Orifice Flange Assemblies
The orifice flange assembly is a special piping fitting that measures the rate of flow of fluids in the pipeline. It is made up of flanges, an orifice plate, and pressure tapping points to measure the flow accurately using the principle of differential pressure.
The most important part, the orifice plate, consists of a precision-machined hole through which the fluid passes. The fluid flowing through this restriction leads to a reduction in pressure, which is measured between the flanges. The actual flow rate is subsequently determined by this pressure difference, and the orifice flange assembly is therefore a dependable and frequently employed instrument in process control and instrumentation systems.
Orifice flange assemblies are often utilized in oil and gas, chemical processing, water treatment, and power generation applications due to their low cost, low maintenance, and simple design.
Orifice Flange Assembly Working
An orifice flange assembly is based on the principle of differential pressure to determine the rate of flow of a fluid in a pipeline. The assembly consists of two flanges with an orifice plate clamped between them. The flow is restricted by a hole drilled into this orifice plate.
Working Process in Steps:
Flow Restriction
When the fluid moves along the pipe and reaches the orifice plate, a constriction occurs as a result of forcing the fluid to flow through the small hole at the center.
Pressure Drop
In the orifice, the velocity of the fluid is accelerated and the pressure reduced. This pressure drop is between two tapping points on the upstream and downstream sides of the flange.
Differential Pressure Measurement
These pressure taps are then connected to a differential pressure transmitter or manometer, which measures the difference between pressure upstream and downstream of the orifice.
Flow Calculation
The flow rate is then determined using established flow equations like the Bernoulli equation by using the measured pressure difference and the known physical properties of the fluid (density, viscosity, etc.).
The orifice flange assembly offers an easy but precise way of checking the flow of fluids in pipelines and is particularly applicable in industrial process control.
Orifice Plate Types
Orifice plates play a significant role in the system of differential pressure flow measurement. Various designs are employed based on the nature of the fluid, flow regime, and the intended application.
Concentric Orifice Plate
Design: It has a middle hole that is circular.
Application: Suitable in clean liquids, gases, and steam.
Benefit: It gives high accuracy when applied with fully developed flow and clean fluids.
Eccentric Orifice Plate
Design: The hole is not centered but more towards the bottom of the plate.
Application: Can be used in fluid containing suspended solids, or slurries, or gases containing condensate.
Segmental Orifice Plate
Design: It has a bottom segment-shaped opening on the plate.
Application: It is best suited to measure flows that contain large quantities of suspended solids or fibrous matter.
Benefit: Lowers blockage and pressure drop through the plate.
Quadrant Edge Orifice Plate
Design: It has a rounded inlet edge (quarter-circle profile).
Application: It is normally applied to low Reynolds number flows (viscous or low-velocity fluids).
Benefit: It is more accurate in the laminar or transitional flow conditions.
Multi-Hole Orifice Plate
Design: It contains a number of tiny holes rather than one large one.
Application: Applied where the recovery of pressure or noise is a consideration.
Benefit: It offers a more constant pressure drop and minimizes vibration or cavitation.
The various types of orifice plates are chosen depending on the type of fluid, the profile of the flow, and the application requirements to provide precise and convincing measurement of the flow.
Benefits of Orifice Flange Assembly
Economical Flow Monitoring
Some of the least expensive differential pressure flow meters, particularly on large pipe sizes and large flow rates.
Easy to Install and Easy to Design
It is simple in design, having few components, and easy to install, operate, and maintain.
Various Applications
Applicable to liquids, gases, and steam in the oil & gas, water treatment, and chemical processing industries.
Correct Installation and High Accuracy
Delivers repeatable and dependable flow measurements when properly installed with proper straight lengths of the pipes and oriented.
No Movable Parts
Cuts down on mechanical wear and tear, and reduces the level of maintenance required and extends operational life.
Standardized Construction
Is based on internationally agreed standards (such as ISO, AGA, and API), part compatibility, and interchangeability.
High Pressure and Temperature Compatible
It can be applied under harsh operating conditions when the right material is chosen, which provides durability.
Is Easy to Combine with Instrumentation
Provided with pressure taps to be connected to differential pressure transmitters or flow indicators.
The orifice flange assembly is a trusted solution for flow measurement, known for its accuracy, durability, and cost-efficiency, especially in demanding industrial environments.
Disposal Steps Recommended
Decontamination
Clean the flange, orifice plate, and related components carefully to eliminate any chemical deposits or accumulated fluids, particularly when the system has contained hazardous or toxic materials, prior to disposal.
Material Segregation:
Segregate the components according to type of material:
Any metal components (such as stainless steel or carbon steel flanges) may be taken to a scrap metal recycling center.
Gaskets or seals (typically PTFE, rubber, or graphite) are usually disposed of as non-metal industrial waste.
Hazardous Classification
In case the assembly was utilized in direct contact with dangerous media (e.g., acids, hydrocarbons, or poisonous gases), treat it as hazardous industrial waste and dispose of it in line with local environmental regulations.
Reuse or Refurbishment
In case the orifice flange remains mechanically good, it may be refurbished or reused in non-critical applications. This saves money and is economical.
Documentation and Handover
Keep adequate disposal records, and where necessary, give the equipment to the relevant waste management or recycling authorities to safely process.
Adequate disposal of an orifice flange assembly guarantees environmental protection, safety in the workplace, and compliance with the regulations.
FAQs
Orifice Flange Assembly is a flow meter found in the pipeline. It is made up of two flanges, orifice plate between the two flanges and pressure taps to measure the pressure drop across the orifice to calculate flow rate.
The orifice plate is a restriction in the flow path and therefore a pressure drop occurs. This decrease is utilized in the determination of the flow rate based on the principles of differential pressure.
It is widely applied in such industries as oil and gas, chemical processing, power plants, and water treatment, where precise and continuous flow measurement is needed.
The flow rate is calculated by the difference of pressure across the orifice plate (using taps in the flanges) according to Bernoulli equation or ISO/API flow equations.
The major constituents are:
- Orifice plate
- Two flanges (weld neck or slip-on normally) Pressure tapping holes
- Plate removal jack screws Gaskets and sealing bolts
The orifice flange assembly must be mounted in a horizontal line with the pressure taps in the correct position—above the centerline on gases, below on liquids, and at the sides on steam.
When the orifice plate is installed, the beveled edge is to be downstream (in the flow direction). The right orientation is normally marked with an arrow or mark.
Yes, there must be a minimum straight length of pipe upstream and downstream so that the flow can be measured accurately. The lengths are based on the flow type and upstream fittings, e.g., valves or elbows.
Indeed, the flanges should be put in between the orifice plate and the proper gaskets to avoid leakage and have the correct pressure differential measurement.
Horizontal installation is preferred, but in some cases, vertical installation can be done. Nonetheless, the manufacturer guidelines should be adhered to, and the position of the pressure taps should be changed.
Notable considerations are the type of fluid (liquid, gas, or steam), flow rate, the size of the pipe, pressure and temperature conditions, and the accuracy of desired flow measurement to be achieved.
A concentric orifice plate is applicable in clean fluids. In viscous, slurry, or dirty fluids, a plate with an eccentric or segmental shape is suggested to avoid clogging and to obtain precise measurements.
The Reynolds number decides whether the flow is laminar or turbulent. It aids in the choice of the correct orifice bore size and edge profile, appropriate differential pressure generation, and precision.
Yes, the orifice bore is determined using the inside diameter of the pipe. The size of the orifice should permit adequate pressure drop to be measured but not so much restriction of flow.
Orifice plates need straight pipe lengths upstream and downstream of the location of installation to guarantee a fully developed flow profile, which is vital to the accurate measurement of the differential pressure.
Yes, the majority of orifice plates are manufactured using stainless steel, carbon steel, or any other metal, which can be recycled at certified metal recycling centers after cleaning and decontaminating them.
In case the orifice plate was in contact with any dangerous or corrosive fluids, it should be decontaminated according to the safety regulations and afterwards disposed of in accordance with the local environmental and hazardous waste acts.
No international standard exists, but one suggestion is to adhere to the waste management regulations of the plant or industry, and this commonly includes simply scrapping the plate once it is cut or defaced to avoid the possibility of reuse.
Yes, used orifice plates must be stored in a separate place until they are cleaned and confirmed safe to dispose of or recycle, especially where they have traces of harmful materials.
The maintenance or plant engineering department is usually charged with the responsibility to make sure that disposal is safe and legal. In regulated industries, outsourcing is common to certified waste disposal contractors.
