The ultimate aim of the speed regulation of vertical pipe centrifugal pump is to save energy. However, the process of speed regulation must be operated on the premise of safe operation. Therefore, in determining the speed range of the pump, we should pay attention to the following points.

1) the rotor of the pump unit, like other shafts, has its own natural frequency after configuring a certain base. When the rotor of a unit is adjusted to a certain speed, if the vibration frequency caused by the rotor rotation is just close to its inherent vibration frequency, the pump unit will vibrate violently due to resonance, which will cause damage to the pump. Usually, the rotational speed of the pump when it produces resonance is called the critical speed. The precondition of the safe operation of the speed regulating pump is that the speed after the speed regulation can not coincide with the critical speed, the proximity or the multiple of the critical speed. Otherwise, the pump unit will be damaged by the possibility of resonance. Therefore, a large range of speed regulation must be careful, and close attention should be paid to the critical speed of the pump.

2) pump speed to the rated speed is higher than the original water pump, the impeller and the motor rotor of the centrifugal force will increase; if the poor uniformity of material poor crack resistance or casting when possible mechanical damage crack, crack phenomenon may appear serious when the impeller fly. Therefore, the speed of the pump is generally not easily adjusted to the high speed (higher than the rated speed). Stainless steel chemical pump

3) the speed regulating device is expensive and usually adopts the way of parallel operation of speed regulating pump and speed pump. When the water in the pipe network changes, the constant speed pump units to control major, to fine tune the use of speed pump. The proportion of speed regulating pump and fixed speed pump allocation table should give full play to the speed range of each speed control pump and the principle of high energy saving effect after speed regulation.

4) if the lift of the operating point is equal to the starting lift of the speed control pump after the speed regulation, the speed control pump does not function (i.e. the flow rate of the speed regulation pump is zero). Therefore, the reasonable range of the pump speed control should be based on the variable speed and constant speed pumps can run in a high effective section within the respective conditions to determine this.

5) in a certain speed range, the efficiency decreases with the decrease of the pump speed. Generally speaking, the speed of the pump should be at the rated speed of <50%~65% or more. As the type of pump is more, it is particularly important to refer to the product instructions or samples of different manufacturers when they are selected.

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