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Exceptional Process Control Opportunities - Smart and Wireless Instrumentation, Valves, PID, and Tuning

Exceptional Process Control Opportunities - Smart and Wireless Instrumentation, Valves, PID, and Tuning Experitec Kansas City Technology Open House Seminar – March 26, 2010 http://www.modelingandcontrol.com/ Welcome Gregory K. McMillan

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Exceptional Process Control Opportunities - Smart and Wireless Instrumentation, Valves, PID, and Tuning

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  1. Exceptional Process Control Opportunities - Smart and Wireless Instrumentation, Valves, PID, and Tuning Experitec Kansas City Technology Open House Seminar – March 26, 2010 http://www.modelingandcontrol.com/

  2. Welcome Gregory K. McMillan Greg is a retired Senior Fellow from Solutia/Monsanto and an ISA Fellow. Presently, Greg contracts as a consultant in DeltaV R&D via CDI Process & Industrial. Greg received the ISA “Kermit Fischer Environmental” Award for pH control in 1991, the Control Magazine “Engineer of the Year” Award for the Process Industry in 1994, was inducted into the Control “Process Automation Hall of Fame” in 2001, and was honored by InTech Magazine in 2003 as one of the most influential innovators in automation. Greg is the author of numerous books on process control, his most recent being Essentials of Modern Measurements and Final Elements for the Process Industry. Greg has been the monthly “Control Talk” columnist for Control magazine since 2002. Greg’s expertise is available on the web site: http://www.modelingandcontrol.com/

  3. Newest Book - The Latest on Smart and Wireless Instrumentation Royalties are donated to the University of Texas Research Campus for Energy and Environmental Resources for Development of Wireless Instrumentation and Control

  4. Top Ten Ways to Make Process Control Enticing (10) Travel programs focusing on the process control systems of cruise ships (9) Sci-fi flicks devoted to the process control systems in star ships (8) Reality shows where teams compete to improve process control performance (7) Entourage shows where groupies use process control to keep their star from self-destruction (6) Sport analysis programs where commentators and listeners talk about the dynamics and feedforward control opportunities in football (5) Robot movies where advanced parallel processing robots optimize plants (4) Detective shows where a special investigator with cute compulsive obsessive habits and an incredibly keen mind for details solves mysterious process control problems (3) “Who done it” novels where the culprit is a bad acting control valve (2) Web video with cute animal antics in the foreground and engineers talking about process control opportunities in the background (1) “Cash for clunkers” programs to replace inefficient old distributed control systems, transmitters, and valves

  5. Fundamentals - Effect of Step Size on Small Valve Response

  6. Control Valve Deadband and Stick-Slip Deadband is 5% - 50% without a positioner ! Deadband Pneumatic positioner requires a negative % signal to close valve Stroke (%) Digital positioner will force valve shut at 0% signal Stick-Slip is worse near closed position 0 Signal (%) dead band Deadband (backlash) and stick-slip (sticktion) is greatest near the closed position

  7. Valve pressure drop ratio (DPR) for installed characteristic: Characteristic 1: DPR= 0.5 Characteristic 2: DPR= 0.25 Characteristic 3: DPR= 0.125 Characteristic 4: DPR= 0.0625 Installed Characteristic (Linear Trim)

  8. Valve pressure drop ratio (DPR) for installed characteristic: Characteristic 1: DPR= 0.5 Characteristic 2: DPR= 0.25 Characteristic 3: DPR= 0.125 Characteristic 4: DPR= 0.0625 Installed Characteristic (Equal Percentage Trim)

  9. Limit Cycle in Flow Loop from Valve Stick-Slip Process Variable (kpph) Square Wave Oscillation Controller Output (%) Saw Tooth Oscillation

  10. Limit Cycle in Level Loop from Valve Deadband Level (%) Controller Output (%) Rounded Oscillation Manipulated Flow (kpph) Clipped Oscillation

  11. Real Rangeability Minimum fractional flow coefficient for a linear trim and stick-slip: Minimum fractional flow coefficient for an equal percentage trim and stick-slip: Minimum controllable fractional flow for installed characteristic and stick-slip: Cxmin= minimum flow coefficient expressed as a fraction of maximum (dimensionless) DPr= valve pressure drop ratio (dimensionless) Qxmin= minimum flow expressed as a fraction of the maximum (dimensionless) Rv= rangeability of control valve (dimensionless) R = range of the equal percentage characteristic (e.g. 50) Xvmin= maximum valve stroke (%) Sv= stick-slip near closed position (%)

  12. Best Practices to Improve Valve Performance Actuator, valve, and positioner package from a control valve manufacturer Digital positioner tuned for valve package and application Diaphragm actuators where application permits (large valves and high pressure drops may require piston actuators) Sliding stem (globe) valves where size and fluid permit (large flows and slurries may require rotary valves) Next best is V-ball or contoured butterfly valve with rotary actuator and positioner Low packing, sealing, and seating friction Booster(s) on positioner output(s) for large valves on fast loops (e.g., compressor anti-surge control) Valve sizing for a throttle range that provides good linearity [4]: 5% to 75% (sliding stem globe), 10o to 60o (v-ball) 25o to 45o (conventional butterfly) 5o to 65o (contoured and toothed butterfly) Online diagnostics and step response tests for small changes in signal Dynamic reset limiting (FRSPID_OPTS) using digital positioner feedback

  13. Volume Booster with Integral Bypass (Furnace Pressure and Surge Control) Signal from Positioner Adjustable Bypass Needle Valve Air Supply from Filter-Regulator Air Loading to Actuator

  14. Open bypass just enough to ensure a non-oscillatory fast response Port A Terminal Box Supply Bypass Port B Increase air line size ZZZZZZZ Control Signal 1:1 Increase connection size Volume Booster Digital Valve Controller Air Supply High Capacity Filter Regulator Must be functionally tested before commissioning! Booster and Positioner Setup (Furnace Pressure and Surge Control)

  15. Open Loop Backup Configuration SP_Rate_DN and SP_RATE_UP used to insure fast getaway and slow approach Open Loop Backup Configuration Open loop backup used for prevention of compressor surge and RCRA pH violation

  16. PID Controller Disturbance Response

  17. Open Loop Backup Disturbance Response Open Loop Backup

  18. Rise in conductivity Flow cutback via kicker Conductivity Kicker for Evaporator

  19. pH Kicker for Waste Treatment MPC-1 MPC-2 Waste RCAS RCAS middle selector ROUT AC-1 kicker AC-2 AY AY splitter splitter AT AT AT AY AY Attenuation Tank AY middle selector middle selector filter FT FT AY AY Stage 2 Stage 1 AT AT AT AT AT AT Mixer Mixer FT

  20. Question: Which Measurement • Removes the most common nonlinearity in a control loop? • Compensates for pressure disturbances? • Is used in most cascade control systems? • Is used in most feedforward control systems? • Is essential to close the material balance for a process? • Makes the following advanced control tools more effective? • Model Predictive Control (DeltaV PredictPro) • Adaptive Control (DeltaV Insight) • Neural Network Predictions (DeltaV Neural) • Projections to Latent Structures Predictions (DeltaV Analytics) • Dynamic Models (MIMIC Advanced Modeling) Answer: Flow http://www.isa.org/InTechTemplate.cfm?template=/ContentManagement/ContentDisplay.cfm&ContentID=81073

  21. Ratio Control Examples • Coolant/Feed flow ratio for crystallizer, cooler, extruder, or exothermic reactor temperature control • Steam/Feed flow ratio for distillation column, evaporator, heater, dryer, or endothermic reactor temperature control • Distillate/Feed or reflux/feed flow ratio for column temperature control • Reagent/Feed flow ratio for pH control • Reactant/Reactant flow ratio for continuous and fed-batch reactor control • Catalyst/Reactant flow ratio for continuous and fed-batch reactor control • Makeup/Recycle flow ratio for continuous and fed-batch reactor control • Purge/Product flow ratio for continuous and perfusion process contaminant control • Stock/Dilution flow ratio control for stock consistency control • Additive/Feed flow ratio for blend control (e.g., percent solids) • Air/Fuel flow ratio for boiler or furnace combustion control (oxygen control) • Feedwater/Steam flow ratio for boiler drum level control (three element control) • Blowdown/Feedwater flow ratio for boiler total dissolved solids (conductivity control) • Supply/Demand flow ratio for header pressure control • Vent/Demand flow ratio for compressor surge control • Lime/Liquor flow ratio for slaker control The best setpoint and process gain is the operating point and slope on a plot of composition, pH and temperature versus a flow ratio http://www.modelingandcontrol.com/2009/03/what_have_i_learned_-_ratio_co.html

  22. Coriolis Flow Measurement Opportunities • Live Process Flow Diagrams (PFD) for Plant Performance Analysis • The first document you have on a project is typically a process flow diagram (PFD). The PFD defines the process. It is the ultimate source of info and sets the plant performance and design. • What if a plant had a live online PFD? What if we had temperature, pressure, mass flow, and inferential measurements of the composition in every important process stream? • What if a plant had online process metrics for yield, efficiency, and production from live PFDs • Reactant, Catalyst, Recycle, Dilution, and Reagent Ratio Control • True mass flow independent of temperature, density, composition, phases, viscosity, velocity, and installation enables tight control of component concentrations for reaction and neutralization • Crystallizer, Evaporator, and Column Product Composition Control • Inferential measurement of concentrations or percent solids in feed and product streams enable feedback and feedforward control of composition by manipulation of heat input or temperature • Batch Charge Control • Coriolis meters can potentially provide more accurate batch charges than weigh tanks because Coriolis meters retain a better long term installed accuracy than load cells since Coriolis does not suffer from drift or installation effects and doesn’t require periodic calibration checks • Fermentation Alcohol Yield Optimization • Measurement and totalization of carbon dioxide vent flow provides an inferential measurement of conversion of sugars to alcohol that can be used to optimize batch cycle time or efficiency • Centrifuge and Dryer Moisture Control • Measurement of percent solids in feed enables feedforward control http://www.modelingandcontrol.com/mt/mt-search.cgi?IncludeBlogs=1&search=Live+Process+Flow http://www.modelingandcontrol.com/EssentialBookCoriolisExcerpt.pdf

  23. Radar Level Measurement Opportunities • Raw material and product storage tanks require the best level measurement accuracy, when used in the calculations for: • Inventory accounting and optimization • Custody transfer • Batch charge (rate of change of level) • Continuous feed rates (rate of change of level) • Material balances (process holdup) • Column distillate receivers require the best level measurement resolution, sensitivity, and repeatability for direct material balance control • a small change in level must quickly translate to a change in reflux flow to balance a change in vapor flow. This inherent self-regulation provides some internal reflux control and helps decouple the energy balance from the material balance. • When the temperature loop makes a change in the distillate flow, the change in controller output has no effect on column temperature until the overhead receiver controller makes a change in the reflux flow • Crystallizers and reactors (batch and continuous) require the best level measurement accuracy to control and maximize crystallization and reaction • Continuous feed rate and batch cycle time set percent conversion for a given level • Level sets production rate for a given residence time and batch cycle time http://www.isa.org/InTechTemplate.cfm?template=/ContentManagement/ContentDisplay.cfm&ContentID=81073

  24. tm tm tm tm Measurement Filter (Transmitter Damping) Effect For compressor, incinerator pressure, and polymer pressure control it is critical to make sure transmitter is fast enough! http://www.modelingandcontrol.com/2007/04/analog_control_holdouts.html

  25. Transmitter Damping and Signal Filtering Effect Attenuation of Oscillation Amplitude by Transmitter Damping or Signal Filters: When a measurement or signal filter time (tf) becomes the largest time constant in the loop, the above equation can be solved for (Ao) to get the amplitude of the original process variability from the filtered amplitude (Af)

  26. Sample Time Table Typical Values Practical and Ultimate sample times are for conservative and aggressive tuning, respectively

  27. Sample Time Guideline Notes The term “sample time” is used in the broadest sense as the time between updates in sampled data from digital measurements and controllers and from analyzers The table should be useful for determining whether DCS scan or module execution times, wireless communication time intervals, model predictive control execution time, and at-line analyzer cycle time will affect control system performance. * - denotes loop uses a variable speed drive with a negligible dead time, deadband, and resolution limit as the final element. If a control valve or damper is used for these loops, you can multiply the sample times for asterisked items by a factor of 5. ! - denotes an integrating response whose integrating process gain is the inverse of the process time constant shown !! - denotes a runaway response that can accelerate and reach a point of no return For surge control, it assumed that a volume booster has been added to the each of the positioner outputs to reduce the pre-stroke dead time to less than 0.2 seconds. A valve with excessive sticktion and backlash will add significant deadtime to the response to unmeasured disturbances that deteriorates the ultimate limit to possible performance. For inline (static mixer) pH control, the largest time constant comes from the sensor lag or the process variable filter time with a nominal value of 5 seconds. For the vessel pH control it is assumed the mixing time is less than 30 sec and the reagent delivery time delay is negligible by injection of the reagent into a recirculation line just before it enters the vessel. The lower value for the time constant is for a set point on a steep titration curve that cause the pH to move much faster than for a linear response. The response can look like a runaway as the pH accelerates through the neutral region. For level control set point changes, the deadtime observed is usually about 10 times larger than the actual process deadtime due to level measurement sensitivity limits and noise. For unmeasured disturbances the deadtime observed is often about 20 times larger than the actual process deadtime because of the amount of time it takes the controller output to work through the resolution limit and deadband of the control valve. http://www.modelingandcontrol.com/2009/09/largest_opportunities_in_proce_1.html

  28. Technological advances in sensing element technology Integration of multiple measurements Compensation of application and installation effects Online device diagnostics Digital signals with embedded extensive user selected information Wireless communication Advances in Smart Measurements The out of the box accuracy of modern industrial instrumentation has improved by an order of magnitude. Consider the most common measurement device, the differential pressure transmitter (DP). The 0.25% accuracy of an analog electronic DP has improved to 0.025% accuracy for a smart microprocessor based d/p. Furthermore, the analog DP accuracy often deteriorated to 2% when it was moved from the nice bench top setting to service outdoors in a nasty process with all its non-ideal effects of installation, process, and ambient effects [1][16]. A smart d/p with its integrated compensation for non-ideal effects will stay close to its inherent 0.025% accuracy. Additionally a smart DP takes 10 years to drift as much as the analog d/p did in 1 year.

  29. (10) Reliable from day one (9) Always on the job (8) Low maintenance - minimal grooming, clothing, and entertainment (7) Many programmable features (6) Stable (5) Short settling time (4) No frills or extraneous features (3) Relies on feedback (2) Good response to commands and amenable to real time optimization (1) Readily tuned Top Ten Reasons Why an Automation Engineer makes a Great Spouse or at Least a Wedding Gift

  30. WirelessHART Network Topology • Wireless Field Devices • Relatively simple - Obeys Network Manager • All devices are full-function (e.g., must route) • Adapters • Provide access to existing HART-enabled Field Devices • Fully Documented, well defined requirements • Gateway and Access Points • Allows access to WirelessHART Network from the Process Automation Network • Gateways can offer multiple Access Points for increased Bandwidth and Reliability • Caches measurement and control values • Directly Supports WirelessHART Adapters • Seamless access from existing HART Applications • Network Manager • Manages communication bandwidth and routing • Redundant Network Managers supported • Often embedded in Gateway • Critical to performance of the network • Handheld • Supports direct communication to field device • For security, one hop only communication Network Manager

  31. WirelessHART Features • Wireless transmitters provide nonintrusive replacement and diagnostics • Wireless transmitters automatically communicate alerts based on smart diagnostics without interrogation from an automated maintenance system • Wireless transmitters eliminate the questions of wiring integrity and termination • Wireless transmitters eliminate ground loops that are difficult to track down • Network manager optimizes routing to maximize reliability and performance • Network manager maximizes signal strength and battery life by minimizing the number of hops and preferably using routers and main (line) powered devices • Network manager minimizes interference by channel hopping and blacklisting • The standard WirelessHART capability of exception reporting via a resolution setting helps to increase battery life • WirelessHART control solution, keeps control execution times fast but a new value is communicated as scheduled only if the change in the measurement exceeds the resolution or the elapsed time exceeds the refresh time • PIDPLUS and new communication rules can reduce communications by 96%

  32. Wireless Opportunities Wireless temperatures and differential pressures for packed absorber and distillation column hot spot and flow distribution analysis and control Wireless temperatures and differential pressures for fluidized bed reactor hot spot and flow distribution analysis and control Wireless pressures to debottleneck piping systems, monitor process filter operation, and track down the direction and source of pressure disturbances Wireless temperatures and flows to debottleneck coolant systems Wireless instrumentation to increase the mobility, flexibility, and maintainability of lab and pilot plant experiments. Wireless pH and conductivity measurements for Selecting the best sensor technology for a wide range of process conditions Eliminating measurement noise Predicting sensor demise Developing process temperature compensation Developing inferential measurements of process concentrations Finding the optimum sensor location http://www.isa.org/InTechTemplate.cfm?template=/ContentManagement/ContentDisplay.cfm&ContentID=80886

  33. Top Ten Signs of a WirelessHART Addiction (10) You try to use the network manager to schedule the activities of your children (9) You attempt to use RF patterns to explain your last performance review (8) You use so much resource allocation in your network manager, you eat before you are hungry (7) You propose your wireless device for the “Miss USA” contest (6) You develop performance monitoring indices for your spouse (5) You implement network management on your stock portfolio (4) You carry pictures of your wireless device in your wallet (3) You apply mesh redundancy and call three taxis to make sure you get home from your party (2) You recommend a survivor show where consultants are placed in a plant with no staff or budget and are asked to add wireless to increase plant efficiency (1) Your spouse has to lure you to bed by offering “expert options” for scheduling

  34. Separations Research Program University of Texas (UT) at Austin The Separations Research Program was established at the J.J. Pickle Research Campus in 1984 This cooperative industry/university program performs fundamental research of interest to chemical, biotechnological, petroleum refining, gas processing, pharmaceutical, and food companies. CO2 removal from stack gas is a focus project for which WirelessHART transmitters are being installed

  35. Wireless Lab pH and Conductivity(Inferential Measurements of Solvent and CO2)

  36. Life Depends Upon Process Conditions Months >100% increase in life from new glass designs for high temperatures 25 C 50 C 75 C 100 C Process Temperature

  37. New High Temperature Glass Stays Fast Glass electrodes get slow as they age. High temperatures cause premature aging

  38. pH / ORP Selection Preamplifier Location Type of Reference Used Ranging Temperature Comp Parameters Solution pH Temperature Correction Isopotential Point Changeable for Special pH Electrodes Smart Wireless pH Configuration

  39. Smart Wireless pH Dashboards

  40. The same dynamic control response was observed for SP changes Filtering of 10 sec was applied to wired measurement, zero filtering for WirelessHART measurement. Original plant PID tuning was used for both wired and wireless control GAIN =0.12 RESET = 20.3 RATE = 0 Wired Measurement Used in Control Wireless Measurement Used in Control Column Steam Flow Control Performance Wired versus Wireless

  41. The same dynamic control response was observed for SP changes Original plant PID tuning was used for both wired and wireless control GAIN=2.5 RESET=4 RATE=1 Same filtering of 2 sec was applied to wireless and wired input Wired Measurement Used in Control Wireless Measurement Used in Control Column Pressure Control Performance Wired versus Wireless

  42. Column Steam and Pressure Control Performance Wired versus Wireless Comparable control performance as measured by IAE was achieved using WirelessHART Measurements and DeltaV v11 PID option vs control with wired measurements and PID. The number of measurement samples used in control with WirelessHART and v11 PID option versus Wired transmitter and PID was reduced by a factor of 10X for flow control and 6X for pressure control – accounting for differences in test duration.

  43. Installation at Broadley James • Hyclone 100 liter Single Use Bioreactor (SUB) • Rosemount WirelessHART gateway and transmitters for measurement and control of pH and temperature. (pressure monitored) • BioNet lab optimized control system based on DeltaV

  44. Elimination of Ground Noise Spikes by Wireless Incredibly tight pH control via 0.001 pH wireless resolution setting still reduced the number of communications by 60% Temperature compensated wireless pH controlling at 6.9 pH set point Wired pH ground noise spike

  45. Traditional and Wireless PID (PIDPLUS) • PID integral mode is restructured to provide integral action to match the process response in the elapsed time (reset time is set equal to process time constant) • PID derivative mode is modified to compute a rate of change over the elapsed time from the last new measurement value • PID reset and rate action are only computed when there is a new value • PID algorithm with enhanced reset and rate action is termed PIDPLUS http://www.modelingandcontrol.com/repository/WirelessPrimeTime.pdf

  46. Wireless Temperature Loop Test Results

  47. Wireless pH Loop Test Results

  48. Control Studies of pH Resolution and Feedforward(Bioreactor batch running 500x real time) Feedforward Feedforward Batch 1 Batch 2 Batch 1 Batch 2 Batches 1 and 2 have 0.00 pH resolution and standard PID Feedforward Feedforward Batch 3 Batch 4 Batch 3 Batch 4 Batches 3 and 4 have 0.01 pH resolution and standard PID

  49. Control Studies of pH Resolution and Feedforward(Bioreactor batch running 500x real time) Feedforward Feedforward Batch 5 Batch 6 Batch 5 Batch 6 Batches 5 and 6 have 0.02 pH resolution and standard PID Feedforward Feedforward Batch 7 Batch 8 Batch 7 Batch 8 Batches 7 and 8 have 0.04 pH resolution and standard PID

  50. Control Studies of pH Refresh Time and Feedforward(Bioreactor batch running 500x real time) Feedforward Feedforward Batch 9 Batch 10 Batch 9 Batch 10 Batches 9 and 10 have 30 sec x 500refresh time and standard PID Feedforward Feedforward Batch 11 Batch 11 Batch 12 Batch 12 Batches 11 and 12 have 30 sec x 500 refresh time and wireless PID

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