Tao Chaojian Pan Youyi Dong Wenrun Wang Rongxiao Sun Zhipeng
Abstract The kiln is an important ceramic production equipment. When gas is supplied to the kiln, the gas source must be stable and the operation process must not be stopped. When using a gas turbine flow meter as a meter for the gas used in kiln operations, the turbine flow meter may occasionally become stuck in the application process. The cause of this phenomenon is now analyzed to reduce the occurrence of this phenomenon. , and put forward technical advice and guidance on the use of the site.
Keywords gas turbine flowmeter;kiln;shock;lubrication;dirty
Doi:10.3969/j. Issn. 1000—0771.2013.3.23
0 Preface
The kiln is an important ceramic production equipment and is a major part of the investment made by ceramic production companies. In the ceramic production process, once the furnace is put into use, it will basically not stop operation unless there is a shutdown or an emergency security incident.
In general, the number of kiln ignition heads is relatively large. For safety reasons, the ignition head is equipped with an emergency control device. The flow rate of a single ignition head is about 2 to 8 m3/h. The flow of the ignition head is controlled by a manual micro ball valve.
Usually, the gas consumption of the furnace is very stable. When the furnace temperature is reached, the opening of the ball valve becomes smaller and the flow rate decreases; otherwise, the ball valve is fully opened and the flow rate increases. Because of the manual delay, the change in flow rate is not very abrupt and relatively slow, so it will not cause air flow impact on the flowmeter. However, there are special circumstances. We once discovered that the flow of a certain field in Xinjiang resulted in the replacement of 3 flow According to the survey, the main reason for the investigation is that the kiln furnace flow fluctuation is very large, and the flow rate of the flowmeter causes the turbine to jam. This situation is related to the design of the furnace gas mode. It takes a short time at the site (within one day of normal operation). Observations can be clearly understood.
The change of the gas flow rate in the furnace is affected by the furnace temperature. In general, the flow fluctuation range is much smaller than the flow range of the turbine flowmeter by 20:1, so the turbine flow meter is very suitable for the type selection. In the gas flow meter, the turbine flowmeter has a long history of development, rich experimental data, mature technology, with the advantages of high accuracy, good repeatability, low pressure loss, etc., has long been selected as a statutory measuring instrument in developed countries, and has been widely For business measurement occasions. The waist wheel (Roots) flowmeter has a wider range than the turbine flowmeter and less pressure loss, but has higher requirements for the cleanliness of the air quality; the orifice flowmeter has a narrow measuring range, large pressure loss, and long-term working edge sharp wear. The accuracy is declining, so it is not recommended for the kiln; the vortex flowmeter has a pressure loss slightly larger than the turbine flowmeter and the range is about 10:1 to 15:1. In the case where the flow rate range meets the kiln, Its non-movable parts do not have the advantages of rotational wear and do not require regular lubrication and can be used in kiln furnaces.
However, any kind of flowmeter has its limitations in field applications. Therefore, in order to better apply the flowmeter and make the trade between the supply and demand sides fair and prevent the occurrence of doubts, it is necessary to analyze the cause of the failure of the on-site flowmeter and propose technical measures to prevent such failures from occurring in the flowmeter so as to ensure The flow meter can operate stably and reliably on this occasion and achieve fair and equitable measurement.
1 turbine flowmeter impeller stuck cause analysis
We have compiled many years of on-site service data and analyzed the cause of the turbine flowmeter impeller seizure as follows:
1.1 bearing damage caused by airflow impact
The airflow impact is the most important reason for the jamming of the impeller, resulting in the following reasons for the stuck impeller:
1) The gas volume in the furnace fluctuates greatly. Turbine flowmeters are not suitable for fields with intense pulsating flow or pressure pulsation. Although the kiln does not fluctuate in terms of normal gas usage, it does not rule out abnormal flow fluctuations in special circumstances.
2) The valve opening and closing operations are not standardized. At present, kiln gas metering mostly uses one-for-one meter configuration, and no Wanfang data channel is installed. The on/off valve operation should strictly follow the manufacturer's operating regulations. When the on/off valve is too fast or irregular, the airflow will greatly increase the impact on the flowmeter.
3) Pressure rises and falls during pressure regulation. Pressure and flow debugging before normal operation need to be adjusted. Even after normal operation for a period of time, pressure may need to be adjusted due to unsatisfactory ignition or process. During this process, if the pressure regulation rate is too high, the impact of the flowmeter will cause jamming.
1.2 Insufficient bearing lubrication
High-precision instrument bearings need to be lubricated. Bearings that work for a long time, if they do not have lubricating oil, will be damaged due to frictional heat and eventually cause the flowmeter to jam.
1.3 The pipeline is not clean
The hazard of cleaning the pipeline is not great. The welding slag and contaminated impurities in the pipeline are accompanied by the impact of airflow on the impeller, which will cause the bearing to be unbalanced and damaged. When the impeller is made of engineering plastics, it will even fly away. At the same time, excessive dirt may cause some dust to enter the bearing and cause jams.
1.4 The quality of the bearing itself
Bearings of high-precision instrument bearings are not easily detected when they are purchased, and they lack the means of inspection. In general, imported bearings only check the packaging and marking during incoming inspection. At the same time, the bearings are inspected at the flowmeter assembly inspection: the bearings are qualified, then the bearings are qualified; the tests are unqualified, and various factors including the quality of the bearings are rechecked. From a statistical point of view, as long as the supplier brand is good, the problem of unqualified quality of the bearing itself can basically be avoided. However, this does not exclude the possibility of quality problems in a very small number of bearings.
2 technical measures adopted for the stuck impeller
2.1 pipeline configuration
1) According to the provisions of GB/T 21391-2008 (Natural gas flow measurement using gas turbine flowmeters), the recommended configuration during installation is shown in Figure 1. In addition, the installed straight pipe section can be installed according to the manufacturer's figure 1 Turbine flow meter Recommended piping configuration
2) During the pressure regulation process, the pressure should be adjusted slowly to protect the flowmeter;
3) In the case of flow overload, it is recommended that the flowmeter
Install flow restrictors (restriction orifices or restrictor nozzles) downstream.
2.2 Filter
In field applications, it is recommended to install a filter between the flow meter and the upstream valve.
2.3 Pipe Purging
The purge of the pipeline must be thorough, and when the flowmeter is installed at the end of purging, care must be taken to avoid secondary pollution, that is, there should be dirt, solid particles, etc. on the flowmeter gasket. Or filter pad installed at a front meter, using remove about one to two weeks later, a large solid particles can be avoided, welding slag, from entering the flow meter to a certain extent.
2.4 Open / Close valve operating
Strictly follow the manufacturer's requirements for valve opening/closing operations. When opening the valve, first open the upstream valve slowly, wait until the pressure is balanced at both ends of the flowmeter, and then slowly open the downstream valve; when closing the valve, first slowly close the downstream valve, and then slowly close the upstream valve.
2.5 lubricate
After the installation is completed, before starting the investment, the lubricating oil should be added in accordance with the instructions for use (fuel pump indicator). When the gas quality is relatively dirty, the fueling cycle can be shortened.
3 Other technologies that help in the analysis of causes and measurement disputes
Measure
When the flow meter in the case of large flow metering fails, if it is found to be not timely, it will cause a large amount of gas measurement error or even no measurement, involving a large amount, which easily lead to trade conflicts and economic disputes. Second, even the best products have the potential to fail. To this end, data remote monitoring systems can be used to prevent or analyze historical data from flowmeters and resolve them through negotiation.
3.1 Data Transmission System
The flowmeter is connected to the wired (RS485 communication to E1) or wireless (short-range wireless communication or ZigBee, etc.)
The data collector and data collector are networked with the data monitoring center through GPRS/CDMA, and the wireless data transmission is realized according to the flow meter communication protocol.
3.2 event recording, data recording
In the memory of the flow meter, relevant parameters and process data should be stored and can be read out by communication or display when needed. These records can include event records and data records. The event record refers to when the parameter modification, hardware (including transmission measurement technology 2013.No
4 Conclusion
Flowmeter application field conditions are complex and varied. The technical difficulty of using flowmeters is much greater than design technology. As a mature natural gas measurement instrument, gas turbine flowmeters must first be accurately selected, followed by installation and commissioning according to specifications. Operation, maintenance, and require the use of clean media, bearing lubrication, and avoid air impact, so that we can give full play to the advantages of gas turbine flow meter to make accurate measurement, stable and reliable operation, and to ensure its normal service life. Both supply and demand can be satisfied. However, any product has the possibility of failure. With the continuous development of science and technology, it is necessary to adopt new technologies to prevent the occurrence of problems or facilitate the negotiation of disputes. The application of gas metering technology for remote meter reading and paperless recording technology is mature and effective. Real-time meter reading, data analysis and monitoring can be performed for large-volume customers or important customers through real-time remote meter reading and real-time storage of records. This will not only help the decision-making of gas supply units but also avoid measurement disputes to the greatest extent.
references
[1]GB/T 18940--2003/IS0 9951:1993 Measurement of gas flow in closed pipes
Turbine flowmeter
[2]GB/T 21391--2008 Gas Turbine Flow Meter Used to Measure Natural Gas Flow
[3] Yang Youtao, Wang Zigang. Turbine flowmeter. China Quality Inspection Press, 2011
[4] Yang Youtao, Xu Yinghua, Wang Zigang. Barometer. China Measurement Press, 2007
[5] Wang Chi, Wang Zihe, Zhang Baozhu, et al. Flow measurement technology book. Chemical Industry Press, 2012
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