Becker VRP-B-CH Series Valve Regulator Pilot Instruction Manual | 8
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three categories:
1. Regulator is too sensitive: Position of the regulator will
change frequently while control pressure is stable.
2. Regulator is not sensitive enough: Control pressure
fluctuates while position of the regulator does not change
(or changes very little).
3. Regulator is lagging behind changes in the control pressure:
The control pressure fluctuates while the regulator is
constantly changing its position.
Case # 1 Regulator is too sensitive:
Turn the sensitivity adjustment drum to the left (increasing
numbers on the scale) by small increments. Typically good
control is achieved within one or two divisions on the sensitivity
adjustment drum.
WARNING: Do not turn the sensitivity adjustment drum to the
left (Increasing numbers on the scale) more than one full turn
(11 numbers) from the initial adjustment position. While certain
VRP models will become insensitive on even minimal rotation,
turning more than one full turn will guarantee excessive
deadband on any VRP model.
Case # 2 Regulator is not sensitive enough:
The pilot should be able to meet the response criteria as described
in the adjustment section (20 percent change in output differential
with a 3/4 percent change in sensing pressure). If this adjustment
does not produce satisfactory results, most likely the control valve
torque has elevated. To further improve sensitivity, the control
valve must be lubricated. See the Becker ball valve regulator
maintenance manual for information on how to service the
Becker control valve.
Case # 3 Regulator is lagging behind changes in the
control pressure:
Increase both inlet orifice settings. This will cause the regulator
to move faster. Turn the sensitivity adjustment drum to the left
(Increasing numbers on the scale) in order to maintain the desired
cylinder top and cylinder bottom pressures. Finally, turn the set
point adjustment screw clockwise to increase the set point for the
original desired pressure. Changing the set point will not change
the sensitivity.
If the simultaneous increase of both adjustable orifices did not
produce the desired result (i.e. the regulator is still unstable) it
is necessary to set the adjustable orifices to open and close at
different rates. This can be achieved by doing the following:
1. Open both adjustable orifices to #6 and note the total swing
of the regulator. Leave the top adjustable orifice (controlling
the opening speed of the regulator) at #6, and reduce the
bottom adjustable orifice (controlling the closing speed of the
regulator) to #3. If the swing has stopped, or at least reduced,
the direction of speed adjustment is correct (the closing speed
should be smaller than the opening speed). In order to find
the optimum setting, try several combinations of adjustable
orifice settings.
2. If the swing of the regulator has increased, change the
direction of speed adjustment. Reduce the top adjustable
orifice (controlling opening speed of the regulator) to # 3,
and increase the bottom adjustable orifice to #6.
3. If stability of the unit cannot be achieved through different
adjustable orifice setting combinations, the gain of the
pilot is too high. Leave the adjustable orifices at the setting
combination which generates the smallest swing. Turn the
sensitivity adjustment drum to the left (decreasing numbers
on the scale) by small increments until the stability is achieved.
4. Finally, turn the setpoint adjustment screw clockwise to
increase the setpoint. Changing the setpoint will not change
the adjusted mode.
Inspection Procedure
As with all precision equipment, it is necessary to periodically
test the pilot to insure optimum performance. We recommend
the following procedure once a year:
1. Close the cylinder block valves in order to prevent the control
valve from moving.
2. Close valve on the sensing line.
3. Shut off supply pressure and bleed down at pilot. Note the
settings of the adjustable orifices before removing them from
the orifice assembly. Remove adjustable orifices and clean
then thoroughly. Reinstall using new O-rings, being sure to
install each orifice into the hole from which it was removed
(the orifice and block have matching numbers for this
purpose). Reset adjustable orifices to original settings.
4. Turn on supply pressure.
5. Check the integrity of the pilot balance valve seats by
changing the sensing pressure 3/4 percent above and below
the pilot setpoint. One cylinder pressure gauge should drop
to 20 percent less than power gas when the pressure is raised.
At setpoint the bleed gas should be minimal. If the exhaust
port does bleed gas, you should be able to stop the venting
by turning the adjustment drum a couple of numbers to the
left. If the venting gas will never shut off with both gauges
balanced and reading full power gas pressure, the balance
valve seats are worn. Failure to stop venting supply pressure
is a sign of a worn pilot seat. Shut off power gas supply, bleed
off all remaining pressure, and rebuild pilot according to
procedure in the Assembly section.
6. Reinstate power gas and soap test around all diaphragms,
vents and orifice assembly. Unless a leak is found, it is not
necessary to disassemble the pilot. If any leaks are found
around the diaphragms, all rubber goods must be replaced.
7. Apply a “False Signal” pressure to the sensing chamber.
Observe operation of the gauges. If any gauges are defective,
replace them.
8. Perform the internal friction test.
9. Readjust the VRP-B-CH pilot if necessary.
