Brief description of the verification of crude oil flowmeters

In the dynamic measurement of crude oil between oilfields (between the oil production plant and the oil production plant), the flow meter (,,) method of faulty ground tells the operation to be concise and widely used. The fault of the base of the flowmeter is determined by the verification personnel through the periodic verification. The accuracy of the flowmeter's ground fault given by the on-site verification is directly related to the economic benefits of informing the two. The verification personnel must pay attention to it and avoid man-made measurement errors. .
1. Problems in the flow meter work
1.1 Quality of Flowmeters It is often found in field tests that there are quality problems with flowmeters for some new equipment, such as poor repeatability or poor negligence of bases, counting of counters, counting wheels, and rolling of the lumbar wheels.
1.2 Super planning The use of pipelines to carry relatively small flows, but chose to use a larger flow meter for measurement planning; the larger the pipeline to carry the flow, the smaller the flow meter was chosen. Flowmeters that work under over planning can cause greater measurement errors.
1.3 Verification conditions and pipe training conditions are not the same Pipeline temperature and pressure during over-examination is not the same as its intern working conditions, which constitutes a large amount of measurement errors in the flow meter under normal working conditions. For example, some units increase the temperature of crude oil during inspections, increase the pressure in the pipeline, and then lower the calibration curve of the flowmeter, so that the internship work curve is higher than the calibration curve, resulting in a positive value of the base error when the flowmeter is being interned. Seriously affected the economic interests of the oil recipient.
1.4 Crude Oil Bubbles Using buffer tanks for oil delivery during the verification of the flow meter resulted in the occurrence of many bubbles in the crude oil, affecting the function of the flow meter (Table 1).
With the increase in the amount of foam in crude oil, the flow meter is increasing in negligence and seriously undermines the economic interests of the oil recipient.
1.5 verification process
(1) The calibration pipeline of the new oil station was put into operation without purging, which caused many welding slag and debris to enter the flowmeter with crude oil. In severe cases, the flowmeter will lose the waist wheel or damage the vehicle piston volume tube.
(2) The outlet valve of the normal operation of the flowmeter is not closed. During on-site inspection, it is required to close the outlet valve that the flowmeter normally works, so that the crude oil that flows through the flowmeter enters the vehicle-mounted piston volume tube to ensure the accuracy of the measurement verification and the normal operation of the vehicle-mounted piston volume tube. However, on site inspection, it was discovered that some of the outlet valves of the flowmeter were not closed tightly, which made the metering system of the flowmeter be bypassed. As a result, the pistons of the on-board piston volumetric tubes could not work properly; more than one set of flowmeters were found to share one inspection. Calibration line.
1.6 The environment elements often show the phenomenon of increasing or decreasing the number of pulses, which constitutes a computer that cannot stably flash instant traffic, and the calibration work cannot be performed normally.
1.7 Verification personnel The quality of the verification personnel is not high and their responsibilities are not strong. They do not even understand the flow meter's own use planning and field application planning. When checking, do not clean the gas in the piston volume tube of the vehicle; do not think about the working condition of the flowmeter in practice; read the temperature and pressure values ​​are not careful; do not think about the repeatability of the flowmeter test data.
1.8 New Flowmeter Not Verified Some flowmeters have been put into operation without verification. The factory inspection uses diesel oil with low viscosity, while on-site verification uses crude oil with higher viscosity. Without verification, there will be more serious negligence. The self-inflicted fault before the Shanghai No. 9 II15O flowmeter was not verified was 0.80 to 0.88%; the fault of the Kaifeng Instrument Factory LL-150 flowmeter before the test was not verified was 0.60 to 0.69.
1.9 Standard Equipment Rich in Gas When calibrating the flow meter, it is assumed that the standard equipment is rich in gas, which briefly constitutes a large instantaneous flow variation, some exceeding ±2.5.
1.10 Temperature imbalance between the flow meter and the volume tube The temperature of the internship working temperature of the flowmeter and the temperature of the volume tube are not reached before the balance is reached.
2 Measures to reduce the errors in metrological verification
(1) Strictly control the quality of the flow meter. Purchase from the standard factory and reject rejected products. The on-site inspection shall check the working condition of the flowmeter, and judge whether some of the machinery is faulty by listening to the movement of the rotor and the work of querying the header. Check whether the connection of the pulse sender is connected to some of them and whether the shielded wire is connected. When conditions are checked, the transmitter is checked and the possible elements that affect the quality of the flowmeter are gradually searched and cleaned.
(2) According to the internship flow plan selection flow meter. Two flowmeters are generally used in field devices. In order to satisfy the normal production requirements of oil fields, two flowmeters with the same level of accuracy as those for different measurement plans can be used to ensure the accuracy of 3O to 8O.
(3) The flowmeter verification is online verification, that is, verification is performed under the working conditions of the flowmeter. For positive displacement flowmeters, the operating conditions are mainly temperature and pressure. When the temperature is changed by 1°C, the fault of the flowmeter is changed to 0.07; when the pressure is changed by 1MPa, the fault of the flowmeter is changed to 0.008, and therefore, the inspection is required. The unit being inspected will replace the general pressure gauge with a precision pressure gauge, replace the general alcohol thermometer with a standard mercury thermometer with a 0.1-degree graduation, and must not advance the temperature and pressure arbitrarily. Otherwise, the verification personnel have the right to refuse the verification.
(4) At the time of on-site inspection, the oil delivery party was asked to use the terminal tank to transport oil, and it was forbidden to use the buffer tank to deliver oil.
(5) At the scene, the hose is used to connect the inlet and outlet ends of the flowmeter calibration line, and the oil delivery is done for 15 minutes. Then the vehicle-mounted piston volume pipe and the calibration line are connected and tested to prevent the impurities in the pipeline being tested from entering the vehicle. Piston volume tube. Special emphasis is placed on the fact that the outlet valves for which the flowmeters are certified to work properly must be tightly closed. In the verification process, it is assumed that the reproducibility of a flowmeter is found to be poor, or that the piston of the on-board piston volume tube cannot work downwards, and that the measurement verification equipment checks the number of pulses of several sets of flowmeters. It should be checked whether the valves in the full verification system are normally open or closed. Assuming there is a bypass in the verification system, the flow rate of the tested flow meter will be inconsistent with the detected flow rate of the on-board piston volumetric tube. In order to accurately collect the verification data, it is necessary to do a good job of verifying the flow of the system valves during the inspection and verification of the valves.
(6) After the preparatory work organization for field verification is well-organized, turn on the computer to verify the situation, disconnect the pulse sender connected with the flow juice, check whether the computer has flashes of instantaneous flow, and assume that the computer has no instantaneous flow rate flashes after a few minutes. , you can check. Otherwise, it should be checked after cleaning electromagnetic disturbances.
(7) The gas in the standard section of the volume tube should be purged before the flowmeter verification. Exhaust at the different flow points of the flowmeter to be inspected. The general practice is to have the piston of the on-board piston volume tube work several times more at the beginning of the test, and drain the air to make the instantaneous flow rate stable.
(8) Winter verification requires warm-up of the on-board piston volume tube. Through a period of work, the temperature in the verification system will reach equilibrium, so as to reduce the negligence of the onset of temperature imbalance in the verification system.
(9) Metrological verification is a very rigorous task. To ensure the accuracy of the verification data, it is necessary to ensure that all aspects of the verification work are under strict quality control, so that personnel responsibilities are understood, the working system is sound, and quality is ensured. Perfect system. Any problems presented during the verification process cannot be subjectively decisive, but should be taken from the process and subject to detailed investigation to determine the factors that affect the normal verification of the flowmeter.
(10) Strengthen the practice of informing the relevant personnel about measurement knowledge and know the difference between the factory inspection and the on-site inspection. Be aware that the measurement instrument must be used as the principle of mandatory verification prior to the measurement and notification to ensure the fairness and fairness of the measurement notification. Sex to avoid crude oil measurement.

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