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# A.6 Examples of Piping System Design and Sizing

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Determine the
required pipe size of each section and

*outlet*of the*piping*system shown in Figure A.6.1, with a designated pressure drop of 0.5-inch w.c. (125 Pa) using the Longest Length Method. The gas to be used has 0.60 specific gravity and a heating value of 1,000 Btu/ft^{3}(37.5 MJ/m^{3}).**Solution:**-
Maximum gas demand for
*Outlet*A:

- The length of pipe from the
*point of delivery*to the most remote*outlet*(A) is 60 feet (18288 mm). This is the only distance used. - Using the row marked 60 feet (18288 mm) in Table
402.4(2):
*Outlet*A, supplying 35 cfh (0.99 m^{3}/hr), requires^{1}/_{2}-inch pipe.*Outlet*B, supplying 75 cfh (2.12 m^{3}/hr), requires^{3}/_{4}-inch pipe.- Section 1, supplying
*Outlets*A and B, or 110 cfh (3.11 m^{3}/hr), requires^{3}/_{4}-inch pipe. - Section 2, supplying
*Outlets*C and D, or 135 cfh (3.82 m^{3}/hr), requires^{3}/_{4}-inch pipe. - Section 3, supplying
*Outlets*A, B, C and D, or 245 cfh (6.94 m^{3}/hr), requires 1-inch pipe.

- If a different gravity factor is applied to this example,
the values in the row marked 60 feet (18 288 mm) of
Table 402.4(2) would be multiplied by the appropriate
multiplier from Table A.2.4 and the resulting cubic
feet per hour values would be used to size the
*piping*.

Determine
the required CSST size of each section of the piping
system shown in Figure A.6.2, with a designated pressure
drop of 1 psi (6.9 kPa) for the 2 psi (13.8 kPa) section and 3-inch w.c. (0.75 kPa) pressure drop for the 13-inch w.c. (2.49
kPa) section. The gas to be used has 0.60 specific gravity and
a heating value of 1,000 Btu/ft

Solution:

^{3}(37.5 MJ/ m^{3}).Solution:

- Size 2 psi (13.8 kPa) line using Table 402.4(18).
- Size 10-inch w.c. (2.5 kPa) lines using Table 402.4(16).
- Using the following, determine if sizing tables can be
used.

- Total gas load shown in Figure A.6.2 equals
110 cfh (3.11 m
^{3}/hr). - Determine pressure drop across regulator [see notes in Table 402.4(18)].
- If pressure drop across regulator exceeds
^{3}/_{4}psig (5.2 kPa), Table 402.4(18) cannot be used.

Note: If pressure drop exceeds^{3}/_{4}psi (5.2 kPa), then a larger regulator must be selected or an alternative sizing method must be used. - Pressure drop across the line regulator [for 110
cfh (3.11 m
^{3}/hr)] is 4-inch w.c. (0.99 kPa) based on manufacturer's performance data. - Assume the CSST manufacturer has tubing sizes or EHDs of 13, 18, 23 and 30.

- Total gas load shown in Figure A.6.2 equals
110 cfh (3.11 m
- Section A [2 psi (13.8 kPa) zone]

- Distance from meter to regulator = 100 feet (30480 mm).
- Total load supplied by A= 110 cfh (3.11 m
^{3}/hr) (furnace+ water heater+ dryer). - Table 402.4(18) shows that EHD size 18 should
be used.

Note: It is not unusual to oversize the supply line by 25 to 50 percent of the as-installed load. EHD size 18 has a capacity of 189 cfh (5.35 m^{3}/hr).

- Section B (low pressure zone)

- Section C (low pressure zone)
- Distance from regulator to water heater is 10 feet (3048 mm).
- Load is 30 cfh (0.85 m
^{3}/hr). - Table 402.4(16) shows that EHD size 13 should be used.

- Section D (low pressure zone)
- Distance from regulator to dryer is 25 feet (7620 mm).
- Load is 20 cfh (0.57 m
^{3}/hr). - Table 402.4(16) shows that EHD size 13 should be used.

Determine the required CSST size for Section G (retrofit application) of the

*piping*system shown in Figure A.6.4, with a designated pressure drop of 0.5-inch w.c. (125 Pa) using the branch length method. The gas to be used has 0.60 specific gravity and a heating value of 1,000 Btu/ft^{3}(37.5 MJ/m^{3}).**Solution:**- The length of pipe and CSST from the
*point of**delivery**appliance*(barbecue) at the end of Section G is 40 feet (12192 mm), A + B + G. - Use this branch length to size Section G.
- Assume the CSST manufacturer has tubing sizes or EHDs of 13, 18, 23 and 30.
- Using the row marked 40 feet (12192 mm) in Table 402.4(15), Section G, supplying 40 cfh (1.13 m
^{3}/hr) for the barbecue requires EHD 18 CSST. - The sizing of Sections A, B, F and E must be checked to ensure adequate gas carrying capacity since an
*appliance*has been added to the*piping*system (see A.6.1 for details).

Determine the required semirigid copper tubing size of each section of the piping system shown in Figure A.6.3, with a designated pressure drop of 1-inch w.c. (250 Pa) (using the Branch Length Method). The gas to be used has 0.60 specific gravity and a heating value of 1,000 Btu/ft

^{3}(37.5 MJ/m^{3}).**Solution:**- Section A

- The length of tubing from the
*point of delivery*to the most remote*appliance*is 50 feet (15240 mm), A+ C. - Use this longest length to size Sections A and C.
- Using the row marked 50 feet (15240 mm) in Table 402.4(10), Section A, supplying 220 cfh (6.2 m
^{3}/hr) for four appliances requires 1-inch tubing.

- The length of tubing from the
- Section B

- The length of tubing from the
*point of delivery*to the range/oven at the end of Section B is 30 feet (9144 mm), A+ B. - Use this branch length to size Section B only.
- Using the row marked 30 feet (9144 mm) in Table 402.4(10), Section B, supplying 75 cfh (2.12 m
^{3}/hr) for the range/oven requires^{1}/_{2}-inch tubing.

- The length of tubing from the
- Section C

- The length of tubing from the
*point of delivery*to the dryer at the end of Section C is 50 feet (15240 mm), A+ C. - Use this branch length to size Section C.
- Using the row marked 50 feet (15 240 mm) in Table 402.4(10), Section C, supplying 30 cfh (0.85 m
^{3}/hr) for the dryer requires^{3}/_{8}-inch tubing.

- The length of tubing from the
- Section D

- The length of tubing from the
*point of delivery*to the water heater at the end of Section D is 30 feet (9144 mm), A+ D. - Use this branch length to size Section D only.
- Using the row marked 30 feet (9144 mm) in Table 402.4(10), Section D, supplying 35 cfh (0.99 m
^{3}/hr) for the water heater requires^{3}/_{8}-inch tubing.

- The length of tubing from the
- Section E

- The length of tubing from the
*point of delivery*to the furnace at the end of Section E is 30 feet (9144 mm), A+ E. - Use this branch length to size Section E only.
- Using the row marked 30 feet (9144 mm) in Table 402.4(10), Section E, supplying 80 cfh (2.26 m
^{3}/hr) for the furnace requires^{1}/_{2}-inch tubing.

- The length of tubing from the

A test

If the volume of the

Therefore, the gauge could be expected to register 18 psig (124 kPa) when the ambient temperature is 40°F (4°C).

*piping*system is installed on a warm autumn afternoon when the temperature is 70°F (21°C). In accordance with local custom, the new*piping*system is subjected to an air pressure test at 20 psig (138 kPa). Overnight, the temperature drops and when the inspector shows up first thing in the morning the temperature is 40°F (4°C).If the volume of the

*piping*system is unchanged, then the formula based on Boyle's and Charles' Jaw for determining the new pressure at a reduced temperature is as follows:where: | ||

T_{1} |
= | Initial temperature, absolute (T_{1} + 459) |

T_{2} |
= | Final temperature, absolute (T_{2} + 459) |

P_{1} |
= | Initial pressure, psia (P_{1} + 14.7) |

P_{2} |
= | Final pressure, psia (P_{2} + 14.7) |

P_{2} |
= | 32.7 - 14.7 |

P_{2} |
= | 18 psig |

Therefore, the gauge could be expected to register 18 psig (124 kPa) when the ambient temperature is 40°F (4°C).

Using the layout shown in Figure A.6.1 and

*ΔH*= pressure drop, in w.c. (27.7 in. H_{2}O= 1 psi), proceed as follows:- Length to A = 20 feet, with 35,000 Btu/hr.

For^{1}/_{2}-inch pipe,*ΔH*=^{20feet}/_{100feet}× 0.3 inch w.c. = 0.06 in w.c. - Length to B = 15 feet, with 75,000 Btu/hr.

For^{3}/_{4}-inch pipe,*ΔH*=^{15feet}/_{100feet}× 0.3 inch w.c. = 0.045 in w.c. - Section 1 = 10 feet, with 110,000 Btu/hr. Here there is
a choice:

For 1-inch pipe,*ΔH*=^{10feet}/_{100feet}× 0.2 inch w.c.

For^{3}/_{4}-inch pipe,*ΔH*=^{10feet}/_{100feet}× [ 0.5 inch w.c. +^{110,000Btu}/_{hr-104,000Btu/hr}× (10 inches w.c. - 0.5 inch w.c.)]=0.1 × 0.57 inch w.c0.06 inch w.c.

*Note that the pressure drop between 104,000 Btu/hr and 147,000 Btu/hr has been interpolated as 110,000 Btu/hr.* - Section 2 = 20 feet, with 135,000 Btu/hr. Here there is
a choice:

*Note that the pressure drop between 121,000 Btu/hr and 148,000 Btu/hr has been interpolated as 135,000 Btu/hr, but interpolation for the*^{3}/_{4}-inch pipe (trivial for 104,000 Btu/hr to 147,000 Btu/hr) was not used. - Section 3 = 30 feet, with 245,000 Btu/hr. Here there is
a choice:

*Note that interpolation for these options is ignored since the table values are close to the 245,000 Btu/hr carried by that section.* - The total pressure drop is the sum of the section
approaching A, Sections 1 and 3, or either of the
following, depending on whether an absolute
minimum is needed or the larger drop can be
accommodated.

Minimum pressure drop to farthest*appliance*:

*ΔH*= 0.06 inch w.c. + 0.02 inch w.c. + 0.06 inch w.c.

= 0.14 inch w.c.

Larger pressure drop to the farthest*appliance*:

*ΔH*= 0.06 inch w.c. + 0.06 inch w.c. + 0.3 inch w.c. = 0.42 inch w.c.

*Notice that Section 2 and the run to B do not enter into this calculation, provided that the appliances have similar input pressure requirements.*

For SI units: 1 Btu/hr= 0.293 W, 1 cubic foot= 0.028 m^{3}, 1 foot= 0.305 m, 1 inch w.c. = 249 Pa.

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