Jaguar Caravan Multiple and Cascading Boilers
17
GAS PIPING
This section contains sizing and construction recommendations
for fuel supply piping to Caravan gas-fired modular boiler sys-
tems. Gas-fired equipment must conform not only to codes of
local regulatory agencies, but also to additional specifications that
may be imposed by the utility or gas supplier. Therefore, the fol-
lowing information should be considered only as a guideline.
Figure 6 illustrates a typical gas supply line installation. It consists
of a main between the utility’s meter box and the boiler system, a
main shut-off valve sediment trap, gas header pipe and drip legs
on individual boilers.
Individual gas lines to individual boiler modules should be equal
to or greater than the boilers supplied gas connection diameter.
Size of gas main and header pipes depends on volume of gas
required and acceptable pressure drop between meter and mod-
ules gas regulator valves. Minimum pressure required at each
valve is 3 inches of water column for natural gas measured while
all boilers and other gas-fired equipment on the same meter are
firing. Final pressure of gas header must vary no more than +0.3
in. of water column.
Gas main sizing
To determine the correct pipe diameter for the gas main serving a
specific Caravan system, proceed as follows:
a. Follow the building plans, find total length of straight pipe
between supply from gas meter and boiler gas header.
b. Using data in Table 2, calculate equivalent linear length of
screw pipe fittings used in fabrications of main. Add this to
figure from step (a) to obtain equivalent total length.
c. Find Caravan gas consumption in cubic feet per hour from
Table 1.
d. Multiply the system total hourly gas consumption by flow
correction value from local utility. If not available, use
1000 btu/cu.ft. (correction value = 1)
e. Locate system’s total equivalent pipe length in Table 3.
f.
Move vertically to the system’s corrected flow rate calculated
in step (c). If this value falls between two of those listed,
selected larger value.
g. From this point move horizontally to the left column and read
suggested pipe diameter for gas main.
Table 2. Equivalent linear length in feet of standard iron pipe fittings for natural gas
Number
of boilers
Cubic feet
per hour
2
780
3
1170
4
1560
5
1950
6
2340
7
2730
8
3120
Table 1. Gas consumption rate.
Pipe
Size
Inches
Elbow
Valve
Return
Bend
Side
Outlet
Tee
Standard
Medium
Sweep
Long
Sweep
Gate
Globe
Angle
1/2
3/4
1
1-1/4
1-1/2
2
3
0.84
1.17
1.57
2.19
2.63
3.55
5.72
0.52
0.73
0.98
1.37
1.64
2.23
3.59
0.41
0.57
0.77
1.07
1.29
1.74
2.81
0.031
0.044
0.057
0.082
0.098
1.320
2.130
2.50
3.50
4.68
6.54
7.84
10.60
17.08
1.12
1.84
2.11
2.94
3.52
4.77
7.69
1.25
1.75
2.34
3.27
3.92
5.30
8.84
1.66
2.33
3.11
4.35
5.21
7.05
11.40
9. GAS LINE SIZING AND LAYOUT
