Preparations for Startup
3-10
750-392
CBEX-DE
3.8.2 — 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 information on the gas heating value.
3.8.3 — 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.
TABLE 3-3. Pressure/Altitude Correction Factors
Altitude Feet Above Sea
Level Correction Factor
1000 1.04
2000 1.07
2500 1.09
3000 1.11
4000 1.16
5000 1.21
6000 1.25
7000 1.30
8000 1.35
9000 1.40
NOTE: For undersized or oversized gas trains or altitudes above 9000 feet, contact your local Cleaver-Brooks repre-
sentative.
OUTPUT x 100%
OUTPUT x 100
EFFICIENCY
INPUT =
GAS FLOW =
INPUT
GAS BTU/FT
3
3
=
EFFICIENCY x GAS BTU/FT
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