Poor stability regulator using process, use these methods can be solved

Regulating valve and control valve, it is in the field of industrial automation process control, by accepting conditioning control unit of the output control signal, from engine operation to change the medium flow rate, pressure, temperature, liquid level of the process parameters such as the final control element. And valve general, the executing agency. Problems because of its heavy, hard to find, often do not please painfully, involving system put into operation, the system completely, the regulating quality, environmental pollution, etc. Everyone here, Katie instrument and meter plant to clean the 11 kinds of solution to the problem of the regulating valve stability after met this kind of problem will not be overwhelmed. 1. Change the direction of unbalanced force function method in the stability analysis, the unbalanced force with known and at the same time, the direction of valve clearance is on the valve closed trend, the poor stability. To the valve work under the condition of the unbalanced force, choose to change its direction method, often is the flow of changing the flow closed type to open type, generally can easily solve the problem of the stability of the valve. 2. Avoid valve itself not region execution of work some valve limited by its own structure, while working on some opening stability is poorer. 1) two-seater valve, opening within 10%, because the ball away, flow closed ball, under the instability problem; (2) unbalanced force change near the slope produces alternating, its stability is poor. Such as butterfly valves, alternating point at about 70 degrees; The two-seater valve opening in the 80 ~ 90%. Encounter this kind of valve, without region work necessarily poor stability, avoid region. 3. Replace the stability good stability of valve valve its unbalanced force change is small, good guide. Commonly used in ball valve, sleeve valve has this feature. When single, two-seater valve stability is poorer, replace the sleeve valve stability will be improved. 4. Increase the spring stiffness method actuator depends on the ability to resist load changes impact on the stroke of spring stiffness, the greater the stiffness, the smaller the impact on the trip, the better stability of the valve. Increase the spring stiffness is a common simple way to improve the stability of the valve, such as the scope of 20 ~ 100 kpa spring spring to 60 ~ 180 kpa takong spring, adopted mainly take the valve positioner, otherwise, use the valve to the other with locator. 5. Lower response speed method when the system requires the regulator response or adjustment speed should not be too fast, the response of the valve and regulating speed is faster, need to fine tune, such as flow regulating valve of flow control changes is very big, or the system itself is a rapid response system and regulating valve and a locator to speed the valve movement, it will be unfavourable. This will produce a overshoot, vibration, etc. To this, should reduce the response speed. Method are: (1) change the linear feature to logarithmic characteristics; (2) with the locator can be changed to converter, relay. 6. Symmetric screw bolt, thin gasket sealing method is used in & other; O” Ring seal valve structure, adopt a greater deformation of thick gasket ( Such as winding) , if pressure asymmetry, bearing asymmetry, easy to make the seal damage, tilt and generate deformation, seriously affect the sealing performance. Therefore, in the maintenance, assembly of this kind of valve, must be symmetrical to tighten the hold-down bolts ( Pay attention to a tight) 。 Thick gasket to such as thin gasket is better, so easy to reduce the slope, guarantee the seal. 7. Increase the width of sealing face, stop flat valve core shut down and down and ways to reduce the leakage of flat valve core ( As the two type of valve, valve plug sleeve valve) In without a guide in the seat and guide surface, due to the valve in the work, the valve core is a lateral force, from flowing into depend on outflows, the greater the tolerance clearance, valve core this unilateral phenomenon more serious, and deformation, different heart, or valve core sealing surface chamfering small ( Generally is 30 & deg; Chamfering to guide) , so close to closing, valve spool seal face chamfer end in the valve seat sealing surface, caused by closing the valve core to beat, even close does not reach the designated position, make the valve leakage increase greatly. The simplest and the most effective solution is to increase the valve core sealing surface size, the minimum diameter of the end face of valve core is smaller than the seat diameter 1 ~ 5 mm, have enough guide, to ensure that the valve core guide into the seat, keep a good sealing surface contact. 8. Promote closed change flow direction, to solve the problem, eliminate surge method of two type of valve to improve the cutting effect, often used as flow closed form. In liquid medium, due to the flow closed type is the role of unbalanced force pressure of closed, valve core has effect on promoting shut, also known as the suction effect, speed up the valve core movement speed, slight water hammer and surge in the system. Solution to the above phenomenon is as long as the flow away, instead of surge can be eliminated. Such as promoting the close and affect the valve does not work, also can consider to take this approach to solve. 9. Fluid damage method to overcome the most typical is a two-seat valves, fluid into in the middle, and the valve core is perpendicular to the import, fluid to bypass valve core is divided into two beams. Fluid impact on valve core, make on the export side, causing friction and damage of the lining sleeve for the valve core and guidance, lead to movement disorders, high flow may also make the valve core bending, erosion, serious when even rupture. The solution: (1) improve the guide parts material hardness; (2) increase the ball up and down the middle size valve core, make a rough shape; Choose a substitute other valve. If use the sleeve valve, fluid flow of people around the edges of the sleeve of the plug less lateral thrust.