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2015-10-12 11:36:26 Click:241
The Reasons and Countermeasures for the Decline of Accuracy of Crude Oil Flowmeters in the Verification Cycle
Abstract: Some crude oil flowmeters are of poor quality and cannot meet the quality requirements for crude oil metering. Some crude oil flowmeters enter the factory, because the on-site conditions are not available, they are not tested and they are directly installed on site and put into use; some crude oil flows There are no nameplates or nameplates lost in the transportation process after opening the box. Some use the nameplate of the photoelectric pulse counter to replace the nameplate of the crude oil flowmeter. As a result, the technical parameters such as the pressure rating of the crude oil flowmeter are not clear; some crude oil flowmeters are installed due to installation technology. Failure to meet the requirements, the installation of crude oil flow meter tilted, flange gasket into the tube and other phenomena.
Keywords:
I. Analysis of the causes of excess error in the verification cycle of crude oil flowmeters
1. Crude oil flow meter quality and selection are not strict
(1) quality itself
Some crude oil flowmeters have poor quality and cannot meet the quality requirements for crude oil metering. Some crude oil flowmeters enter the plant, because the on-site conditions do not exist, and they are not verified, they directly enter the site for installation and put into use; some crude oil flowmeters are opened. There is no nameplate or nameplate lost in the transportation process. Some use the nameplate of the photoelectric pulse counter to replace the nameplate of the crude oil flowmeter. As a result, the technical parameters such as the pressure rating of the crude oil flowmeter are not clear; some crude oil flowmeters cannot be installed due to installation technology. At the request, there were occurrences of tilting of the installation position of the crude oil flowmeter and intrusion of the flange gasket into the pipe.
(2) Installation quality
There is no straight pipe section requirement for positive displacement flow meters. Some crude oil flowmeters do not have straight lengths of sufficient length before and after, and the inlet and outlet of the flowmeter are directly connected to the elbow; some use the filters and air traps installed before the flowmeter to remove them.
(3) reasonable selection
Some crude oil flowmeters have an unreasonable selection, mainly because the diameter of the flowmeter does not correspond to the flow rate of the pipeline; some types of flowmeters do not meet the requirements. This type of sand control type should be selected for ordinary types; some pressure levels do not meet the requirements. Affected the use of crude oil flow meter.
2. The error caused by the volume tube
(1) The volumetric tubes used for the verification of crude oil flowmeters have not been subjected to regular verification or prolonged the verification period, the volumetric tubes have not been subjected to periodical verifications or are prolonged at random; the volumetric tubes have not been subjected to periodical inspections, resulting in a standard volume value exceeding difference.
(2) The volume pipe was repaired by changing the value. It was not verified by the national station, but was put into use directly after the self-check. At the time of on-site inspection, the volume tube was not operated in strict accordance with the user's manual of the volumetric tube. Part of the pipelines and valves of the volumetric tube leaked, which directly affected the measurement accuracy of the crude oil flowmeter volume tube, and also resulted in inaccurate calibration results.
3. The error caused by the verification method
(1) When calibrating crude oil flowmeters, they are not strictly in accordance with the crude oil flowmeter verification procedures, and are verified when the crude oil flowmeter is unstable.
(2) It is not verified under the condition that the crude oil flowmeter works. Especially for the sake of saving time, it is often tested when the oil temperature passing through the crude oil flowmeter and the oil temperature of the volumetric tube have not reached equilibrium.
(3) Leakage occurred in the calibration pipeline and the outlet valve of the crude oil flowmeter.
(4) The rational curve of the actual use of the crude oil flow meter was not taken into consideration in the verification process.
(5) The newly commissioned crude oil flow meter does not exclude the gas in the metering chamber for verification.
(6) The gas in the standard volume of the volumetric tube is not removed and the test is performed.
4. Crude oil quality difference
There are two kinds of oils commonly used in the development of oil fields: one is to measure the purified oil processed by a centralized treatment station, and the other is to measure the impurities and sand that have been processed from a single well and a pressurized point without a centralized treatment station. oil. The bad oil quality affects the measurement accuracy of the crude oil flow meter in two situations: First, the oil carries solid impurities such as sand, welding slag, wax, and exfoliation on the inner wall of the pipeline; second, the organic or inorganic substances contained in the oil exceed the standard. Such as iron salts and other easy to stick to the oil filter or flow meter's measuring chamber. Both of these conditions will lead to inaccurate measurement.
5. Human factors
(1) Individual metrological verification personnel are not very responsible and do not operate properly in accordance with the verification procedures under the normal conditions of use of crude oil flow meters, making the data collected on site untrue and reliable, leading to inaccurate verification results; there are also individual metrological verification personnel There is no patience. Although the verification result is within the allowable range, it is at the margin of the measurement error limit. For example, a 0.2-grade crude oil flowmeter has an error of ±0.19% in its verification result. Although it is not out of tolerance, it will not be adjusted and will be used after verification. It is possible to overrun the cycle at any time.
(2) Individual crude oil flowmeter maintenance personnel are not very responsible. When the crude oil flowmeter is repaired, it is careless to remove the rotor of the crude oil flowmeter. The rotor is not assembled during installation, and the relevant screws, nuts, bearings and other components are tightened. If it is not tightened, the loosened part will not be loosened, and the accessories will not be replaced, resulting in loose parts, wear, and deviation after installation.
(3) The awareness of the legal system of individual units and individuals is weak, and even violates the measurement laws and regulations, deliberately destroying the measurement accuracy of crude oil flow meters.
Second, countermeasures
1. Strictly control the quality of products entering the factory to prevent poor quality crude oil flow meters from entering the metering site
(1) For the new form of entry into the factory, the metrological verification department shall strictly control the quality. The crude oil flowmeter newly put into operation will undergo a verification after being worn-in for one week under the maximum flow rate of 80%. The inspection will be scrapped if it is not qualified, or it will be returned to the factory for replacement and maintenance; the qualified and put into use shall be used to ensure that the quality crude oil flowmeter is put into use and eliminated. The occurrence of various quality accidents.
(2) Do a good job in the selection of crude oil flowmeters and the selection of installation locations.
1 Selection of installation location: In the engineering design, the selection of the installation location of the crude oil flowmeter should be done, and sufficient space should be left to ensure the installation quality of the crude oil flowmeter, and the replacement and maintenance of the latter. Crude oil flow meter installation must strictly implement GB/T9109.2-1988 "Determination of crude oil dynamics volumetric volumetric flowmeter installation technology" to avoid measurement error caused by poor installation quality.
2 Selection: According to the pipeline design of the transmission capacity, the transmission medium, pressure level, etc. select the appropriate diameter of the crude oil flow meter to ensure that the flowmeter operates within the specified range, to avoid the use of over-range to bring greater measurement error.
2. Volume tube
To strictly follow the requirements of JJG209-2010 "Volume Tube" verification procedures, periodic verification is strictly prohibited, super cyclic use is strictly prohibited, and the volumetric tube verification data is managed to ensure the accuracy and reliability of the volumetric tube; The volumetric tube instruction manual is used to check whether the valves and pipelines of the volume tube are leaky at any time and the gas in the volumetric tube is exhausted. At the same time, the measurement data between the volume tube and the same grade volume tube is compared during the verification period of the volume tube. To ensure the accuracy of volumetric tube measurement.
3. Verification method
(1) In strict accordance with the JJG667-1997 "Liquid Volumetric Flowmeter" verification procedures for verification, select a good flow rate and related working conditions, consider the reasonable use of the flow curve, for verification.
(2) Based on the reasons for the inaccuracy within the verification period, a detailed analysis of specific issues. The misalignment of crude oil flowmeters in the verification cycle can be classified as scrapped and basic error tolerances. Among them, scrapping refers to crude oil flowmeters that have produced an excess error before installation, or due to external factors causing wear and damage to crude oil flowmeter movements and accessories. The phenomenon of poor performance can't be used continuously after metrological verification. For this situation, the error can only be eliminated after the crude oil flowmeter is returned to the factory for repair and verification. However, in the verification of crude oil flowmeters, the error should be minimized. For better quality crude oil flowmeters, it is best to minimize the error during calibration.
4. Strengthen the treatment of crude oil quality and improve oil quality
After years of field investigation, it has been found that the worse the crude oil quality, the greater the measurement error of the crude oil flowmeter; conversely, the better the crude oil quality, the smaller the error. Therefore, improving the oil quality of crude oil is an important part of improving the measurement accuracy of crude oil flowmeters and preventing crude oil flowmeters from exceeding their tolerances during the verification period. On the one hand, the centralized processing stations are required to make full use of the settling tanks to increase the processing capacity of crude oil, regularly clear the sediment and crude oil in the sedimentation tanks, and eliminate the flow of crude oil containing more impurities through the flowmeter; Implementation of management regulations for flushing and sewerage in pipeline laying and repair, and timely updating and renovating of the old pipe network.
5. Strengthen training and supervision and inspection
(1) Strengthen measurement supervision and inspection. The inspection units and the verification personnel shall take occasional spot checks and follow-up investigations to carry out on-line monitoring of the quality of the verification work and the crude oil flow meter in use, so as to ensure the qualified rate of use of crude oil flow meters. Individuals who artificially destroy the measurement performance of crude oil flowmeters should be given greater penalties.
(2) Strengthen the technical training of crude oil flow meter maintenance personnel, strengthen the technical training of employees through the improvement of the internal staff assessment management mechanism, carry out on-the-job training, technical competition and QC quality management activities, and comprehensively improve the technology of crude oil flowmeter maintenance personnel Level and quality awareness.
(3) Reinforce the measurement of laws and regulations on measurement of crude oil production units, further raise the awareness of measurement and legal system, eliminate the occurrence of damages to violations of measuring instruments, effectively control the accuracy of crude oil flow meters during the verification period, and ensure the fairness of crude oil measurement. It will be conducted in an impartial manner to safeguard the economic interests of both parties.
Friendship reminder: To purchase crude oil flowmeters, please dial the national unified service hotline 400-0592-364. Please provide technical parameters of crude oil flowmeters such as pipe diameter, medium temperature, medium pressure, flow range, media name, and output signal. And requirements. Understand the brand name, detailed information, product prices, and instructions for using the crude oil flow meter. Please read this page in detail.
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