VRG CONTROLS LLC.
8 of 60
JUNE 2021
VPC “BV” SERIES VALVE PILOT CONTROLLERS
INSTRUCTION MANUAL
VPC “BV” SERIES VALVE PILOT CONTROLLERS
INSTRUCTION MANUAL
VRG Controls LLC.
8 of 54
APRIL 21, 2019
Variable
Description
Unit
Qc
Critical Flow Across Inlet Orifice
scfh
P
1
Supply Pressure
psig
Cv
Flow Factor
--
G
Specific Gravity of Gas
--
T
Gas Temperature
*F
TABLE 4.0
CRITICAL FLOW EQUATION
Qc=312.9 X (P
1
+14.7) X Cv X
1
G X (T + 460)
Where:
TABLE 5.0
FLOW COEFFICIENT TABLE (CV)
Adjustable Orifice Flow Coefficients
Installed Orifice
0
1
2
3
4
5
6
7
Standard
0.006
0.009
0.018
0.044
0.069
0.096
0.111
0.126
Medium (M)
0.042
0.045
0.062
0.089
0.134
0.172
0.211
0.249
Large (L)
0.042
0.063
0.172
0.328
0.461
0.578
0.634
0.675
Adjustable Orifice Setting
Notes:
1.
Equation above may be utilized to determine supply regulator consumption requirements and
steady state bleed rates for control valves operated with a VPC BV Valve Pilot Controller.
2.
When applications do not utilize Adjustable Orifice, then the VPC internal Balanced Valve
becomes the limiting factor to determine flow rates and resultant stroking times. VPC Internal
Balanced Valve Cv=1.45.
Variable
Description
Unit
t
Stroke Time
Sec.
H
Actuator Cylinder Stroke Length
in.
D
Actuator Cylinder Diameter
in.
Cv
Limiting Flow Coefficient
--
G
Gas Specific Gravity
Typ. 0.6 Natural Gas
T
Gas Temperature
*F
TABLE 6.0
ESTIMATED TRAVEL TIME
Where:
t=0.148 X
G
T + 460
H X D
Cv
2
X
