Page 45 - 2018_IFGC

GAS PIPING INSTALLATIONS

402.4 Sizing tables and equations. This section applies to shall be determined using the longest run of piping
piping materials other than noncorrugated stainless steel tub- and the load of the section.
ing. Where Tables 402.4(1) through 402.4(37) are used to 2. The pipe size of each section of branch piping not
size piping or tubing, the pipe length shall be determined in previously sized shall be determined using the
accordance with Section 402.4.1, 402.4.2 or 402.4.3.
length of piping from the point of delivery to the
Where Equations 4-1 and 4-2 are used to size piping or most remote outlet in each branch and the load of
tubing, the pipe or tubing shall have smooth inside walls and the section.
the pipe length shall be determined in accordance with Sec-
402.4.3 Hybrid pressure. The pipe size for each section
tion 402.4.1, 402.4.2 or 402.4.3.
1 of higher pressure gas piping shall be determined using the
1. Low-pressure gas equation [Less than 1 / pounds per longest length of piping from the point of delivery to the
2
square inch (psi) (10.3 kPa)]: most remote line pressure regulator. The pipe size from
the line pressure regulator to each outlet shall be deter-
Q 0.381 mined using the length of piping from the regulator to the
D = -------------------------------------------- (Equation 4-1) most remote outlet served by the regulator.
∆
0.206
H

19.17 ---------------  402.5 Noncorrugated stainless steel tubing. Noncorrugated
C × 

L
r
stainless steel tubing shall be sized in accordance with Equa-
tions 4-1 and 4-2 of Section 402.4 in conjunction with Sec-
1
2. High-pressure gas equation [1 / psi (10.3 kPa) and tion 402.4.1, 402.4.2 or 402.4.3.
2
above]: 402.6 Allowable pressure drop. The design pressure loss in
any piping system under maximum probable flow conditions,
Q 0.381 from the point of delivery to the inlet connection of the appli-
D = ------------------------------------------------------------- (Equation 4-2) ance, shall be such that the supply pressure at the appliance is
2
( P – P ) 2 × Y 0.206 greater than or equal to the minimum pressure required by the
2
1
18.93 -------------------------------- appliance.
C × L 402.7 Maximum operating pressure. The maximum operat-
r
ing pressure for piping systems located inside buildings shall
not exceed 5 pounds per square inch gauge (psig) (34 kPa
where:
gauge) except where one or more of the following conditions
D = Inside diameter of pipe, inches (mm). are met:
Q = Input rate appliance(s), cubic feet per hour at 60°F 1. The piping joints are welded or brazed.
(16°C) and 30-inch mercury column.
2. The piping joints are flanged and pipe-to-flange con-
P = Upstream pressure, psia (P + 14.7). nections are made by welding or brazing.
1
1
P = Downstream pressure, psia (P + 14.7). 3. The piping is located in a ventilated chase or otherwise
2
2
L = Equivalent length of pipe, feet. enclosed for protection against accidental gas accumu-
∆H= Pressure drop, inch water column (27.7-inch water lation.
column = 1 psi).
4. The piping is located inside buildings or separate areas
TABLE 402.4 of buildings used exclusively for any of the following:
C AND Y VALUES FOR NATURAL GAS AND
r
UNDILUTED PROPANE AT STANDARD CONDITIONS 4.1. Industrial processing or heating.
EQUATION FACTORS
GAS 4.2. Research.
C r Y
4.3. Warehousing.
Natural gas 0.6094 0.9992
4.4. Boiler or mechanical rooms.
Undiluted propane 1.2462 0.9910
5. The piping is a temporary installation for buildings
3
For SI: 1 cubic foot = 0.028 m , 1 foot = 305 mm, under construction.
1-inch water column = 0.2488 kPa,
1 pound per square inch = 6.895 kPa, 6. The piping serves appliances or equipment used for
1 British thermal unit per hour = 0.293 W.
agricultural purposes.
402.4.1 Longest length method. The pipe size of each 7. The piping system is an LP-gas piping system with an
section of gas piping shall be determined using the longest operating pressure greater than 20 psi (137.9 kPa) and
length of piping from the point of delivery to the most complies with NFPA 58.
remote outlet and the load of the section.
402.7.1 Operation below -5°F (-21°C). LP-gas systems
402.4.2 Branch length method. Pipe shall be sized as fol- designed to operate below -5°F (-21°C) or with butane or a
lows:
propane-butane mix shall be designed to either accommo-
1. Pipe size of each section of the longest pipe run date liquid LP-gas or prevent LP-gas vapor from condens-
from the point of delivery to the most remote outlet ing into a liquid.
32 2018 INTERNATIONAL FUEL GAS CODE ®
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