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1、HOW TO IDENTIFY THE CALIBRATION PERIODS OF THE ROTARY METERS OPERATIONAL INISTANBUL BY EXAMINING PRESURE LOSSESAhmet YETK .trSerkan KELEER .trA.Abdulkadir AKGNGR .trINTRODUCTIONThere is no doubt that metrology has an important role in economy,

2、 industry, production as well as in our daily life. With its scientific, commercial, ethical and social implications, accurate and reliable measuring is so important that, if failed, will create technical and social problems affecting families, communities, regions, nations, and international relati

3、onships. In the industrialized countries, the accuracy and reliability of measurements are tested according to a nation wide web of calibrations. According to one definition calibration is “a series of operations that under certain conditions helps to identify the difference between a value on a mea

4、suring device and the value that it should show according to a given reference”.A gas distribution company is responsible for accurate measuring and accurate billing of the gas sold. Accurate and reliable measurement is crucial for both the distribution company and the consumer.We can classify gas m

5、easurement into three groups: industrial, commercial and residential. Major gas measurement devices are rotary meters, turbine meters and diaphragm meters. Amongst them, diaphragm meters are used at houses, whereas rotary and turbine meters are used by the businesses and industry. There are particul

6、ar problems associated with the use of these three types of meters.This article aims to examine the pressure loss of rotary meters being used in Istanbul, without removing them, and demonstrate the relationship between pressure loss and calibration.The method we are going to use involves connecting

7、a sensitive manometer onto the input and output pressure connections in order to obtain the pressure difference between the input and output connections of the rotary meter, while gas continues to flow through. Then, the obtained results are compared with the reference values to indicate the extent

8、of pressure loss at that particular meter.The results will offer us an insight to the measurement levels of the rotary meters being used in Istanbul. They will also have reflections with regards to the calibration of the rotary meters. The meters with a pressure loss beyond the standard value appear

9、 to have more problems when calibrating. While demonstrating the calibration status of the existing rotary meters in Istanbul, this study will also provide a point of reference for EU and other countries on our continent. While in some European Countries the rotary meters are calibrated every 16 yea

10、rs, it is 10 years in Turkey. This study will provide clear outcomes on the required calibration periods for the rotary meters. The study will also have implications on the gas pollution and reducing such pollution.This article will focus on and analyse the rotary meters being used in Istanbul, whil

11、e its findings will help demonstrating the relationship between pressure loss and calibration.APPLICATIONFigure1.The inside of RotarymeterFigure.2.Rotarymeter working principlePressure problems were experienced where rotary meters supplied gas at low pressure to snap- acting loads. The impellers. in

12、ertia could first cause a pressure buildup and then create inadequate pressure due to reversal of the impellers. This caused pilot outage. In most cases, a check valve downstream of the meter solved this problem. Since the changes to aluminum to reduce inertia on new rotary meters, thousands of rota

13、ries have been installed on low-pressure applications with minimal problemsA differential rate test should be performed when the meter is first installed and under the actual conditions of gas line pressure and specific gravity that will exist in service. This test consists of a series of differenti

14、al pressure readings taken between the inlet and outlet of the meter at several gas flow rates within the meters range of capacity.The test is particularly important when line pressure will be higher than 15 mbar, so that direct comparison with later tests can be made. Below 15 mbar, the field tests

15、 on gas can be compared directly with factory test results on air obtained from an individual referencemeter test curve or a characteristic accuracy curve. In either case, an increase of up to 50% in differential pressure at any flow rate can be tolerated without affecting the meter accuracy more th

16、an 1%. This has been proven by exhaustive factory and field tests.1outletinletConducting the Differential Rate Test1.2.Pressurize the meter by slowly opening the inlet and discharge valves.Adjust the bypass and the inlet valves until the meter operates at a selected flow rate in the lower range of i

17、ts capacity.With flow stabilized, time the passage of a predetermined volume of gas as registered on the counter or instrument.Record the differential pressure reading, line pressure,Repeat the test several times to obtain an accurate average reading.Obtain similar differential readings at as many d

18、ifferent flow rates as possible within the meters range. At least three points are required within the 25% to 100% range to establish data for an accurate curve.Convert the gas flow to displaced CFH, and plot a curve of differential pressure versus flow rate..7.The meter condition and perform

19、ance can be checked periodically by running a similar differential rate test at a single selected point. If the differential pressure has increased by 50% or more over the original reading at this rate, check the meter for causes of increased resistance. valve grease, pipeline dirt, worn bearings, a

20、nd too heavy or too much oil.Accompanying new meters is a test data sheet stating the meter accuracy at the flow rates agreed upon by the manufacturer and the utility (usually 10% and 100% of capacity.) This sheet establishes the normal pressure differential at the existing conditions of flow rate (

21、meter speed), line pressure and gas specific gravity, for comparison with future tests. Later increases in differential pressure indicates worn bearings or a build-up of foreign deposits on impellers or casing. The differential pressure at a given meter speed is a function of the gas specific gravit

22、y and line pressure. An increase in line pressure or specific gravity increases the differential. Thus, the same test conditions must be maintained in later tests to permit direct comparison with the original test.Mechanical drag is the primary factor that can affect the proof of rotary meters. A si

23、gnificant increase in rotating resistance requires more gas energy to turn the impellers, and a greater pressure drop across is indicated across the meter. Thus, the differential-rate test is accepted by many state utility commissions as a means of periodically substantiating the original accuracy o

24、f a meter as represented by the curve of a factory-performed referencemeter prover test134.THE FORMULATION OF PRESSURE LOSS P2 = P1 x d(Pm / Patm) x (Q / Qmax)2 P2 = Pressure loss P1 = Pressure loss according to flow and meter type Pe = Operational pressurePm = Mutlak BasnPatm = Atmospheric pressure

25、 Pm = Pe + PatmQ = Project flowQmax = Maximum flow according to meter typed = Air density = 1 kg/m3Natural gas = 0,6 kg/m3The data necessary to calculate the loss of pressure are the flow data and the meter data2Another pressure loss calculation method Schlumberger(Actaris)2Table 1.The choice of pre

26、ssure loss for RotarymeterISTANBUL STUDYIn the study every single meter in Istanbul in the Bosphorus region was examined .In the study a total of 711 meters were examined .The measurement interval of these meters is 1:20 There were lubrication problems with 458 meters. The wrong type of lubricant ha

27、d been chosen. 256 meters suffered from faulty installation. The customers in question were notified in writing and requested to correct their installations in the event of not correcting the installation of their meters they were further informed that their natural gas supply would be cut off . In

28、general the pressure of the meters examined is between 21 mbar and 300 mbar. Some examples of the study is provided below.MEASUREMENT OF PRESSURE LOSSAll the meters suffering from lubrication problems and those installed improperly in the Bosphorus region had their pressures checked. The meters with

29、 the highest loss of pressure were uninstalled and recalibrated .Below the pressure loss measurement method is shown.Diagram3. Rotarymeter pressure loss measurement.Rotarymeter pressure loss curvePressure lossEXAMPLES OF WORK CARRIED OUT.The last two meters in the list were dismantled and recalibrat

30、ed. The calibration values are given belowCUSTOMER NAMETYPEP LOSS(mbar)BRANDFLANGE DIAMETERCLASSDECSRIPTIONPegasus HouseG652SCHLUMBERGER2150Wrong Installationzen merkeziG 1005DRESSER3300Unlubricated Meter6.Gazetecil. sit. B blokG 652.2INSTROMET2150Unlubricated MeterProfesrler sit. B4 blokG651.8DRESS

31、ER2150Unlubricated MeterAKIN ESTATEG 1604.5SCHLUMBERGER3300Meter sloping Faulty oil plug unable to lubricateMMARLAR ESTATEG 1004.3DRESSER3300Cabin prevents lubricationCarfarmaG 1002.7DRESSER3150Unlubricated Meter excessive pressure lossDou naatG 1003.3DRESSER3150Installation error counter/numerator

32、against a wallPirelli apt.G 652.5DRESSER2150Excess lubricant levelSezai zderici sit. Tel no:3519194G 652.3DRESSER2150Meter sloping .Lubricant topped up4.Gazetecil. sit. C2 blokG 652.6DRESSER2150Faulty installation. No filter.Gazete muh.sit.G 1605.4SCHLUMBERGER3150Front section oil level normal . Bac

33、k section could not be examined due to fittings .Faulty installationMotor JeansG 1004.7SCHLUMBERGER3150Faulty back oil plug .Faulty installationCrystalHotelG 1003.7INSTROMET2150Unlubricated Meter. Sloping installationGoldenAge 1G 1004.5INSTROMET3150Improper cabin and meter installation. Unable to lu

34、bricate. No seal.Kathane MunicipalityG 1607.5ELSTER3150Unlubricated Meter. Sloping installationSoyhan EstateG 1006Dresser3150Improper cabin and meter installation. Unable to lubricate. No seal.CONCLUSIONDuring the work carried out and in the subsequent calibration, it was observed that there is a re

35、lation between calibration and loss of pressure.The pressure losses were the values obtained during the meters maximum values. It would not seem possible to observe such pressure losses at minimum and above levels.It has also been observed that faulty meter installation, inadequate filtration of the gas, and the inability to regulate the control the lubrication on a