Pump speed issue
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I encountered a problem today, so please share your opinions: For a double-suction centrifugal pump with a flow rate of 1800–4000 cubic meters per hour and a head of 60–70 meters, is it better to choose a rotation speed of 1450 revolutions per minute or 970 revolutions per minute? Could someone please advise on the advantages and disadvantages of these two rotational speeds?
This post was last edited by lxn_663 on 2010-10-12 at 20:24. Theoretically, a lower rotation speed is beneficial for the pump. It is beneficial for both mechanical seals and bearings, but pumps with low speeds have a higher cost.
Reply to 2# lxn_663: Seals are rarely used in pumps, and there isn’t much difference in bearings based on usage experience. Power shouldn’t have much of an impact, right?
Generally, low-speed pumps must have a small net positive suction head to operate properly. It is recommended to use a low-speed pump!
Low-speed pumps have low efficiency, but their moving parts have a long lifespan
There are two reasons for choosing a low-speed pump: first, it has a low cavitation margin, and second, it provides a high flow rate but low head pressure; therefore, it is recommended to use a low-speed pump.
For this pump, it’s better to choose a motor with 1450 horsepower, as it’s easier to find and the overall cost is lower. The price of 970 is estimated to be about 30% higher. Do we also need to consider the long-term benefits of investment? It is recommended to choose the low-speed option for durability.
For this pump, it’s better to choose a motor with 1450 horsepower, as it’s easier to find and the overall cost is lower. The price of 970 is estimated to be about 30% higher. Do we also need to consider the long-term benefits of investment? It is recommended to choose the low-speed option for durability.
May I ask if the two speeds you mentioned refer to the speed of the pump selected, or that of the motor? Although motors with lower speeds have a longer lifespan, the lower the speed of a motor, the higher its price. Motors with speeds of 1450 and 2950 are the most commonly used in the market, while those with a speed of 970 are used less frequently. Think first about whether it will be convenient to use such a motor
Reply to 4# wanglq2009: Low-speed pumps have a larger net positive suction head. The greater the net positive suction head, the lower the likelihood of cavitation occurring in the pump; moreover, the installation height is higher, and it is proportional to the flow rate.
This post was last edited by luoheng116 on 2010-11-25 at 16:37. If the pump model has been selected, the original poster can use this formula to calculate the approximate rotational speed: 60×(2gH)½ / n = ─────────── D, where D is the diameter of the impeller in meters, H is the head in meters, and ½ represents the square root