This document provides guidelines for preliminary sizing of liquid and gas piping systems. It discusses parameters to consider like velocity, pressure drop, Reynolds number and friction factor. For liquid piping, it recommends velocity ranges of 0.5-5 m/s and pressure drops of 0.034-0.083 bar/100m for pump suction and 0.15-0.627 bar/100m for pump discharge. It also lists velocity ranges for different gas and steam systems and formulas to calculate Reynolds number, friction factor and pressure drop based on parameters like density, velocity, pipe diameter and length.

1. Page | 1
PRELIMINARY PIPE SIZING:
1.1 Sizing of liquid piping system:
The sizing criteria for liquid piping system will depend on application. The parameters could be
a pressure drop or velocity constraints.
The velocities shall be kept low enough to prevent problems with erosion, hammer, pressure
surges, noise, and vibration.
 Velocity (momentum) constraints:
Velocities may be determined in the range of 0.5 to 5 m/s.
 Pressure constraints
1. Preliminary pipe sizing of pump suction piping should be based on a pressure drop of
0.034 to 0.083 bar/100 m.
2. Preliminary pipe sizing of pump discharge should be based a pressure drop of 0.15 to
0.627 bar/100 m.
1.2 sizing of gas and steam piping systems:
 air and other gases
𝜌𝑣2
≤ 20000
𝑘𝑔
𝑚𝑠2⁄
 Saturated steam (dry):
15 to 30 m/s
 Superheated steam
30 to 60 m/s
 Vacuum pipes:
10 to 100 m/s
1.3 Reynolds number:
The Reynolds number indicates whether the product flow is laminar or turbulent.
Laminar flow can be expected in pipes if the Reynolds number is < 2300.
Turbulent flow can be expected when the Reynolds number is > 4000.
𝑅𝑒 =
𝜌𝑣𝐷𝑖
𝜇
1.4 Friction factor:
The friction factor depends on the type of the flow and can be determined using Moody’s
chart.
In laminar flow: the friction factor can be calculated using the following formula:
𝑓 =
64
𝑅𝑒
In turbulent flow, the friction factor can be calculated using colobrook equation:
1
√𝑓
= −2log (
2.51
𝑅𝑒√𝑓
+
𝜀
3.72𝐷
)
Generally, friction factor can be calculated using the following formula:
𝑓 = 8 {(
8
𝑅𝑒
)
12
+ ({2.457ln(
7
𝑅𝑒
0.9
+ 0.27
𝜀
𝐷
)}
16
+ (
37530
𝑅𝑒
)
16
)
−3
2⁄
}
1
12⁄

2. Page | 2
1.5 Pressure drop calculations:
Assumption:
 Constant density
 Constant viscosity
These assumptions can be applied in case of incompressible fluids, while in case of compressible
fluids, the density and viscosity change with the pressure drop and possible temperature change.
△ 𝑃 = 𝑓
𝐿
𝐷
×
1
2
𝜌𝑣2
Δp: pressure drop (N/m2
)
f: friction factor
L: total length = pipe length + fittings equivalent length
D: inside diameter of pipe (m)
ρ: density (Kg/m3
)
V: average linear flow velocity (m/s)
Δh: head loss (m)
g: acceleration due to gravity (9.807 m/s2
)
m: mass flow (Kg/s)
µ: viscosity (Pa.s)
ɛ: internal pipe wall roughness (m)
Material ɛ (mm) ɛ (inches)
Concrete 0.3 - 3.0 0.012 - 0.12
Cast Iron 0.26 0.010
Galvanized Iron 0.15 0.006
Asphalted Cast Iron 0.12 0.0048
Commercial or Welded Steel 0.045 0.0018
PVC, Glass, Other Drawn Tubing 0.0015 0.00006