Design Criteria: 3' Frictional Pressure Drop per 100' Pipe Length with a Maximum Velocity of 10 ft/sec

Figure - 1 Friction Loss for CLOSED Piping Systems: Schedule 40 Steel *Source: Carrier Systems Design*

Figure - 2 Friction Loss for OPEN Piping Systems: Schedule 40 Steel *Source: Carrier Systems Design*

**PLASTIC Physical Dimensions and Sizing Criteria (ASPE Data Book)**

Figure - 3 Friction Loss for Copper Piping Systems: Types K, L, & M *Source: Carrier Systems Design*

**ALUMINUM , BRASS Handbook for Mechanical Engineers : Baumeister & Marks**

EL = L/D* D (EL = Equivalent Length. L=Pipe Length, D = Pipe Diameter)

Velocity Pressure Factor (K) forWater : K = C*D**E: Pressure Drop (PD) = K*VP

EL = L/D* D (EL = Equivalent Length. L=Pipe Length, D = Pipe Diameter)

Velocity Pressure Factor (K) forWater : K = C*D**E: Pressure Drop (PD) = K*VP

**LOW PRESSURE STEAMPIPE SIZING CRITERIA : Flow Rates of Steam (lbs/hr)**

**HIGH PRESSURE STEAMPIPE SIZING CRITERIA : Flow Rates of Steam (lbs/hr)**

**CONDENSATE FLOWRATE (lbs/hr) Condensate Return Pressure = 0 psig**

Example: 6800 lbs per hour of steam flow in a 2 ^{1}/_{2} inch pipe at 100 psig pressure.

What is the pressure (psi) drop per 100 ft length of pipe and the flow velocity?

Answer: psi/100' = 11 velocity = 32,000 fpm

Figure - 17 Steam Flow Rates at Various Pressures and Velocities for Schedule 40 Pipe *Source: ASHRAE*

Downstream Pressure

- inlet upstream pressure is more than 5 psig (35 kPa)
- fittings factor 1.2 - equivalent pipe length = pipe length + 20%

For natural gas the nominal BTU/cf varies from about *900 to 1100 BTU/cf*. In general it is common to set

- 1 Cubic Foot (CF) = Approx 1,000 BTUs
- 1 CFH ≈ 1 MBH
- 1 Btu/h = 0.293 W

- pressure less than 1
*1/2 psig*pressure drop 0.5*inches water*column - specific gravity of natural gas energy content in natural gas 10
*1 Cubic Foot (CF) = Approx 1,000 BTUs 1 CFH = 1 MBH*- common to use fittings factor 1.5 - equivalent pipe length

in table above = pipe length + 50%

For natural gas the nominal *BTU/cf* varies from about

900 to 1100 BTU/cf. In general it is common to set

*The capacity of a low pressure natural gas (less than 1 psi) pipe line can be calculated with the Spitzglass formula like*

*q = 3550 k ( h / l SG) ^{1/2} (1)*

*where*

q = natural gas flow capacity (cfh) | h = pressure drop (inWater Column) |

l = length of pipe (ft) | k = [d^{5} /(1 + 3.6/d + 0.03 d)]^{1/2} |

d = inside diameter pipe (in) | SG = specific gravity |

For natural gas the nominal *BTU/cf* varies from about *900 to 1100 BTU/cf* . In general it is common to set

*1 Cubic Foot (CF) = approx 1,000 BTUs*

*1 CFH = 1 MBH*

The specific gravity of natural gas varies from *0.55 to 1.0* .

The downstream pressure in a houseline after the meter/regulator is in general in the

range of 7 to 11 inches Water Column, or about 1/4 psi.

**Example - Natural Gas Pipe Capacity**

The capacity of a *100 ft* natural gas pipe with a nominal diameter *0.5 inches* (actual ID *0.622 in* )

and 0.5 inches WC pressure drop can be calculated as

*k = [(0.622 in )5 /(1 + 3.6 / (0.622 in) + 0.03 (0.622 in))]0.117*

*q = 3550 0.117 ( (0.5 in) / (100 ft) 0.60 ) 1/2 = 37.9 cfh*

Specific gravity of natural gas is set to *0.60*.

## Horizontal Fixture Branches and Stacks | ## Building Drains and Sewers |

## HORIZONTAL RAINWATER PIPE SIZING | ## HORIZONTAL RAINWATER PIPE SIZING |

Varkie C. Thomas, Ph.D., P.E.
Research Professor
College of Architecture
Illinois Institute of Technology
Chicago, Illinois, USA

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