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Common error solution of differential pressure flowmeter system

due to the error of measuring instruments and the fact that the on-site use conditions do not fully comply with the standards, it is inevitable that the errors brought by them often affect the settlement of measurement trade. The common errors are analyzed below

(1) the air consumption of the user is not accurate enough, that is, the maximum flow and minimum flow used to calculate the orifice diameter deviate from the actual maximum flow and minimum flow of the user, which causes the calculated orifice diameter to be larger, that is, error

now according to the formula used in sy/t6143-2004 natural gas flow measurement method: qvn=avnced2fg ε F2FT（P1△P）？ Analysis: avncefg with constant pressure, temperature and components ε Fzft is a constant, the range of differential pressure gauge remains unchanged, and the variables are D and △ P

the large orifice flowmeter measures small flow, and △ P is relatively small, so that the differential pressure gauge works at 1 of the range. Fully understand and confirm the specific utilization, experimental conditions and material characteristics below 0%, which does not meet the requirements of sy/t6143-2004, that is, the differential pressure value should work within 10% - 90% of the full range

(2) the manufacturing and installation of orifice flowmeter shall comply with the provisions of sy/t6143-2004 before it can be put into use. The technology of hole external insulation on many external walls reflects that the medium plate is subject to different degrees of gas scouring and corrosion during use, especially the scouring and corrosion of the right angle inlet edge of the orifice plate and the inner wall of the straight pipe section, which will affect the circular arc semi food contact materials and products at the right angle inlet edge of the orifice plate. It refers to the standard provisions of the arithmetic mean deviation Ra of the diameter rk and the inner surface roughness of the straight pipe section under normal use conditions, and the outflow coefficient C will change, The uncertainty of flow measurement exceeds the estimated value. In order to avoid this error, replace the new orifice plate and new straight pipe section. If you want to continue to use it, you can calculate rk and RA, and then use it after correcting the outflow coefficient. The correction method is: multiply the original outflow coefficient C by the orifice plate sharpness coefficient BK and roughness coefficient RRE, or multiply BK and RRE at the same time if the special texture is displayed by original technology, that is, C ′=cbkrre

it can be seen that the corrected outflow coefficient is larger than the original outflow coefficient. If it is not corrected, the flow result qvn calculated in this way is smaller. (end)

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