ABSTRACTCalibration is a process that relates the standard to practical measurement. For most gas measuring devices, these, however depend on the flow rate, the condition of the gas such as line pressure and temperature and gas composition. The gas meter builds on earlier pressure based designs by adding a reference chamber to avoid errors associated with atmospheric pressure fluctuations. The calibration was done using the Master Meter or Prover. The main objective of this experiment is to carry out performance test and to compare percentage error between gas meter when conducted individually and simultaneously. A standard for flow calibration should replicate as closely as practicable the conditions under which the flow meter will be used. Full replication is impossible, and the key to success is to be as close as practicable, and to recognize the nature and performance of the flow meter type being tested. The apparatus used in gas meter calibration was calibration station model SOLTEQ/CLB/0104/RR, air compressor and stop watch. The percentage error in simultaneous verification of diaphragm gas meter for the first two minutes is -53.84%, -48.15%, -42.86%, -48.15% and -42.86% for each meter 1, 2, 3, 4 and 5 respectively. The percentage error for individual verification of diaphragm gas meter only occurred in meter 3 and meter 4 which are 5.66% and 2.1% for the first two minutes. The percentage error for the next four minutes is -150%, -138.09%, -127.27%, -127.27% and 127.27% for meter 1, 2, 3, 4 and 5 respectively in the simultaneous experiment. Percentage error in individual experiment after four minutes occurred in meter 3 and meter 5 which are -1.81% and 5%. All the gas meters need to be calibrated before it can use in any operation. The accuracy of reading can be affected due to the differences in pressure and velocity that flows through each meters. The accuracy of experiment can be affected badly when using 5 meters simultaneously rather than using individual meters at a time. It can be conclude that meter no. 1 and meter no. 2 are well calibrated with 0% error for both 2 minute and 4 minute in individual experiment. It proves that the objective of the experiment was achieved.

INTRODUCTIONAccording to Chattopadhyay (2006), a flow meter is a device that measure flow rate, which is the quantity of fluid per unit of time in an open or closed circuit. There is several operating principal of the flow meter, such as differential pressure meter, velocity meter, area meter, positive displacement meter, orifice meter, turbine meter, magnetic meter, gas ionization meter, NMR meter, ultrasonic meter etc. In this experiment, the type of meter that is going to be used is a gas flow meter, used to measure the volume of the gas flow.

Figure 1: A gas flow meter In this particular study, there is five gas flow meters to be calibrated. There is several method of flow meter calibration that being applied worldwide, and divided into two which is in-situ and laboratory. Some of the calibration test that can be used is D/P Transmitter Calibration, Magnetic flow meter Calibration, Calibration using a Master Meter (Prover), Gravimetric method and other methods. In here, the calibration was done using the Master Meter or Prover. (Cable, 2005)

THEORYStandards for flow measurement are based on a comparison of the quantity of fluid passed, or passing, through the flowmeter with the quantity measured by the standard. Standards can be based on the measurement of mass or volume. The required mass or volume quantity can be calculated from the measured quantity from a knowledge of the fluid density at the test flowmeter. Standards may be static or dynamic, and this choice is made on the basis of the output and end use of the flowmeter. Some flowmeters are used to measure quantity and have a fast response time; others are designed to measure flow rate and have a slow response time. Calibration of a flowmeter should cover a significant flow-rate range for the flowmeter and establish a performance across that range. A standard for flow calibration should replicate as closely as practicable the conditions under which the flowmeter will be used. Full replication is impossible, and the key to success is to be as close as practicable, and to recognize the nature and performance of the flowmeter type being tested. The factors that should be addressed are the fluid viscosity, the installation effects due to bends and fittings, temperature, and pressure. The standard should also have a defined traceability and uncertainty chosen to match the expectation of the final measurement. The choice of standard must also recognize the dynamic performance of the flowmeter and the nature and resolution of the output. As a calibration is a comparison, the quantity measured by the standard must match the quantity measured by the flowmeter and this must take cognizance of the resolution of the flowmeter. A flowmeter used to measure very large quantities of fluid over a long period of time may not have a resolution suitable for measuring the smaller quantities measured by a standard. Calibration is not an absolute operation, but a comparison between the reading of a flow meter and that of a standard. Therefore to consider what properties are required from a standard. Firstly the standard should measure the same quantity as the flow meter. For flow measurement, the standard is a system comprising of a measure of quantity and the subsidiary measurements to determine the fluid conditions, properties and influence factor. Another feature of the standard is that there must be confidence that the measurement taken by the standard accurate.However, the quantity measured by the standard may be different from the quantity passed through the test device due to changes in volume between the meter and the standard, which are usually related to the influence factors such as temperature, pressure, viscosity and expansion. As the measurement of fluid flow is dynamic and all measurement devices are affected in some way by the conditions of use, it is impossible to have a standard which fully reproduces the conditions under which the meter will be used in practice. The combination of fluid influence the factor come together to define a set of operations which are used to provide the calibration. This is expresses in a way which gives a meaningful expectation of how the device is used.The result of a flowmeter calibration will normally provide two related figures: one related to the flow rate and the other as a performance indicator. Flow rate will be expressed as mass per unit time, volume per unit time, Reynolds number, or some other flow raterelated measure. The performance indicator relates the expected performance of the meter to the measured performance. Examples of performance indicators are K-factor, error, and meter factor.In general, all the methods for the calibration of gas flowmeters have analogies with liquid methods. The main difference between the calibration of a gas and a liquid flowmeter is the compressibility of the gas and the fact that the gas has to be contained in a closed container. As gas is compressible, the volume measured at the standard and the volume measured at the test device have to be corrected to a common or to a standard condition.Gas flowmeters can also be calibrated using mass as the reference quantity. This can be done gravimetrically by weighing high-pressure gas collected from, or delivered to, a test meter. Alternatively, the mass can be calculated using PVT (pressure/volume/temperature) calculations if a fixed volume is used. Critical flow nozzles provide an extremely stable calibration device. In this device, when the velocity of gas reaches the speed of sound in the throat of the nozzle, the mass flow will be a function of the upstream pressure and the properties of the gas only. The equation is given by

APPARATUSGas Meter Calibration unit:1. Calibration station model SOLTEQ/CLB/0104/RR.2. Air compressor.3. Stop watch

Calibration meterControl valve

PROCEDURESimultaneous Verification of Diaphragm Gas Meter1. The initial reading of each meter is recorded. (Reference wet type meter and individual diaphragm gas meter 1,2,3,4 and 5). Also, the initial pressure and temperature reading was recorded of the related position by using online touch screen system.2. Necessary isolation valves nos were opened: (V-SAT, V-REF, V-1, V-2, V-4, V-5, V-7, V-8, V-10, V-11, V-13 and V-14).3. The gas supply from the cylinder was opened from cylinders.4. Isolation valves (V-3, V-6, V-9, V-12, V-15, and V-LOAD was ensured to be fully closed.5. V-LOAD valve was gradually opened.6. Simultaneously, the stopwatch started.7. At the end of the two minutes, the pressure, temperature and meter reading at each individual meter including the wet type gas meter reading section are recorded.8. At the end of 4 minutes, repeat the above instruction (no. 7).9. Isolation valve V-LOAD was closed instantaneously.10. Stopwatch was stopped.11. The gas supply from the cylinders was stopped by closing the valve V-SAT.12. The results were tabulated.Individual Verification of Diaphragm Gas Meter1. The initial reading of reference wet type meter and meter no.1 was recorded. Also, the pressure and temperature reading of the related position was recorded by using online touch screen system. 2. Necessary isolation valves nos was opened: (V-SAT, V-REF, V-1, V-2, V-6, V-12, and V-15).3. The gas supply from the cylinder was opened from cylinders.4. Isolation valves (V-3, V-4, V-5, V-7, V-8, V-10, V-11, V-13, V-14 and V-LOAD was ensured to be fully closed.5. V-LOAD valve was gradually opened.6. Simultaneously, the stopwatch started.7. At the end of the two minutes, the pressure, temperature and meter reading at each individual meter including the wet type gas meter reading section are recorded.8. At the end of 4 minutes, repeat the above instruction (no. 7).9. Isolation valve V-LOAD was closed instantaneously.10. Stopwatch was stopped.11. The gas supply from the cylinders was stopped by closing the valve V-SAT.12. The results were tabulated.

RESULTSPART 1: SIMULTANEOUS VERIFICATION OF DIAPHRAGM GAS METERTemperature (c)Pressure (mbar)Initial volume, Vi (L)Final volume, Vo (L)Vo - Vi(L)

First 2 minutes

Meter no 124.8-0.816115801160626

Meter no 224.8-0.739120341206127

Meter no 324.7-2.291116041163128

Meter no 424.5-1.106108581088527

Meter no 524.9-0.058112181124628

Ref Meter25.023.014287302877040

4 minutes

Meter no 124.721.884116061162620

Meter no 224.718.392120611208221

Meter no 324.714.030116311165322

Meter no 424.59.363108851090722

Meter no 524.95.317112461126822

Ref Meter24.524.616287702882050

PART 2: INDIVIDUAL VERIFICATION OF DIAPHRAGM GAS METER

A. DIAPHARGM METER 1 AND REFERENCE METERTemperature (c)Pressure (mbar)Initial volume, Vi (L)Final volume, Vo (L)Vo - Vi(L)

First 2 minutes

Meter no 124.76.554116371167235

Ref Meter24.526.101351643519935

4 minutes

Meter no 124.718.894116721170937

Ref Meter24.523.123352993533637

B. DIAPHRAGM METER 2 AND REFERENCE METERTemperature (c)Pressure (mbar)Initial volume, Vi (L)Final volume, Vo (L)Vo - Vi(L)

First 2 minutes

Meter no 224.632.810120921214149

Ref Meter24.437549352413529049

4 minutes

Meter no 224.633.033121411219251

Ref Meter24.537.707352903534151

C. DIAPHRAGM METER 3 AND REFERENCE METERTemperature (c)Pressure (mbar)Initial volume, Vi (L)Final volume, Vo (L)Vo - Vi(L)

First 2 minutes

Meter no 324.731.654116621171553

Ref Meter24.537.431352493529950

4 minutes

Meter no 324.731.864117151177055

Ref Meter24.537.635353003535656

D. DIAPHRAGM METER 4 AND REFERENCE METERTemperature (c)Pressure (mbar)Initial volume, Vi (L)Final volume, Vo (L)Vo - Vi(L)

First 2 minutes

Meter no 424.637.766109151096348

Ref Meter24.537.697353563540347

4 minutes

Meter no 424.631.801109651101549

Ref Meter24.537.733354033545249

E. DIAPHRAGM METER 5 AND REFERENCE METERTemperature (c)Pressure (mbar)Initial volume, Vi (L)Final volume, Vo (L)Vo - Vi(L)

First 2 minutes

Meter no 525.133.452112751131540

Ref Meter24.638.082354523549240

4 minutes

Meter no 525.133.402113151135540

Ref Meter24.638.010354923553038

CALCULATED PERCENTAGE OF ERROR & CORRECTION FACTOR (2 minutes)Meter YSimultaneouslyIndividually

% errors% correction% errors% correction

Meter no 1-53.8435.000.000.00

Meter no 2-48.1532.500.000.00

Meter no 3-42.8630.005.66-6.00

Meter no 4-48.1532.502.1-2.1

Meter no 5-42.8632.500.000.00

CALCULATED PERCENTAGE OF ERROR & CORRECTION FACTOR (4 minutes)Meter YSimultaneouslyIndividually

% errors% correction% errors% correction

Meter no 1-150.0060.000.000.00

Meter no 2-138.0958.000.000.00

Meter no 3-127.2756.00-1.811.78

Meter no 4-127.2756.000.000.00

Meter no 5-127.2756.005.00-5.26

CALCULATIONExample from first four minutes from meter 5Where,Meter 5= 40Reference meter= 38

Percentage error

Percentage correction

DISCUSSIONBased on the result obtained, it can be seen that the percentage of error when the experiment was conducted individually is higher compared to the experiment for simultaneous verification of diaphragm gas meter. The percentage error in simultaneous verification of diaphragm gas meter for the first two minutes is -53.84%, -48.15%, -42.86%, -48.15% and -42.86% for each meter 1, 2, 3, 4 and 5 respectively. The percentage error for individual verification of diaphragm gas meter only occurred in meter 3 and meter 4 which are 5.66% and 2.1% for the first two minutes. The percentage error for the next four minutes is -150%, -138.09%, -127.27%, -127.27% and 127.27% for meter 1, 2, 3, 4 and 5 respectively in the simultaneous experiment. Percentage error in individual experiment after four minutes occurred in meter 3 and meter 5 which are -1.81% and 5%. The flow of the gas through the instrument is divided into many valves. When the experiment was conducted simultaneously, the gas was forced to enter many valves which can cause lower error rate than the individual measurement. It is essential to distinguish between the error and the uncertainty in any result obtained from calibration process which normally be presented in most calibration certificates. Error could be easily defined as the difference between the measured and true values and is unknown while the uncertainty is half the range within the true value is expected to lie with a stated probability. The uncertainty must never be quoted separately from the probability or confidence level which is associated since the two are interdependent. Four kinds of error that can be present in any measurement are spurious error, random error, constant systematic error and variable systematic error. When the experiment was conducted, the temperature throughout the experiment was always in room temperature and does not affect the calibration. The recorded pressure is also different for each meter. This shows that every valve have different errors. When the gas calibration was conducted simultaneously, the pressure shown for every meter was lower than the individual experiment. This proved that it was better to calibrate the gas separately rather than simultaneously.

CONCLUSIONAll the gas meters need to be calibrated before it can use in any operation. The accuracy of reading can be affected due to the differences in pressure and velocity that flows through each meters. The accuracy of experiment can be affected badly when using 5 meters simultaneously rather than using individual meters at a time. It can be conclude that meter no. 1 and meter no. 2 are well calibrated with 0% error for both 2 minute and 4 minute in individual experiment. It proves that the objective of the experiment was achieved.RECOMMENDATIONa) Repeat the experiment 3 times to get the accuracy of the result.b) Be sure read and understand the manual to prevent from opening n closing the wrong valve during the conduction of the experiment. c) It is best to observe and record the flow rate of gas through the gas meter instead of the reading on the monitor.

REFERENCES1.Lab Manual for Gas Calibration. Faculty of Chemical Engineering (2014)2.http://www.eia.gov/countries/country-data.cfm?fips=my, retrieved on 24th October 20143. Spitzer, D.W. (ed.) (2001) Flow Measurement: Practical Guides for Measurement and Control, 2nd edn, ISA International, Research Triangle Park, NC.4. Cornish.D (1994/5) Instrument Performance Mass Control, 27(10):323-85. Cable, M. (2005). Calibration: A Technician's Guide. ISA.6. Chattopadhyay. (2006). Flowmeters & Flow Measurement. Asian Books Private Limited.

13