【Q&A Question 167】October 04, 2016
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【Q&A Question 167】October 04, 2016: Why can’t a centrifugal pump be operated in reverse for a long time? The answer key will be available after responding; scoring is based on answering the key points. Answer: 1. Due to the design of the pump’s outlet position, when the pump operates in reverse, the flow rate at the outlet decreases significantly, or even comes to zero ； 2. Prolonged reversal will cause the motor temperature to rise, as well as increase the vibration displacement of the pump.
The screws on the impeller back cap can come loose, leading to accidents
1. Due to the design of the pump’s outlet location, when the pump operates in reverse, the flow rate at the outlet decreases significantly, or even comes to a stop； 2. Prolonged reversal will cause the motor temperature to rise, as well as increase the vibration displacement of the pump.
1. Due to the design of the pump’s outlet location, when the pump operates in reverse, the flow rate at the outlet decreases significantly, or even comes to a stop； 2. Prolonged reversal will cause the motor temperature to rise, as well as increase the vibration displacement of the pump.
The impeller of a centrifugal pump consists of a set of shaft sleeves with threads on them that are screwed onto the shaft; the direction of screwing is opposite to the direction in which the shaft rotates. Therefore, when the pump rotates in the forward direction, these sleeves become tighter and tighter. If the pump rotates in the reverse direction, it’s easy for the shaft sleeves to come loose, causing the impeller to become loose and resulting in friction.
Because the impeller will loosen, and the seal will experience dry friction (with an effect ring)
Since the impeller of a centrifugal pump consists of a set of shaft sleeves with threads that are screwed onto the shaft, and the direction of screwing is opposite to the rotation direction of the shaft, when the pump rotates in the forward direction, these sleeves become tighter as they spin; whereas if the pump rotates in the reverse direction, it’s easy for the shaft sleeves to come loose, causing the impeller to become loose and resulting in friction. Furthermore, the head is very low during reversal, to the point where no fluid can be pumped out.