Vane Pumps Operating Condition Adjustment Method
The operating point of the Vane Pumps is determined by the intersection of the performance curve of the pump and the characteristic curve of the pumping device. When selecting and using the pump, the performance parameters of the operating point of the pump often deviate from the highest efficiency point, which does not meet the actual needs, causing Decreased work efficiency, severe overload or insufficient load of the power machine, too much or too little water from the pump, too high or too low lift, cavitation, etc. At this time, you must change the performance curve of the pump or the characteristic curve of the pumping device. Move the operating point to meet the requirements. This method is called adjusting the operating point of the pump. There are 5 commonly used adjustment methods: variable speed adjustment, reducing diameter adjustment, variable angle adjustment, variable adjustment adjustment and shunt adjustment.
I. Speed adjustment
Changing the speed of the pump can change the performance of the pump to achieve the purpose of adjusting the operating point of the pump. This method of adjustment is called variable speed adjustment.
There are two ways to change the speed of the pump, one is to use a variable speed power machine, and the other is to use a variable speed transmission equipment. The speed of the internal combustion engine can be automatically adjusted according to the load; the methods of variable speed of the motor mainly include frequency conversion, variable resistance, variable pressure, variable capacity adjustment, etc.
Second, reducer adjustment
Turning the outer diameter of the impeller of a centrifugal pump or a mixed flow pump can change the performance of the pump, thereby adjusting the operating point of the pump, and expanding the use of the pump. This adjustment method is called reducing adjustment, also called turning adjustment or cutting adjustment. Turning regulation has been widely used in pump manufacturing. In order to expand the use of water pumps, single-stage single-suction cantilever centrifugal pumps and double-suction centrifugal pumps made in China, in addition to standard diameter impellers, most often have one or two small variants of the impeller (A, B) . If necessary, the unit can also be used to cut the impeller of the bicycle to achieve the purpose of adjusting the operating point of the pump.
Third, variable angle adjustment
Axial flow pumps have low heads and narrow high-efficiency zones. A slight change in the working head of the axial flow pump will cause a significant decrease in working efficiency. Neither throttling nor turning adjustments apply to axial flow pumps. But axial flow pumps have huge wheels, making it easy to install adjustable blades. Adjusting the operating point by changing the installation angle of the axial flow pump blade is called variable angle adjustment
Fourth, variable valve adjustment
For a pumping device equipped with a gate valve in the outlet pipe, when the gate valve is closed, the pipeline characteristic curve becomes steeper because a local resistance is added to the pipeline resistance. Therefore, its operating point moves along the curve of the pump toward the upper left side where the flow rate decreases. The smaller the gate valve is closed, the greater the additional resistance, and the smaller the flow becomes. This method of changing the operating point position of the pump by closing the small gate valve is called variable valve adjustment or throttling adjustment.
Five, shunt regulation
A branch pipe or a bypass pipe is connected to the water outlet pipe of the water pump to lead out part of the water flow to change the operating point of the water pump, which is called shunt adjustment. In principle, the split flow adjustment is the same as that of the vane pump on the branch line. Only the potential of the machine is realized and the pumping efficiency is improved. However, this adjustment requires an additional pipeline, so first of all, calculation must be performed to verify the economics of the adjustment. This situation is the same as a water pump supplying water to the effluent basins of different heights. The axial flow pump unit and the centrifugal pump unit working in series can avoid the overload and vibration of the power machine by applying split flow adjustment during startup.
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