Becker VRP-CH Series Valve Regulator Pilot Instruction Manual | 7
Copyright 2023 Baker Hughes Company. All rights reserved.
Principles of Operation
The Becker VRP-CH pilot and double-acting cylinder actuator
can be used in conjunction with varying valve types to provide
a complete package for stable, accurate pressure control over
a wide range of applications. The energy for control valve
operation comes from the pressure differential between the pilot
supply and discharge pressures.
The power gas channels through two adjustable orifices that
independently feed the top and the bottom portion of the
cylinder. After passing through each adjustable orifice, gas
flow is divided. One passage leads to the respective port of the
cylinder while the other is exhausted through the internal nozzle
of the pilot.
At equilibrium, distances between each internal nozzle and its
respective seat are equal, resulting in equal amounts of pilot
output pressure to the top and to the bottom of the cylinder as
well as bleed gas. The control valve remains stationary.
When the control pressure rises above the setpoint, the pilot
pistons move downward. As the distance between the bottom
internal nozzle and its seat increases, the distance between the
top internal nozzle and its seat decreases. The bottom nozzle
starts to bleed more gas, and the top nozzle starts to bleed
less. This causes an increase in cylinder bottom pressure and
a decrease in cylinder top pressure. The pressure differential
creates the force needed to close the valve and lessen the flow
of gas. When the control pressure returns to the setpoint, the
pilot output pressures automatically return to equilibrium at
the new valve position. If the control pressure falls below the
setpoint, the opposite reaction takes place.
Your VRP-CH pilot will come factory adjusted for your particular
application. The use of the adjustment procedures will be
necessary upon installation of a rubber goods replacement kit
or any other disassembly or reassembly of the pilot.
Adjustment Procedure
The sensitivity adjustment drum in the center of the pilot
determines the sensitivity of the unit. The setpoint adjustment
screw determines the setpoint at which the pilot operates. The
variable orifices determine the speed of response of the pilot.
Initial Adjustment
1. Adjust the supply regulator to the desired power gas pressure.
Refer to the original invoice paperwork supplied with the
product for the appropriate power gas pressure setting. It is
imperative that adequate supply gas pressure be supplied
to the VRP-CH for proper operation of the system and all
accessories. The adjustable orifices are used to control the
volume of gas that is supplied to the VRP-CH. The stroking
speed of the system is proportional to the numerical value
of the adjustable orifice. Adjustable orifice settings are
typically equal for both orifices. However, a few applications
may require unequal settings for each adjustable orifice.
Refer to Fine Tuning for more information on using unequal
adjustable orifice settings. Set both orifices according to the
table below.
Notes:
• If the VRP-CH is NOT equipped with VB Series Volume
Boosters, set the variable orifices to the recommended value
per the Table below. If equipped with volume boosters, see
note below the table below. To determine the cylinder bore,
look at the model number stamped on the stainless steel
tag on the top of the cylinder. The cylinder bore will be the
first number following the first capital letter “H”. This one or
two digit number following the first “H” will be the diameter in
inches and will be followed by another letter (For example, a
unit with the model number 6H8F6FG-PCH has an 8” bore).
• If equipped with a PS sensor and/or VB-250, volume boosters,
see page 17.
Figure 1 - VRP-CH Pilot Principles of Operation
