Process Control PDF

Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... Process Control What is a process? ¢ The word 'Process' used popularly in process control a...

Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... Process Control What is a process? ¢ The word 'Process' used popularly in process control and the process industry refers to the ways and methods applied in changing or refining raw materials into end products suitable for use. * The raw materials which can either be in a liquid, gaseous or a mixture of solid and liquid (slurry) are, during processing, transferred, measured, mixed, heated or cooled, filtered, stored, or handled in some other way to produce an end product. * Process industries include the chemical industry, the oil and gas industry, the food and beverage industry, the pharmaceutical industry, the water treatment industry, and the power industry. 1 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... What is process control? * Process Control refers to the methods used to control process variables during the manufacture of a product. * The manufacturing process for a product is controlled for the following reasons: 1. To reduce product variability - Reducing product variability leads to increase in product quality. 2. Increase efficiency - Increase in the efficiency of a manufacturing process will ensure that minimum resources are required to produce a product which consequently saves money for the manufacturers. 3. Ensure process safety - Every process must be controlled to operate safely. If this does not happen, the consequences of a run-away process can be catastrophic as witnessed in the 1986 nuclear plant disaster in Chernobyl, which exploded and burned. Control point instrumentation * The instruments (and sensors) that control these process variables can be referred to as control point instrumentation. * For this lesson we concentrate on these control point instrumentation items: ¢ Resistance temperature detectors Thermocouples Pressure transducers Flow meters * O, sensors * Servo motors 2 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... Process variable ¢ In industrial process control, the Process Variable or PV is measured by a sensor or instrument in the field and acts as an input to a controller, which takes action based on the value of it. * Common process variables include: * Level ° Flow * Temperature * Pressure Density PH (acidity or alkalinity) * Mass Conductivity *... and more Resistance Temperature Detector 3 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... What is a resistance temperature detector? ¢ Aresistance temperature detector (aka RTD) is a temperature sensor that uses the changes in the electrical resistance of a metal (as the metal is heated or cooled) to measure changes in temperature. ¢ For the readings to be interpretable, the metals used in RTDs must have a known electrical resistances that can be used for reference. What’s inside an RTD? ,.. u ate, ‘eal RTD Insulated Leads P ‘s Probe Sheath PackedinMgQ a * Copper, nickel, and platinum are all popular eigammerbly metal wires used in the construction of RTDs h ¢ Maximum ranges for RTDs are as follows: ¢ Platinum: -200 to 850°C ¢ Nickel: -90 to 260°C — Thermowell == Spring Loaded * Copper: -200 to 260°C —— Mounting Fitting onan Terminal Retainer * Platinum is most commonly used in industrial Re abl.. < = a applications. Head ¢ RTDs are sealed into and protected by a metal sheath, making a probe. ¢ These probes are attached to a housing for protection and to house the wiring — the housing and probe can then be inserted into a well 4 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... RTD protection ¢ Depending on the application, RTDs can be inserted into a well for protection from No well damage or heat — note the ceramic well (it can handle much higher temperatures) ¢ It may not be necessary for the Probe to be inserted into a well Ceramic well Stainless Steel well How are RTDs constructed? ¢ Resistance Temperature Detector construction is done in one of three ways: ¢ Wire wound RTDs * coiled element RTDs ¢ and thin film RTDs. gle Platinum Thin-Film Ceramic core Leads Layer Platinum coils ———— “Ceramic Substrate Wire Wound Coiled Element Thin Film 5 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... Wire wound RTD ¢ Ina wire wound RTD, a resistance wire is wound around a non-conducting core, which r _-~ Platinum resistance wire is usually made of ceramic. leadwires The sensor maker carefully trims the length Protective overcoat —“ of resistance wire to achieve the specified Insulated cylindrical core —! resistance at 0°C. This is called the “RO” resistance. E.g. the RO electronics resistance of a Pt100 = 100 O. Wire-wound RTD element Lead wires are attached to the resistance wire, and then a glass or ceramic coating is r ,~ Platinum resistance wire applied over the wire for protection. lead wires As temperature increases, the length of Protective overcoat —“ resistance wire increases slightly. Insulated cylindrical core —! electronics Wire-wound RTD element 6 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... Wire wound RTD ¢ Care must be taken in the design to ensure that the resistance wire does not twist or r _-~ Platinum resistance wire otherwise deform as temperature increases; leadwires the mechanical strain causes an unwanted Protective overcoat —“ change in wire resistance. Insulated cylindrical core —! Laboratory-grade RTDs used by calibration and standards laboratories eliminate this electronics source of error by loosely winding resistance wire around a non-conducting support Wire-wound RTD element structure. This type of laboratory grade RTD can be extremely accurate but is fragile and not suited for most industrial applications. Coiled element RTD In a coiled element RTD, the resistance wire is rolled into small coils, which loosely fit into a ceramic form that is then filled with non- — Platinum resistance wire conductive powder. Powder packing The resistance wire is free to expand and contract as temperature changes, minimizing error caused by mechanical strain. The powder increases the rate of heat transfer into the coils, thereby improving the response time. Pltumcotg cee Ss Coiled element RTDs are usually protected by a metal sheath in forming RTD temperature Ceramic insulator probes. * Most common in the industrial sector 7 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... Thin film RTD ¢ Thin film RTDs are mass-produced and cost less than the other RTD types. * They are smaller, and have a faster response time than the others, which is desirable in many applications. ¢ They are made by depositing a thin pathway of platinum on a ceramic base. ¢ The manufacturer adjusts the resistance at 0°C by opening parallel shunts in the pathway with a laser beam. Platinum Thin-Film Layer Leads “——— Ceramic Substrate Thin film RTD ¢ The more shunts are opened, the higher is RTD leadwires the resistance at 0°C. Thin film RTDs are not as accurate as the other types because: Resistance pattern - The RO resistance cannot be adjusted as precisely as in the other types. - The ceramic base and platinum coating Ceramic substrate have slightly different expansion rates - Ro Is adjusted this creates a strain error at higher by opening —e PR temperatures. electronics - Because thin film RTDs are smaller, the Platinum Thin-Film RTD excitation current causes a slightly Layer = Leads higher error due to RTD self-heating. “Ceramic Substrate 8 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... How does an RTD work? ¢ AnRTD is a sensor whose resistance changes as its temperature changes. * The resistance increases as the temperature of the sensor increases. Resistance ¢ The resistance vs temperature relationship is 0 well known and is repeatable over time. SSE Temperature How does an RTD work? Degrees Qo ¢ Platinum RTDs found in industrial 0 100.00 applications, usually conform to the IEC 10 103.90 60751 standard. 20 107.79 35 aie * Commercial platinum grades are produced aS fis Ga which exhibit a change of resistance of ue al 0.385 0/°C. 60 123.24 ¢ The sensor is usually made to have 70 127.07 100 9 at O°C. 80 130.89 90 134.70 100 138.50 9 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... How does an RTD work? ¢ AnRTD is a passive device and does not produce an output on its own. ¢ External electronic devices are used to measure the resistance of the sensor by passing a small electrical current through the sensor to generate a voltage. * Typically, 1 mA or less measuring current, 5 mA maximum without the risk of self- heating. How does an RTD work? * There are 2-wire, 3-wire, and 4-wire lead configurations — the most common being the 3-wire configuration /\4 White —_ Red (2) White ASD Red(2) — White (2) 2-Wire Single 3-Wire Single 4-Wire Single 10 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... How does an RTD work? * Two wire sensors are typically used in applications where accuracy is not critical. The two-wire configuration allows for the Red White simplest measurement technique but suffers from an inherent inaccuracy due to the resistance of the sensor leads. 2-Wire Single In the two-wire configuration, there is no way to directly compensate for the resistance of the lead wires which will cause an offset increase in the resistance measurement. How does an RTD work? Three wire sensors are the most common and give a good combination of accuracy and convenience. ¢ Three wire sensors are built with a Red (2) White compensation loop to allow the measurement to factor out the resistance of 3-Wire Single the leads. Cont’d 11 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... How does an RTD work? ¢ With this configuration, the controller/measurement device makes two measurements: 1. The first measurement measures the Red (2) White total resistance of the sensor and the connecting lead wires. 3-Wire Single 2. The second measurement is the resistance of the compensation loop resistance. By subtracting the compensation loop resistance from the total resistance, an account net resistanceis determined. How does an RTD work? The four-wire sensor configuration and measurement techniques allow measurement of the sensor resistance without the influence of the lead wires. Red (2) White (2) While this technique gives the best accuracy, many industrial controllers/measurement 4-Wire Single devices cannot make a true four wire measurement. 12 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... Using a 2-wire TD__— RTD —'@® Remember? ¢ Unbalanced seston bridges Caanare may invariably used to measure the resistance. ¢ When measuring the resistance of the sensing element, all external factors must be minimized or compensated for, in order to obtain an accurate reading (low resistant lead wires). * A major cause of error can be the resistance of the lead wires, especially in two lead configurations. Wheatstone bridge bw NA a Using a 3-wire RTD ¢ When the lead wire resistance is comparably high, however, it must be compensated. Compensation can be achieved with a three-lead configuration. ¢ As shown in the three-lead diagram, one side of the power supply is taken to one side of the RTD via L3. * This puts L1 and L2 in opposite arms of the bridge, so they cancel each other out and have no effect on the bridge output voltage. 13 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... Thermocouple What is a thermocouple? ¢ Athermocouple is an electrical device consisting of two dissimilar electrical conductors forming an electrical junction. A thermocouple produces a temperature- dependent voltage as a result of the Seebeck effect (heating joined dissimilar metals), and this voltage can be interpreted to measure temperature. * They are housed the same way an RTDis, as on the left. While the RTD utilizes resistance to interpret change in temperature, the thermocouple uses the change in voltage/emf to interpret the change in temperature. 14 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... Key differences between RTDs and Thermocouples * The thermocouple suits a wider variety of applications. RTDs generally operate in the range between -200 to 600 °C. In contrast, a thermocouple offers even wider operating ranges, as low as -346 °C and as high as 2320 °C. * Thermocouples offer a response time of 0.1 to 10s which is better than the response time of RTDs ranging between 1 to 50s. * On the basis of sensitivity, thermocouples are said to be more sensitive than RTD. This is so because they react faster than an RTD with the variation in temperature. * Thermocouples are generally cheaper than RTDs. An RTD will often cost two or three times more than a thermocouple with the same temperature and style. Savings can be made on RTD installation, which is cheaper, as inexpensive copper wire is used. Key differences between RTDs and Thermocouples * For applications that require greater accuracy, RTDs are preferred as they generate more accurate results than thermocouples. ¢ The stability offered by RTD is quite higher than the thermocouple. The design of the RTD provides a more accurate repeatability in the results for a longer time for the same input. Whereas the chemical change occurring in thermocouple causes drift in its reading. * The phenomenon of self-heating exists in RTDs but is negligible in the thermocouple. 15 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... Types of thermocouples ¢ Thermocouples are available in different combinations of metals or calibrations. * The most common are the “Base Metal” thermocouples known as Types J, K, T, Eand N. As you can see, each thermocouple type also has a corresponding colour code. lo CONSTANTAN COPPER- Peasy i are) (magnetic) NICKEL SE hy a ine Over Max Color Coding Se) Temp Thermocouple intrinsically Code Cu-Ni rl] oe ET Ce eo tery A NICKEL- NICKEL- 21010 1200°C} ~ CHROMIUM aor fr ~H6 to 2193°F Ni-Cr Lah (magnetic) 27010 1372°C) ASA to 2501°F CONSTANTAN COPPER | COPPER- cu NICKEL CuNi wack. | CRT 27010 100°C} ~ CHROMIUM “ASAto 1832°F Wi-Cr CHROMIUM | “Wvioxer Ni-Cr Cu-Ni ; 27010 130°C) 450 to 2372°F | NICROSIL NISIL Ni-Cr-Si Ni-Si-Mg Types of thermocouples ¢ There are also high temperature calibrations - also known as Noble Metal thermocouples - Types R, S, U, B, G, C, and D Tah a) aa) Se) PLATINUM- | PLATINUM Oey ay ard Temp Cem Temp Oy Thermocouple Intrinsically Use 13% RHODIUM Pt Ser) er] cE TC) Range A Code Pt-13% Rh PLATINUM: PLATINUM ~50 10 1768°C 0226 13% RHODIUM pt ~$8 0 3214°F Pt-13% Rh PLATINUM- | PLATINUM NONE 4] Puram 10% RHODIUM Pt ESTABLISHED 10% RHODIUM PLATINUM Pt ~50 to 1768°C $80 3210F Pt-10% Rh Pt-10% Rh NONE COPPER ESTABLISHED Gu COPPER | COPPER-LOW Cu NICKEL PLATINUM Cu-Ni NONE ESTABLISHED 30% RHODIUM Pt-30% Rh NO STANDARD G TUNGSTEN | TUNGSTEN- PLATINUM- | PLATINUM- NONE ESTABLISHED w 26% RHEMIUMI 303°Cfea Ot02x20°C | 01038564 eae 30% RHODIUM] 6% RHODIUM y W-26% z Re J NotNotlorOxdiang fc | 210208" (W) Pt-30% Rh | Pt-6% Rh NONE +) TuNGsT va Vacuum, inert, Hydrogen. Beer Enitenet| NO STANDARO Cc ESTABLISHED § aoe RHENUM! Soecaso | ae distri USE ANS! -5% Re | W-26% Re | Wot for Oxdizeg COLOR CODE (W5) TUNGSTEN | TUNGSTEN- a facuum. tert, Hydrogen. +) TUNGSTEN- | TUNGSTEN- |BearectEnbetienert| NO STANDARD D W 26% RHENIUM ESTABLISHED (FCap RHENIUM || 25%Waswne, —| 3% WoeRe, Not Practical Below | RHENIUM || MCCA ere | 063508] weer USEOe ANSI oo Cane (w3) 7 W-26% Re * Not official symbol or standard designation 16 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... Temperature ranges * Each calibration has a different temperature range and environment, although the maximum temperature varies with the diameter of the wire used in the thermocouple. ¢ Although thermocouple calibration dictates the temperature range, the maximum range is also limited by the diameter of the thermocouple wire. That is, a very thin thermocouple may not reach the full temperature range. TTL Maximum EMF (mV) IEC 584-33 PC Re ec ar Ue Cae PR IEC eat Temp Temp Thermocouple Intrinsically Code +Lead - Lead heheh Pr CUTS are Reducing, Vacuum, CONSTANTAN | _ Inert. Limited Use x BS Fe COPPER- in —_ atHigh |-210 to 120°C} -8.095 to yd : emperatures. = 193°F| 69.553 } (magnetic) pity Not Recommended for alias ut Low Temperatures. Clean Oxidizing and Inert. +] NICKEL NICKEL- | Limited Use in Vacuum Cy -| CHROMIUM ALUMINUM or Reducing. Wide |-270to 1372°C} -6.458 to A Ni-Cr Ni-Al Temperature | -454 10 2501°F| 54.886 (magnetic) Range, Most Popular Calibration Accuracies * It is important to remember that both accuracy and range depend on such things as the thermocouple alloys, the temperature being measured, the construction of the sensor, the material of the sheath, the media being measured, the state of the media (liquid, solid, or gas) and the diameter of either the thermocouple wire (if it is exposed) or the sheath diameter (if the thermocouple wire is not exposed but is sheathed). Maximum EMF (mV) IEC 584-3 Alloy Combination men's, TT TC = Grade OverTousMax Color Coding Uae; Pee i) PR) am is 11 Ser: - Lead Range Ee ET Reducing, Vacuum, Or IRON CONSTANTAN | _ Inert. Limited Use CL Fe COPPER: | inOuidungatiion emperatures. |-210%0 sek 1200], 2193°F| -8095%0 69.553 YY» y. LEE A J > ‘ 4 (magnetic) yi Not Recommended for on ce) YY Low Temperatures. Clean Oxidizing and Inert. NICKEL- NICKEL- Limited Use in Vacuum CHROMIUM ALUMINUM or Reducing. Wide |-270 to 1372°C| -6.458 to £8 0 Weal Temperature | -45410 2501°F| 54.886 i Bg Ni-Gr (magnetic) Range, Most Popular Calibration 17 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... Pressure Transducer What is a pressure transducer? ¢ A pressure transducer, often called a pressure transmitter, is a transducer that converts pressure into an electrical signal. * This electrical signal (digital or analog) will increase or decrease proportionally to the pressure change. * The electrical signal is used by other devices such as controllers, alarms, and other closed- loop systems. 18 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... What is a pressure transducer? ¢ The electrical signal increasing and decreasing proportionally to the pressure change. Pressure Transducer Source SET The transducer electrical signal ¢ The most common conversion of pressure into an electrical signal is achieved by the physical deformation of strain gauges, which are bonded into the diaphragm of the pressure transducer and wired into a Wheatstone bridge configuration. ¢ The strain pattern is flexible ¢ With tension, the area narrows and resistance increases. ¢ With compression, the area thickens and resistance decreases. 19 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... The transducer electrical signal ¢ Pressure applied to the pressure transducer produces a deflection of the diaphragm which introduces strain to the gauges. ¢ The strain will produce an electrical resistance change proportional to the pressure. Different transducer outputs ¢ Pressure transducers are generally available with three types of electrical output: ¢ Millivolt output * 0-10 Voltage output * 4-20 mA output 20 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... Millivolt output * mV output transducers are economical, but because of their low output signal they should not be located in electronically “noisy” areas and require a regulated power supply for their input power. * The distances between the transducer and the readout instrument should also be kept relatively short. Voltage output ¢ Voltage output transducers include integral signal conditioning and have much higher output levels and can be used with unregulated power supplies. * They are less susceptible to electrical noise and can be used in much more industrial environments. 21 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... 4-20 mA output ¢ 4-20 mA output transducers are less affected by electrical noise and resistance in signal wires, making them the best (and most common) choice, especially for long distance transmission. Mass Flow Meters 22 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... What is a mass flow meter 2. “ce ePleri) ° Conventional flow meters (orifice plates, a venturis, vortex, turbine meters, etc) are volumetric measuring devices, and they a @ require pressure and temperature - transmitters to compensate for density changes within a combustion process. * These conventional flow measurements are not very accurate, because the relationship between process pressure or temperature and density are not always precisely known. ¢ Thermal mass flow meters can measure flow more accurately than the conventional flow meters Honeywell Maxon's SMARTLINK® Thermal Mass Flow Meter What is a mass flow meter ¢ The thermal mass flow meter measures gas mass flow directly, with no need for additional hardware. * The meter uses a constant temperature TEMPERATURE SENSOR differential technique with two matched, (Reference Sensor) platinum RTDs in a rugged, stainless probe assembly. FLOW SENSOR (Self Heated) 23 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... What is a mass flow meter * One RTD measures fluid temperature; an intelligent bridge circuit heats the second RTD element, maintaining a constant temperature differential above the temperature of the process fluid. TEMPERATURE SENSOR ¢ Based on the amount of power delivered to (Reference Sensor) the heated element, the on-board microprocessor establishes a precise mass FLOW SENSOR flow rate. (Self Heated) * The highly integrated sensor probe and electronic design permits fully automated factory calibration, providing every manufactured unit with out-of-the-box measurement accuracy. * The efficiency of any combustion source can be optimized by operating at the most efficient air-to-fuel ratio and the thermal mass flow meter is a highly accurate and repeatable mass flowmeter for monitoring fuel and air * Thermal mass flow meters can measure natural gas (or propane) fuel and combustion air flow rates simultaneously, and this data can then support a combustion control system in optimizing the efficiency of a boiler, heater, oven, or other combustion sources. 24 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... O, Sensors Typical O, setup ¢ A good burner setup is typically adjusted to «-2oma Fring Rate Convo about 3% excess oxygen, which is about 15% excess air. FGR rr I" * This is because there are many ambient and atmospheric conditions that can affect oxygen/air supply. * For example, colder air is denser and contains more oxygen than warm air; wind speed affects every chimney/flue/stack differently; and barometric pressure further affects draft. * Therefore, an excess oxygen/air setting at the time of tuning assumes there will still be enough oxygen available for complete combustion when conditions worsen. 25 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... Using an automatic O, trim system eal) ¢ Although it may be possible to manually monitor and adjust the burner on a daily basis, it is not practical. * Automatic O, systems continuously monitor the flue gases and adjust the burner air supply. * They are generically called ‘O, Trim Systems’. Using an automatic O, trim system ¢ PLC-based control system designed to maintain the proper fuel-to-air ratio of a boiler/burner, the system will automatically compensate for changes in temperature, barometric pressure, or fuel characteristics, as well as correcting for normal hysteresis. 26 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... Using an automatic O, trim system * The system can be used with single-point 4-20mA Firing Rate Contro positioning, or jackshaft-type, combustion controls or with parallel positioning or I" alternate fuel firing. S55 Parallel positioning system * Acomplete system includes: * oxygen and firing rate sensors.* control panel, which houses the PLC * an actuator or variable speed drive (VSD) system, which trims either the fuel or airflow. 27 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... O, sensor and biomass systems * In order to reduce emissions, modern biomass boilers or gas burners have been designed to carefully control the amount of solid fuel they burn. * The O, sensor is a critical component in this process, its goal is to work together with the boiler’s auger, inlet and exhaust air fan and electronic control unit (ECU) to achieve the lowest possible output of environmentally harmful exhaust gas emissions and biomass fuel consumption, whatever the fuel quality. O, sensor and biomass systems ¢ In gas appliances it allows an optimum Steel core wire (AWG19) oe combustion. Rubber bushing * The O, Sensor does this by monitoring the Porous PTFE filter (grommet) percentage of unburned oxygen present in the burner’s exhaust gases. _— Stainless steel housing ¢ This data is fed to the boiler’s ECU, which adjusts the A/F (air/solid fuel) mixture. __- M18x1.5 Hex thread Zirconia sensor element with a built-in heater * The correct air/solid fuel mixture enables the burner to run efficiently, reducing solid fuel Element double protection cover consumption and CO,, NO,, HC emission. 28 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... Servo Motors What is a servo motor? ¢ Aservomotor is a rotary actuator or linear actuator that allows for precise control of angular or linear position, velocity and acceleration. ®\ Where do you think this might be useful? ¢ It consists of a suitable motor coupled toa sensor for position feedback. ¢ It also requires a relatively sophisticated controller, often a dedicated module designed specifically for use with Siemens servo motor servomotors. 29 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... Why use a servo motor? ¢ Aservo motor can be used to replace the single point positioning system that uses one modulating motor to operate/position air dampers and fuel valves ¢ In this case, the servo motors are used ina parallel positioning system, which gives better control and more consistent/accurate positioning. ¢ The parallel positioning system, referred to as a Fuel Air Ratio Control (FARC) system, drives combustion air dampers, gas valves, FGR dampers, etc. independently of each other. 30 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... FARC system * The FARC system allows for precise adjustments of these components for best burner efficiency. 4-20mA Firing Rate Control Limits & Operating Control | FGR Examples of servo motors Burner air damper Flue gas recirculation dampers Dning - Boiling Point 31 of 32 2025-01-29, 8:20 p.m. Firefox https://learn.bcit.ca/content/enforced/1108254-908 16.2025 10/Control... Examples of servo motors Air damper control Gas valve control 32 of 32 2025-01-29, 8:20 p.m.