# Orifice plate (diaphragm) flow and pressure drop calculation

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1.
Introduction

2. Pressure drop through an orifice

3. Orifice flow and pressure drop
calculation tool

## 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 orifice plate or diaphragm.

## 2. Pressure drop through an orifice

The following correlation is given by Gibson, it is reproduced in many
books.It relates the flow through the orifice and the pressure drop.

**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**

## 3. Orifice flow and pressure drop calculation tool

You can access to an Excel calculation tool in order to assess the
flow and pressure drop through an orifice plate : Excel
calculation tool

**Source**

Gibson et al., Hydraulics and its
applications, 5th edition, Constable London, 1952