Fluid and Piping Calculations
Recommended Fluid Velocities

Suction Lines  24 fps
sch. 40 piping

Return Lines  1015 fps
sch. 40 piping

Medium Pressure  1520 fps
5002900 psi
sch. 80 or 160 piping or tubing with similar internal area

High Pressure Lines  <30 fps
30005000 psi
tubing is normally used
The internal area of piping is determined by using the formula A=πr^2. Let A stand for the area we are finding. π or 3.14159 multiplied by the radius (half the diameter) of the piping squared.
NOTE: There are a few key factors to keep in mind when calculating the internal area of hydraulic piping or tubing.

Tubing is measured by the O.D.
1/2" stainless steel hydraulic tubing has a wall thickness of .049" so the actual I.D. is approx .402" not .500"
ex.) A=π(.201^2) The internal area of 1/2" x .049" wall tubing is .127 in^2

Piping is measured by the I.D.
1/2" Schedule 40 black pipe has an I.D. of approx. .622" but as the wall thickness increases (Sch. 80) the I.D. will get smaller (.546") since the outside diameter doesn't change.
ex.) A=π(.311^2) The internal area of 1/2" sch. 40 piping is .304 in^2

Hydraulic hose is indicated by the inside diameter of the hose and will have the same I.D. regardless of the hoses pressure rating.
ex.) A=π(.25^2) The internal area 1/2" hydraulic hose is .196 in^2
When calculating velocity you should always double check the I.D. measurement of the piping or tubing you're using. Manufacturing tolerances allow for a range of wall thicknesses.
Note: This information is provided as a quick reference resource and is not intended to serve as a substitute for qualified engineering assistance. While every effort has been made to ensure the accuracy of this information, errors can occur. As such, neither Badger Fluid Power LLC, any of its affiliated companies, nor its employees will assume any liability for damage, injury or misapplication as result of using these calculators.