VPR pneumatic valve positioner (referred to VPR locator) is the special attachment Japan Yamatake - Honeywell regulating valve the VFR cam deflection. It is in accordance with the signal of the pneumatic regulator regulating valve right quick action, to accurately adjust the valve flow and ensure the flow characteristics. I plant the introduction of production in the mid-eighties, and has been widely used in the automatic control system in the petrochemical, power, light industry and chemical industry.
To the proper use and maintenance, the need to explain how it works, as shown in Figure 1. The input signal is increased, the bellows expansion to drive bezel (ie leverage) * near the nozzle end. Reduce the gap nozzle back pressure, Down Following the actuator diaphragm promote the spool. Air intake off a small increase in the output pressure to open a large exhaust port, the actuator stem moves down regulating valve spool turned on or off. As the spool rotates, the cam is also rotated to pull the feedback spring, through the cam follower, so that the baffle tends to leave the nozzle, until the bellows is the torque generated by the feedback spring torque mutually balanced. Because of this moment are balanced, to ensure that the adjusted accurate correspondence relationship between the valve opening degree of the input signal, to achieve the correct positioning of the spool.
The following analysis is a common cause of failure and measures. Simple exclusion measures will be omitted.
No output pressure fault locator
1. No signal pressure ① pneumatic regulator failure; a large number of ② signal pipeline leak.
Bellows a large number of air leaks, fill solder or replace
3. No supply pressure or supply pressure is too low.
4. The blockage of the orifice of the bellows, with a diameter of less than 0.2mm wire dredge.
5. Locator zero position adjustment is wrong, that baffle and nozzle gap is too large. Use the tools to re-adjust.
Cam installed in the wrong place. Because a cam includes the percentage of the gas open air off type; gas open and gas shut-linear characteristics, the four mounting holes, easily installed wrong.
7. The baffle is not perpendicular to the nozzle end, still a lot of exhaust baffle nozzle end face contact.
8. The end face of the nozzle holes pits and requires replacement. End face glitches, reground.
9. The nozzle base adhesive at the leak.
Fault II signal decreases, the output pressure does not reduce
1, the zero position adjustment is inappropriate, the nozzle flapper gap is too small.
2. Following the bulkhead at the throttle of the actuator tube aperture too small or clogged, use 0.3mm wire dredge.
3. Bypass institutions switch position error, the switch should be in the "ON" position.
4. Deviation spring is too hard or choose the wrong supply pressure 0.22MPa spring wire diameter of 1.3mm, 0.28 to 0.5MPa when the spring wire diameter of 1.4mm.
5. The cam installation location error.
Three failures supply, no signal, the control valve has completed most of the trip
1, following the the of SR2.3 spherical disengagement of the the actuator valve seat and spool or sealed well.
2, in the initial position, the baffle and the nozzle surface has been brought into close contact.
Failure four basic error (linear) failed
1. Feedback spring force of spring force or zero adjustment is wrong.
2. Cam installed in the wrong location or itinerary pointer installed wrong.
3. Following the the actuator spool and the movable valve seat Seoul where line unsealed.
4. Bellows stiffness is too low, design requirements 4.9N/mm.
5. The output pipeline leak or the implementing agency.
6. Adjust packing compression is too big.
Than five adjustment between the fault initial point error
1. The cam is not in contact with the movable member the sleeve with the cam.
2. Feedback the spring wrong choice, standard stroke spring wire diameter of 0.8mm, split range signal is 0.7 mm.
Failure six locator hysteresis (variation) fail
1. Zero position stroke adjustment is wrong.
2. The pivot arm assembly of loose fasteners.
3. Zero position adjustment did not tighten the locking screws.
4. Bellows poor flexibility, small differences in the amount of displacement of the pros and cons of travel.
5. The cam follower of the sleeve hole and the outer peripheral coaxial degree beyond the design requirements.
6. Following actuator deviation difference of the spring parallel to the surface at both ends.
7. The shaft and bearing radial or axial gap is too big.
8. The unstable supply pressure.
9. The sleeve and the camshaft radial or axial clearance.
10. The feedback spring has not been standing treatment.
Article explains:
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