Wednesday, June 12, 2019

Useful Pipe Engineering Basics & Formula's (Download PDF)

Velocity of Fluid through Piping :-

0.3208 X GPM / Internal Area

What is the velocity of 10 gpm going through a 1/2″ diameter schedule 40 pipe?

GPM = 10
Internal Area = 0.304 (see note below)
0.3208 X GPM / Internal Area = 0.3208 X 10 X 0.304 = 10.55 feet per second

Note: The outside diameter of pipe remains the same regardless of the thickness of the pipe. A heavy duty pipe has a thicker wall than a standard duty pipe, so the internal diameter of the heavy duty pipe is smaller than the internal diameter of a standard duty pipe. The wall thickness and internal diameter of pipes can be found on readily available charts.

Hydraulic steel tubing also maintains the same outside diameter regardless of wall thickness.

Hose sizes indicate the inside diameter of the plumbing. A 1/2″ diameter hose has an internal diameter of 0.50 inches, regardless of the hose pressure rating.

Suggested Piping Sizes :-
Pump suction lines should be sized so the fluid velocity is between 2 and 4 feet per second.
Oil return lines should be sized so the fluid velocity is between 10 and 15 feet per second.
Medium pressure supply lines should be sized so the fluid velocity is between 15 and 20 feet per second.
High pressure supply lines should be sized so the fluid velocity is below 30 feet per second.

Pneumatic Valve Sizing :-

All these pneumatic formulas assume 68 degrees F at sea level
All strokes and diameters are in inches
All times are in seconds
All pressures are PSI.

Valve Sizing for Cylinder Actuation

SCFM = 0.0273 x Cylinder Diameter x Cylinder Diameter x Cylinder Stroke / Stroke Time x ((Pressure-Pressure Drop)+14.7) / 14.7

Cv Required = 1.024 x SCFM / (Square Root of (Pressure Drop x (Pressure-Pressure Drop+14.7)))

Pressure 2 (PSIG) = Pressure-Pressure Drop

Flow Coefficient for Smooth Wall Tubing

Cv of Tubing =(42.3 x Tube I.D. x Tube I.D. x 0.7854 x (Square Root (Tube I.D. / 0.02 x Length of Tube x 12)

SCFM to Atmosphere = Valve Cv x (Square Root of (((Primary Pressure x 0.46) + 14.7) x (Primary Pressure x 0.54))) / 1.024

Pressure Drop Max (PSIG) = Primary Pressure x 0.54

Air Flow Q (in SCFM) if Cv is Known

Valve Cv x (Square Root of (Pressure Drop x ((PSIG – Pressure Drop) + 14.7))) / 1.024

1.024 x Air Flow / (Square Root of (Pressure Drop x ((PSIG-Pressure Drop) + 14.7)))


  1. When the installation is in progress your presence should be there, many times, when owner is not there, plumbers ignore to work properly and try to finish the work as soon as possible for them. plumber BA

  2. I have read your article; it is very informative and helpful for me. I admire the valuable information you offer in your articles. Thanks for posting it.

  3. First, professionals are able to access the latest equipment and boast of up-to-date training. This enables them to perform their tasks without creating any problems. Whether you want to improve indoor air quality and stop allergies or reduce energy costs caused by inefficiency. Duct Replacement Services Melbourne