PTT 402 Biotechnology Facility Design Lecture 4 Instrumentation

PTT 402 Biotechnology Facility Design Lecture 4 Instrumentation and Control of Bioprocess Zulkarnain Mohamed Idris zulkarnainidris@unimap. edu. my

Basic Control System A bioprocess is significantly different from a standard of chemical reaction in many ways that affect its instrumentation. Bioprocessing reactions are said to be easy to control because: The processes are fairly stable. 2. Most of the major variables (such as temperature, p. H, dissolved oxygen) tend to change slowly over time in the absence of major equipment failures. 1. However, the major problem with bioprocess are: Once the cell population has died, the process is over-loss of substantial amount of money and time. 2. The instrumentation must be absolutely sterile-all sensors measuring process variables must be installed and maintained in a sanitary manner. 1. Objective of good measurement and control strategy thus to provide optimal conditions for growing the culture and producing the desired product. Basically, the control system consists of several classes of instrumentation. The primary importance are measuring devices (sensors, transmitters, controllers and final control elements). The combination of a sensor, a transmitter, controller and final control element constitutes a control loop.

Basic Control System Well-instrumented fermentor

Basic Control Loop Process Sensor Final Control Element Measuring Element Transmit Element Controller Transmitter

Basic Control Loop Set point (computes the error) Transmitter (converts the transmission signal: pneumatic or electrical signal) Fluid Controller (compares the measured variable to desired value) Final control element (acts on the manipulated variable to produce desired result) Fluid Orifice(Flow Sensor)

Sensors ü A device, such as a photoelectric cell, that receives and responds to a signal stimulus. or ü A device, usually electronic, which detects a variable quantity and measures and converts the measurement into a signal to be recorded elsewhere. ü A sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. ü For example, a mercury thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated glass tube. ü A thermocouple converts temperature to an output voltage which can be read by a voltmeter. ü For accuracy, all sensors need to be calibrated against known standards.

Temperature Sensor 1. Thermocouple A thermocouple is a junction between two different metals that produces a voltage related to a temperature difference. Thermocouples are a widely used type of temperature sensor and can also be used to convert heat into electric power.

Temperature Sensor 2. Resistance Temperature Detector (RTD) ü Resistance Temperature Detectors (RTD), as the name implies, are sensors used to measure temperature by correlating the resistance of the RTD element with temperature. ü Most RTD elements consist of a length of fine coiled wire wrapped around a ceramic or glass core. The element is usually quite fragile, so it is often placed inside a sheathed probe to protect it. ü The RTD element is made from a pure material whose resistance at various temperatures has been documented. The material has a predictable change in resistance as the temperature changes; it is this predictable change that is used to determine temperature.

Temperature Sensor

Flow Sensor 1. Turbine Meter ü Turbine meters are best suited to large, sustained flows as they are susceptible to start/stop errors as well as errors caused by unsteady flow states. ü In a turbine, the basic concept is that a meter is manufactured with a known cross sectional area. A rotor is then installed inside the meter with its blades axial to the product flow. ü When the product passes the rotor blades, they impart an angular velocity to the blades and therefore to the rotor. This angular velocity is directly proportional to the total volumetric flow rate.

FLOW SENSOR 2. Magnetic Flow Meter Measurement of slurries and of corrosive or abrasive or other difficult fluids is easily made. There is no obstruction to fluid flow and pressure drop is minimal. The meters are unaffected by viscosity, density, temperature, pressure and fluid turbulence. Magnetic flow meters utilize the principle of Faraday’s Law of Induction; similar principle of an electrical generator. When an electrical conductor moves at right angle to a magnetic field, a voltage is induced.

FLOW SENSOR 3. Orifice Meter • An orifice meter is a conduit and restriction to create a pressure drop. • A nozzle, venture or thin sharp edged orifice can be used as the flow restriction. • To use this type of device for measurement, it is necessary to empirically calibrate this device. • An orifice in a pipeline is shown in the figures with a manometer for measuring the drop in pressure (differential) as the fluid passes through the orifice.

FLOW SENSOR 4. Venturi Meter A device for measuring flow of a fluid in terms of the drop in pressure when the fluid flows into the constriction of a Venturi tube. A meter, developed by Clemens Herschel, for measuring flow of water or other fluids through closed conduits or pipes. It consists of a venturi tube and one of several forms of flow registering devices.

TRANSMITTER Transmitter is a transducer* that responds to a measurement variable and converts that input into a standardized transmission signal. *Transducer is a device that receives output signal from sensors. Pressure Level Transmitter Differential Pressure Transmitter

CONTROLLER Controller is a device which monitors and affects the operational conditions of a given dynamical system. The operational conditions are typically referred to as output variables of the system which can be affected by adjusting certain input variables. Indicating Controller Recording Controller

FINAL CONTROL ELEMENT Final Control Element is a device that directly controls the value of manipulated variable of control loop. Final control element may be control valves, pumps, heaters, etc. Pump Control Valve Heater

Instrumentation Symbology Instruments that are field mounted. -Instruments that are mounted on process plant (i. e sensor that mounted on pipeline or process equipments. Field mounted on pipeline

Instrumentation Symbology Instruments that are board mounted -Instruments that are mounted on control board.

Instrumentation Symbology Instruments that are board mounted (invisible). -Instruments that are mounted behind a control panel board.

Instrumentation Symbology Instruments that are functioned in Distributed Control System (DCS) - A distributed control system (DCS) refers to a control system usually of a manufacturing system, process or any kind of dynamic system, in which the controller elements are not central in location (like the brain) but are distributed throughout the system with each component sub-system controlled by one or more controllers. The entire system of controllers is connected by networks for communication and monitoring.

Instrumentation Symbology

FC FE FI FT FS FIC FCV FRC LIC PC PG PI PR Flow Controller Flow Element Flow Indicator Flow Transmitter Flow Switch Flow Indicating Controller Flow Control Valve Flow Recording Controller Level Indicating Controller Pressure Gauge Pressure Indicator Pressure Recorder PT PTD Pressure Transmitter Pressure Transducer LC LG LR LT LS Level Controller Level Gauge Level Recorder Level Transmitter Level Switch LCV LRC Level Control Valve Level Recording Controller TE Temperature Element

PS PIC PCV PRC PDI PDR PDS PDT Pressure Switch Pressure Indicating Controller Pressure Control Valve Pressure Recording Controller Pressure Differential Indicator Pressure Differential Recorder Pressure Differential Switch Pressure Differential Transmitter TI TR TS TC TT Temperature Indicator Temperature Recorder Temperature Switch Temperature Controller Temperature Transmitter

Signal Lines Symbology

PIPING AND INSTRUMENTATION DIAGRAM (P&ID) Principal of P&ID Example 1 With using these following symbols; LC LV 100 LC V-100 LT Complete control loop for LCV 101

The Piping & Instrumentation Diagram (P&ID) PIPINGSometimes AND also INSTRUMENTATION DIAGRAM (P&ID) known as Process & Instrumentation Diagram Example 2 With using these following symbology; PRV-100 PE V-100 PIC PE Where PE is locally mounted on V-100 PT Where PT is locally mounted PIC Where PIC is function in DCS PT Draw control loop to show that PRV-100 will be activated to relief pressure when the pressure in the V-100 is higher than desired value.

PIPING AND INSTRUMENTATION DIAGRAM (P&ID) Exercise 1 CV-102 TK-102 (p. H adjustment tank) CV-101 p. HT 1 p. HE 2 p. HT 2 p. HIC 1 p. HIC 2 The diagram shows p. H adjustment; part of waste water treatment process. With using above symbols, draw control loop where the process need is: (base feed tank) TK-100 p. HE 1 TK-101 (acid feed tank) The process shall maintained at p. H 6. When the process liquid states below p. H 6, CV-102 will be opened to dosing Na. OH to the tank TK-100. When the process liquid states above p. H 6, CV-101 will be operated to dosing HCl.

PIPING AND INSTRUMENTATION DIAGRAM (P&ID) Answer 1 p. HIC 2 CV-102 TK-102 p. HT 2 p. HE 2 p. HIC 1 p. HE 1 TK-100 (p. H adjustment tank) CV-101 p. HTE 2 p. HT 2 p. HIC 1 p. HIC 2 The diagram shows p. H adjustment; part of waste water treatment process. With using above symbols, draw control loop where the process need is: (base feed tank) p. HT 1 p. HE 1 TK-101 (acid feed tank) The process shall maintained at p. H 6. When the process liquid states below p. H 6, CV-102 will be opened to dosing Na. OH in the base feed tank. When the process liquid states above p. H 6, CV-101 will be operated to dosing HCl in the acid fed tank.

PIPING AND INSTRUMENTATION DIAGRAM (P&ID) Exercise 2 LT 1 FC L 3 Where LT 1 and LIC 1 to control PCV-100 (failure close); L 2 PCV-100 TK-100 LIC 1 PCV-100 close when level reached L 3 L 1 PCV-100 open when level below L 3 FC L 5 PCV-101 LT 2 V-100 L 4 LIC 2 Where LT 2 and LIC 2 to control PCV-101 (failure close); PCV-101 close when level reached L 5 PCV-101 open when level below L 5

PIPING AND INSTRUMENTATION DIAGRAM (P&ID) Answer 2 LIC 1 FC LT 1 L 3 L 2 PRV-100 TK-100 Where LT 1 and LIC 1 to control PRV-100 (failure close); LT 1 LIC 2 FC PRV-101 LIC 1 PRV-100 close when level reached L 3 PRV-100 open when level below L 3 L 5 LT 2 V-100 L 4 LT 2 LIC 2 Where LT 1 and LIC 1 to control PRV-101 (failure close); PRV-101 close when level reached L 5 PRV-101 open when level below L 5

PIPING AND INSTRUMENTATION DIAGRAM (P&ID) Instrumentation Numbering q XYY CZZLL X represents a process variable to be measured. (T=temperature, F=flow, P=pressure, L=level) YY represents type of instruments. C designates the instruments area within the plant. ZZ designates the process unit number. LL designates the loop number.

PIPING AND INSTRUMENTATION DIAGRAM (P&ID) Instrumentation Numbering q LIC 10003 L = Level shall be measured. IC = Indicating controller. 100 = Process unit no. 100 in the area of no. 1 03 = Loop number 3

PIPING AND INSTRUMENTATION DIAGRAM (P&ID) Instrumentation Numbering q FRC 82516 F = Flow shall be measured. RC = Recording controller 825 = Process unit no. 825 in the area of no. 8. 16 = Loop number 16

Type of Process Control Loop • Open Control Loop • Closed Control Loop • On/Off Control Loop • Cascade Control Loop • Ratio Control Loop • Feedforward Control Loop • Feedback Control Loop

Open Control Loop Do not provide automatic controller (Figure 11. 2). The controller is not associated with any final control element. An error is calculated but no action is taken to adjust the process variable (Figure 11. 3). Examples of an open control loop are indicators, recorders, or any situation where constant human interference is applied if necessary. Open-loop control is often used to determine dynamics of control system.

Open Control Loop As a result, the TA is kept increasing over the time due to the shortage of cooling water to remove heat of reaction. Since TA > TS, error is present TS = 32°C TA = 33°C TC= -4°C

Open Control Loop

Closed Control Loop Is the basic of a well-designed control strategy(Figure 11. 4). An error is calculated and the output acts on the final control element such as control valve, which adjusts the process variable according to the desired value (set point). The controller changes the position of the control valve so that the error can be removed (Figure 11. 5). The amount of time that a control loop takes to remove the error depends on the constants of the control algorithm and dynamics of the process.

The control valve adjusts the cooling water flow as needed to reduce the temperature until it returns to 32°C. Closed Control Loop Since TA > TS, error is present TS = 32°C TA = 33°C TC= -4°C

Closed Control Loop

On/Off Control Loop Has an allowable range about a measured variable. The manipulated variable is fully turned on when one extreme of the range is reached, and off when the other extreme of the range is achieved. An example of this action is batch temperature control which the cooling water is turned on at 26°C and off at 28°C to maintain an average temperature of 27°C. The response of this system is shown in Figure 11. 6, and unacceptable oscillating temperature pattern that is detrimental to the growth of a culture. The use of on/off control should be restricted to manipulated variables that do not have a major effect on the process.

On/Off Control Loop

Cascade Control Loop The type of controller where the output of one controller is the set point of another (example in Figure 11. 7). Cascade control is applied so as to have the slave loop (for example the speed control) be fasting acting and control most of the possible disturbances, and the master loop (the dissolved oxygen control) respond to the lag in the system. A good guideline for stable cascade control is to have the slave loop response time 5 to 10 times (or more) faster than the master loop response time.

Cascade Control Loop

Ratio Control Loop Is applied when the proportion of two or more variables is to be maintained relative to each other. Their ratio is the measured variable and is compared to the set point The controller determines the error and calculate the output. An example is shown in Figure 11. 8, where the flow of nutrient 1 is to be maintained at a present ratio to the uncontrolled flow of nutrient 2. As the flow rate nutrient 2 varies with the changing process conditions in the line, the signal is compared to the flow signal of nutrient 1.

Ratio Control Loop

Feedforward Control Loop • Feedforward loop is a control system that anticipates load disturbances and controls them before they can impact the process variable. • For feedforward control to work, the user must have a mathematical understanding of how the manipulated variables will impact the process variable. • An advantage of feedforward control is that error is prevented, rather than corrected. • However, it is difficult to account for all possible load disturbances in a system through feedforward control. • In general, feedforward system should be used in case where the controlled variable has the potential of being a major load disturbance on the process variable ultimately being controlled.

Feedback Control Loop • One of the simplest process control schemes. • A feedback loop measures a process variable and sends the measurement tocontroller a comparison for process the point. set Ifvariable at to notis rocess variable to the return set totaken point, is control action point. • The advantage of this control scheme is that it is simple usingle transmitter. • This control scheme does not take into consideration any of the other variables in the process. • Feedback loop are commonly used in the process control industry. • The advantage of a feedback loop is that directly controls the desired process variable. • The disadvantage of feedback loops is that the process variable must leave set point for action to be taken.