CleaverBrooks 4WI, Operation, Service And Parts Manual

Page: 102 / 216

Adjustment Procedures
6-16 750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual
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 6.4.
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.
As an example, assume that a 600 horsepower boiler is installed at 2,000 feet above sea level, is equipped with a
standard gas train and burner, and that 1,000 Btu natural gas is available with an incoming gas pressure of 3 psig.
The pressure and flow requirements can be determined as follows:
Pressure
Correction for the 2,000 feet altitude must be made since altitude has a bearing on the net regulated gas pressure.
The standard gas train requires 37.5” WC gas pressure at sea level, Table 6.1. Table 6.2 indicates a correction factor
of 1.07 for 2,000 feet. Multiplying the results in a calculated net regulated gas requirement of approximately 40.1”
WC. This is the initial pressure to which the regulator should be adjusted. Slight additional adjustment can be made
later, if necessary, to obtain the gas input needed for burner rating.
Flow
Since the gas flow rate is based on standard conditions of flow, correction must be made for the supply pressure
through the meter of 3 psig. Determine the flow rate by dividing the Btu content of the gas into the burner input,
Table 6.3, and “correct” this answer by applying the correction factor for 3 psig, Table 6.4.
TABLE 6-4.
Pressure Correction Factors
1 1.05
2 1.11
3 1.18
4 1.25
5 1.32
6 1.39
7 1.45
8 1.53
9 1.59
10 1.66
11 1.72
12 1.81
13 1.86
14 1.93
15 2.0