Valves are often used accessories in pumps and other equipment, including gate valves, butterfly valves, ball valves, stop valves, safety valves, etc. Today, Hebei Hengsheng Pump Industry will talk to you about the selection, use and maintenance of valves.
A suitable valve can be well adapted to working conditions and achieve a multiplier effect, so how to choose a valve?
There are many types of valves. When selecting, consider the nature of the medium, the working pressure, the working temperature and the range of change, the diameter of the pipeline, the special requirements of the process (throttling, decompression, venting, check, etc.), the installation position of the valve and other factors. Based on the basic principle of “meeting process requirements, safe and reliable, economical and reasonable, and convenient for operation and maintenance”, the corresponding selection is made.
①For pipelines with two-way flow, non-directional valves should be used, such as gate valves, ball valves, and butterfly valves; for pipelines that only allow one-way flow, check valves should be used; for places where flow needs to be adjusted, multiple throttle valves should be selected, A shut-off valve can also be used when precise adjustment is not required.
② For pipelines that require rapid opening and closing, ball valves or butterfly valves should be used; for pipelines that require good sealing, gate valves or ball valves should be used.
③For pressure vessels and pipelines, safety valves should be installed according to their specific conditions. For various gas cylinders, a pressure reducing valve should be installed at the outlet.
④ Steam heating equipment and steam pipes are equipped with traps.
⑤On oil and petroleum gas pipelines, as far as the connection form is concerned, flanged valves should be used more, and threaded valves should be used for pipes with a nominal diameter less than or equal to 25mm; as far as the material of the valve is concerned, try to use as little as possible Choose gate valves with a nominal pressure less than or equal to 1.0MPa or stop valves with a nominal pressure less than or equal to 1.6MPa, because these two valve materials are cast iron, which is not good for safe production.
After choosing the valve, we must use and maintain it correctly to prolong the service life of the valve. What problems should be paid attention to in the use and maintenance of the valve?
The use and maintenance of the valve should generally pay attention to the following points:
①The newly installed valve should have a product qualification certificate, and the appearance should be free of blisters or cracks. The packing gland should be flattened and the switch should be flexible; if necessary, a pressure test should be carried out before the new valve is installed; the pressure and temperature level of the valve used should be consistent with The working pressures of the pipelines are consistent, and low-pressure valves cannot be installed on high-pressure pipelines.
②After opening the valve, it should return half a turn to prevent it from opening by mistake; use a special wrench when closing the valve with great effort. Try to avoid using pipe wrenches. Do not use excessive force or use tools to close the valve too hard.
③The valve packing, large cover, flange, thread and other connections and seals must not leak. If problems are found, they should be fastened or replaced in time. Do not operate under pressure during replacement, especially high temperature and corrosive media to prevent injury .
④ For outdoor valves, especially rising stem gate valves, a protective sleeve should be added to the valve stem to prevent rain and snow erosion, dust and rust. For valves used in water, steam, and heavy oil pipelines, antifreeze and warmth should be done in winter to prevent the valve body from freezing and cracking.
⑤Before starting the automatic valves such as pressure reducing valve, regulating valve, and steam trap, the pipeline should be flushed clean. For steam traps without bypass and flushing pipes, the steam trap should be removed, and the pipeline should be blown clean before installation. .
⑥The steam valve should be preheated and drained before opening, and then slowly open the valve to avoid steam and water impact. When the valve is fully opened, turn the handwheel another half turn to make the threads tight. The water valve and air valve that have been closed for a long time should pay attention to removing the accumulated water.
⑦The valve should be kept clean at all times, and can not rely on the valve to support other heavy objects, let alone stand on the valve; the valve body and handwheel should be painted and anti-corrosion according to the management requirements of the process equipment. The valves on the system pipeline should be numbered according to the process requirements, and the number should be listed when opening and closing the valve to prevent misoperation.