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Dear customers & visitors, as Microsoft is closing down its SharePoint soon, .TT pocketEngineer softDesign is relocating its home to Google site at
 Natural or LP Gas Pipe Sizing for Android (a PocketGas r4.0)

high & low pressure gas pipeline hydraulic calculations - find flowrate, pipe size & pressure drop





To take a glance at all pocketEngineer software and OS requirements, click Overview.


For Windows OS, see pocketGas.


Note: aPocketGas (Android) and pocketGas (Windows) are not the same.



a PocketGas (Gas Pipe Sizing Calculator): 

your mobile design partner for Gas pipe design & sizing 

Natural Gas or LPG (propane) pipe sizing for high pressure & low pressure systems is as easy as 1, 2, 3 with aPocketGas (Gas Pipe Sizer) program. aPocketGas calculates gas flowrate, pipe size and pressure drop. The oldest and most common equation - Weymouth equation - is used in the high pressure gas calculation. NFPA model for high pressure calculation is also included. For low pressure gas calculation,  NFPA equation is used.

Aim: creating a mobile design environment
for the practising engineers & designers in today's mobile world.

Results: Instant solutions at your fingertips



- a mobile design tool app for Gas pipeline hydraulics

- calculate both High pressure (for infra & building distribution pipeline ) and Low pressure (for building internal pipeline) gas pressure systems

- 2 models for high pressure calculations: Weymouth and NFPA. 1 model for low pressure calculation: NFPA

- options to find flowrate, pipe size and pressure drop / downstream pressure

- gas input module with NFPA + IFGC appliance gas input values selection. Convert gas input to flowrate.

- pipe size table module. Select nominal or internal pipe diameter from built-in pipe material. 

- built-in data, guides, etc

- "save to file" function for printing

- individually selectable SI-IP units

- for Android OS


 The selectable SI-IP units available are:


 Parameters High Pressure Low Pressure
 pressurekPa/psi/in.wg/bar  Pa/psi/in.wg/bar
 pipe diameter mm/inmm/in 
 pipe lengthkm/m/mile/ft  m/ft
 pipeline temperature oC/oF
 flowratecmh/cfh  LPS/cmh/cfh




Design Explained 1: High Pressure System 

The Weymouth equation is used for calculating flows and pressure in high pressure gas system. The Weymouth equation does not use Moody friction factor, but uses a pipeline efficiency factor, E. The equation is developed empirically for compressible, turbulent flow with high Reynolds number in long pipelines. The Weymouth equation is one of the oldest and most common equation (as compared to the Panhandle A & B equations) in high pressure gas calculations. The Weymouth equation is considered to be more conservative than the Panhandle A & B equations.


The Weymouth equation in English units is presented as follows (with elevation effects ignored):




It is worth noting that the Weymouth's formula has expressed Moody friction factor as a function of the pipe diameter, i.e. f = 0.008/d1/3.


For NFPA / IFGC formula, refer to NFPA 54 or International Fuel Gas Code.


Design Explained 2: Low Pressure System 

For pressure less than 10 kPa (1.5 psi), the following equation presented in SI units from NFPA / ASHRAE is used to determine gas flow capacity. AGA's International Fuel Gas Code (IFGC) uses the same equation.


 Q = 0.0001d 2.623 [dP/(C*L)]0.541


where  Q = flow rate at 15 oC and 101 kPa (l/s)

           d = inside diameter of pipe (mm)

         dP = pressure drop (Pa)

          C = factor for viscosity, density and temperature

          L = pipe length (m)



Design Explained 3: Pipe Size Table


The built-in Pipe Size Table module is designed as a separate module for a quick access to pipe nominal or internal diameters. Making it a greater navigation experience for users, you can select a pipe norminal or internal diameter within the pipe sizing calculation module. The pipe materials available are:


a) Copper pipe (EN)

b) Copper pipe (ASTM) 

c) Ductile iron pipe (EN)

d) Ductile iron pipe (ANSI)

e) PVC plastic pipe (ASTM)

f) HDPE pipe (ASTM)

g) HDPE pipe (ISO)

h) Steel pipe (EN)

i) Steel pipe (ANSI)

j) Stainless steel pipe (ANSI)


Design Explained 4: Gas Input Calculator

In the planning & design process, you often need to convert a given appliance gas input to flowrate for the purpose of pipe sizing. The Gas Input Calculator exactly does this. It is desigend to function as a gas input to flowrate converter, or as a appliance gas input calculator. The built-in appliance gas input values are adopted from NFPA + IFGC.




Comparisons: Weymouth vs NFPA / IFGC for Lower End of High Pressure System 


Inlet pressure = 5 psi (gauge), Pressure drop = 3.5 psi, Flowrate = 84656 cfh, Gas = Natural Gas, Specific gravity = 0.6, Pipeline temperature = 60 oF, Pipe = smooth wall.


 Pipe Lengh (ft)

Calculated Pipe Diameter (in)

Weymouth formula

 NFPA / IFGC formula


 2.6 2.5


 4.0 4.0


 6.2 6.4




Gas Sizing Example 1: High Pressure System


Calculate the outlet (downstream) pressue in a 17.5 inch (444.5 mm) natural gas pipeline, 20 miles (32.2 km) long. The gas flow rate is 6,250,000 cfh (176,875 cmh) at a flowing temperature of 70 oF (21.1 oC). The inlet pressure (absolute) is 1014.7 psia (6996.2 kPa) and the gas gravity is 0.6. High Density Polyethylene (HDPE) pipe is used, Assume the pipeline efficiency is 0.98, and compressibility factor is 0.85. Ignore elevation effects.


The following results are computed by aPocketGAS program:



Gas Pipeline Hydraulic Calculations
(High Pressure - Weymouth model)
Find Downstream Pressure, P2

upstream pressure, P1 (gauge)1000 psi6894.9 kPa
downstream pressure, P2 (gauge)935.74 psi6451 kPa
mean pressure, Pm (gauge)968.2 psi6675.6 kPa
pressure drop, Pd6.4 %6.4 %
pipe diameter, d17.5 in444.5 mm
pipe length, L20 mile32.2 km
pipeline temp, T70 oF21.1 oC
gas compressibility, z0.850.85
gas sp. gravity, g0.60.6
eff. factor, E0.980.98
FlowRate, Q6250000 cfh176875 cmh
upstream velocity, V113.04 ft/s3.97 m/s
downstream velocity, V213.92 ft/s4.24 m/s
upper limit (erosional) velocity, Vmax52.31 ft/s15.95 m/s


Note: Standard atmospheric conditions used in aPocketGAS program = 520 oR (15 oC) & 14.7 psi (101.3kPa).



Gas Sizing Example 2: Low Pressure System

A restaurant serving about 300 persons requires a total gas damand of 1000 cfh (7.8611 l/s) for its cooking equipment. The total pipe length measured from the gas meter to the restaurant kitchen is 60 ft (18.29 m). Natural gas with 0.60 specific gravity is used. The pressure drop from the gas meter to the kitchen shall not exceed 0.3 in. w.g. (74.6 Pa). Determine the required pipe size.


The following results are computed by aPocketGAS program:




Gas Pipeline Hydraulic Calculations
(Low Pressure <10kPa - NFPA model)
Find Pipe Diameter, d

 pressure drop, Pd 74.6 Pa0.3 in.wg 
 pipe internal diameter, d 49.7 mm 1.96 in
 pipe length, L18.29 m  60 ft
 Correction factor, Cr 0.610.61 
 FlowRate, Q7.8611 l/s 1000 cfh 



Gas Sizing Example 3: Medium Pressure System  



Natural Gas:

Medium gas pressure system with pressure available at point D = 60 psi. The 1st regulator is set to deliver 5 psi at the outlet of the regulator. The upstream piping system shall deliver pressure no less than 20 psi at point A to the 1st regulator. Size the gas pipe line from D to A.


Information available:

Building 1 estimated gas demand = 20,000 cfh

Building 2 estimated gas demand = 20,000 cfh

Building 3 estimated gas demand = 30,000 cfh


Pipe length D-C (including fittings) = 250 ft

Pipe length C-B (including fittings) = 200 ft

PIpe length B-A (including fittings) = 200 ft


Working illustrations (by no means this is the only approach):

Allowable pressure drop from D to A = 60-20 = 40 psi.

Total pipe length from D to A = 650 ft.

Allocate pressure losses equally from D to A. Therefore, pressure loss = 40/650 = 0.0615 psi per ft.


(Note: you can distribute the pressure losses any way you wish as long as the sum of the total pressure drop does not exceed the allowable pressure drop.)


Pipe section 

 Upstream pressure 



Downstream pressure



Pipe Size (in.)

using aPocketGas program 

 D-C 6044.625 


 C-B 44.62532.325 


 B-A 32.32520.025



Note: All gas appliances will have their own pressure regulator.





Note: For Compressed Air Pipe Sizing, see CompAir.

Experience yourself the mobility of aPocketGas (Android)

at Android Market  


Download now:

product detail 


OS requirements: Android


for Windows OS, see pocketGas                            


To Purchase & Download to your Android device



 @ Android Market


in invidually selectable SI-IP units 



Calculation Options




High Pressure -Weymouth model




High Pressure - Weymouth model 






 High Pressure - NFPA model



Low Pressure - NFPA model




 Gas Input Calculator

(convert gas input to flowrate)




Gas Input Calculator

(select & calculate appliance gas input)



Pipe Size Table

(select nominal or internal diameter)





txtRW module

(view saved result file)