China Measurement & Control
Your position now:
Orifice flowmeter errors and correction reasons
During the use of the orifice flow meter, the process pipeline needs to be purged multiple times, and the orifice flow meter must be disassembled and assembled frequently. If the size of the orifice plate is the same, an error will occur if you pay little attention to it, and the normal phenomenon will occur when the orifice plate flowmeter is replaced. The upstream and downstream surfaces of the orifice plate flowmeter are reversed. When installing, the medium flow direction in the pipe and the direction of the orifice plate flowmeter must be determined, otherwise the measured value will be lower. It is caused by carelessness. When installing the orifice plate, make sure that the face marked with "+" on the orifice plate flowmeter is on the upstream side of the flow direction. The main function of the impulse pipeline is to transmit the differential pressure signal generated by the orifice plate flowmeter. The laying length of the impulse tube should be a distance between 3 and 20 meters. If the impulse tube is too short, the flowmeter's Flow measurement fluctuations will increase; if it is too long, measurement lag will occur.
In the industrial production process, most of the gas measurement is used with standard orifice orifice flowmeters and differential pressure transmitters. Although the accuracy of the differential pressure transmitter can reach 0.075, but because of various aspects The reason is that the measurement error is also very large. When the differential pressure transmitter is used in industrial measurement, this problem will be more obvious. Therefore, it is of great significance to find the cause of the measurement error and the method to overcome. Orifice flowmeters are mainly composed of impulse tubes, orifice plates, and differential pressure transmitters. Orifice flowmeters The throttling device element will convert the flow of the medium into differential pressure. The differential pressure is transmitted to the positive and negative pressure chamber of the differential pressure transmitter diaphragm box through the pressure guiding pipeline. The isolation diaphragm of the positive and negative pressure chamber is passed through silicone oil. The filling liquid transmits the differential pressure to the measuring diaphragm, which can offset the measuring diaphragm from left to right.
The upstream and downstream surfaces of the orifice flowmeter may be damaged or the flange gasket of the orifice plate may protrude into the pipeline. The transportation of the orifice flowmeter or the installation process of the flowmeter may cause damage to the upstream or downstream surface or It is the flange pad protruding from the pipeline that will cause the measurement error of the flow meter. The construction personnel should carefully check the orifice plate before installing the orifice plate flowmeter. If the upstream and downstream surfaces of the orifice plate are damaged, they should be replaced in time. The design of the standard orifice plate flowmeter is obtained through a large number of experiments. It can be used directly without actual calibration. During the installation process of the orifice plate flowmeter, irregularities or even errors may occur, which will cause flow. Generate measurement errors. The front and rear straight pipe sections of the orifice plate flowmeter do not meet the requirements. The front and back straight pipe sections are to ensure the stable flow of fluid in the pipeline, but because the process pipeline often has resistances such as bifurcations and turns, the fluid will be stable due to The phenomenon becomes disturbance, which causes the measurement error. The installation position of the throttling device that requires reasonable design can be used for the front and rear straight pipe sections.
Installation and use of V-cone flowmeter