Control Valve Characteristic (1)

8/10/2019 Control Valve Characteristic (1)

1/12

1

CCB 3072

PROCESS INSTRUMENTATION AND CONTROL LABORATORY

MAY 2014

LAB REPORT

LAB INSTRUCTOR: Mohamed

EXPERIMENT CONTROL VALVE CHARACTERISTIC

GROUP 10

GROUP MEMBERS NOORSYAKIRAH BINTI CHE JALIR

KINOSRAJ A/L KUMARAN

SITI HALIZAH BT ABU BAKAR

NORHAMIZAH HAZIRAH BINTI AHMAD JUNAIDI

15277

15352

15578

15647

LAB INSTRUCTOR Mohamed

DATE OF EXPERIMENT 22TH

JULY 2014

DATE OF SUBMISSION 5ST

AUGUST 2014


2/12

2

TABLE OF CONTENT

NO CONTENT PAGES

1.0 Introduction 3

2.0 Objectives 4

3.0 Methodology 4-7

4.0 Result 8-10

5.0 Discussion 11-12

6.0 Conclusion 12

7.0 References 12

8.0 Appendices 13


3/12


4/12

4

2.0OBJECTIVE

In this experiment, students are expected to learn:

a. To classify three common types of control valve characteristics used in real lifeb. To determine the characteristic curves for each of the control valve type

3.0METHODOLOGY

1. Calibration of thermocouples

a. Experimental Setup and Procedure

Thermocouples can be calibrated up to 6500C using the constant temperature bath (Figure

8.5)

Figure 8.5 Calibration of Thermocouple

A platinum resistance thermometer together with Model 756301 digital thermometer is used as the

Master Standard Unit. A thermocouple together with UM330 digital indicator is used as the Unit

Under Test.

1. Connect the equipment as shown in Figure 8.5.Use a Type K thermocouple as the UUT.

2. Set the constant temperature bath temperature to 400C and allow the temperature to

stabilize. We can consider the temperature to be stabilized if the MSU reading does not

change for say 5 minutes. Note the MSU reading and the UUT reading.3. Select a minimum of FIVE (5) bath temperatures between 400C and 3000C to develop a

calibration curve for the type K thermocouple. After each change wait for about 15 minutes

for the temperature to stabilize. Record all the relevant data.

4. Repeat the experiment for the type J thermocouples.


5/12

5

2. Step response of thermocouples

In this section the dynamic response of the thermocouple is determined by step testing. The

experimental setup for performing step response testing is shown in figure 8.8.

Figure 8.8 Step response of thermocouples

Experimental Set-up and Procedure

1. Connect the equipment as shown in figure 8.82. Keep the thermocouple in the air outside the constant temperature bath.

3. Adjust the bath temperature at say 700C.

4. Suddenly dip the thermometer into the bath and keep it there. This way we are introducing

a step change

5. Note the change in temperature with respect to time.

6. After the temperature reading has become constant, do the reverse step by suddenly taking

out the thermometer from the bath and keeping it in the air. Wait till the temperature again

stabilizes.

3. Thermocouple transmitter

The function of the temperature transmitter is to convert the mV output given by different types of

thermocouples to standard 4-20 mA output. Yokogawa YTA110 transmitter will be calibrated in this

experiment. In this experiment distributor is introduced to supply 24 VDC to the transmitter and

convert its 4-20 mA output to 1-5 V.

a. Experimental Set-up and Procedure

Figure 8.11 Thermocouple Transmitter Calibration

1. Connect the equipment as shown in figure 8.11.


6/12

6

2. Adjust the bath temperature for 400C. After the temperature has stabilized read the value

given by the digital thermometer and the digital indicator.

3. Repeat the experiment by selecting a minimum of FIVE (5) bath temperatures between 400C

and 3000C

4. Record all relevant data.

4. Resistance thermometer transmitter


Two and three wire connections in resistance thermometers

Figure 8.13 Resistance thermometer connections

1. Make connections as shown in figure 8.13 for 3 wire connection2. Disconnect the lead wires from the YTA110 transmitter. Measure the resistance of the lead

wire (terminal B and B) using the wheatstone bridge. The lead wire resistance for terminal A

and B is same as lead wire resistance for terminal B and B.

3. Reconnect the two lead wires to the transmitter YTA 110.

4. For the three wire connection read the output of the transmitter on UM330 Digital Indicator.

5. Connect brain terminal to the transmitter. Change sensor type from 3 wire to 2 wire.

6. Read the output of the transmitter on UM330 Digital indicator.

7. Adjust the temperature bath for 500C.

8. Repeat step 1 to 6 with the lead wires in the temperature bath.

9. Record all relevant data.


7/12

7

5. Resistance thermometers


Figure 8.15 Calibration of resistance thermometer up to 3000C

1. Connect the equipment as shown in figure 8.15. Use a 2 wire resistance thermometer as the

UUT. Short circuit terminal 2 and 3 at the back of UM330.

2. Set the constant temperature bath to 400C and allow the temperature to stabilize. We can

consider the temperature to be stabilized if the MSU reading does not change for say 5

minutes. Note the MSU reading and the UUT reading

3. Select a minimum of FIVE (5) bath temperatures between 400C and 3000C to develop a

calibration curve for the 2 wire resistance thermometer. After each change wait for about 15

minutes for the temperature to stabilize. Record all the relevant data

4. Repeat the experiments for the 3 wire resistance thermometer. Record all relevant data.


8/12

8

3.0 RESULTS

1. Linear Valve

P = 2psi

Valve

opening

Flow meter

(L/min)

0 0.98

14 7.95

36 20.09

64 36.6

85.7 48.81

99.9 51.75

90.7 50.12

59.9 36.2731.1 18.7

5 2.64

P = 0.5 psi

Valve

opening

(%)

Flow meter

(L/min)

0 0.98

10 9.36

20.5 21.38

50.4 42.49

90.7 52.68

83.3 52.79

70.5 50.56

40.8 40.96

29 32.17

1.8 3.97

0

10

20

30

40

50

60

0 20 40 60 80 100 120

Flow

Rate(L/min)

Valve Opening (%)

Flow Rate vs Valve Opening graph

0

10

20

30

40

50

60

0 20 40 60 80 100

Flow

Rate(L/min)

Valve Opening (%)



9/12

9

2. Equal Percentage Valve

P = 2 psi

Valve

opening(%)

Flow meter

(L/min)

0 1.04

6.7 2

20.4 3.38

47.5 8.29

75.2 29.65

98.3 50.38

62.7 18.97

49.8 9.79

37.7 6.1212 2.76

P = 0.5 psi

Valve

opening (%)

Flow

meter

(L/min)

0 1.0910.3 2.38

15.3 2.91

31 4.74

73 13.27

99 16.34

85.1 15.71

63.7 12.38

34.1 5.4

3.7 1.8

0

10

20

30

40

50

60

0 20 40 60 80 100 120

Flow

rate(L/min)

Valve Opening (%)

Flow rate vs Valve Opening graph

0

2

4

6

8

10

12

14

16

18

0 20 40 60 80 100 120

Flow

Rate(L/min)

Valve Opening (%)

Flow rate vs Valve Opening graph


10/12

10

3. Quick Opening Valve

P = 2 psi

Valve

opening(%)

Flow meter

(L/min)

0 1.13

3.6 1.16

19 29.03

35.2 44.47

67.5 51.64

94.2 52.35

83.5 53.27

44.5 49.73

18.8 27.862 4.76

P = 0.5 psi

Valve

opening

(%)

Flow meter

(L/min)

0 2.242.7 12.07

20.8 47.86

45 50.91

65.9 58.2

99.3 59.76

80.9 59.6

73.1 59.14

30 53.78

1.4 10.14

0

10

20

30

40

50

60

0 20 40 60 80 100

Flow

Rate(L/min)

Valve Opening (%)


0

10

20

30

40

50

60

70

0 20 40 60 80 100 120

Flow

Rate(L/min)

Valve Opening (%)



11/12

11

4.0 Discussion

As stated in the objectives, we want to determine and compare the characteristic of a linear control

valve, equal percentage control valve, and quick opening control valve. All the graphs can be

referred on the result section. We have done 2 times of different pressure for this particular

experiment. For this part of the experiment, we kept the differential pressure transmitter reading at

2psig. This is because when there is a constant pressure drop maintained across the valve, the

characteristic of the valve alone controls the flow, thus resulting to the characteristic known as

inherent flow characteristic.

All the 3 graphs if combine together will show us that linear type of valve will show that the flowrate

percentage are increases linearly as the valve opening is drawn wider (Graph 1). However, for Equal

percentage valve, the flowrate increases slowly as the valve is open more bigger. We can also see

that the flowrate is increases gradually after 50% opening (Graph 3). For the third valve, which is

quick opening valve the flowrate increases drastically and are seem to approach the maximum

flowrate at about 70% opening (Graph 5). Also not forgotten, the experiment was done by keeping

the upstream pressure indicator reading to 0.5kgf/cm2. Theoretically, valves of any size or inherent

flow characteristic, when subjected to the same volumetric flow rate and differential pressure will

have the same orifice pass area. However, different valve characteristics will give different valve

openings for the same pass area.

On the other hand we also conducted our second experiment where the pressure is constant at 0.5

psig. We still study about the 3 types of opening. The first one produce Graph 2 shows that the

flowrate are going up as the opening become larger. But we can see that a small change on the

opening almost does not give effect on the flowrate. Differently from Graph 4, the flowrate line

almost seems linear. At 100% opening the flowrate reach it maximum at 62 L/min. Lastly, the Graph

6 shows that the air was increasing and it almost reach the maximum flowrate (constant) from 75%

opening. We can likely say that, for quick opening valve, the valve just need to be slightly open.

At the end we are able to study the 3 types of controller and how it is function. This is important as

we want to make sure that our plant is safe and environmental friendly. We can prevent explosion,

fire or accidents to happen in the plant.


12/12

12

ERRORS AND RECOMMENDATIONS

impossibility of maintaining the differential pressure and upstream pressure at 2 psig and

0.5kgf/cm2, respectively. The values were constantly fluctuating and the method used to

keep the pressure values at this rate was a bit tiresome. It was therefore important for the

success of the experiment to have someone constantly watch the values and ensure that

they are within the acceptable range.

parallax error. Even though the differential pressure transmitter was digital, the upstream

pressure indicator was not. Therefore, maintaining the upstream pressure at 0.5kgf/cm2

catered for some error due to parallax. The ingenuity of the results depended partly on

whether the student assigned on reading the pressure indicator was not under the influence

of parallax.

5.0 CONCLUSION

In conclusion, we were able to accomplish the objectives of this experiment which were to

calibrate Type K, and Type J thermocouples, able to analyze the principles of a thermocouple

transmitter and calibration of a thermocouple transmitter and we are also achieve to calibrate

Platinum Resistance thermometers. From the result that we get, we can say that the measurement

for temperature for type K is the best by using MMU because is more sensitive and less percentage

error if we compare with UUT. For second experiment, we can conclude as thermocouple J get more

accurate reading by using UUT compare to the thermocouple K. From our 3rd

experiment, It is found

that 2-wire has the least percentage error while 3-wire ans MSU has also the same percentage error.

2-wire has the least percentage error due to its less amount of resistance. Lesser amount of

resistance results in high sensitivity thus lowering the error. For our 4th

experiment, two-wire

configurations are the simplest resistance thermometer configuration. It is used when high accuracy

is not required. The resistance of the connecting wires is always included with that of the sensor

leading to errors of the signal. Three-wire configuration: this configuration can be used to minimize

the effects of lead resistances. The two leads to the sensor are on adjoining arms and there is a lead

resistance in each arm of the bridge and therefore the lead resistance is cancelled out. Due to someerrors that happen during the experiment, some of our result will not be same as the theoretical.

6.0 REFERENCES

Coughanowr, D. R, Process System Analysis and Control, 2nd

edition McGraw Hill New York

1991.

Emerson Process Management "Control valve handbook, fourth edition, Fisher Controls International

LLC, 2005.

Documents

Control Valve Characteristic (1)