Adjustment Procedures
6-10
750-368
CBEX Elite 100-1200 HP
6.11.2 — Gas Flow
The volume of gas flow is measured in terms of cubic feet and is determined by a meter reading. The gas flow
rate required for maximum boiler output depends on the heating value (Btu/cu. ft.) of the gas supplied and boiler
efficiency. The supplying utility can provide the information.
INPUT = OUTPUT x 100%
EFFICIENCY
GAS FLOW = INPUT
GAS BTUs/FT
3
= OUTPUT x 100
EFFICIENCY x GAS BTUs/FT
3
6.11.3 — Pressure Correction
The flow rate is based on a “base” pressure, which is usually atmospheric or 14.7 psia.
Meters generally measure gas in cubic feet at “line” or supply pressure. The pressure at which each cubic foot is
measured and the correction factor for the pressure must be known in order to convert the quantity indicated by
the meter into the quantity which would be measured at “base” pressure.
To express the volume obtained from an actual meter reading into cubic feet at base pressure, it is necessary to
multiply the meter index reading by the proper pressure factor obtained from Table 6.3.
Conversely, to determine what the meter index reading should be in order to provide the volume of gas required
for input, divide the desired flow rate by the proper pressure correction factor. This answer indicates the number
of cubic feet at line pressure which must pass through the meter to deliver the equivalent number of cubic feet at
base pressure.
TABLE 6-3. Pressure Correction Factors
11.05
21.11
31.18
41.25
51.32
61.39
71.45
81.53
91.59
10 1.66
11 1.72
12 1.81
13 1.86
14 1.93
15 2.0
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