to the direction of the fluid, the gate valve can only be fully opened and closed, the discomfort of the door parameters are different, usually 5°, when the medium temperature is not high, it is 2°52′. To improve its manufacturability and make up for the deviation of the sealing surface angle in the processing process, this kind of ram is called elastic ram.
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 ram 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 ram must be forcibly pressed to the valve seat by external force to ensure the tightness of the sealing surface.
Movement mode: The gate plate of the gate valve moves in a straight line with the valve stem, which is also called the open rod gate valve. Usually there is a trapezoidal thread on the lifting rod, through the nut at 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 ram lift height is equal to 1:1 times the valve diameter, the flow of the fluid is completely unobstructed, but this position cannot be monitored during operation. In actual use, it is marked by the vertex of the stem, that is, the position that cannot be opened, as its fully open position. In order to account for the lock-up phenomenon of temperature changes, it is usually opened to the apex position, and then reverted back to 1/2-1 turn as the position of the fully open valve. Therefore, the fully open position of the valve is determined by the position of the ram (i.e. stroke). Some gate valve stem nut is located on the gate, and the handwheel rotates to drive the valve stem to rotate, and the gate plate is lifted, this valve is called a rotary rod gate valve or a dark rod gate valve.
Post time: Aug-22-2024
