Questions about pipeline flow rate
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I have a question for the experts regarding the flow rate of the salt water pump. The salt water pump (centrifugal pump) we are using has a flow rate of 80 cubic meters per hour, a head of 38 meters, and a power rating of 18.5 KW, as indicated on its nameplate. In reality, the pump’s current has reached 100% (36A), while the outlet pressure is only 0.6 MPA; the outlet valve is open to 50% only – opening it any further causes the pump to shut down. The temperature of the pump’s motor has reached 75 degrees (with an external temperature of 10 degrees). Saltwater cannot enter the equipment located at a height of 28 meters, so there is no flow of fluid. Experts, could this be a problem with the pump’s motor? Please analyze it in detail for me, thank you! ! ! ! ! ! Note: The density of saltwater is 1.26
You can close the outlet valve completely and test the outlet pressure; if the motor still operates at high power, it might be a problem with the pump. If it returns to normal, it might be a pipeline issue. We have encountered similar problems before; it was due to the pipes being blocked by protective gaskets
The nameplate on the pump indicates the data for calibrating it with fresh water in the factory. It’s best to contact the supplier and ask about the characteristic curves when using saline as the medium, to determine what the actual operating conditions will be like
This post was last edited by xyc114 on 2016-2-23 at 11:27. It’s definitely blocked. The outlet pressure is 0.6 MPa. Think about it: ρgh = P. Without a pump, 1.26*1000*10*h = 0.6*1000000, which gives h = 47.6 meters – this is the height of the water column under static conditions. And yet, here there is flow involved. It’s far greater than 28m, so it will definitely get blocked. Moreover, the pump does not deliver any output; all of the electrical energy is converted into heat energy.
It’s impossible to block it, because I reduced the flow at the inlet that leads to the cooler below; as a result, there is still flow above, and I can hear the sound of water flowing. Earlier on, I used circulating water for circulation, and although the current was high, there was still flow above. If the outlet of the pump is completely closed, the current drops immediately; when the outlet valve is gradually opened, the current rises slowly. When the valve is opened to 50% of its capacity, the motor current reaches 100%, while the outlet pressure remains at 0.55–6.0 MPA
It’s impossible to block it, because I reduced the flow at the inlet that leads to the cooler below; as a result, there is still flow above, and I can hear the sound of water flowing. Earlier on, I used circulating water for circulation, and although the current was high, there was still flow above. If the outlet of the pump is completely closed, the current drops immediately; when the outlet valve is gradually opened, the current rises slowly. When the valve is opened to 50% of its capacity, the motor current reaches 100%, while the outlet pressure remains at 0.55–6.0 MPA
Generally, you can add a return line on the pump’s outlet pipeline, leading back to the pump’s inlet, and that will solve the problem.
What is the operating pressure for a 28-meter-high device?
It’s possible that the resistance in the pipes and equipment is too high, resulting in a pump head that is too low
Saltwater flows away from the cooler; the cooler has low resistance, resulting in high flow rates and low head pressure, which causes the equipment to be overloaded
I think what was said on the 8th floor makes sense. Is your 28-meter-high equipment under pressure? Your water pump needs to overcome the combined effect of the height of the water column and the pressure in the equipment in order to function properly