Stainless steel submersible pumps are different in impeller structures, hydraulic performance and size. In order to divide them into groups and put the similar models into one group, we need a comprehensive parameter. The parameter shall reflect the common features of water pumps.
This comprehensive parameter is specific speed of the stainless steel submersible pump, signified by ns.
1.The definition of specific speed
Scale down the size of stainless steel submersible pump at its highest efficiency or scale it up until the effective power reaches 0.7355 kw, head 1 m, flow quantity 0.075 m3/s. By then, the rotation speed of this model pump is the specific speed of the real pump it comes from.
2.Calculation formula of specific speed
ns=3.65n multiplied by the square root of Q and then divided by H. You can get it through the principle of similarity.
3.Matters need attention when using this calculation formula
Q and H refer to the flow quantity and head of the stainless steel submersible pump when it is at its highest frequency. N refers to the designed rotation speed of the pump.
The specific speed of each stainless steel submersible pump is certain.
In case of single stage double suction centrifugal pump, we calculate with half of the flow quantity. In case of horizontal multistage pump or vertical multistage stainless steel submersible pump, we should calculate with the flow quantity of one stage of impeller.
We calculate the specific speed on the base of the stainless steel submersible pump delivering clear water at 20 centigrade degrees.
The unit of each parameter should be same as the model pump.
4.Discussion about the specific speed
Specific speed is not the actual rotation speed of the stainless steel submersible pump. It is just a uniform standard for the performance of each kind of pump.
Therefore, its unit is not meaningful, often omitted.
Although the specific speed of the stainless steel submersible pump is calculated through the principle of similarity, but it also contains the main parameters of the actual pump, like Q, H and n.
Hence, it reflects the main performance of the stainless steel pump.
For more information, please contact info@welpump.com.
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