It shall also meet the requirements of 5. The bevelled surface shall be well finished. It is considered so if the edge radius is not greater than 0, 4d. If d W 25 mm, this requirement can generally be considered as satisfied by visual inspection, by checking that the edge does not reflect a beam of light when viewed with the naked eye. If there is any doubt as to whether this requirement is met, the edge radius shall be measured.
The orifice bore is the region of the orifice plate between edges G and H. This being the case, small defects for example, a single nick are acceptable. Care shall be taken that the edge and bore are not damaged when making these measurements. This requirement is deemed to be satisfied when the difference in the length of any of the measured diameters complies with the said requirement in respect of the mean of the measured diameters. In all cases, the roughness of the orifice bore cylindrical section shall not be such that it affects the edge sharpness measurement.
H The location of the pressure tappings characterizes the type of standard orifice meter. Flu Both l1 and l2 spacings are measured from the upstream face of the orifice plate. The spacing l'2 of the downstream pressure tapping is nominally 25,4 mm and is measured from the downstream face of the orifice plate.
The edges shall be flush with the internal surface of the pipe wall and as sharp as possible. To ensure the elimination of all burrs or wire edges at the inner edge, rounding is permitted but shall be kept as small as possible and, where it can be measured, its radius shall be less than one-tenth of the pressure tapping diameter. No irregularity shall appear inside the connecting hole, on the edges of the hole drilled in the pipe wall or on the pipe wall close to the pressure tapping.
No restriction is placed on the minimum diameter, which is determined in practice by the need to prevent accidental blockage and to give satisfactory dynamic performance. The upstream and downstream tappings uK shall have the same diameter. H axial planes, but are normally located in the same axial plane. Both types of tappings may be located either in the pipe or its flanges or in carrier rings as shown in Figure 4. The minimum diameter is determined in practice by the need to prevent accidental blockage and to give satisfactory dynamic performance.
For any values of E ft. If not, each annular chamber shall connect with the inside of the pipe by at least four openings, the axes of which are at equal angles to one another and the individual opening area of which is at least 12 mm 2.
If there are several individual pressure tappings in the same upstream or downstream plane, their centrelines shall form equal angles with each other.
The diameters of individual pressure tappings are specified in 5. The pressure tappings shall be circular and cylindrical over a length of at least 2,5 times the internal diameter of the tappings measured from the inner wall of the pipeline. La The upstream and downstream pressure tappings shall have the same diameter.
The thickness f of the slot shall be greater than or equal to twice the width a of the annular slot. The area of the cross-section of the annular chamber, gh, shall be greater than or equal to half the total area of the opening connecting this chamber to the inside of the pipe.
The surface finish shall meet the pipe roughness requirements see 5. This also applies to the distance requirement given in 6. For orifice plates with flange tappings: b. The pipe internal roughness shall satisfy the following specification if the uncertainty values in this part of id- ISO are to be met, i.
The discharge coefficient equation see 5. Information regarding pipe roughness may be found in 7. The work on Flu which Tables 1 and 2 are based is described in the references [2] to [4] in the Bibliography. The roughness requirements relate to the orifice fitting and the upstream pipework. The downstream roughness is not as critical.
Where D is less than mm, it is necessary to calculate the maximum and minimum values of Ra using Tables 1 and 2. H specified in 5. In particular, it is not permitted to enter into the equation pairs of values of L1 and L'2 which do not match one of the three standardized tapping arrangements. Equation 4 , as well as the uncertainties given in 5. These values are not intended for precise interpolation. Extrapolation is not permitted.
Test results for the determination of H are only known for air, steam and natural gas. However, there is no known objection to using Equation 5 for other gases and vapours of which the isentropic exponent is known. Values of the expansibility [expansion] factor as a function of the isentropic exponent, the pressure ratio and the diameter ratio are given for convenience in Table A.
Figure 5 shows the pressure profile through an orifice metering system. The general requirements for flow conditions at the primary device are given in 7. The requirements for use of a flow conditioner are given in 7. For some commonly used fittings, as specified in Table 3, the minimum straight lengths of pipe indicated may be used and detailed requirements are given in 6. However, a flow conditioner as specified in 6. Downstream of a header the use of a flow conditioner is strongly recommended.
Many of the lengths given in 6. Additional work which contributed to the lengths in 6. For research and calibration work in particular, it is recommended that the upstream values b. H specified in Table 3 be increased by at least a factor of 2 to minimize the measurement uncertainty. Flu 6. It is recommended that control of the flowrate be achieved by valves located downstream of the orifice plate.
Isolating valves located upstream of the orifice plate shall be set fully open, and these valves shall be full bore. The valve should be fitted with stops for alignment of the ball in the open position. The valve shown in Table 3 is one which is of the same nominal diameter as the upstream pipe, but whose bore diameter is such that a diameter step is larger than that permitted in 6.
H 0,60 42 13 30 18 42 18 44 18 65 h 25 29 18 30 18 9 5 26 11 14 7 30 15 5 3 7 3,5 0,67 44 20 44 18 44 20 44 20 60 18 36 18 44 18 12 6 28 14 18 9 30 15 5 3 7 3,5 0,75 44 20 44 18 44 22 44 20 75 18 44 18 44 18 13 8 36 18 24 12 30 15 5 3 8 4 NOTE 1 The minimum straight lengths required are the lengths between various fittings located upstream or downstream of the orifice plate and the orifice plate itself.
Straight lengths shall be measured from the uK downstream end of the curved portion of the nearest or only bend or of the tee or the downstream end of the curved or conical portion of the reducer or the expander. NOTE 2 Most of the bends on which the lengths in this table are based had a radius of curvature equal to 1,5D. Such an installation is not, however, recommended. Since in practice such conditions are difficult to achieve, the following information may be used as a guide for normal installation practice.
If either of the minimum straight lengths is selected from Column B i. The required length between the valve and the 2nd fitting according to 2 should be added to the length between the orifice plate and the 1st fitting specified in Table 3; see Figure 6.
It should be noted that b. The distance between the orifice plate and the fitting shall be measured along the pipe axis. Key 1 expander uK b. In each case, the La second fitting from the orifice plate is two bends in perpendicular planes the separation between the bends is 10 times the diameter of the bends and the orifice plate has diameter ratio 0,4.
If the valve has length 1D an additional total length of 9D is required which may be either upstream or downstream of the valve or partly upstream and partly downstream of it. Internet Download Manager. VLC Media Player. MacX YouTube Downloader. Microsoft Office YTD Video Downloader. Adobe Photoshop CC. VirtualDJ Avast Free Security.
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Spotify removes shuffle button after Adele's request. Cowboy Bebop review. Crypto group loses Constitution auction. The results are shown instantly after clicking a button, and you can go back to make any modifications and recalculate data. ISO lets you print information, save it to file, as well as to set the measurement unit to customary or metric. There are no other noteworthy options available here. We have not come across any issues throughout our evaluation, since the app did not hang, crash or pop up error messages.
It has a good response time to commands and works well on later operating systems, although it has not been updated for a while.
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