16 | Baker Hughes
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Flow Calculations
Q
c
= 312.8 x P
1
x C
V
x
1
G x (T + 460)
Critical Flow
Variables:
Q
c
= critical flow across the inlet orifice in scfh
P
1
= supply pressure to the pilot in psig
C
v
= flow factor
G = specific gravity of the gas
T = temperature of the gas in °F
Steady State Consumption
Variables:
Q
ssc
= steady state consumption
Q
c1
= critical flow across the top orifice in scfh
Q
c2
= critical flow across the bottom orifice in scfh
C
v
= 0.00447 x n1.656242
n = number of the orifice setting on orifice block (1 through 6)
Q
ssc
= Q
c1
+ Q
c2
Supply Regulator Capacity
Q
src
= 2Q
c
Variables:
Q
src
= supply regulator capacity
C
v
= 0.0869 (calculated with n = 6)
Travel Time
Minimum travel time (the time the valve takes to move from
one extreme position to another) is achieved when the signal
deviates 5 percent or operation.
a) Pilot bleeds to the atmosphere:
t
1
= 0.148 x
G
T + 460
S x D
2
C
v
Variables:
t = time in seconds
S = cylinder stroke in inches
D = cylinder diameter in inches
C
v
= flow factor (for orifice or booster)
C
v
(Booster)
= 3.13
b) Pilot bleeds to a pressure system:
T= t
1
+ 0.0003906 x S x D
2
x P
2
Gas Consumption Table
Supply Gas
Pressure
(psig or psid)
Orifice Number
2
3
4
5
6
100
29
56
90
130
176
150
41
80
130
187
253
200
54
105
169
244
330
250
66
129
210
301
407
Consumption (SCFH) for monitor and standby valve. For pilot
gas consumption while in control, multiply by 2.
Appendix
