Cavitation Calculation of Positive Displacement Pump

(1) Selection of reference plane Rotor pumps (usually horizontal pumps) are used. The reference plane is the pump shaft centerline. For reciprocating pumps (including metering pumps), the reference plane is the plunger (or piston) centerline. (2) Calculation of cavitation parameters For positive displacement rotary pump, the device has a NPSH NPSH. NPSH with vane pump. The same calculation method (see Table 2-24). Volume reciprocating pumps, the device NPSH NPSH. It should also be included in the acceleration head loss The reason for the Hacc acceleration head loss is the non-uniform flow in the suction line. If the suction pipe is equipped with suction buffer tank, regardless of the first loss of acceleration. Hacc can be calculated as follows. Where L - suction pipe length, m; Q - pump flow, L / h; N - pump reciprocation frequency, r / min; D - suction pipe diameter, mm. Suitable for single cylinder pump. For a double cylinder pump, flow Q is half the total flow (single cylinder flow); for a three cylinder pump, it is divided by 2.5; for inlet buffer, multiply by 0.2. (3) the harmfulness of cavitation Positive displacement pump cavitation will produce the same noise and vibration, generally does not occur over-current components of the corrosion damage. However, for safety reasons, the allowance should still be taken for the NPSHa-NPSHr> s.

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