I´he heard that when you restrict flow by partially closing a valve inmediately at the discharge of a centrifugal pump you run the risk of overheating the liquid and even breaking the pump shaft. In our plant we have several slurry pumps with HP ratings from 50 to 150 HP, no problems as of this moment with them, but we sometimes have to restrict their flowrate by closing the pump´s discharge butterfly-type valve, located a couple of feet form the discharge. The reason we do this is that flow regulating valves located much farther downstream from the pump sometimes fail or wear-out and therefore tend to increase flowrate and overload the motor, so we partially close the discharge to control flowrate until we can schedule a maintenance shutdown to replace flow-control valves (by the way we are in the process of replacing them with other type of valves more suitable for throttling slurry flow)
In the meantime, any risk on the pump by semi-closing discharge valve? How can we know if we are on the verge of breaking a pump shaft, or does that happens only with smaller or larger pumps? Our pump´s shafts range in diameter from 2.5" to 4", if my memory serves me right, and flowrates vary from about 1000 gpm to 3000 gpm.
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