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What is a multi-purpose pump control valve? What are the operating characteristics of the pump need to control the valve? Pump control valve can achieve these controls? And it with the traditional gate valve, butterfly valve, check valve and uniform, Valve in the principle, function, etc. What is the difference in quality.
In this paper, the author of the piston multi-function pump control valve (hereinafter referred to as the control valve), for example, through its structure, main functions, working principle of the analysis, put forward the views on the above issues for readers to refer to.
First, the structure
The main features of the control valve structure is to cancel the valve seat in the middle of the positioning mechanism and the upper valve spring, and the valve flap on the underside of the design of the baffle to minimize the media overcurrent mechanical loss and valve Vortex loss in the lower dome. To the cylinder piston as a driving element, under the pressure of the media itself driven by the valve for up and down movement, to achieve the valve open or closed. Pistons, opening and closing pieces, together with the cylinder body arranged on the valve body, streamlined, wide valve body cavity, not only head loss than similar products to reduce more than 30%, and has good cavitation resistance.
Servo system with solenoid valve commutation mechanism (hereinafter referred to as solenoid valve) and pressure pipe to form the servo system, take the pressure water at both ends of the control valve as the driving source, through the electric signal instruction, pressure water at either end can achieve the pump control valve in setting Time and speed of the implementation of the pump on or off.
Second, the pump operating characteristics and control valve features, working principle
1, pump start characteristics and control
a) Centrifugal pump zero-flow start-up characteristics and control (ie off the valve start)
Centrifugal pumps in the zero-flow conditions, the minimum shaft power, rated shaft power of 30% -90%, so the centrifugal pump start feature is zero flow start (ie, off the valve start). After the pump reaches the rated speed, the control valve slowly opens at the set speed.
Working principle: When the pump is started (before), the pressure water flows through the solenoid valve with delay to the upper chamber of the piston in the cylinder, while the lower chamber of the piston opens to the atmosphere via the solenoid valve at the lower end of the cylinder. At this time, the control valve is in the closed state.
Motor compensation start over, the pump is running, the solenoid valve to perform commutation command, cut off the pressure on the piston cavity, close the lower end of the cylinder to the atmosphere loop, while the pressure water through the solenoid valve into the cylinder piston lower chamber, open the piston Upper chamber open to the atmosphere of the loop, the piston cavity of the water through the solenoid valve discharge valve, the control valve at a set speed slowly open to complete and meet the centrifugal pump at zero flow axis power minimum starting characteristics to ensure that the pump unit Safe operation.
b) axial flow pump start the flow characteristics and control (that is, fully open valve start)
Axial flow pump at zero flow conditions, the maximum shaft power, rated shaft power of 140% to 200%, so the axial flow pump starting characteristics should be large flow start (ie, fully open valve start).
Working principle: The control valve to meet the axial flow pump fully open valve to start the working principle is the centrifugal pump off the valve to start the reverse run, the solenoid valve first work, the valve fully open, the pump restart. See a), do not go into details.
Axial flow pump before the start, when the valve inlet pressure is zero, the control valve using the valve outlet side of the media pressure valve opens, and start the centrifugal pump is the use of the valve inlet side of the medium pressure valve opens. One of the key features of the pump control valve is its ability to open or close the control valve at either end of the valve.
c) Control the start-up characteristics of the mixed flow pump
Mixed flow pump in the zero flow conditions shaft power between the above two pumps, rated power of 100% to 130%, so the start-up characteristics of the mixed flow pump should also be between the two pumps, the pump can be selected generally start With the slow opening of the control valve simultaneously.
How it works: working principle and control of zero-flow centrifugal pump start feature the same, as long as you cancel the delay can be set solenoid valve.
2, stop the pump and its control
a) control of the zero-flow pump centrifugal pump (that is, after the first shut-off valve)
For the centrifugal pump, first slowly close the control valve, and then stop the pump is the importance of: then the medium flow tube speed from the rated flow rate gradually reduced to zero, the speed gradient is minimal, which can effectively prevent the pump from happening and Pump reversal; Pump shaft power gradually reduced from the rated power of the operating power, is conducive to unit safety.
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