Piping
Systems
Equivalent length key pipe
components
Singularity coefficient key
pipe components
Partially filled pipe
Sonic Velocity
Valves types
Valves Cv
Control valve sizing for
gases
Pressure safety valves
Colebrook correlation
Churchill correlation
Velocity in pipes
Flow regimes
Orifice calculations

1. Introduction
The fluid velocity in a pipe is
a fundamental data to calculate to be able to characterize
the flow in a pipe, thanks to the Reynolds number, and size
a pipe circuit calculating the pressure drop expected for a
certain flow. When designing the pipe, it is necessary to
chose a fluid velocity to have good compromise in between
pressure drop and economics, some recommendations are given
below.
2. Calculation
With :
Q = Volumetric flowrate (m^{3}/s)
D = Pipe diameter (m)
u = Fluid velocity in pipe (m/s)
3.
Recommendations
Fluid 
Recommended velocity 
Water

1.52.5 m/s [1]
12.5 m/s [2] 
Air 
1030 m/s [1]
30 m/s [2] 
Steam

2040 m/s [1]
HP : 45 m/s [2]
LP : 30 m/s [2] 
Gas Process flows 
1545 m/s 
Dry gas 
30 m/s [2] 
Wet gas 
18 m/s [2] 
These values are given as an indication for presizing. Each
company should have its own guideline to be followed.
In addition to the sources given below, one may also wish to
consult Applied Process Design for Chemicals and
Petrochemicals plants, Ludwig, Gulf, page 85 which is
giving values for specific applications like sodium hydroxide,
ethylene, vinyl chloride...
Source
[1] Mecanique et Rheologies des fluides en Genie
Chimique, Midoux, Tec et Docs, 1993
[2] Rules of Thumbs for Chemical Engineers,
Brannan, Gulf, 2005
