Orifice plate k factor calculation

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Orifice plate k factor calculation

This calculator let you calculate the orifice plate diameter based on ISO standard.

This standard refers to the flow measurement with area reduction instruments, for circular pipes with the section completely filled with fluid. How to calculate orifice plate size? The flow measurement using an orifice plate is based on the application of energy conservation to a flow, measuring the difference in pressure between two points P1 and P2at this points the flow has different speeds.

This speed change is caused by a reduction in area.

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The orifice plate installed in the pipeline causes an increase in flow velocity and a corresponding decrease in pressure. The equation that governs the use of these devices will be Bernoulli's equation in case of incompressible flows liquids or the first law of thermodynamics in compressible flows gases. It should be noted however that the energy equation can be written in a very similar way to the Bernoulli equation under certain flow conditions, therefore the equation used in common practice comes from the Bernoulli equation and a factor to correct the compressibility of the fluid.

Orifice plates are still the most widely used type of flowmeter in the world today. If you are interested in other orifice calculation like how to calculate flow through an orifice?

We have prepared a customized document with your own data. Feel free to download it for your own purposes. We don't like spam either, but if we want to keep you informed we need you to provide us a minimal contact information. Thanks for your collaboration. Tagname of the instrument.

This is the identifier of the field device, which is normally given to the location and function of the instrument. Plant, Area and Notes.

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Information Referred to the physical installation of the instrument. Plant and Process Area where the instrument is installed.

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Notes about the instrument. Fluid Name or Composition. Fluid is called a type of continuous medium formed by some substance whose molecules have only a weak force of attraction. A fluid is a set of particles that are held together by weak cohesive forces and the walls of a container; The term encompasses liquids and gases. State of the matter. It could be Liquid, Gas or Steam. Flow qm. Mass of a substance which passes per unit of time. Temperature T. Operating Temperature of the fluid in Celsius units.

The flowing temperature is normally measured downstream from the orifice and must represent the average temperature of the flowing stream in degrees Celsius. Temperature has two effects on volume. A higher temperature means a less dense gas and higher flows, but when this higher flow is corrected to base temperature, the base flow is less. Pressure In P1. Considering the direction of the fluid, we define P1 as the pressure gauge or absolut existing in the pipeline before the restriction orifice.An orifice plate is a device used for measuring flow rate, for reducing pressure or for restricting flow in the latter two cases it is often called a Template:Dfn.

Either a volumetric or mass flow rate may be determined, depending on the calculation associated with the orifice plate. It uses the same principle as a Venturi nozzle, namely Bernoulli's principle which states that there is a relationship between the pressure of the fluid and the velocity of the fluid. When the velocity increases, the pressure decreases and vice versa. An orifice plate is a thin plate with a hole in it, which is usually placed in a pipe.

When a fluid whether liquid or gaseous passes through the orifice, its pressure builds up slightly upstream of the orifice [1] —86 but as the fluid is forced to converge to pass through the hole, the velocity increases and the fluid pressure decreases. A little downstream of the orifice the flow reaches its point of maximum convergence, the vena contracta see drawing to the right where the velocity reaches its maximum and the pressure reaches its minimum.

Beyond that, the flow expands, the velocity falls and the pressure increases. By measuring the difference in fluid pressure across tappings upstream and downstream of the plate, the flow rate can be obtained from Bernoulli's equation using coefficients established from extensive research. Orifice plates are most commonly used to measure flow rates in pipes, when the fluid is single-phase rather than being a mixture of gases and liquids, or of liquids and solids and well-mixed, the flow is continuous rather than pulsating, the fluid occupies the entire pipe precluding silt or trapped gasthe flow profile is even and well-developed and the fluid and flow rate meet certain other conditions.

Under these circumstances and when the orifice plate is constructed and installed according to appropriate standards, the flow rate can easily be determined using published formulae based on substantial research and published in industry, national and international standards. Plates are commonly made with sharp-edged circular orifices and installed concentric with the pipe and with pressure tappings at one of three standard pairs of distances upstream and downstream of the plate; these types are covered by ISO and other major standards.

There are many other possibilities. The edges may be rounded or conical, the plate may have an orifice the same size as the pipe except for a segment at top or bottom which is obstructed, the orifice may be installed eccentric to the pipe, and the pressure tappings may be at other positions.

Variations on these possibilities are covered in various standards and handbooks. Each combination gives rise to different coefficients of discharge which can be predicted so long as various conditions are met, conditions which differ from one type to another.

Once the orifice plate is designed and installed, the flow rate can often be indicated with an acceptably low uncertainty simply by taking the square root of the differential pressure across the orifice's pressure tappings and applying an appropriate constant.

Orifice plates are also used to reduce pressure or restrict flow, in which case they are often called restriction plates.

There are three standard positions for pressure tappings also called tapscommonly named as follows:. The measured differential pressure differs for each combination and so the coefficient of discharge used in flow calculations depends partly on the tapping positions.

The simplest installations use single tappings upstream and downstream, but in some circumstances these may be unreliable; they might be blocked by solids or gas-bubbles, or the flow profile might be uneven so that the pressures at the tappings are higher or lower than the average in those planes. In these situations multiple tappings can be used, arranged circumferentially around the pipe and joined by a piezometer ring, or in the case of corner taps annular slots running completely round the internal circumference of the orifice carrier.

Standards and handbooks are mainly concerned with Template:Dfn plates. In these, the leading edge is sharp and free of burrs and the cylindrical section of the orifice is short, either because the entire plate is thin or because the downstream edge of the plate is bevelled.

Exceptions include the Template:Dfn or Template:Dfn orifice, which has a fully rounded leading edge and no cylindrical section, and the Template:Dfn or Template:Dfn plate which has a bevelled leading edge and a very short cylindrical section.

The orifices are normally concentric with the pipe the Template:Dfn orifice is a specific exception and circular except in the specific case of the Template:Dfn or Template:Dfn orifice, in which the plate obstructs just a segment of the pipe.

Standards and handbooks stipulate that the upstream surface of the plate is particularly flat and smooth. Sometimes a small drain or vent hole is drilled through the plate where it meets the pipe, to allow condensate or gas bubbles to pass along the pipe. Standards and handbooks stipulate a well-developed flow profile; velocities will be lower at the pipe wall than in the centre but not eccentric or jetting. Similarly the flow downstream of the plate must be unobstructed, otherwise the downstream pressure will be affected.

To achieve this, the pipe must be acceptably circular, smooth and straight for stipulated distances. Sometimes when it is impossible to provide enough straight pipe, flow conditioners such as tube bundles or plates with multiple holes are inserted into the pipe to straighten and develop the flow profile, but even these require a further length of straight pipe before the orifice itself.

Some standards and handbooks also provide for flows from or into large spaces rather than pipes, stipulating that the region before or after the plate is free of obstruction and abnormalities in the flow. Flow rates through an orifice plate can be calculated without specifically calibrating the individual flowmeter so long as the construction and installation of the device complies with the stipulations of the relevant standard or handbook. The calculation takes account of the fluid and fluid conditions, the pipe size, the orifice size and the measured differential pressure; it also takes account of the coefficient of discharge of the orifice plate, which depends upon the orifice type and the positions of the pressure tappings.The discharge coefficient is a dimensionless number used to characterise the flow and pressure loss behaviour of nozzles and orifices in fluid systems.

Orifices and nozzles are typically used to deliberately reduce pressure, restrict flow or to measure flow rate. This article gives typical values of the discharge coefficient for common orifice and nozzle designs.

There are two distinct uses for nozzles and orifice plates. The first is to restrict flow where high accuracy is generally not important and the second is flow measurement where calculation accuracy is critical.

Flow measurement

For the purpose of flow restriction an orifice plate is typically used and it is generally acceptable to use typical values of the discharge coefficient as presented in this article for the orifice sizing calculation.

For the purpose of flow measurement either an orifice or nozzle may be used and the accuracy of the discharge coefficient has greater importance. For orifice plate installation the discharge coefficient will vary depending on the location of the pressure tappings. Common arrangements are:. When using these devices the vendor should be consulted for the exact discharge coefficient. The discharge coefficient may be directly related to the resistance coefficient via the follow equation:.

For simple pressure loss or flow rate calculations where high accuracy is not critical the following typical values may be used:. Where a higher degree of accuracy is required, such as for flow rate measurement, the relationships below may be used.

Orifice plate

Email Name. Summary The discharge coefficient is a dimensionless number used to characterise the flow and pressure loss behaviour of nozzles and orifices in fluid systems. Definitions : Discharge Coefficient : Discharge Coefficient at infinite Reynolds number : Full pipe diameter : Constricted diameter mm : Resistance Coefficient : Reynolds Number measured at full pipe diameter and velocity : Area Ratio.

Equipment Type min max Orifice Plate, thin sharp edged - - 0. Article Created: February 11, Discharge Coefficient. Flow Orifice.Flow measurement is the quantification of bulk fluid movement. Flow can be measured in a variety of ways. The common types of flowmeters with industrial applications are listed below:. Flow measurement methods other than positive-displacement flowmeters rely on forces produced by the flowing stream as it overcomes a known constriction, to indirectly calculate flow.

Flow may be measured by measuring the velocity of fluid over a known area. For very large flows, tracer methods may be used to deduce the flow rate from the change in concentration of a dye or radioisotope. Both gas and liquid flow can be measured in volumetric or mass flow ratessuch as liters per second or kilograms per second, respectively.

These measurements are related by the material's density. The density of a liquid is almost independent of conditions. This is not the case for gases, the densities of which depend greatly upon pressure, temperature and to a lesser extent, composition.

Orifice Plate - Find Orifice Size

When gases or liquids are transferred for their energy content, as in the sale of natural gasthe flow rate may also be expressed in terms of energy flow, such as gigajoule per hour or BTU per day. The energy flow rate is the volumetric flow rate multiplied by the energy content per unit volume or mass flow rate multiplied by the energy content per unit mass.

Energy flow rate is usually derived from mass or volumetric flow rate by the use of a flow computer. Gases are compressible and change volume when placed under pressure, are heated or are cooled. A volume of gas under one set of pressure and temperature conditions is not equivalent to the same gas under different conditions.

Gas mass flow rate can be directly measured, independent of pressure and temperature effects, with thermal mass flowmetersCoriolis mass flowmetersor mass flow controllers. For liquids, various units are used depending upon the application and industry, but might include gallons U.

A primary flow element is a device inserted into the flowing fluid that produces a physical property that can be accurately related to flow. For example, an orifice plate produces a pressure drop that is a function of the square of the volume rate of flow through the orifice. A vortex meter primary flow element produces a series of oscillations of pressure. Generally, the physical property generated by the primary flow element is more convenient to measure than the flow itself.

The properties of the primary flow element, and the fidelity of the practical installation to the assumptions made in calibration, are critical factors in the accuracy of the flow measurement. A positive displacement meter may be compared to a bucket and a stopwatch.

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The stopwatch is started when the flow starts and stopped when the bucket reaches its limit. The volume divided by the time gives the flow rate. For continuous measurements, we need a system of continually filling and emptying buckets to divide the flow without letting it out of the pipe.

These continuously forming and collapsing volumetric displacements may take the form of pistons reciprocating in cylinders, gear teeth mating against the internal wall of a meter or through a progressive cavity created by rotating oval gears or a helical screw. The piston meter operates on the principle of a piston rotating within a chamber of known volume. For each rotation, an amount of water passes through the piston chamber.

Through a gear mechanism and, sometimes, a magnetic drive, a needle dial and odometer type display are advanced. An oval gear meter is a positive displacement meter that uses two or more oblong gears configured to rotate at right angles to one another, forming a T shape. Such a meter has two sides, which can be called A and B. No fluid passes through the center of the meter, where the teeth of the two gears always mesh.

On one side of the meter Athe teeth of the gears close off the fluid flow because the elongated gear on side A is protruding into the measurement chamber, while on the other side of the meter Ba cavity holds a fixed volume of fluid in a measurement chamber.Semiconductors, medical equipment, lasers, optics and aviation and aerospace.

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Chemical Engineering The industry gateway for chemical engineering and plant operations. Toggle Menu. Introduction A fluid passing though an orifice constriction will experience a drop in pressure across the orifice. This change can be used to measure the flowrate of the fluid. To calculate the flowrate of a fluid passing through an orifice plate, enter the parameters below. The default calculation involves air passing through a medium-sized orifice in a 4" pipe, with answers rounded to 3 significant figures.

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Formula Home. A fluid passing though an orifice constriction will experience a drop in pressure across the orifice. Pipe inlet diameter upstream of orifice, D i :. Orifice diameter less than the inlet diameterD o :.

Pressure difference across the orifice, D p :.

Fluid density, r :.In this article, we are looking at the flow of water through an orifice and we will define the orifice as an opening with closed perimeter in an element of a flow system. For us this orifice will be a fire sprinkler head or water mist nozzle in a fire protection system, we can use the k-factor formula for almost any rounded orifice.

The formula above is theoretical and once we take into account the effects of friction, turbulence and the contraction of the water stream the formula can be simplified to what we know as the k-factor formula for fire protection system by reducing its complexity to a single constant "k". When we start any hydraulic calculation for a water based fire protection systems such as a fire sprinklers, water mist systems the k-factor formula is the first which we will need to use and as it is so fundamental all fire protection engineers must have a good understanding of how it works.

In its most common form, the formula allows us to calculate the discharge flow from the nozzle fire sprinkler, water mist or a deluge nozzle if we are given the head pressure and k-factor, we can also calculate the k-factor or the pressure required with this formula. The discharge from a sprinkler head or water mist nozzle can be calculated from the formula below:. The units which we use are important and much not be mixed. We can also use K-factors for many other applications in fire hydraulics such as flow from a fire hydrant, wet riser outlet, hose reel or foam monitor.

In fact, the list is almost endless and this is why it is important to be familiar with the above formulas. We only need to use K-factors to one decimal place so For all other types of sprinkler heads the manufactures data sheet should be referred to for the k-factor and minimum head pressure.

As a designer, you must check the k-factor value for the nozzle or head manufacturer and ensure its application is correct. You should also seek guidance from the design standard which is applicable. The graph below shows the relationship between the k-factor, pressure and flow.

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You can clearly see from this that for same pressure with a high k-factor nozzle the flow from the head or nozzle increases. We can sometimes use this to our advantage by selecting the correct sprinkler head k-factor to provide the design density required with the minimum energy requirement water pressure. As an example if we have the pressure of 1. As the k-factor has increased by 50 each time the increase in flow has also increased by the same amount each time. If you like this article then you may also be interested in our online K-factor calculator.

K-Factor formula for fire sprinklers Hydraulic calculation for fire protection engineers. The relationship between the k-factor, pressure and flow. K-Factor formula.And even more If you already have a registered account please log in using the form on top of the page.

Select the annual subscription and enable full service for only 0. On exclusive calculator page you can use the online calculator without interference from advertisements, additional text, links and other content that is not required for the calculations themselves. A pure experience of using a calculator as with a desktop application. An exclusive version of the calculator is available to registered users.

Choose the right subscription duration and start using the exclusive service. Use this calculator to quickly calculate the actual flow rate through the orifice plate flow meter with only a few inputs.

This calculator performs the flow rate calculation from the measured pressure drop caused by the orifice plate inserted in the pipeline. The calculator is suitable for liquids and perfect gases, a subsonic flow of single phase fluid.

It is not applicable for pulsating flow. The pipeline should be circular. The calculator is not applicable for rectangle pipes. This calculator is not suitable for multiphase fluids, like a flow of liquids that contain solid particles or flow of liquids that contain undissolved gases.

Also, it is not suitable for gases that are not ideal, i. To calculate flow rate, you have to enter the orifice plate throat diameter as well as pipe interior diameter, together with fluid properties - density and viscosity. For a gas as flowing fluid, instead of the density, you can enter gas constant, pressure and temperature at actual conditions. Density is then calculated using a perfect gas state equation.

You should enter density on real flow conditions - pressure and temperature. The calculator is doing calculation according to ISO You can expect to have correct and reliable results only if the orifice plate meets the conditions from the standard.

For the flow of a perfect gas, the pressure loss created by the orifice must be higher than 0. If the orifice plate properties or flow conditions are not according to the ISO calculator displays the message.

If you want to do calculation regardless of the limitations in the standard, you can choose not to use ISO constraints in the calculation. Read all about available deployments. In any way of utilizing calculator, Internet connection is required, for authentication at least.