From simple shut-off valves to a wide range of valves in very complex automatic control systems, the varieties and standards are very complex. The valve can be used to control the activities of various types of fluids such as air, water, steam, various corrosive media, oil, liquid metal and other media. It is understood that from 2015 to 2018, the growth rate of China's industrial valve occupation market will be stable at about 8%, much higher than the global growth rate of industrial valve occupation. It is estimated that the demand for industrial valves will reach $100 billion by 2030.
As we all know, valves are used to open and close pipelines, control the flow direction, adjust and manipulate the parameters of the conveyed medium, and there are various varieties of them. According to its function, it can be divided into conditioning valves, check valves, shut-off valves, etc.
The conditioning valve also includes a self-operated flow conditioning valve and a self-operated differential pressure conditioning valve; There are three types of check valves: swing type, lifting type and clamp type; There are many types of shut-off valves, including gate valves, butterfly valves, ball valves, globe valves and other common valves.
Of course, because of the variety of valves, the functions are different, the operation methods are different, and the operation precautions are also different. First, gate valves. It can only be fully opened and closed, not conditioned and saved. Because most gate valves are forced sealed, that is, when the valve is closed, the ram should be pressed to the valve seat by relying on strong external force to ensure the tightness of the sealing surface.
However, it is worth noting that there are some issues that users need to be aware of when operating gate valves. For example, the handwheel, handle and transmission organization are not allowed to be used for lifting, and it is forbidden to bump; For gate valves with bypass valves, the bypass valve should be opened before opening; If the valve is opened and closed frequently, it should be smoothed at least once a month. More importantly, the gate valve is only used for the operation of the medium on all kinds of pipelines or equipment that is fully open and closed, and is not allowed to be used for saving, otherwise the expected effect cannot be achieved.
Second, butterfly valves. Generally speaking, the butterfly valve opening and closing part is a disc-shaped butterfly plate, which is reversed by about 90° with the disc opening and closing parts, so as to achieve the effect of opening and closing or conditioning. Because the opening and closing torque of the valve is small, the butterfly plate on both sides of the rotating shaft is basically the same as the effect of the medium, so it is more labor-saving for the user to open and close. The author understands that the butterfly valve has a small flow resistance when it is completely open. When the opening is between about 16° and 65°, it can be used for sensitive flow control.
Of course, users also need to pay attention to the use of butterfly valves. In general, the open position of the user should be determined by the rotating viewpoint of the butterfly plate. If the butterfly valve also has a bypass valve, the same as the gate valve, the bypass valve should be opened before opening.
At the same time, before opening the butterfly valve, check whether the inside of the valve (including the sealing ring and valve shaft) is clean, free of impurities and foreign substances, so as not to affect the opening and closing. When operating the valve, it is best to stand on the side of the valve handwheel, and it is forbidden to stand in the opposite direction of the valve stem to prevent the leakage of the medium in the pipeline and the spraying of people.
Third, ball valves. It can be used for fluid conditioning and manipulation, and is mainly used in pipelines to block, distribute and change the direction of movement of the medium. When the user needs to operate the ball valve, it is necessary to tighten the bolts on the flange symmetrically, gradually and evenly. If the user carries out the decomposition operation, it is best to find out that the pressure of the upstream and downstream pipelines of the ball valve has been discharged before the disassembly and decomposition operation can be carried out to prevent safety accidents caused by the retention of internal pressure.
Fourth, safety valves. It belongs to the active valve category, which is mainly used in boilers, pressure vessels and pipelines, and the control pressure does not exceed the specified value, which plays an important role in protecting personal safety and equipment operation.
It is worth noting that the safety valve must be tested under pressure before it can be used. At the same time, the operation of the safety valve has its own pressure range, and the pressure operation must be carried out according to the practical needs when it is used. In addition, it is necessary to regularly check the safety valve in use to ensure the safe operation of the equipment.
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