Orifice Plate Report - de Villa [PDF]

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ORIFICE PLATE



PREPARED BY LEOBERT G. DE VILLA



What is an Orifice Plate ? An Orifice Plate is an instrumentation device which is used for measuring the gas or liquid flow rate, reducing the pressure of flowing fluid or gas, and restricting the flow rate. Sometimes an orifice plate is also known as a restriction plate as it restricts the flow rate of liquid or gas.



Construction Orifice plates are placed at the joints in the pipes. These are thin metallic plates which have a hole in between them. The working of orifice plates is based on the “Bernoulli’s Principle” which provides a direct relationship between the fluid (liquid or gas) pressure and its velocity.



PRINCIPLE When a liquid / gas, whose flow-rate is to be determined, is passed through an Orifice Meter, there is a drop in the pressure between the Inlet section and Outlet Section of Orifice Meter. This drop in pressure can be measured using a differential pressure measuring instrument.



Since this differential pressure is in direct proportion to the flow-rate as per the Bernoulli's Equation hence the differential pressure instrument can be configured to display flow-rate instead of showing differential pressure.



Advantages and Disadvantages of Orifice Plate



Advantages They have a simple construction & less space required They are inexpensive They are easily fitted between flanges They have no moving parts They have large range of sizes They are suitable for most gases and liquids They are well understood and proven Price does not increase dramatically with size



Disadvantages  Easily gets clogged due to impurities in gas or in unclear liquids  Flow straighteners are required at the inlet and the outlet to attain streamline flow thereby increasing the cost and space for installation.  Accuracy is affected by density, pressure and viscosity fluctuations.  Their installation causes some unrecoverable pressure loss  Requires straight pipe to ensure accuracy is maintained  Pipeline must be full especially for liquid flow measurement



Types of Orifice Plates and their Application SQUARE EDGE (STANDARD) BORE For the common square edge concentric bore orifice, the bore and bevel is the standard method of limiting the plate edge thickness. Unless otherwise specified, plates will be beveled to the current accepted standards. concentric orifice plate is recommended for clean liquids, gases, and steam flows when Reynolds numbers range from 20,000 to 107 in pipes under six inches.



QUADRANT EDGE BORE The quadrant edge bore is an orifice with the inlet edge rounded. Instead of beveling, the plate is counterbored to the desired edge thickness. The radius of the quartercircle bore is a function of the orifice-to-pipe ratio (d/D). Thickness at the throat is equal to the radius. This bore is specifically designed for viscous fluids such as heavy crudes, syrups, and slurries with Reynolds Numbers below 100,000.



ECCENTRIC BORE Eccentrically bored orifice plates are plates with the orifice off-center, or eccentric, as opposed to concentric. The bore of the eccentric orifice normally is inscribed in a circle which is 98% of the pipe diameter, so that solids or slurries may pass through. Eccentric orifice plates are used in many industries including heavy and light chemicals, steel, paper, nuclear and petrochemicals.



SEGMENTAL BORE Segmentally bored orifice plates are provided for measurement where solids are entrained in a gas or liquid flow stream. The circular portion of the bore is inscribed within a circle which is normally 98% of the pipe diameter. The segmental opening may be placed either at the top or bottom of the pipe. Industries using these bores include sewage treatment, steel, chemical, water conditioning, paper and petrochemical.



ORIFICE PLATE.webm



Development Development of the orifice plate with a cone swirler flow conditioner



Conclusion Orifice plates are one of the most popular devices for the measurement and control of fluid flow. In flow control applications, orifice plates are used as restriction devices to regulate fluid flow or reduce the flowing pressure downstream of the orifice plate. But due to pipe fittings along the upstream of the orifice plate, fluid flow become unstable which creates turbulence. The development of the orifice plate with a cone swirler flow conditioner is a great solution however it uses rotational movement which can cause heavy maintenance in the long run. This conclude that by installing straight pipes before the orifice plate will lessen the turbulence instead of applying cone swirler flow conditioner.



Refereces https://www.sciencedirect.com/topics/engineering/orifice-plate https://www.omega.com/en-us/resources/orifice-plate-flow-meter https://en.wikipedia.org/wiki/Orifice_plate http://www.wermac.org/specials/orificeplate.html https://www.instrumentationtoolbox.com/2013/03/basics-of-orifice-flow-meter.html https://www.petropedia.com/definition/8066/orifice-plate http://scharfautomation.com/blog/2015/10/03/orifice-meter/ https://www.engineeringtoolbox.com/orifice-nozzle-venturi-d_590.html https://www.emerald.com/insight/content/doi/10.1108/02602280510577861/full/html?mo bileUi=0 https://www.youtube.com/watch?v=GXDJvva1g9A https://www.youtube.com/watch?v=2xXszFeSY48



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