Orifice flowmeter is a high-range differential pressure flow device that combines standard orifice with multi-parameter differential pressure transmitter (or differential pressure transmitter, temperature transmitter and pressure transmitter) to measure the flow of gas, steam, liquid and natural gas.Widely used in petroleum, chemical, metallurgy, electric power, heating, water supply and other fields of process control and measurement.Orifice flowmeter is widely used in coal, chemical industry, transportation, construction, textile, food, medicine, agriculture, environmental protection and People's Daily life and so on each domain of national economy, is the development of industrial and agricultural production, save energy and improve the quality of our products and improve the economic benefit and the management level of the important tools in the national economy occupies an important position.In process automation instruments and devices, flow meters have two major functions: as a process automation control system of the detection of instrumentation and measurement of the total number of materials table.
In order to improve the accuracy of hd-lgbh orifice flowmeter in natural gas metering, it is an essential and important work to analyze and master the causes of errors in the use of the measuring device itself.
1 hole plate is not installed correctly
The sharp side of the orifice plate shall face the flow direction of the fluid as the inlet end and the horn mouth shaped side as the outlet end.If you put it backwards, the display will be much smaller.
Solution: check the orifice plate installation direction and install orifice plate correctly.
2 Wear edge of orifice plate inlet
If the orifice plate is used for a long time, especially when the medium under test is mixed with solid particles and other sundries, the geometric shape and size of the orifice plate will change. If the orifice plate becomes larger or the orifice edge becomes blunt, the measurement pressure difference will be smaller and the flow rate display will be low.
Solution: reprocess the orifice plate to make the opening meet the requirements;Replace if serious.
3 Transmitter zero drift
If it is used for a long time, the zero point of the transmitter may drift. If it is negative drift, the difference pressure displayed will decrease and the flow displayed will also decrease.
Solution: the zero point of the transmitter is corrected.
4 The length of upstream and downstream straight pipe segment is insufficient
If the length of the upstream and downstream straight pipe segment is not enough, the gas will not be fully developed, which will cause a large error in the measurement results. If there are multiple elbows in the upstream straight pipe segment, the measurement results will be low.
Solution: transform steam pipe to make the length of upper and lower straight pipe reach the specified requirements.Install a rectifier before throttling device.
5 The three-valve group of the differential pressure transmitter leaks air
If the high pressure valve or the balance valve in the three-valve group leaks, it will lead to small difference pressure reduction in the measurement, and the measurement result will be low.
Solution: if the high pressure valve in the three-valve group leaks, tighten the valve and replace it if necessary.If the balance valve in the three-valve set leaks, tighten the valve and replace if necessary.
6. The isolation liquid level varies
The liquid level in the primer pipe from the condenser to the differential pressure transmitter is to separate the high temperature medium from the differential pressure transmitter and protect the differential pressure transmitter.If the liquid level on the low pressure side is lower than that on the high pressure side, the measurement differential pressure will be reduced, and the measurement flow will be reduced.
Solution: check whether the height of the high and low side condensing tanks is consistent. If not, correct it.Check that the condensing tank is higher than the steam pipe, and if it is lower than the pipe, raise the condensing tank.
The accuracy of the whole orifice flowmeter also depends on the accuracy of the differential pressure transmitter and the flow indicator.However, when the accuracy of other parameters is not high, the use of high-precision differential pressure transmitter can not play a great role.The function of measuring display instrument is mainly to monitor the stability of operating parameters and so on.Therefore, to improve the accuracy of measurement should be a comprehensive estimate, so as to make the choice of the best technical and economic scheme.