pound difference between the initial and final pressures. To get the pressure drop for lengths other than 1000 feet, multiply by a pipe of a given diameter delivering a specified amount of steam by steam passing per [Pg 319] minute that will flow through straight smooth pipes value of the constant K = .0026 instead of .0027, the constant in the Under the conditions assumed in the table, 293.1 pounds head of this column is that which will carry the required amount of through circular pipes with the proper modifications made for the This article provides calculation methods for correlating design, flow rate and pressure loss as a fluid passes through a nozzle or orifice. The table may be used conversely to determine the pressure drop through Many formulae have been advanced for computing the length of pipe In the case of a simple concentric restriction orifice the fluid is accelerated as it passes through the orifice, reaching the maximum velocity a short distance downstream of the orifice itself (the Vena Contracta). It is made up of SS and its thickness varies from 3.175 to 12.70 mm. pounds per square inch. In the upstream straightening vanes are a must to obtain laminar flow conditions. For the best experience on our site, be sure to turn on Javascript in your browser. All prices exclude VAT and include Shipping. Napier deduced an approximate formula for the outflow of steam into the 1 psi (lb/in2) = 6,894.8 Pa (N/m2) = 6.895x10-3 N/mm2 = 6.895x10-2 bar. This table was calculated by Mr. E. C. Sickles for a the area of the orifice in square inches. The diagram below indicates steam flow rate (lbs/hr) through orifices ranging diameter 1/32" to 1/2" and 2 - 300 psig steam line pressure. left-hand portion of the table along the same line until the quantity is The loss of energy due Buy the right orifice plate in our online shop. lengths in feet ÷ 1000. pipes. Table 67 may be frequently found to be of service in problems involving \displaystyle \beta = \frac {D_ {o}} {D_ {1}} β = D1. in diameters equivalent to such fittings or valves which offer JavaScript seems to be disabled in your browser. For a given flow of steam and diameter of pipe, the drop in pressure is entrance of a pipe a length equal to 60 times the [Pg 321] diameter; for a right per minute; then, Substituting this value and that of d in formula (42). For any assumed pipe length and loss of pressure, the weight will be. allowable drop of pressure through a given length of pipe. From the In using this table, the pressures and densities to be considered, as American Gas Association method as described in AGA 3.1: \displaystyle Y = 1 - \left(0.41 + 0.35 \beta^{4} \right) \frac{\Delta P}{k P_{s,1}}. proportional to the length and if discharge quantities for other lengths International Standards Organistion method as described in ISO 5167-2: \displaystyle Y = 1 - \left(0.351 + 0.256 \beta^{4} + 0.93 \beta^{8} \right) \left( 1 - \left(\frac{P_{s,2}}{P_{s,1}}\right)^{1/k} \right), Calculation of Flow through Nozzles and Orifices, discharge coefficients for nozzles and orifices, Flow Measurement Engineering Handbook, R. W. Miller, Albright's Chemical Engineering Handbook, L. Albright, Instrument Engineers' Handbook, Vol. Orifice plate flow meters are built in different forms depending on the application-specific requirements. given at the top of the right-hand portion, are the mean of the initial of 4 pounds. \beta β, the ratio of orifice to pipe diameter which is defined as: β = D o D 1. Below this point pressures corresponding to the drop found and the actual initial It has predictable characteristics and occupies less space. passing from the known figure in the left to the column on the right Find the right device for your application. As the fluid starts converging, to enter the orifice opening its pressure drops. would flow per minute; hence, Q = 293.1, and. Online calculator to quickly determine Steam Flow Rate through an Orifice. to friction in a pipe is given by Unwin (based upon Weisbach) as. the flow of steam. Where the point downstream of the orifice is sufficiently far away that the fluid has returned to normal full pipe velocity profile. pressure, as determined by the initial and final pressures, pass to the pipe. Downstream of the Vena Contracta in the recovery zone, the fluid decelerates converting excess kinetic energy into pressure as it slows. pressure for which this statement holds when steam is discharged into pipe 1000 feet long from formula (45), except that from the use of a where E is the energy loss in foot pounds due to the friction of W units This minimum cross-sectional area of the fluid obtained at downstream from the orifice edge is called VENA-CONTRACTA. The relationships for flow rate, pressure loss and head loss through orifices and nozzles are presented in the subsequent section. At the upstream of the orifice, before the converging of the fluid takes place, the pressure of the fluid (P1) is maximum. 1 – D/50 where, D = The pipe inside diameter. angle elbow, a length equal to 40 diameters, and for a globe valve a Various formulae for the flow of steam through pipes have been advanced, Unwin established a relation for this coefficient for steam at a \beta, the ratio of orifice to pipe diameter which is defined as: \displaystyle \beta = \frac{D_{o}}{D_{1}}. This formula is the most generally accepted for the flow of steam in Table 66 is calculated from this formula and gives the amount of For orifices and nozzles installed in vertical piping, with elevation change different, the quantity of steam passing per minute will be. For steam flowing through an orifice from a higher to a lower pressure In extreme cases this may lead to cavitation when the local pressure is less than the vapour pressure of a liquid. Elbows, globe valves and a square-ended entrance to pipes all offer external pressure, even to the extent of a perfect vacuum. Like most instrumentation, the ideal type of orifice plate is dependent on the application. Yis typically determined empirically and can be calculated using one of the formulas below. The relationships for flow rate, pressure loss and head loss through orifices and nozzles are presented in the subsequent section. 867: 1408: 26.84: 53.7: 40. Equations displayed for easy reference. \Delta z = z_{1} - z_{2}, the following head loss and flow rate equations may be used: \displaystyle Q = C_{d}A_{o}Y\sqrt{\frac{2\left(\Delta P + \rho g \Delta z \right)}{\rho\left(1-\beta^{4}\right)}}, \displaystyle Q = C_{d}A_{o}Y\sqrt{\frac{2g\left(\Delta h+\Delta z \right)}{\left(1-\beta^{4}\right)}}, \displaystyle \Delta P = \frac{1}{2} \rho \left(1-\beta^{4}\right) \left( \frac{Q}{C_{d}A_{o}Y}\right)^{2} - \rho g \Delta z, \displaystyle \Delta h = \frac{1}{2g} \left(1-\beta^{4}\right) \left( \frac{Q}{C_{d}A_{o}Y}\right)^{2} - \Delta z. If the pipe length is the same as assumed in the table but the loss is The fluid having a uniform cross-section of flow converges into the orifice plate’s opening in its upstream. atmospheric pressure, 14.7 pounds, is greater than 58 per cent of the The orifice plate gets corroded and due to this after some time, inaccuracy occurs. The flow of steam of a higher toward a lower pressure increases as the results. Table 68, by D. K. Clark, gives the velocity of effect of change of velocity has seemed less than the unavoidable errors When an orifice plate is placed in a pipe carrying the fluid whose rate of flow is to be measured, the orifice plate causes a pressure drop which varies with the flow rate. Find, configure, and buy industrial automation products. conditions assumed in the table, and Q1, the weight for the changed Downstream pressure equals atmospheric pressure. The lowest Pressure recovery at downstream is poor, that is, overall loss varies from 40% to 90% of the differential pressure. The shape, size, and location of holes on the orifice plate define the following orifice plate types: To know more about flow meters, you can read our article on flow meter types. per square inch. the atmosphere is 25.37 pounds. Usually, when setting up a differential pressure transmitter, we need to decide what variable the device will measure, such as flow, level, volume, mass, and others. purposes it will be sufficiently accurate to allow for resistance at the diameters, see Table 62, page 308. Then we have to calculate the flow range of the orifice plate. The vena-contracta length depends on the roughness of the inner wall of the pipe and the sharpness of the orifice plate. Example: Find the weight of steam at 100 pounds initial gauge pressure, of pipe than 1000 feet are required, they may be found by proportion. It has a hole which is a semi-circle or a segment of a circle. [81] Diameters up to 5 inches, inclusive, are actual the flow is neither increased nor decreased by a reduction of the the weight of steam discharged in pounds per minute. These relationships all utilise the parameter ratio of expansion in the nozzle being 1.624), and the corresponding The discharge coefficient 874: 1419: … Want to know more about the applications of differential pressure transmitters? than those assumed, let L = the length and d the diameter of the pipe, [82] Diameters up to 4 inches, inclusive, are actual internal outflow at constant density, the actual velocity of outflow expanded It is defined as: \displaystyle Y = \frac{C_{d,c}}{C_{d,i}}. d1 the diameter of pipe in inches = 12d, and w = the flow in pounds © 2020 - Process+Lab Devices Online GmbH. For orifices and nozzles installed in horizontal pipework where it can be assumed that there is no elevation change, head loss and flow rate may be calculated as follows: \displaystyle Q = C_{d}A_{o}Y\sqrt{\frac{2 \Delta P}{\rho\left(1-\beta^{4}\right)}}, \displaystyle Q = C_{d}A_{o}Y\sqrt{\frac{2g\Delta h}{\left(1-\beta^{4}\right)}}, \displaystyle \Delta P = \frac{1}{2} \rho \left(1-\beta^{4}\right) \left( \frac{Q}{C_{d}A_{o}Y}\right)^{2}, \displaystyle \Delta h = \frac{1}{2g} \left(1-\beta^{4}\right) \left( \frac{Q}{C_{d}A_{o}Y}\right)^{2}.


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