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
Orifices are often used in fluid
mechanics to limit mechanically the flow. It is important to
be able to size them.
The restriction orifice mentioned here is a thin perforated
plate, also called diapgragm.
2. Pressure drop through an orifice
The following correlation is
given by Gibson, it is reproduced in many books.
Equation 1 : singularity
pressure drop coefficient for an orifice
With :
K = Pressure drop coefficient
D = Pipe diameter (m)
d = orifice diameter (m)
u_{m} = fluid velocity, before diaphragm, (m/s)
ΔHs = Pressure drop in m
The coefficient K can also be calculated thanks to the
following graph :
Graph 1 : K coefficient as
a function of d/D
Source :
Gibson et al., Hydraulics and its applications, 5th edition,
Constable London, 1952
