Coal mine with the measurement and calculation formula of the centrifugal pump cavitation

Coal mine with the calculation of the centrifugal pump centrifugal pump cavitation of pump equipment and normal use have a vital role in the selection of calculation error, a centrifugal pump can work in the condition of cavitation, reduce the service life of pump. Coal mine with centrifugal pump commonly used three kinds of NPSH: (1) effective NPSH ( NPSHa) , after the pump is installed system characteristic parameters of the entry side is provided by a suction device; (2) must be NPSH ( NPSHr) , is determined by the performance parameters of the pump itself; The first level (3) NPSH3, pump head fell by 3% when the NPSH required.

mine measured with centrifugal pump cavitation is, in fact, the centrifugal pump at the entrance and exit pressure measurements, is often USES a pressure gauge and pressure transmitter. NPSH is the entrance for the centrifugal pump unit mass of liquid than gasification pressure of surplus energy is one of the important indicators of the centrifugal pump performance at the same time through the test and the calculation of relevant parameters, to determine whether centrifugal pump NPSH satisfies the requirement of centrifugal pump performance. Coal mine with centrifugal pump working schematic diagram as shown in the figure below:

test field of the pump NPSH is equal to the pump inlet total suction pressure minus the gasification of liquid pressure, computation formula is:

type: P1 for water pump inlet pressure gauge pressure less than atmospheric pressure when negative Pa; P to the test surface atmospheric pressure Pa; P for the liquid in the temperature of gasification pressure Pa; V as the pump inlet velocity, m/s. P for liquid density kg/m3; Z for pump import datum ( The level of the center line of a pump inlet interface) And NPSH datum of height difference, m import velocity V is obtained through the flow Q and inlet pipe diameter D relation is:

type: Q for water pump flow m3 / h; D as the inlet pipe diameter, effective NPSH (m. NPSHa) By the parameters in the suction pipe and the centrifugal pump installation height as well as the flow pump, has nothing to do with the structure of the centrifugal pump design, therefore, the greater the NPSHa less prone to cavitation in this, cavitation test of centrifugal pump is for coal mines with centrifugal pump suction devices are, at this time of NPSH effectively by type ( 3) Computing:

type: p, to breathe on the surface of the liquid pressure, Pa; H for suction height of geometry, m; H for the suction pipe damage height m

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