Introduction to Orifice assembly

1. Orifice Assembly
………let the restriction do measurement

2. Compiled by
Mr. Harshal Revandkar
(harshal.revandkar@chemtrols.com)
Engineer (Metering and Measurement)
Chemtrols Industries Ltd.
Under the guidance of
Mr. R. C. Ramchandran
Manager (Flow Elements)
Chemtrols Samil (I) Pvt Ltd.

3. Principles of Fluid Flow in Pipes
laminar flow : the fluid travels as parallel layers
(known as streamlines)
Turbulent flow: The fluid does not travel in
parallel layers, but moves in a haphazard
manner
NR < 2000 – laminar flow
NR > 4000 – Turbulent flow
2000 < NR < 4000 – transition region

4. Why to measure flow ????
Control
Billing
Alarm and indication

5. Techniques used in flow measurement
Variable area
Magnetic
Vortex
Pressure difference
Ultrasonic

6. Principle of pressure difference method

7. Pressure difference type flow elements
Orifice plate
Flow nozzle
Venturi tube

8. Orifice plate
The orifice plate is the simplest and
cheapest. It is simply a plate with a
hole of specified size and position cut
in it, which can then clamped between
flanges in a pipeline
The increase that occurs in the velocity
of a fluid as it passes through the hole
in the plate results in a pressure drop
being developed across the plate.
After passing through this restriction,
the fluid flow jet continues to contract
until a minimum diameter known as
the vena contracta is reached.

9. Principle of working
The whole principle is based on Bernoulli's
principle
Which states that, for an flow of a
nonconducting fluid, an increase in the
speed of the fluid occurs simultaneously
with a decrease in pressure.

10. Types of Orifice plate
Concentric
Eccentric
Segmental
Quadrant Edge

11. Concentric
These are most commonly used for
flow measurement. This has special
features such as simple structures,
high accuracy, and ease of installation
& replacement.
The orifice plates are correctly
finished to the dimensions, surface
roughness, and flatness to the
applicable standard.
These plates are recommended for
clean liquids, gases & steam flow,
when the Reynold number 7 ranges
from 1000 to 10000

12. Eccentric
For liquids containing solid particles that
are likely to sediment or for vapours likely to
deposit water condensate, this orifice plate
is used with its eccentric bore bottom flush
with the bottom of the piping inside surface
so that the sedimentation of such inclusions
are avoided.
Likewise, for gases or vapours, it may be
installed with its eccentric bore top flush
with the ID of the piping to avoid stay of gas
or vapour in its vicinity.
For Liquids
For gases

13. Segmental
Segmental orifice plates are most
useful where there are impurities and
also if there are suspension in the
fluids.
This avoids build up in front of the
orifice plate. The orifice hole is placed
at the bottom for gas service and top
for liquids.

14. The inlet edge of the bore of this
orifice plate is rounded to a quarter
circle.
This orifice plate is usually used for
viscous fluids & Reynolds number
between 2000 to 10000.
Quadrant Edge

15. Conical Entrance
These conical entrance orifice plates
are used for low Reynolds number in
the range of 80 to 2000 and give more
constant or predictable discharge
coefficient.
At lower Reynolds numbers, the
discharge coefficient of square edge
orifice plate may change by as much as
30%. These are more usable for viscous
service.

16. Orifice Flanges and support assembly
Two orifice flanges are called an orifice
flange union. Each flange comes with two
pipe taps for measuring the pressure drop
of the flow through an orifice plate
Support assembly consist of
Gasket
Carrier Ring
Stud and bolts

17. Corner Tap : In this arrangement,
openings for the pressure taps are
located in the upstream and
downstream flanges holding the
orifice plate
Flange Tap : This design places one
pressure tap hole 1 inch upstream
and the other 1 inch down-stream
form the orifice plate. Being closely
located to the face of the flange, they
are accessible for inspection..They
should not be used in pipe sizes less
than 2 inches where the ratio is high,
because the downstream tap is
located in a highly unstable pressure
region.
Orifice Tapings

18. D and D/2 taps are located in the
pipe wall one pipe diameter
upstream of the face of the plate
and half pipe diameter downstream
from face
These taps are also called as
Radius Taps. The pipe line sizes of
10" and above are recommended
to have these taps
D and D/2 tapings

19. Tapings at glance

20. Design of orifice plate
Design: per ISO 5167-2/ ASME MFC3M
Nominal size: ≥ 1½" (40 mm)
 Nominal pressure rating: as per customer
requirements
β-ratio: 0.20 ... 0.75
Accuracy: ≤ ±0.5 % of full scale flow rate
Repeatability: 0.1 % of flow rate

21. Factors need to be consider while design
1. Pipe Internal Diameter
2. Coefficient of thermal expansion for pipe and orifice
3. Meter range
4. Normal flow
5. Density (operating , NTP)
6. Viscosity
7. Differential pressure
8. Specific heat ratio
9. Operating pressure
10. Operating temperature
11. Pipe ID at operating temperature
12. Distance of tap
13. Reynolds number

22. 14. (Ceβ)^2 , Original
15. Emperical value of β
16. Iterated value of β
17. Pressure ratio
18. Expansion factor
19. Velocity approach factor
20. Discharge coefficient
21. (Ceβ)^2 , iterated
22. Permanent pressure loss
23. Orifice diameter at 20 °C
24. Vent/Drain hole (if required)
25. Corrected orifice diameter (if V/D hole present)
26. Radius of location of vent/ drain hole
27. Yield stress (for thickness calculation)

23. What we offer our clients…
Maximum operating temperature up to 800 °C
Maximum operating pressure up to 400 bar
Materials (Stainless steel , Hastelloy C276 , Monel 400,Duplex
and Super Duplex, Others on request)
Accuracy ≤ ±0.5 % of actual flow rate
Repeatability of measurement of 0.1 %
Cost Efficient (cheapest as compare to other flow elements)

24. Advantages of Orifice plate
High-quality
 High accuracy
A wide range
Very reliable
Low cost
low pressure drop across the meter
All mechanical units can be installed in remote
locations

25. Limitations
Bulky, especially in the larger sizes.
The fluid must be clean for measurement
accuracy
A sudden change in the flow rate can damage
the meter
Only for limited ranges of pressure and
temperature
Require a good maintenance schedule and are
high repair and maintenance meters
Need to be replaced after specific time

26. Targeted Customers
Water suppliers
Petrochemical industries
Oil industries
Natural gas industries
LPG suppliers
Refineries
Power industries

27. We did it….
Client : Indian Oil Corporation Ltd ,Bongaigaon
Project : Supply of Orifice plates for liquid flow measurement
Year : march 2015
Client : Indian Oil Corporation Ltd ,Kothari
Project : Supply of Orifice plates for liquid/gas flow measurement
Year : march 2015
Client : Indian petrochemical corporation ltd, Mthura
Project : Supply of Orifice plates for liquid/gas flow measurement
Year : april 2015

28. Our highly reputed clients
And many more…..