Many friends have a question about the submersible sewage pump, that is, what is the method of flow regulation. The following will tell you the specific operation process.
1. Outlet throttling: For low and medium speed pumps, this is a common and inexpensive flow adjustment method. Throttling to the dead point may cause overheating of the fluid in the pump, a bypass can be used to maintain the necessary flow, or a different adjustment method can be used. This is very important for the aforementioned pumps handling hot water or volatile liquids.
2. Suction port throttling: If there is sufficient NPSH available, then some power can be saved by throttling in the suction line. Jet engine fuel line pumps often use throttling in because throttling can cause overheating or vaporization of the liquid. At very low flow rates, the impeller of these pumps is only partially filled with liquid, so the input power and temperature rise are about 1/30 of the fully operating impeller position at outlet throttling. This is equivalent to throttling. Special designs reduce the cavitation damage of these pumps to an insignificant level, but the energy levels are also considerably lower.
3. Bypass adjustment: All or part of the flow can be diverted from the discharge pipeline of the pipeline pump, and lead to the suction port of the pump or other appropriate points through the bypass pipe. One or more flow orifices and suitable control valves can be installed in the bypass. Metering bypass is often used to reduce boiler feed pump flow, primarily to prevent overheating. Considerable power savings can be achieved if the excess flow of the bypass propeller pump is used instead of the outlet throttling.
4. Speed adjustment: When this method is used to adjust the flow, the required power can be reduced to a minimum, and the overheating phenomenon during the flow adjustment process can be eliminated. Steam turbines and internal combustion engines are easily adapted to speed regulation with little additional cost. Various mechanical, magnetic, and hydraulic variable speed devices, as well as DC and AC variable speed motors, can be used to adjust the speed. Often, variable speed motors are prohibitively expensive, and adjustable vane adjustment should only be used when economical studies for the particular situation justify it.
5. Air supply: supplying air to the suction port of the pipeline pump is also a method of adjusting the flow rate, which can save some power compared with the outlet throttling. In general, the presence of air in the liquid being delivered is not desired, and too much air always runs the risk of the pump losing its priming head, so this method is rarely used in practice except in isolated cases.
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