Weak current College】 【control valve common troubleshooting methods (6).

<br> <br> 8. control valve stability less solution (5) <br> 1) change the imbalance force direction method <br> In stability analysis, known unbalance loads with the same direction as the valve closes, which is produced on .the valve, the valve closes trend poor stability. Work on the valve in the unbalanced force conditions next, choose to change their role in the direction of the flow, usually closed to the flow opening, in General can easily solve the problem of the stability .of the valve. <br> 2) avoid valve itself unstable area work method <br> The valve is governed by its own structure of restrictions in certain open degree while working on poor stability. ① double seat valve, opening in less than 10 per .cent, due to open at the stream on the ball, the ball at the stream, the instability problems; ② unbalanced force change of slope near the produce alternating current, its stability is poor. Such as the butterfly, alternating points in about 70 degrees .; two-seater valve in 80-90 per cent of the opening. In this type of valve, in unstable areas work necessarily poor stability, avoid instability in the area of work. <br> 3) replace the good stability of the valve < .br> Stability of the valve to its unbalanced force changes in the direction of smaller, the better. Commonly used ball valve, the valve sleeve is a great feature. When the stability of single and two-seater valve is poor, replace a sleeve valve .stability will be enhanced. <br> 4) increases the spring stiffness method <br> Executive body resistance load changes influence the trip depends on the capacity of the spring stiffness, rigidity, the greater the effect on the trip, the stability of the valve ., the better. Increased spring rate is increased valve stability of common simple method, such as 20 ~ 100KPa spring scope of spring into 60 ~ 180KPa great stiffness spring, using this method is primarily of valve with Locator, or the use of the valve to .the other with a locator. <br> 5) reduce the speed of response method <br> When asked to respond or adjust speed control valve should not be too fast, the valve response and adjust the speed and relatively fast, such as flow needs .fine tuning and control valve's flow regulation changes but very large, or the system itself has been a rapid response system and control valves and valves with Locator to accelerate action, this is a disadvantage. This will result in an overshoot, vibration, etc. This .should reduce the speed of response. Approach: ① line characteristics to logarithmic characteristic; ② belt positioner can be changed to converters, relay device. <br> Tighten bolts 4) symmetric, using thin washer sealing method <br> In the "O" .-rings seal the valve structure, the use of a large deformation of thick spacer (such as winding tablets), clamping force is not symmetrical, asymmetrical and easy to make the seal is damaged, skew and deformation, seriously affect seal performance. Therefore, .for this type of valve repair, Assembly, it must be symmetrical to tighten the clamping screw (note not a tight). Thick gasket can be converted to thin the gasket is better, so easy to decrease the inclination, guarantee seal. <br> .5) increases the width of the Suppression of the sealing surface of valve shuts down beats flat plate and reduce the leakage volume of method <br> Flat cartridge (such as two-valve, sleeve valve plug), in seat no boot and guiding surfaces ., because the valve in the work of the valve under lateral forces from the stream into the side by side to the outflow, the valve clearance increases, the more serious side, coupled with the phenomenon of deformation, different, or the valve sealing surface chamfer .small (generally 30 ° chamfer to boot), and therefore close to closed, the sealing surface of valve production of chamfer faces over the seating surface, resulting in a closed valve beat, even off is not in place, make the valve leakage rate increased .significantly. The simplest and most effective solution is to increase the size of the valve sealing surface, so that the valve end of the minimum diameter ratio seat diameter small 1 ~ 5mm, have enough guidance role, to ensure that the valve guide into the seat ., keep the good sealing surface contact. <br> 6) change flow direction, solve problems, eliminate promoting off-surging method <br> The two-valve to increase cutting results, usually closed-use as a stream. On liquid medium, .because the stream closed-unbalanced force whose role is the core voltage, promoting close interaction, also known as the suction effect, accelerates the valve movement speed, produce minimal water hammer, causing the system to surge. On the phenomenon of the solution is to .just put flows into a stream, the surge will be eliminated. Similar to this effect by promoting clearance to the valve is not functioning, you can also take this into account. <br> 7) overcome fluid destruction law <br> The most typical .of the valves is a two-seater valve, fluid from the Middle into the spool perpendicular to the import, fluid bypass valve core is divided into upper and lower beam out. Fluid shock in the spool, so that it depends on the export side, .causing friction, injury of the valve and the guiding surface lining, leading to action disorders, high flow also may make the valve core, erosion, serious or even break. The solution: ① improving steering parts material hardness; ② increases the size of the .middle and bottom ball valve, so that it is rough shape; ③ selecting other valve maintenance. Such as sleeve valve, the flow of fluid from the sleeve surrounds, on the plug of the lateral thrust greatly reduced. <br> 8) overcome fluid .produced by rotating force making the valve core rotation method <br> On the "V"-shaped mouth spool, because the media into the role of asymmetry, in "V"-shaped mouth on the valve core tangential force does not produce a consistent ., so that the rotation of the rotation. Especially on the valve DN ¡ .ý 100 more strongly. Thus, there may be a valve and actuator push rod connection disengaged, without spring actuator is likely to cause distortion of the diaphragm. Solution: ① will spool anti rotation direction to a point, to balance the role of the spool .on the tangential force; ② further lock valve and actuator connection and, if necessary, increase a anti rotation of splint; ③ "V"-shaped opening of the valve replaced by piston-shaped cartridge; ④ use or changed to sleeve type structure; .⑤ such as caused by the rotation of resonance, eliminate resonance can solve the problem. <br> 9) adjustment of the butterfly valve plate frictional force to overcome the opening beats method <br> Using the "O"-rings and seal rings, .linings for soft sealed butterfly's valve, the valve is closed, due to the soft seals deformation, so that the valve plate closes in place and a wrap of the valve plate, can achieve very good off the effect. But when you want to open the .valve, actuator to force open the valve plate is increasing, when added to soft seal friction on the valve plate are equal, the valve plate. Once started, this friction is dramatically reduced. In order to achieve the balance of power, the valve plateHeavy .open, this force with the opening of the media of unbalance torque of actuator opens the torque balance, valve to stop in this opening. This violent and sudden jump open opening can be as high as 30 to 50 per cent, which will produce a series .of questions. At the same time, is closed due to the soft seal to produce a larger change, easy to produce permanent deformation or valve plate extrusion bad, scratching, affect life expectancy. The solution is to adjust the soft seals on the valve plate .start of friction, which is guaranteed to reach the desired cutting requirements and to make the valve is normally started. Specific measures are: ① adjusted interference; ② by spacing or adjust the executing agency, the pre-tightening force, output power to reduce excessive .gate close to open the pose difficulties. <br> <br> <br>.