MSc. PETROLEUM AND GAS ENGINEERING

School of Computing, Science and Engineering

COURSE LECTURER: DR.ABOOBAKER ABBAS

DATE OF SUBMISSION: 15/05/2015

PRESSURE GAUGE LAB REPORT

UNIVERSITY OF SALFORD, MANCHESTER

SIDHARTH SOHAN THERROTH@00410200

ContentsABSTRACT..................................................................................................................................2

THEORY......................................................................................................................................4

APPARATUS...............................................................................................................................5

PROCEDURE..............................................................................................................................7

DATAS AND ANALAYSIS.........................................................................................................8

CONCLUSION..........................................................................................................................10

SOURCES OF ERROR...........................................................................................................11

REFERENCE............................................................................................................................11

List of FiguresFigure 1 DEAD WEIGHTS........................................................................................................................6Figure 2 TESTER.....................................................................................................................................6Figure 3 (ACTUAL PRESSURE ) VS (GAUGE PRESSURE)...........................................................................8Figure 4 (% ERROR) VS ( ACTUAL PRESSURE).........................................................................................9

List of TablesTable 1: PRESSURE GAUGE READING.....................................................................................................8Table 2: % ERROR..................................................................................................................................9Table 3: Avg. PRESSURE GAUGE DATA.................................................................................................10

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ABSTRACT

Methodology that establishes a relation with two values on the same equipment; one of them obtained from the measuring instrument and the other which corresponds to the standardized data is known as Calibration. Result of this helps in identifying the range of adjustment required for the values obtained upon conducting an experiment. Moreover, metrological properties can also be known like the effect of other quantities it is associated with.

The calibrated observations are documented as calibration reports or certificate. In order to obtain the indicated readings corresponding to the measured quantity values, required adjustments are done after calibrating the instrument.

At times, the instrument is recorded for zero adjustment corresponding to a quantity of null value.

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OBJECTIVE

Calibration of Pressure Gauge

THEORY

Working Principle of Dead Weight Testers

Pressure measured in bar/Pascal is given as

P=FORCEAREA

FORCE = Mass x 9.8067(~9.81m/s2)

The above principle is used to generate a very stable and accurate pressure. A piston unit housed inside a cylinder is loaded upon by a series of weights.

Area (effective) is an approximation of the avg.areas of both piston and cylinder. The accuracy with which a piston and cylinder is manufactured results in the performance of a tester. They must of very good surface finish and accurate geometry. These are usually manufactured from high chromium steels in order to prevent corrosion problems. Piston would not be in compression when the weights are not accompanied by the air supply.

Psupplied = LOAD

DOWNWARDPRESSURE

Therefore applied load/weight is directly proportional to the obtainable pressure gauge calibration meter readings.

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A PPARATUS

1. Pressure gauge able to measure up to 100 lb/in2bar

2. A pressure gauge calibrator consisting of piston-cylinder unit, two control valves, standard gauge connection and some weights.

The apparatus can basically be divided into three elements:

- Piston-cylinder unit

- Weight

- Tester

Fig.1

Fig. 2

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PROCEDURE

i. The test equipment has to be thoroughly cleaned for calibration to avoid any slight errors or contamination of the gauge.

ii. Based on the conversion table given, the required weight was loaded on to the dead weight piston which already has a self weight of 0.1 bar. This value had to be subtracted from the total weight given in the table and the corresponding remaining weight was added using the weights provided. (i.e. if the amount of weight required was 0.69 bar from table, we would add weights equivalent to 0.68 bar only as the piston already weighs 0.1 bar)

iii. The valve to release pressure on the left had side was closed.iv. For rising pressure, slowly open the right-hand valve supplying

pressure and the increment in pressure was noted. v. The weights were spun slowly as the desired pressure was

approached and right when the piston floats mid way b/w the two stops, the gauge reading was taken. All the pressure was then released.

vi. For the fall in pressure, the valves were closed as previously and after crossing the actual pressure, alternate valves were closed and opened to validate pressure drop in the tester.

vii. Repeat step 5 to obtain the data. viii. Remaining weights relating to the successor pressure reading was

weighed and the above methodology was followed to procure the complete observation readings as instructed.

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DATAS AND ANALAYSIS

Table 1: PRESSURE GAUGE READING

ACTUAL PRESSURE

(psi)LOAD(bar)

PRESSURE INCREMENT PRESSURE DECREMENT

GAUGE PRESSURE

(psi)

ABSOLUTE ERROR

GAUGE PRESSURE

(psi)

ABSOLUTEERROR

10 0.69 9.4 0.6 9.5 0.520 1.38 19.6 0.4 19.2 0.830 2.07 29.1 0.9 28.9 1.140 2.76 39.2 0.8 39 150 3.45 48 2 48.1 1.960 4.14 58.6 1.4 58.8 1.270 4.83 69.3 0.7 69.2 0.880 5.52 78.4 1.6 78.5 1.590 6.21 89 1 89 1

100 6.9 97.7 2.3 98 2

0 20 40 60 80 100 1200

20

40

60

80

100

120

decrementincrement

GAUGE PRESSURE (psi)

ACT

UA

L PR

ESSU

RE (p

si)

Figure 3 (ACTUAL PRESSURE ) VS (GAUGE PRESSURE)

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Table 2: % ERROR

ACTUAL PRESSURE

(psi)% ERROR

INCREMENT DECREMENT

10 6 520 2 2.530 1 2.340 1 1.550 0.4 0.860 1.16 1.1670 0.85 180 0.25 190 0.33 0.55

100 1.2 1.4

% error = error

actual pressurex 100

0 20 40 60 80 100 1200

1

2

3

4

5

6

7

Error (%) DecrementError (%) Increment

Actual Pressure (psi)

Erro

r %

Figure 4 (% ERROR) VS ( ACTUAL PRESSURE)

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Table 3: Avg. PRESSURE GAUGE DATA

ACTUAL PRESSURE

(psi)AVG.

PRESSURE ERROR%

ERROR10 9.45 0.55 5.520 19.55 0.45 4.530 29.5 0.5 540 39.5 0.5 550 49.7 0.3 360 59.3 0.7 770 69.35 0.65 6.580 79.5 0.5 590 89.6 0.4 4

100 98.7 1.3 1.3

%ERROR (AVG.) 4.68

CONCLUSION

Calibration experiment of the equipment was successfully conducted and based on the result obtained, a deviation in readings of the calibrated values was observed on comparison with the theoretical values. A similarity was found in the readings obtained during varying pressures of each load applied. However, the slight difference would be due to human error. Error values tend to increase more for higher values of the load applied due to the supply of air making it difficult to lift the weights. Wear and usage has its effect on the equipment and this would also catalyse for the deviation caused in the readings.

% error seemed to be greater for decrement readings than increment. The average pressure reading does not lie within a safe limit denoting that the instrument has to be corrected for any further use as the calibration results show large variations.

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S OURCES OF ERROR

Chances of any leakage in the air supplied through the valves. Inaccuracy while noting the reading due to parallax error. Application of external force/load while weight is spun. Pressure loss in the hydraulic mechanism of the piston. Improper calibration can cause variations in the readings obtained.

REFERENCE

1. E. Connor, Gas Quality Measuring Devices on Gas Measurement University of Salford, 1969

2. DH- Budenberg, An-Introduction-to-Dead-Weight-Testers @ http://www.scribd.com/doc/18933664 (25th Nov, 2009)

3. Practical Manual on pressure gauge calibration, 2009.

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