VRG Controls VPC BV Series User Manual

VRG CONTROLS LLC. 9 of 60 JUNE 2021
VPC “BV” SERIES VALVE PILOT CONTROLLERS
INSTRUCTION MANUAL
VRG Controls LLC. 9 of 54 APRIL 21, 2019
VPC “BV” SERIES VALVE PILOT CONTROLLERS
INSTRUCTION MANUAL
HOW IT WORKS DESCRIPTIONS:
DIRECT ACTING VPC-SA-BV
When the SENSING pressure is equal to the VPC setpoint, the net
force on the VPC power module is zero. This is the equilibrium
or “balanced” condion where the sensing pressure that pushes
down on the sensing diaphragm and the control spring force
that pulls up on the sensing diaphragm are equal. When the VPC
achieves equilibrium, the SUPPLY balanced valve and EXHAUST
balanced valve assemblies will remain closed maintaining a
constant OUTPUT pressure to the control valve. The VPC will
exhibit ZERO emissions at this state. From this posion two
possible scenarios can occur, the sensing pressure can rise above
or below the set point.
If the sensing pressure rises above the VPC setpoint the net force
on the VPC power module is downward. The EXHAUST balance
valve will close. The SUPPLY balance valve opens, increasing the
ow of SUPPLY gas to the OUTPUT port. The combinaon of these
acons creates a rise in output pressure. If the sensing pressure
falls below the VPC setpoint the net force on the VPC power
module is upward. Now the SUPPLY balanced valve will close.
The EXHAUST balanced valve opens, increasing the ow of gas to
the EXHAUST port. The combinaon of these acons decreases
the OUTPUT pressure. In order to control how much gas passes
through the balanced valve, adjustable orices are installed to
restrict the ow via the SUPPLY and the EXHAUST.
DIRECT ACTING VPC-SA-BV-ID
The VPC is inherently an INTEGRAL funcon device. A DERIVATIVE
funcon may be added to the OUTPUT of the VPC by incorporang
a VOLUME TANK in conjuncon with an adjustable orice on the
OUTPUT signal. The DERIVATIVE component aects the rate at
which the OUTPUT signal change is applied to the control valve
unit. If the DERIVATIVE orice number is increased this will cause a
slower resultant change in OUTPUT pressure (signal) to the control
valve. Conversely, if the DERIVATIVE orice number is decreased
it will permit a more rapid change in OUTPUT pressure (signal)
to the control valve unit. The DERIVATIVE funcon is typically
incorporated to introduce addional stability when the VPC is
applied in conjuncon with a pneumac valve posioner or when
the installed system is has a rapidly aected downstream system
such as a power plant fuel gas feed or two-stage pressure cut
applicaon.
REVERSE ACTING VPC-SA-BV-ID
In this case, the SUPPLY pressure and the EXHAUST pressure are
routed dierently by changing the ORIFICE manifolds. The VPC
will exhibit behavior in a “reverse” scenario. When SENSING
pressure rises above the set point the net force on the VPC power
module pushes downward. The SUPPLY balanced valve will close
and the EXHAUST balanced valve will open, causing gas to vent
through the EXHAUST port. This results in a decrease of OUTPUT
pressure. If the SENSING pressure falls below the VPC setpoint,
the net force on the VPC power module is upward. The SUPPLY
balanced valve will open and the EXHAUST balanced valve will
close causing an increase in OUTPUT pressure. Any VPC “Single
Any VPC “Single Acng” model maybe easily converted
between Direct Acng and Reverse Acng by simply
swapping the posion of the SUPPLY/EXHAUST and OUTPUT
manifolds.
VPC-SA-BV-GAP
For “How it Works” descripon of the VPC-SA-BV-GAP,
reference Direct Acng VPC-SA-BV at top of this page. The
VPC-SA-BV-GAP will dier in construcon by not having
ADJUSTABLE ORIFICES installed. The “GAP Controller”
will dier operaonally as it operates with a “snap acng”
or “on-o” logic. The “on-o” logic produces a HIGH
SETPOINT and LOW SETPOINT which area separated by a
“BAND.” This “BAND” or dierence between the two (2)
setpoints is achieved by widening the deadband via the
SETPOINT ADJUSTMENT DRUM.
DOUBLE ACTING VPC-DA-BV
When the SENSING pressure is equal to the VPC-DA-BV
setpoint, the net force on the VPC-DA-BV power module is
zero. This is the equilibrium or “balanced” condion where
the sensing pressure that pushes down on the sensing
diaphragm and the control spring force that pulls up on
the sensing diaphragm are equal. When the VPC-DA-BV
achieves equilibrium, the OPEN balanced valve and CLOSE
balanced valve assemblies will remain closed maintaining a
constant OUTPUT pressure to the top and boom chambers
of the control valve actuator.
From this posion two possible scenarios can occur, the
sensing pressure can rise above or below the set point.
If the sensing pressure rises above the VPC-DA-BV
setpoint the net force on the VPC-DA-BV power module is
downward. The OPEN balance valve will open and divert
pressure from the OPEN chamber of the double acng
actuator to EXHAUST. The CLOSE balance valve will remain
closed and full SUPPLY pressure shall connue to be applied
to the CLOSE side of the double acng actuator. The
combinaon of these acons creates a dierenal pressure
to be applied to the double acng actuator that will move
the valve toward the closed posion.
If the sensing pressure falls below the VPC-DA-BV setpoint
the net force on the VPC-DA-BV power module is upward.
The CLOSE balance valve will open and divert pressure
from the CLOSE chamber of the double acng actuator to
EXHAUST. The OPEN balance valve will remain closed and
full SUPPLY pressure shall connue to be applied to the
OPEN side of the double acng actuator. The combinaon
of these acons creates a dierenal pressure to be applied
to the double acng actuator that will move the valve
toward the open posion.
Addion of an NVD No-Vent Device will eliminate emissions
when the control valve remains in the full-open or full-
closed posions such as a standby, overpressure monitor or
relief type applicaon.

VRG Controls VPC BV Series Specifications

General

Brand	VRG Controls
Model	VPC BV Series
Category	Controller
Language	English