20
APPENDIX B: GAS PIPE SIZING
For accurate gas pipe sizing, be sure to use total equiv-
alent pipe length: Add the equivalent foot-length of all fit-
tings, such as elbows, tees and valves, used in the gas
pipe run to the straight length of pipe. This can be deter-
mined from National Fuel Gas Code tables. For the initial
determination only, add 20% for the fittings to the straight
length of piping to get a total equivalent length. However,
once a diameter has been selected, total equivalent
length must be verified.
You need to know:
1. Total Btuh input of all modules in the heating plant.
2. Heating value, Btu per cubic foot, of the natural gas
which can be obtained from the local gas utility.
3. Total equivalent lengths of the gas main and the gas
headers which must be sized separately.
Tables B1 and B2 are pipe sizing tables for natural gas
and propane gas piping. They apply for sizing black iron
pipe only and are based on total equivalent pipe length
and maximum capacity of the pipe, in cubic feet of gas
per hour for natural gas or in thousands of Btu per hour
for propane. Natural gas sizing table assumes a 1000
Btu/cu.ft. heating value for natural gas.
Gas Headers (Natural Gas)
1. Determine cubic feet of gas per hour for each bank of
modules, using the following formula:
Module Bank Btuh Input = Cubic Feet Per Hour
NG Heating Value
2. Determine length of the header, which is typically de-
pendent on length of the bank of modules which it serv-
es. Use the “Length” column in Figure A2. In most cases,
the header is straight pipe only.
3. In Table B1, find appropriate pipe length in upper por-
tion of table under "Length of Pipe, Feet" heading.
4. Move down the column; match the cubic feet per hour
from Step 1. Higher capacity selection is acceptable.
5. Move across to the left-hand column "Nominal Iron
Pipe Size, Inches" and read required pipe size.
Gas Main (Natural Gas)
1. Determine the cubic feet of gas per hour for the total
heating plant, using the following formula:
Heating Plant Btuh Input = Cubic Feet Per Hour
NG Heating Value
2. Determine total equivalent length of gas main. Re-
member, if exact number/type of fittings are not known,
for initial determination only, add 20% for fittings to the
straight length of piping to get a total equivalent length.
3. In Table B1, find appropriate pipe length in upper por-
tion of table under "Length of Pipe, Feet" heading.
4. Move down the column; match the cubic feet per hour
from Step 1. Higher capacity selection is acceptable.
5. Move across to the left-hand column "Nominal Iron
Pipe Size, Inches" and read required pipe size.
6. Once a diameter has been selected, verify the total
equivalent length.
Maximum Capacity of Pipe in Cubic Feet of Natural Gas per Hour for Gas Pressures of
0.5 Psig or Less and a Pressure Drop of 0.3 Inch Water Column
(Based on a 0.60 Specific Gravity Gas)
Nominal
Iron Pipe
Size,
Inches
Internal
Diameter,
Inches
Length of Pipe, Feet
10
32
72
132
278
520
1,050
1,600
3,050
4,800
8,500
17,500
20
22
49
92
190
350
730
1,100
2,100
3,300
5,900
12,000
30
18
40
73
152
285
590
890
1,650
2,700
4,700
9,700
40
15
34
63
130
245
500
760
1,450
2,300
4,100
8,300
50
14
30
56
115
215
440
670
1,270
2,000
3,600
7,400
60
12
27
50
105
195
400
600
1,150
1,850
3,250
6,800
70
11
25
46
96
180
370
560
1,500
1,700
3,000
6,200
80
11
23
43
90
170
350
530
990
1,600
2,800
5,800
90
10
22
40
84
160
320
490
930
1,500
2,600
5,400
100
9
21
38
79
150
305
460
870
1,400
2,500
5,100
125
8
18
34
72
130
275
410
780
1,250
2,200
4,500
150
8
17
31
64
120
250
380
710
1,130
2,000
4,100
175
7
15
28
59
110
225
350
650
1,050
1,850
3,800
200
6
14
26
55
100
210
320
610
980
1,700
3,500
1/4"
3/8"
1/2"
3/4"
1"
1-1/4"
1-1/2"
2"
2-1/2"
3"
4"
.326
.493
.622
.824
1.049
1.380
1.610
2.067
2.469
3.026
4.026
TABLE B1
