From simple gate valves to highly complex valves in automated control systems, the variety and specifications of industrial valves are vast. Valves can be used to control the flow of various types of fluids, including air, water, steam, various corrosive media, oils, and liquid metals. It is understood that from 2015 to 2018, the growth rate of China's industrial valve market will remain stable at around 8%, far exceeding the global growth rate. The demand for industrial valves is projected to reach $100 billion by 2030.
As is well known, valves are pipeline accessories used to open and close pipelines, control flow direction, and regulate and control the parameters of the conveyed medium. They come in various types. According to their function, they can be divided into regulating valves, check valves, shut-off valves, etc.
Control valves include self-operated flow control valves and self-operated differential pressure control valves; check valves come in three types: swing, lift, and wafer; shut-off valves encompass a wide range of categories, including gate valves, butterfly valves, ball valves, globe valves, and other common valves.
Of course, due to the variety of valve types and their different functions, their operating methods and precautions also differ. Firstly, gate valves. These can only be fully opened or fully closed; they cannot be used for regulation or throttling. Since most gate valves use forced sealing, when the valve is closed, external force is required to press the gate against the valve seat to ensure a tight seal.
However, it is worth noting that users need to pay attention to some issues when operating gate valves. For example, the handwheel, handle, and transmission mechanism must not be used for lifting and must be protected from impacts; for gate valves with bypass valves, the bypass valve should be opened before the main valve is opened; if the valve is frequently opened and closed, it should be lubricated at least once a month. More importantly, gate valves are only for the operation of media in various pipelines or equipment that are fully open or fully closed, and must not be used for throttling, otherwise the expected effect cannot be achieved.
Secondly, butterfly valves. Generally, a butterfly valve's opening and closing element is a disc-shaped plate. This disc rotates approximately 90° back and forth to achieve opening, closing, or regulation. Because the valve requires relatively low opening and closing torque, and the media exerts roughly equal force on both sides of the disc, it is relatively easy for users to open and close. I understand that butterfly valves have low flow resistance when fully open. When opened between approximately 16° and 65°, they can provide sensitive flow control.
Of course, users also need to pay attention to certain precautions when using butterfly valves. Generally speaking, the opening position should be determined according to the rotation angle of the butterfly plate. If the butterfly valve also has a bypass valve, like the gate valve, the bypass valve should be opened first before the main valve is opened.
Meanwhile, before opening the butterfly valve, check that the inside of the valve (including the sealing ring and valve stem) is clean and free of impurities and foreign objects to avoid affecting its opening and closing. When operating the valve, it is best to stand to the side of the valve handwheel; it is strictly forbidden to operate it directly in front of the valve stem to prevent leakage of media from the pipeline that could cause injury.
Thirdly, ball valves. They can be used for fluid regulation and control, primarily in pipelines for shut-off, distribution, and changing the flow direction of the medium. When operating ball valves, users should ensure that the bolts on the flange are tightened symmetrically, gradually, and evenly during assembly. If disassembly is to be performed, it is best to first verify that the pressure in the upstream and downstream pipelines of the ball valve has been released before proceeding with disassembly to avoid safety accidents caused by residual internal pressure.
Fourth, safety valves. These are automatic valves, mainly used in boilers, pressure vessels, and pipelines to control pressure and ensure it does not exceed specified values, playing a vital role in protecting personal safety and equipment operation.
It is important to note that safety valves must undergo a pressure test before use. Furthermore, safety valves have their own operating pressure range, and the pressure applied must be in accordance with actual requirements during use. Additionally, safety valves should be inspected regularly to ensure safe operation of the equipment.
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