Regulating valve abnormal vibration adjustment method

Vibration valve is one of the more difficult to deal with valve operation. Vibration not only accelerate the damage of the control valve, but also affect the product quality and safety in production. In this paper, with the research of intelligent positioner, the precautions and methods to deal with the vibration problem in the field are given.

Actuators leak

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As the actual valve position deviation due to leakage of a given valve position, resulting in repeated inflatable servo amplifier so that the valve can not be stable at a given valve position, resulting in valve vibration.

2.1 leak site

(1) pneumatic film actuator

Pneumatic diaphragm actuator diaphragm breakage, push rod and spring tray loose, O-ring breakage, the reaction between the actuator push rod and the lower diaphragm seal leakage, usually V-ring wear, top mounted hand wheel mechanism Membrane seal leakage.

(2) straight stroke cylinder actuator

Straight stroke cylinder actuator (including for the fork-type corner actuator) piston ring leakage (blow-by), the piston cylinder head seal leaks, limit screw seal leaks, the output shaft and the cylinder head Between the leaks sealed.

(3) double rack structure angular travel actuator

Double-rack structure Angle stroke actuator piston back seal leakage, cylinder head and cylinder seal leakage, the output shaft connected to the cylinder block up and down the support ring leakage, cylinder head limit screw leakage.

(4) external accessories

External accessories such as leaks for each positioner output line connector, gas operated gearboxes or relays, quick disconnect valves, one-way governors, and leakage of retention valves.

2.2 leak treatment

For different air leaks, take a different approach.

(1) If the valve has no strict switching time limit, the pneumatic fittings and process fittings should be reduced as much as possible. For example, the auxiliary components such as quick release valve, air speed increasing gear, one-way speed governor, reducing and bending pass should be eliminated.

(2) regular cleaning and filling oil to keep the putter, stem clean and rust-free, chrome layer can not afford to skin lubrication sufficient to ensure that the seal is not worn, no leakage.

(3) Inspection, the pneumatic diaphragm actuator exhaust port (the role of the exhaust port in the next film cover, the reaction in the membrane cover) and single-acting piston exhaust port and other parts of the leak detection found leakage Timely repair process.

Control valve stuck

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Valve Jamming Includes stem and packing, plug and seat, and actuator jamming.

3.1 jamming reason

(1) Stem seal packing pressed tight, causing the stem to run resistance increases. Due to the improvement of NC machining accuracy, the stem surface finish is very high, too tight packing increases the resistance between the stem and packing, causing pre-tension spring return overshoot, causing the valve long-period vibration (vibration cycle is normal More than 30s).

(2) Improperly adjust the packing gland against the spring-loaded stuffing box, resulting in increased stem operating resistance and preload spring or packing damage.

(3) low temperature valve does not use its corresponding filler, resulting in increased frictional resistance.

(4) Stem deformation or packing gland dislocation, causing the valve stem friction packing gland, resulting in increased operational resistance, while causing the filler to accelerate wear and tear caused by medium leakage. Valve stem deformation usually have 2 kinds of reasons. ① is the role of implementing agencies as the gas pressure set point exceeds the valve nominal value, the thrust caused by valve stem deformation is too large. ② operating valve manual mechanism caused by excessive force stem deformation.

(5) stuffing box into the foreign body stuck, resulting in increased stem resistance. Foreign body valve stem is not clean during the operation into the dust, rust or rain and snow. In addition, the cold box or pipeline due to severe cold, the valve rod at icing, ice and through the valve stem movement into the stuffing box.

(6) internal plug spool, the main reason for the guide sleeve part of the jam (some manufacturers called oil-free bearings), medium crystallization or scaling in the valve, valve cavity and other foreign matter. Due to the purging is not clean, equipment corrosion, pipe or container parts fall off and other reasons there is a foreign body in the valve cavity.

(7) jamming of the actuator, the main reason is the spring break or overlap, double gear rack teeth wear, actuator limit screw or limit plate and other parts off.

3.2 jam processing

(1) Keep the stem clean and lubricated, timely replacement of dust seals and shields.

(2) Combine with the professional equipment to eliminate the cold outside the valve stem caused by icing.

(3) According to the valve manual to maintain the packing, packing performance to prevent failure.

(4) According to the air cylinder and valve factory manual to adjust the air pressure, not due to the valve is not in place and free to increase air pressure, or excessive manual operation agencies.

Process conditions are poor

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(1) the valve design parameters and the actual working conditions are quite different, the actual pressure difference is much higher than the design pressure, causing the actuator thrust is too small, serious lack of valve support stiffness, the adjustment process valve opening affected by the conditions, Valve with the vibration medium conditions, this phenomenon in the valve for the opening-type valve on the performance is particularly prominent. Occurrence of this situation, the temporary measure taken is to use the valve before and after the control valve throttling valve to reduce the pressure before and after the control valve. And optimize the transformation based on operating conditions, such as the use of multi-stage pressure reducing valve trim reasonable design hole size, increasing the actuator thrust or preload.

(2) large pipe vibration, loose feedback mechanism or retainer, causing the valve position feedback fluctuations. When this happens, reinforce the pipe and carefully check the feedback mechanism to eliminate backlash and backlash errors.

(3) the process medium pressure or flow pulsation is too large, such as reciprocating compressors and metering pumps intermittent feeding system control valve, due to the oscillation of the working conditions caused by the valve vibration. When this condition occurs, increase the compressor or pump outlet buffer to reduce material pulsation.

Locator parameters set unreasonable

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In order to ensure that the positioner can meet different types, different sizes of control valve smoothly, quickly and accurately reach a given valve position, its hardware and software are equipped with a corresponding adjustment method (Table 1), to prevent excessive or overshoot oscillation. Meanwhile, in order to effectively monitor the actual output of the power amplifier, some positioners also monitor the position of the spool of the power amplifier and participate in the calculation as an inner loop.

Table 1 Locator



(1) Siemens SIPARTPS2 series locator

Siemens SIPARTPS2 series locators have a current limiter set on the hardware and software sets the dead zone for 34.DEBA controllers (0.15% by default). Rotating the restrictor clockwise reduces airflow and reduces actuator response. Rotating the restrictor counterclockwise increases air flow and accelerates the actuator response. Vibration should be reduced when the air flow. Appropriate to enlarge the dead zone can also effectively reduce vibration.

(2) Fisher DVVC6000 and DVC2000 locator

FisherDVC6000 and DVC2000 positioner (using two-stage stem positioning algorithm) is not set in the hardware adjustment components, the amplifier's dynamic response depends on the software settings. For the vibration of the valve can be based on the situation weakened response, increased damping. Regulating the accuracy of the less demanding conditions, you can increase the integral dead zone, reducing the integral gain, or even turn off the integration to reduce the possibility of valve vibration.

(3) ABB locator

The ABB Positioner (TZID-C) has no damping adjustment hardware on the hardware, but a filter into the nozzle baffle to check to prevent valve airing from getting into the nozzle.

(4) Yamatake azibilAVP3000 locator

Yamatake azibilAVP3000 locator main parameters for the dynamic characteristics of data set. The dynamic characteristic data setting is determined by the selected actuator type. The dynamic characteristic parameters P, I and D can only be set when the actuator is set to "0" or expert mode.

(5) Flowserve logix3200 locator

Flowserve logix3200 positioner (using two-stage stem positioning algorithm) I / P conversion piezoelectric nozzle baffle structure, servo amplifier spool valve assembly. The operation panel is provided with A-H eight-speed gain selection switch, the minimum gain in A-range and the maximum gain in H-position. The gain of the positioner can be quickly selected during calibration.

(6) YTC2300 locator

South Korea YTC2300 locator hardware is equipped with flow adjustment knob, the actuator is appropriate to reduce the air flow to prevent vibration.

Conclusion

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Resolve the problem of vibration control valve can improve the level of intelligent manufacturing, expansion valve applications. While reducing labor intensity and improving the working environment, it also makes the production process more secure and stable.