Citation
Unit Operations Laboratory Automated Process Controls Design Project

Material Information

Title:
Unit Operations Laboratory Automated Process Controls Design Project
Creator:
Harvin, David K.
Publication Date:
Language:
English

Subjects

Subjects / Keywords:
Control valves ( jstor )
Diameters ( jstor )
Differential pressure ( jstor )
Experiment design ( jstor )
Flow velocity ( jstor )
Pressure sensors ( jstor )
Process control ( jstor )
Pumps ( jstor )
Sensors ( jstor )
Transmitters ( jstor )
Genre:
Undergraduate Honors Thesis

Notes

Abstract:
With a constantly growing focus on personal safety, environmental regulation, and process efficiency within industrial manufacturing, automated control has become a staple point in process design and daily operations for every industry. The focus of this honor thesis involves the construction and implementation of a student experiment for the Chemical Engineering Unit Operations Laboratory involving theory, design, application, and development of operational procedures. This began with identifying an overall goal for the experiment in order to find the desired theory and design to achieve the set goal. For the purposes of this experiment, and to maintain safety within the laboratory for mechanical and chemical concerns, the established goal was to maintain a designated height of water within a storage tank under varying conditions. These conditions include specific feed flow rate ratios, varying disturbance flow rates, and tank draining under two different conditions: gravity-driven or pump-driven. In order to accomplish this task, students are expected to learn about and implement a PI and PID type control loop. ( en )
General Note:
Awarded Bachelor of Science in Chemical Engineering, summa cum laude, on May 2, 2017. Major(s): Chemical Engineering
General Note:
College or School: College of Engineering
General Note:
Advisor: Dmitry I. Kopelevich. Advisor Deptarment or School: Chemical Engineering

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
Copyright David K. Harvin. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.

Downloads

This item is only available as the following downloads:


Full Text

PAGE 1

David Harvin A thesis submitted in partial fulfillment of the requirements for graduating Summa Cum Laude with a Bachelor of Science in Chemical Engineering from the Herbert Wertheim College of Engineering a t th e University of Florida Spring 2017 Committee Chair: Dr. Dmitry Kopelevich

PAGE 2

ii

PAGE 3

iii

PAGE 4

iv ................................ ................................ ................................ ................................ ........... ii ................................ ................................ ................................ .......................... iii ................................ ................................ ................................ .............................. v ................................ ................................ ................................ ................................ ..... 1 ................................ ................................ ................................ ................................ ......... 2 ................................ ................................ ................................ .......................... 3 ................................ ................................ ................................ ................ 3 ................................ ................................ ................................ ............................. 4 ................................ ................................ ................................ ............................ 6 ................................ ................................ ................................ ............. 6 ................................ ................................ ................................ ................................ ...... 7 Preliminary Calculations ................................ ................................ ................................ ................. 9 Pressure Transmitters ................................ ................................ ................................ .................. 9 System Curves ................................ ................................ ................................ ........................... 10 ................................ ................................ ................................ .............. 13 ................................ ................................ ................................ ................ 16 Equipment Evaluation ................................ ................................ ................................ ............... 16 Configuration of Control Module ................................ ................................ ............................. 16 Running Control Schemes ................................ ................................ ................................ ......... 16 ................................ ................................ ................................ ................. 19 Evaluation of Equipment Predictions ................................ ................................ ........................ 19 Control Valve Tun ing ................................ ................................ ................................ ................ 21 PI Control ................................ ................................ ................................ .............................. 23 PID Control ................................ ................................ ................................ ............................ 24 ................................ ................................ ................................ ................................ .... 26 References ................................ ................................ ................................ ................................ ..... 27 ................................ ................................ ................................ ................................ .... 28 Appendix 2 ................................ ................................ ................................ ................................ .... 29

PAGE 5

v ................................ ................................ ................................ ..... 3 ................................ ................................ ........ 5 ................................ ................................ ......... 5 ................................ ................... 5 ................................ ................................ .......... 6 ................................ ....................... 7 ................................ ............... 8 ................................ ............. 8 Figure 9: Predicted system curve for Section 1 ................................ ................................ ............ 11 Figure 10: Predicted system curves for Sections 2 & 3 ................................ ................................ 11 ................................ ................................ ..... 12 F igure 12: ................................ ................................ ....... 12 ................................ ................................ .................. 13 Figure 14: The mounting brackets supporting the pressure sensor ................................ ............... 13 ................................ ........ 13 ................................ ....... 14 Figure 17: The junction box, control valves, and pressure transmitters ................................ ....... 14 Figure 18: Pump P 2 (left) and pump P 3 (right) ................................ ................................ ......... 15 Figure 19: The DeltaV operator picture ................................ ................................ ........................ 17 Figure 20: Chart for tracking process variables ................................ ................................ ............ 17 Figure 21: Settings for tuning controller ................................ ................................ ....................... 18 Figure 22: Predicted & measured pressures for PS 3.1 ................................ ................................ 20 Figure 23: Controller response when ................................ ................................ .......... 22 Figure 24: Controller response when ................................ ................................ .......... 22 Figure 25: Difficulty maintaining set point when ................................ ........................... 23 Figure 26: Response when ................................ ................................ .............. 23 Figure 27: Improved response when ................................ ............................ 24 Figure 28: Instability when ................................ ................................ .......... 24 Figure 29: Tuned response when , ................................ ............... 25

PAGE 6

1

PAGE 7

2

PAGE 8

3 Table 1

PAGE 9

4 Table 1 : Associated names for the sensors shown in the PFD FIC 303 LT 301 FT 301 FT 303 FT 304 FT 302 The primary tank outlet can either be gravity driven or pumped. T he outlet line is piped in in Schedule 40 PVC, w hile both the control valve line s and disturbance line are in Schedule 40 PVC. A panel of switches turns each of the pumps on or off. The differential pressure sensor for the tank is mounted directly beneath it on the supporting box, and a door on the re ar side allows access to pressure The differential pressure sensors which transmit readings from the orifice plates on ea ch line are not shown in the model for sake of simplicity.

PAGE 10

5

PAGE 11

6 Table 2 Table 2 : Specifications of purchased equipment The primary tank has diameter 25 cm and a maximum water height of 40.5 cm. Each orifice plate requires a recommended minimum of 10 pipe diameters of straight pipe length upstream from the plate and 5 pipe diameters

PAGE 12

7 downstream. The TE A 2 orifice plate has a bore diameter of 0.31 in, and the TE B 2 has a bore diameter of 0.4 in. Table 3 : Pump specifications

PAGE 13

8

PAGE 14

9 Preliminary Calculations Initially, the Reynolds number was calculated for various pipe diameters to ensure that the system would operate at sufficiently turbulent flow rates. The vis cosity and is the fluid velocity. The wet diameter is the actual inner diameter of the pipe. This resulted in a minimum flow of 1.0 GPM for in pipe and 1.25 GPM for in pipe. The maximum expected flows through either pipe size wer e decided by the pumps, resulting in a n upper limit of 7.9 GPM (or 30 L/min). Pressure Transmitters

PAGE 15

10 Table 4 Table 4 : Predicted pressure drops across orifice plates 0.10 1.76 4.00 7.16 System Curves Figure 9 Figure 10

PAGE 16

11 Figure 9 : Predicted system curve for Section 1 Figure 10 : Predicted system curves for Sections 2 & 3 Figure 12 y = 0.0116x 2 + 0.0152x 8.9846 -15.00 -10.00 -5.00 0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 0.00 10.00 20.00 30.00 40.00 50.00 60.00 Head (m) Q (L/min) y = 0.038x 2 + 0.0848x + 14.621 y = 0.0551x 2 + 0.0539x + 14.65 0.00 10.00 20.00 30.00 40.00 50.00 60.00 0.00 5.00 10.00 15.00 20.00 25.00 30.00 Head (m) Q (L/min) Section 2 Section 3

PAGE 17

12 Figure 12 :

PAGE 18

13 4 1 2 3 1. DeltaV(+) = Red 2. DeltaV( ) = Black 3. P.S.( ) = Black 4. P.S.(+) = Red Figure 14 : The mo unting brackets supporting the pressure sensor

PAGE 19

14 Figure 17 Figure 17 : The junction box, control valves, and pressure transmitters The series 629 Pressure Transmitters were not receivin g sufficient power to both maintain the connection to the DeltaV system and power the LED screen. This was alleviated in testing by connecting a second ary power supply to the sensor. D uring installation, wires were provided to each sensor from the power su pply for the control valves. The power provided by the control valve supply proved insufficient however, so individual power supplies were wired to each sensor as a temporary workaround. 1 3 4 1. DeltaV(+) = Brown 2. DeltaV( ) = White 3. Unused 4. Unused

PAGE 20

15 In Figure 18 pump P 2 sends water through Section 2 of the system which splits the flow between the two control valves, while pump P 3 feeds the manual disturbance line (Section 3) running along the back of the table. Section 2 also contains valves which can be used to manually adjust the flow rat es with the control valves manually set to 100% open. Figure 18 : Pump P 2 (left) and pump P 3 (right)

PAGE 21

16 Equipment Evaluation Once construction of the experiment was completed, heights were marked on tank T 1 to time the rate at which the level changed when filling or draining from each individual pipe in order to compare the observed behavior to the previous predictions for pressure readings and operating points The heights were measured and marked in inc rements of one inch. The lines in Section 2 were allowed to run individually with all valves 100% open. The differential pressure of each sensor was recorded, as was the time required for each one inch change in height in the tank. The same process was us ed for Section 3; however, data was collected for four different openings of the ball valve which controls flow through the line: fully open, and approximately , , and closed. For testing Section 1, the tank was filled to a set height before being allo wed to drain first by gravity alone, and second by pump P 1. Configuration of Control Module After the transmitters and control valves were sufficiently powered and connected to the DeltaV system, a control module was assigned for each control valve by us ing the PID_LOOP template found in DeltaV Explorer. For each, IO_IN was set to the device tag for the corresponding flowmeter (e.g. FT_303 for control module FIC_303), and the IO_OUT was set to the control valve (FY_303 for FIC_303). The value for PV_SCALE was set to psid the units of the pressure transmitter but could easily be adjusted for volumetric flow by using a calculation block to make the appropriate conversion in the DeltaV Control Studio. Also, the ENABLE_LEARNING value was changed to TRUE. Runni ng Control Schemes For this experiment, only the behavior of CV 2.1 was investigated. A chart to display the pressure readin g from the transmitter, the set point, and the percent open of the valve. was brought up by selecting TREND from the FIC_303 facepla te (shown in Figure 19 )

PAGE 22

17 Figure 19 : The DeltaV operator picture Figure 20 shows the chart used to track process variables associated with the FIC 303 module. PV is the process variable ( pressure reading ) from FT_303, SP is the set point when the valve is in AUTO mode, and OUT is a measure of the control valve opening (from 0 100%). Figure 20 : Chart for tracking process variables

PAGE 23

18 The settings for tunin g the controller were changed in the Detail window ( Figure 21 ), which is also accessible from the faceplate. The Detail window allows for different adjustments such as the limits on the set points and tuning parameters, to be cha nged. Gain, Reset, and Rate refer respectively to the Proportional, Integral, and Derivative actions of the controller. These values were adjusted to compare the response of the controller to disturbance ( in this case, changing the set point) Figure 21 : Settings for tuning controller

PAGE 24

19 Evaluation of Equipment Predictions Table 5 Figure 22 Table 5 : Predicted and measured differential pressures in Section 3

PAGE 25

20 Figure 22 : Predicted & measured pressures for PS 3.1 Table 6 Table 6 : Predicted & measured pressures for PS 2.1 and PS 2.2 Table 7 Appendix 2 Table 7 : Predicted & measured pressures for PS 1.2 Gravity 3.16 0.36 6.26 1.60 4.36 172.5% Pump 2.56 0.14 7.67 4.45 6.57 47.6% 0 2 4 6 8 10 12 14 16 18 20 0 1 2 3 4 5 6 7 8 p (psid) Q (GPM) Predicted Measured

PAGE 26

21 Table 8 Table 8 : Comparison of predicted and measured pump operating points Pump % Error Predicted Measured P 1 8.3 7.67 8.2% P 2 4.8 3.90 23.0% P 3 4.4 6.55 32.9% Control Valve Tuning In the detail screen (shown in Figure 21 ) for the desired control module, the values for the tuning parameters were adjusted. These include the (proportional) gain the reset or integral gain and the rate or derivative gain corresponding to the general PID controller equation [1] The controller was manually tuned via a trial and error approach. Changing the default values of both and to zero, first the value for was adjusted to observe its effects on the recovery o f the controller after being subjected to a disturbance. Figure 20 shows a steady value with a very small gain ( ) which is extremely slow to recover from a disturbance. Increasing reportedly decrease s the recov ery time; however, too large a value for will cause an oscillation which will increase to some maximum amplitude [9] This was confirmed by comFigure 23 (where ) to the response of approximately 25 seconds in Figure 24 (where ). In both cases, the set point was changed suddenly from 1.90 psid to 1.50 psid.

PAGE 27

22 Figure 23 : Controller response when Figure 24 : Controller response when In Figure 25 the controller shows marked difficulty in attempting to maintain a set point after the same distu rbance with Based on this behavior, the value for was set to 2.0 before adding the integral term ideally resulting in a response that should approximate the quarter amplitude decay type.

PAGE 28

23 Figure 25 : Difficult y maintaining set point when PI Control After setting a reasonable value for the integral gain was added to examine its effects. Figure 26 and Fig ure 27 show that increasing from 0 to 0.5 reduced the recovery time significantly, and reduced the o scillatory behavior as expected; however raising the value of too high lead to instability. An example of this case can be seen in Figure 28 Thus, a reasonably reliable PI type tuning for the controller was found to be and via approximate manual tuning methods. Figure 26 : Response when

PAGE 29

24 Fig ure 27 : Improved response when Figure 28 : Instability when PID Control Finally, the PI type controller was changed to a PI D type by setting a non zero va lue for Adding a small led to a small reduction in the time required to reach the set point as shown in Figure 29 Larger values of appeared to cause the controller more issues in reaching the set point. T he tuning where , and was found to respond well to the various set point changes initiated to disrupt the system.

PAGE 30

25 Figure 29 : Tuned response when ,

PAGE 31

26

PAGE 32

27 References [1] D. E. Seborg, T. F. Edgar, D. A. Mellichamp and F. J. Doyle III, Process Dynamics and Controls: 3rd Edition, John Wiley & Sons, Inc., 2011. [2] Omega Engineering, Inc., PV Series Electronically Controlled Proportioning Valves, pp. L 19 L 20. [3] OSIP Pumps, General Catalogue 2014, p. 182. [4] T Mag Pumps, AM Series TM1 & TM2 EOM, 2011. [5] Dwyer Instruments, Inc., Series TE Orifice Plate Flowmeter, Bulletin F TE, 2014. [6] Omega Engineering, Inc., PV Series Electronic Proportioning Valve Manual, M1655, 2015. [7] Dwyer Instruments, Inc., Series 629 Differential Pressure Transmitter, Bulletin E 112, 2015. [8] Dwyer Instruments, Inc., Series 631 Differential Pressure Transmitter, Bulletin E 114, 2011. [9] J. G. Ziegler and N. B. Nichols, "Optimum Settings for Automatic Controllers," Transactions of the ASME, vol. 64, pp. 759 768, 1942. [10] "Minor Loss Coefficients in Pipes and Tubes Components," [Online]. Available: http://www.engineeringtoolbox.com/min or loss coefficients pipes d_626.html. [Accessed 14 Oct 2016].

PAGE 33

28 Friction Loss Coefficients [10]

PAGE 34

29 Appendix 2 Gravity Pump P 1 Height Time Height Time Trial 1 Trial 2 Trial 3 Trial 1 Trial 2 12 3.03 3.21 4.09 12 2.37 2.23 11 2.94 2.05 4.79 11 2.85 2.54 10 2.93 3.66 4.19 10 2.37 2.43 9 3.12 3.22 4.74 9 2.55 2.56 8 3.13 2.97 5.07 8 2.61 2.70 7 3.25 3.31 3.97 7 2.58 2.44 6 2.97 3.15 5.20 6 2.44 2.51 5 3.10 3.11 4.82 5 2.59 2.55 4 3.07 3.17 4.99 4 2.63 2.47 3 2.90 3.25 4.96 3 2.63 2.73 2 4.12 3.52 5.25 2 2.63 2.58 1 3.34 3.39 4.85 1 2.67 2.76 CV 2.1 CV 2.2 Height Time Height Time Trial 1 Trial 2 Trial 1 Trial 2 3 4.94 5 .87 2 5.18 5.17 4 5.65 5.30 3 5.01 4.89 5 5.21 5.07 4 5.33 5.29 6 5.09 5.10 5 4.66 4.86 7 5.07 5.47 6 4.72 4.88 8 5.61 5.47 7 5.03 5.13 9 5.16 4.96 8 5.37 5.21 10 5.00 5.32 9 5.47 5.15 11 5.24 4.97 10 4.76 4.98 12 5.60 5.87 11 5.16 5.03

PAGE 35

30 75% open 50% open 25% open Height Time Height Time Height Time 2 3.49 2 5.05 2 8.09 3 3.68 3 4.06 3 7.70 4 3.18 4 3.73 4 7.28 5 2.78 5 3.48 5 7.56 6 2.93 6 3.58 6 7.49 7 2.71 7 3.43 7 7.50 8 2.63 8 3.07 8 7.29 9 3.00 9 3.93 9 7.91 10 2.73 10 3.63 10 7.43 11 2.54 11 3.39 11 6.87 12 2.98 12 3.30 12 7.87 100% open Height Time Trial 1 Trial 2 1 3.31 3.70 2 3.60 2.64 3 3.34 3.95 4 2.98 3.15 5 2.58 2.62 6 3.26 3.05 7 2.26 2.48 8 2.64 2.68 9 2.83 2.72 10 2.65 2.54 11 2.64 2.54 12 2.87 2.91 13 2.50 2.59 14 5.41 4.00





PAGE 1

. (For Office Use Only) Honors Thesis Submission Form Major: Designation: IAl6. A ..... Graduation Term: Ii I ':l-Name: 0 (J..V; I Karl/ill Additional Authors: Email: Jh"UYi",(! v..f-/.d.u. Advisor Name: 0 1'Vl: &.1 tC'ofellv,e Major: C&""""i cJ Advisor Email: J/{0fe1.L"I/'cJ..@ c.k .,Jr. edc.t Advisor Department: cfu..,...,"u...( Thesis Title: !.&al! Lt:J.I,4 froCI-VI Caw(.Js ProjJ Abstract (200 words max): Student SignaturelDate 4/11-h_a 1-=;Thesis Advisor SignaturelDate /-:;'/zo/?Departmental Honors Coordinator Signature ______ Please indicate your preference for public access to your thesis by initialing the appropriate statement below: ....2 J grant permission to the University of Florida to list the title and abstract of this thesis in a publicly accessible database. __ J do not grant permission to the University of Florida to list the title and abstract of this thesis publicly. If you wish to make the entire thesis publicly available, you must also complete the Internet Distribution Permissions Form, available at http://digital.uflib.ufl.edu/procedures/copyright/GrantofPermissions.doc If you do not include tbis form, your tbesis will be arcbived but will not be viewable online.

PAGE 2

Abstract With a constantly growing focus on personal safety, environmental regulation, and process effi ciency within industrial manufacturing, automated control has become a staple point in process design and daily operations for every industry. The focus of this honor thesis involves the con struction and implementation of a student experiment for the Chemical Engineering Unit Opera tions Laboratory involving theory, design, application, and development of operational procedures. This began with identifying an overall goal for the experiment in order to find the desired theory and design to achieve the set goal. For the purposes of this experiment, and to maintain safety within the laboratory for mechanical and chemical concerns, the established goal was to maintain a designated height of water within a storage tank under varying conditions. These conditions in clude specific feed flow rate ratios, varying disturbance flow rates, and tank draining under two different conditions: gravity-driven or pump-driven. In order to accomplish this task, students are expected to learn about and implement a PI and PID type control loop. ii