Issues with the outlet flow and current of centrifugal pumps
Thread Content
The outlet valve of the centrifugal pump in our unit can only be opened a little; otherwise, the current level will exceed the limit. Call the manufacturer over; they proposed three solutions: 1. Increase the motor power ； 2. Reduce the impeller diameter ； 3. Outside the pump body, a flow-regulable connecting pipeline is added between the inlet and outlet valves. We’re still comparing to see what the actual effect is. What I want to say is: A centrifugal pump is that difficult; learn from the foreigners’ precision! (Maybe I spoke too harshly; I’m a beginner, and I don’t think it should be that difficult!) ）
The manufacturer’s attitude is extremely irresponsible! First of all, it’s necessary to determine what causes the motor to experience overcurrent. If the pump’s performance is just sufficient to meet the requirements, then increasing the motor’s power should be considered; if there is a large margin in the pump’s performance, reducing the diameter of the impeller could be an option. The third method simply doesn’t solve the problem at all!!!
Elder brother: You’re amazing! I don’t understand either; currently, the third method has been basically rejected, while methods one and two are under testing. I’m puzzled that such a small matter can cause so much trouble. It makes me wonder how people view domestic products and domestic technology; I feel quite sad about it
Second floor: Let me ask you again, how can we determine whether the pump’s performance is just sufficient or whether there is a large excess capacity?
Ask the manufacturer for the performance curve of this pump! Equipment parameters such as flow rate, head, and power can all be calculated based on the operating conditions. It’s not a problem if there are some difficulties; what’s important is to base decisions on facts and data!
The third type of root is one that deceives people. You should have calculated it in advance when purchasing the pump. It’s best to purchase a new motor. It’s too troublesome to reprocess the impeller. Temporarily, you can try reducing the inlet valve; if your medium permits it, this method can be used.
The third method is nonsense; if there is a substantial head surplus, the second method can be used. If the first method is used, it’s very likely that the motor foot bolts will not align properly.
Hehe, it’s easier to fabricate an impeller than to buy a motor, right?
In fact, this kind of thing is related to the selection at the beginning. When purchasing pumps, try to choose those whose operating points are in the middle part of the curve; unless under extremely harsh conditions, it is generally possible to find a suitable pump model.
We encountered this issue during our testing as well; when the pump outlet was opened to a maximum of 3 turns, the current would exceed the limit, and the circuit breaker would trip. I thought it was like trying to pull a heavy load with a weak horse, so I wanted to replace it with a larger motor; but in the end I didn’t do that. The opening at the pump outlet remained small, yet the flow rate was still within the designed range. So, the size of the opening at the pump outlet doesn’t matter as long as the flow rate meets the design specifications. It has been working very stably ever since.
The main issue is whether, during the selection process, sufficient consideration was given to the system pressure and the head required of the pump; as a result, an excessively high head was chosen, which led to an increased output power from the pump and consequently overcurrent in the motor. If the head of the pump is chosen to be too high, then excessive restriction by the outlet valve will lead to increased energy consumption. It is better to select a pump that is more suitable; this will result in significant overall economic benefits, and the payback period for the investment will not be long. We encountered this problem, and after some calculations, we replaced it with a new water pump.