Overcurrent in vertical pipeline pumps – what’s the solution?
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This post was last edited by qq172424245 on 2020-6-6 at 12:04. Two new pumps, vertical pipeline pumps; nameplate specifications: ISG80-250A, capacity of 50 cubic meters, lift height of 60 meters, power of 18.5KW-2P. The fluid transported is process water used for flushing; the rated current is 36A. Currently, one pump is drawing 42A and the other 52A – both are operating above their rated current. Visual inspection of the pressure gauge readings: the outlet pressure of 1 pump is 4 kilograms, and that of another pump is 4.3 kilograms. The pump manufacturer explained that the outlet valve needs to be adjusted in order to keep the outlet pressure at around 55 meters (5.5 kilograms), so that the pump can function properly; a pressure of around 4 kilograms definitely results in overcurrent. But the owner refused to adjust the valve. Current solution: Remove the impeller from the pump and send it back to the pump manufacturer for cutting. My thought: Is the pump too big? Is it caused by the actual parameters required on site not matching the pump’s rated capacity? The desired parameters can be achieved by adjusting the outlet valve, but the owner disagreed, so it can only be done by cutting the impeller?
ISG80-250A: flow rate of 50 cubic meters, head of 60 meters. With an efficiency of 60%, the shaft power is 13.6 kW, and the current is 27 A. The operating point of the pump is determined by both the pump’s performance curve and the system’s characteristics curve. The pressure value indicated shows that the pump is operating at a high flow rate; in other words, the system’s characteristic curve is relatively flat, meaning the resistance in the pipes is low. In such cases, it is necessary to adjust the opening degree of the valves in order to increase the resistance in the pipes, so that the reading on the outlet pressure gauge is around 0.6 MPa. At the same time, the impeller can be cut to change the pump’s characteristic curve, or a variable-frequency motor can be used for variable-speed control. In the above situation, cutting the impeller is the most economical and effective method.
By comparing the parameters such as pressure and density specified in the request for quotation with those in actual operation, it is possible to determine whether the issue lies in the design, the operation, or the manufacturer.
The parameters specified for the pump correspond to optimal operating conditions; using these alone as a basis for selection is too one-sided. It’s not accurate to say that the pump chosen is too large – rather, the inlet pressure at the actual site differs from that assumed during selection. Adjusting the valves can indeed solve the problem mentioned by the poster, but from the customer’s perspective, such adjustments increase the losses of the system
It would be best to send over a schematic of your pump in the process; it seems to be a regulation issue. What are the pressure and flow conditions in your process system? It’s not possible to discuss things simply in terms of pressure alone. I guess it should be possible to reduce the current by using the total return water pressure to control it. It’s best to send a simple diagram showing the key process parameters of your system, such as pressure and flow rate. It’s best to describe things based on pictures, so as to avoid trying to understand something without any clues. For reference.
Is the procurement basis consistent with what is provided in the design?
It’s convenient to adjust the valve. But the good thing about your solution is that it just takes a bit more effort