The actual application of regulating valve

   The actual application

    Introduction

    In the production process automation control system, the control valve is an important, indispensable link, automated production process is called "hands", is one of the terminal controlcomponent in automatic control system.

    Control valve flow path is simple, small resistance, generally used for positive (installation). However, pressure drop occasions valve used in reverse, in order to improve the imbalance of power and reduce the damage on the spool, but also conducive to the flow of a medium, to avoid coking and plug valves. Regulating valve used in reverse, in particular should be avoided for a long time to open the case of small opening, in order to prevent the damage caused by the strong oscillation valve. Particularly in the chemical plant trial production stage, because when the trial production of low load, design process conditions can not meet the requirements quickly, using the reverse regulating valve as far as possible to avoid long time to open a small opening status, to prevent thevalve damage.

    Regulating valve is composed of two parts and valve mechanismimplementation. From the hydraulic point of view, the control valve is a throttling element of a local resistance to change, regulating valve is in accordance with the input signal by changing the stroke to change the drag coefficient, so as to achieve the purpose ofregulating flow.

    Structure and use

    1.Regulating valve structure

Regulating valve body except for the angle, the other structures are similar and single seat valve, characterized by the decision of its flow path is simple, small resistance, particularly conducive to the regulation of high pressure drop, high viscosity, suspended solids and granular materials containing fluid. It can avoid coking,bonding and blockage phenomenon, but also to facilitate cleaning and self purification.

    2.Regulating valve is used, the reverse

In general, regulating valve are being installed, namely the bottom side. The only difference in pressure situations and high viscosity,easy to coke, medium containing suspended particulate matter in the case, it recommended the reverse installation of the material side into the bottom out. The purpose of regulating valve used in reverse, in order to improve the imbalance of power and reduce wear on the spool, but also conducive to high viscosity, easy to coke and the flow of medium containing suspended particles, to avoid coking and blocking.

Precise Work Stage

    The use of reverse analysis

Process control valve in high pressure drop conditions, the recommended use of the reverse. In the test run, regulating valveproduced a strong oscillation, and the issue of harsh noise, 4h after the test valve is broken. But this is not quality problem, but due to the use of unreasonable. The following analysis of the causes of its fracture.

     In addition to butterfly valve and the valve is completelysymmetrical in structure, all other structures of the control valveis asymmetric. When changes in the flow direction control valve,due to changes in flow path will cause) changes. The normal flowof control valve are so that the valve is turned in the direction of(positive), production factory provides only the normal flowcirculation) and flow characteristics. When the valve when the reverse, so that both fluid along the flow direction of the spool off,the control valve flow capacity will increase. 

      Water linkage test,the simulation conditions can not quickly reach the normal state,the control valve in the small opening in the state to use for a long time, because the role of unbalanced force, there will be serious instability. So the valve will produce a strong shock and a harsh noise, resulting in valve quickly broken. In normal conditions, the control valve opening is moderate, even a small opening is short,so the normal valve can be used safely.

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