What is the basis and principle of pump selection?

Centrifugal impeller is agitated by rotation of the centrifugal force generated pressure fluid , transmission fluid . In the selection of centrifugal pumps , to determine the use and performance of pumps and pump selection . This option must first select the type and form of pump starts , then choose the pump to what principles it ? Based on what is ?

    A pump selection principle

1 , so that the selected pump type and performance in line with unit flow, head, pressure, temperature , cavitation flow , suction process parameters such requirements.

2, the mechanical aspects of high reliability, low noise, small vibration

3 , the economy and comprehensive consideration to the equipment costs , operating costs, maintenance costs and management fees the lowest total cost .

4 , centrifugal pump with a high speed , small size , light weight , high efficiency , large flow , simple structure, no pulse infusion , stable performance , easy operation and convenient maintenance .

     Therefore, the following exceptions should be used wherever possible centrifugal pumps :

     There measurement requirements , the selection of metering pumps

     Head demanding, flow is very small and not suitable for low flow high head pumps can be used , the choice of reciprocating pump , such as less demanding when cavitation vortex pump can also be used .

     Head low, traffic is heavy , the choice of axial and mixed flow pumps.

     Medium viscosity ( greater than 650 ~ 1000mm2 / s) , can be considered optional rotor pump or reciprocating pump ( gear pump , screw pump )

     Medium containing 75% of gas , flow is small and the viscosity of less than 37. 4mm2 / s , the choice of vortex pump .

     Start priming the pump for frequent or inconvenient occasions , should be used with self- priming pump , such as self- priming centrifugal pumps , self-priming vortex pump , pneumatic diaphragm pumps, electric diaphragm .

    Second, the pump selection basis

     Pump selection basis , should be based on process , drainage requirements, from five aspects to be considered , not only the amount of liquid delivery , installation head , the liquid nature of the piping and the operating conditions , etc.

     1 , the pump flow was selected one of the important performance data , which is directly related to the production capacity of the entire device and transmission capacity . Such as process design institute is able to calculate the pump is normal, minimum, maximum, three kinds of traffic. Select the pump at maximum flow rate as the basis, taking into account the normal flow , in the absence of maximum flow , it is usually preferable to the normal flow of 1.1 times as the maximum flow .

     2, the device system required pump head is selected another important performance data , the general use of amplification after 5% -10% margin to lift selection .

     3 , the liquid nature of the liquid medium including name, physical properties , chemical properties and other properties , physical properties with temperature c density d, viscosity u, medium diameter of solid particles and gas content, etc. , which relate to the lift system , the effective gas NPSH calculations and suitable pump types: chemical properties , mainly referring to the liquid medium corrosive and toxic chemicals , is the choice of materials and choice of what kind of pump shaft seal type of important basis.

     4 , the device piping system refers to a condition highly liquid feeding liquid from the liquid feed to send , such as suction side of the minimum level , the discharge side of the highest level and some data and pipe specifications and lengths , materials , fittings, specifications, quantity , in order to carry out the Department comb head NPSH calculations and checking .

     5, the operating conditions of many things, such as liquid saturated steam power operation T P, suction-side pressure PS ( absolute ) , the discharge side of the vessel pressure PZ, altitude , ambient temperature operation is a gap or continuous pump position is fixed thing can shift .

    Third, central air conditioning circulating pump

     Central air conditioning system works by circulating pump head due to improper selection , leading to project failure case analysis , emphasizing the rational choice importance circulating pump head , and made some selection method, the central air-conditioning design reference value.