The orifice meter scale natural gas measurement error and solution

Abstract: measurement of natural gas orifice meter scale error and solution information produced by excellent flow meter, flow meter manufacturer to offer you the quotation. The reasons for error, orifice meter measuring gas upstream and downstream straight pipe length is insufficient, airflow inadequate development, will lead to larger error caused by measurement results. Measurement standard zui short straight pipe length, is hardly satisfied in actual. More flow meter manufacturers choose model price quote you are welcome to inquire, here is the orifice meter scale natural gas measurement error and solutions the article details. The reasons for error, orifice meter measuring gas upstream and downstream straight pipe length is insufficient, airflow inadequate development, will lead to larger error caused by measurement results. Zui short straight pipe length measurement standard regulations and generally difficult to satisfy in the actual, especially because the reason such as gas transmission process, often have bend upstream of metering device. If it is a single bend or planar double bend will make the measurement results on the high side; For multiple elbow, will make the measurement result is low. Second, solutions should be equipped with rectifier before throttling device, avoid the rotational flow, eddy current effect on the measurement. The temperament of natural gas and air flow conditions, causes of error 1 GB/T21446 - 2008 the standard orifice flow meter was used to measure gas flow standard, through the orifice gas is after purification treatment of gas, air flow should be keep in subsonic, stable or only slowly changing over time. Air is evenly single-phase Newtonian fluid. If gas contains no more than 2% of solid or liquid particles, and evenly dispersed, can also be considered uniform single-phase Newtonian fluid. Air flowing through the orifice plate, the beam should be parallel to the pipe axis, the air flow should be fully developed turbulence without vortex, pipe cross section all points on the spiral Angle is less than 2 & deg; That no spiral. By measuring the survey found that the current measurement in oil and gas in about 50% of the measuring point of the air condition has the following two characteristics. （ 1) Gas flow is not stable, and periodically change significantly over time, the pulsating fluid. The reasons of the pulse source [ 2] : (1) reciprocating compressor, engine and vane booster; (2) pressure regulating valve fierce switch or loose valve core and wear; (3) a large amount of water or oil condensate irregular movement in the pipeline. （ 2) Of water content in temperament, and trace particle entrainment of crude oil and impurities, liquids are produced when the airflow through the throttle device. Temperament, air condition can not meet the GB/T21446 - 2008 the standard orifice flow meter was used to measure gas flow standard stipulated in the request, will generate additional error of measurement. In order to obtain accurate measurement values, it is necessary to inhibit pulsation of the airflow and eliminate the temperament of the moisture and impurities. 2, solution into the gas flowmeter must first through the gas-liquid separator, filter. （ 1) The sounding pipe in a favourable position for eliminating pulse, such as loading or away from the entrance of the pressure regulating valve pulse source. （ 2) In order to reduce the pulsation, and can be in line between the pulse source and the measuring tube with a container, or design a special pulsation attenuator. The throttle valve or current limiter in pulse source and the measuring tube is to reduce the fluctuating between zui effective method, but this method pressure drop is too large, unless conditions permit, or unfavorable use. （ 3) Under the precondition of differential pressure remains high operation, smaller measuring tubes are available, and the orifice plate hole diameter basically remain unchanged. （ 4) In front of the flowmeter respectively equipped with a pressure tube, after the exit with a certain volume of gas liquid separator, brought into the meter, static pressure signal to gas-liquid separation and buffer first before you enter the metering device. （ 5) Of upstream and downstream piping valves should choose bore diameter of ball valve. （ 6) In order to prevent of frozen tube wall, must be for insulation pipeline, and increase the heat insulation compensation measures. （ 7) For the air flow caused by fluctuations in the downstream source measurement point pulse, downstream valve valve position can be adjusted through the flowmeter ( Turn down) , reduce measurement point flow pulsation. The experiment proved that using the method of turning down the measuring tube valve downstream to control the air flow pulsation, effect is obvious, this method in practical use, must be carried out to ensure safety in production situation. Proved by the above method can effectively inhibit moisture and impurity in the airflow pulsation, eliminate temperament, reduce the additional error of measurement meter.

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