vivasat ventures flow division

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vivasat FLOW DIV.ventures

ORIFICE FLOWMETER :

Vivasat Ventures orifice plate is a device used for measuring flow rate. Either avolumetric or mass flow rate may be determined, depending on the calculationassociated with it. It uses the same principle , namely Bernoulli's principle whichstates that there is a relationship between the pressure of the fluid and thevelocity of the fluid. When the velocity increases, the pressure decreases and viceversa.

Vivasat Ventures orifice plate is a thin plate with a hole in the middle or edgedepending on design as per application . It is usually placed in a pipe in which fluidflows. When the fluid reaches the orifice plate, the fluid is forced to converge togo through the small hole; the point of maximum convergence actually occursshortly downstream of the physical orifice, at the so-called vena contracta point .As it does so, the velocity and the pressure changes. Beyond the vena contracta,the fluid expands and the velocity and pressure change once again. By measuringthe difference in fluid pressure between the normal pipe section and at the venacontracta, the volumetric and mass flow rates can be obtained from Bernoulli'sequation.

Bernoulli's theorem and where it is applicable?Bernoulli's theorem states the "total energy of a liquid flowing from one point toanother remains constant." It is applicable for non compressible liquids.

Incompressible flow measurement through Vivasat Ventures’s orifice :

By assuming steady-state, incompressible (constant fluid density), inviscid,laminar flow in a horizontal pipe (no change in elevation) with negligible frictionallosses, Bernoulli's equation reduces to an equation relating the conservation ofenergy between two points on the same streamline:

or:

Vivasat Ventures manufactures orifice plate assemblies for various applications.Applications which go for conditions summarised as below , is applied with the

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most precise measurement of the application with manufacturing of the devicewith 3 axis vertical machining centre ensuring the precision . The process ofmanufacture is completed with X, Y and Z axis serving the completion of themachining of the plate at the same time, leading to most linear hysteresis, andthus leading to most accurate flow measurements. Orifice plate of VivasatVentures caters to all high and differential node of pressure and temperature andoffers an accurate reading of the desired within its limits of performance andapplication.

The different types of orifice plates are:* Concentric* Segmental* Eccentric* Quadrant Edge

Type of orificeplate

Reynolds No. Application

Square edgeconcentric

7500 onwards For all applications with clean of foreignparticles

Conical entrance 80 to 1500 High viscocity measuring capacityleading to ruling off application whichrequires accuracy at lowest reynolds ,thus effectively rid off applications ofmagnetic and vortex

Eccentric 3000 to 12000 For liquids containing solid particles thatare likely to sediment or for vaporslikely to deposit water condensate ,also used for bottom flush application

Quadrant edge 1500-9000 Viscous fluids and all and most forFertiliser and petrochemicals

Segmental 5000-20000 Sedimentation process application

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Concentric:The Concentric Orifice Plate is used for ideal liquid as well as gases and steamservice. This orifice plate beta ratio fall between of 0.15 to 0.75 for liquids and0.20 to 0.70 for gases and steam. Best results occur between value of 0.4 and 0.6.Beta ratio means ratio of the orifice bore to the internal pipe diameters. (45degrees beveled edges are often used to minimize friction resistance to flowingfluid.)

Eccentric:The Eccentric orifice plate has a hole eccentric. Use full of measuring liquidscontaining solids , oil containing water and wet steam. Eccentric plates can beused either flange or vena contracta taps, but the taps must be at 180 degrees or90 degrees to the eccentric opening.

Eccentric orifices have the bore offset from the center to minimize problems inservices of solids-containing materials.

Segmental:The Segmental Orifice Plates has the hole in the form of a segment of circle. Thisis used for colloidal or slurry flow measurement. For best accuracy, the taplocation should 180 degrees from the center of the tangency.

Segment orifices provide another version of plates useful for solids-containingmaterials.

Quadrant Edge:It is commonly used in Europe and are particularly useful for pipe sizes less thantwo (2) inches.

Quadrant edges orifices produce a relatively constant coefficient of discharge forservices with low Reynolds numbers in the range of 100,000 down to 5,000.

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Vivasat Ventures’s Orifice Performance :

Principally, Vivasat Ventures’s orifice plate is a precision instrument. In bestcircumstances, the inaccuracy of Orifice plates can possibly fall in the range of0.75-1.5%. However, there are numerous error causing conditions which canaffect the accuracy of Vivasat Ventures’s Orifice plate. Following factors are usedto judge the performance of Vivasat Ventures’s Orifice plate:

1. Precision in the bore calculations2. Quality of the installation3. Condition of the plate itself4. Orifice area ratio5. Physical properties of the fluid flow under measurement , refer the free length

table mentioned below

Further class of installation depends upon following factors

Tap location and circumstance. Generally, there are three ways to position apressure tap.

Provision of the process pipe Competence of straight pipe runs Gasket intervention Misalignment of pipe and orifice bores Lead line design

Extra detrimental conditions consist of

Dulling of the sharp edge or nicks caused due to corrosion or erosion Warpage of the plate because of waterhammer and dirt Grease or secondary phase deposits on any of the orifice surface

Any of the above said conditions has the tendency to affect the dischargecoefficient of an orifice plate to a large extent.

Permanent pressure drop for incompressible fluids :

Permanent pressure loss is a term every system engineer, designer, or technicianshould be aware of. Whenever a piece of equipment or pipe is added to a flowsystem, pressure is lost. This pressure loss makes the pump or compressor workharder to generate the same flows in the system. If too much pressure loss exists,the system will simply stop flowing. This may be of concern if you are working

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with both low and high pressure systems. Every bit of pressure loss is equal toextra energy used (electricity, steam, or natural gas) to pump or compress thefluid, i.e. more money to operate.

In the case of flowmeters, a loss is incurred because a piece of straight pipe wouldnot have as much loss as the flowmeter. The loss is also permanent. Permanentpressure loss should not be confused with pressure drop. Meters such asdifferential pressure-types have a pressure drop inside the meter section. Thepressure measured upstream of the meter will be greater than the pressure justdownstream of the meter. As you move further downstream of the meter, thepressure recovers to a level not quite as high as the upstream pressure. Thedifference between the upstream pressure and the downstream recoveredpressure equals the permanent pressure loss.Fluid velocity also plays an important role in permanent pressure loss. The fasterthe fluid is moving, the greater the pressure loss. Therefore, a permanentpressure loss value must always be associated with a certain flow rate. Metermanufacturers often state the permanent pressure loss at the maximum statedvelocity of the meter.

There are many different meter types and all have different characteristics ofpermanent pressure loss. Some meters have no restriction in the pipe, sotherefore no permanent pressure loss. In other words, they incur the same loss asa straight piece of pipe. For example, magnetic meters and ultrasonic metersgenerally have no permanent pressure loss as they have no restriction interfacingthe fluid.

Other meters have a very high loss. These meters have physical restrictions due tothe nature of the meter. Examples of high loss meters include curved-tube typecoriolis flowmeters and positive displacement meters.

Permanent pressure loss is just one of the characteristics to consider whenevaluating a flowmeter. A meter with a low loss is not necessarily better than ameter with a high loss. Every characteristic of the meter technology must beweighed according to the needs of the application.

Uncertainty in measuring flow elements :

Uncertainty factor is indicated to give an idea of how the orifice plate behaves onchanges of the flow due to turbulances . the uncertainty is defined as an intervalabout the result of a measurement that may be expected to encompass

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approximately 95 % of the distribution of values that could reasonably beattributed to the measurand. The free length table as indicated above the orificeassembly will behave based on turbulances created and thus the uncertainty willdiffer , alongwith the choice of the beta value of the plate .

Various types of orifice assemblies :

The weld neck flange assembly is designed to transfer stresses to the pipe ,thereby reducing high stress concentrations at the base of the flange . Thepressure tappings are provided through the flange which are at a distance ofapproximately 20mm to 26 mm from the face of the plate .

The slip on flange has a low hub because the pipe slips into the flange prior tothe welding . It is welded both from inside and out to provide sufficient strengthand prevent leakage . The slip on flanges are bored slightly larger than the OD ofthe matching flange

Orifice assembly with carrier ring and flange union is provided to facilitatepressure tapping , by means of corner tappings . This construction is generallyused for lower sizes . refer the table below , a detail comparison with RTJassemblies and it usage . Carrier ring by principle is applicable for ratings upto300# and till 600# only under few conditions .The principle says atmost Carrierring assembly is used upto 2” or may be still higher but only till 300# and if it isused for 600# the size should be reduced and be restricted till 2”

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The reason is due the principle of operation of carrying the vena Contracta in theassembly without affecting the accuracy of the assembly . This means more flow, i.e more size , the carrier allows the vena contracta move further awayattracting bigger free lengths for accuracy and lesser scramped means forcingfor leakage if pressure is more . Here more flow attracts more pressure and thusIt is better to restrict carrier ring within 2” and upto 300-600#

RTJ assembly for high temperature and pressure: The plate holder assembly is acombination of plate holder and an orifice plate designed for ring tongue jointflanges . The plate holder has a function of holding the orifice plate and also thefunction as a gasket to prevent leakage of the process fluid . The plate holder hasa oval or octagonal ring for mounting between ring tongue joint flanges . Thismetallic sealing system is applicable to a fluid of high temperature and highpressure . The pressure tapping system normally is of the flange tap type. Orificeplate is screwed to the plate holder . Generally the plate holder is of the softer

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material . The orifice plate is available in standard material such as SS316, 304,304L, SS316L, PP, Hastealloy , Monel , PTFE , etc depending on applications .

Vivasat Ventures’s Restriction orifice plate and its assemblies :

Restriction plate developed by Vivasat Ventures , wherein the operating principleis to develop pressure gradient across the restriction orifice plate while thephenomenon is to keep a no loss flow . This is equally achieved by Restrictionorifice by us wherein the design is effective for restriction of pressure . In thisplate , the bevel is not encrafted and the plate with relevant thickness is used forrestriction parameters of pressure .

Multistage assemblies with Restriction plates are used .

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Vivasat Ventures manufactured multistage orifice assemblies are another typeof measuring flow with high differential pressure meters effectively removingcavitation and flashing conditions . It also helps in killing pressure and thuseffectively acting as a pressure reducing element . These are basically used todetect flow of fluids, gasses , steam , steam water , acids , alkalies , crudes , highviscous fluids , fluids with solid particles , condensation liquids . Vivasat Venturesmake of multistage assemblies lead to a precise measure of differential pressureleading to the most precise flow rate taking care of all factors of fluid cavitationrelated to its vapour pressure . The design is applicable from ½” to 64” of flowmeasurement . For higher sizes of impact and pressure reducing kindly docontact the design and engineering team of Vivasat Ventures . It is measured atright angles to the flow direction, In a averajing Vivasat Ventures makeMultistage assemblies the kinetic energy of the flowing fluid is transformed intopotential energy for measurement of fluid flow velocity by effectively abruptingto 40% recovery in between two stages and thus , effectively removing thechoking content of the fluid in gas and steam and removing cavitation inespecially liquid state thus essentially reducing industrial noise and restricting tobelow 80 decibels .

Applications :

• Gas and Liquid Flows• High Pressure Drops

Prevents :• Cavitation and Flashing in Liquid flows• Choked flow in gases.• Excessive Noise / Vibration

Restriction orifice plates have traditionally been used to reduce pressures in GASAND LIQUID FLOWS by forcing the flow through a restricted bore. The precisepressure drop is produced by accurately calculating the orifice bore, having takeninto account all the relevant process and flow conditions.

Where very HIGH PRESSURE DROPS in liquid flows are required MULTISTAGERESTRICTION ORIFICE ASSEMBLIES may be required to achieve the desiredpressure drop whilst preventing problems such as CAVITATION, FLASHING andhigh NOISE and VIBRATION levels.

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CAVITATION is a potentially damaging, erosive condition which occurs when theinternal pressure of the liquid passing through the orifice falls below its vapourpressure and vapour bubbles form. Further downstream from the orifice thepressure recovers sufficiently to collapse the bubbles with extreme violence.Cavitation calculations are performed during the design stage of a Multistage ROto calculate cavitation factors at each stage in the orifice assembly.

FLASHING is a similar phenomenon to cavitation except that the process pressurenever recovers sufficiently to collapse the gas bubbles resulting in two phase flow- liquid and gas - downstream of the orifice. Erosion of pipe work and valves andother instrumentation can occur due to the impact of liquid droplets carried athigh speed in the vapour flow.

CHOKED FLOW IN GASES – also know as critical flow – occurs when too large apressure drop is attempted across a single orifice plate, or when too large flowsare forced thru a lesser inlet pipe size . In such cases the flow through the orificewill become sonic, at which point no further increase in flow can be achieved byeither increasing the upstream pressure or lowering the downstream pressure.Vivasat Ventures make multistage RO will enable staged reductions in pressureto prevent choked flow occurring.

Vivasat Ventures make Multistage ROs are manufactured from a wide range ofmaterials and are engineered to meet specific project process conditions andrequirements. Plates are usually welded into pipe with a separation of one pipediameter, the number of plates and orifice bores are determined by calculation.Process connections to existing pipe work can be either standard process flangesor machined ends suitable for butt welding.

vivasat ventures flow division

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