Thermal Instrumentation Question Bank

Thread Content

Thermal Instrumentation Question Bank (Short Answer Questions 1) m~ctcb Chat 1. What are the functions of inductors and capacitors in a direct current circuit? An inductor acts like a resistor, while a capacitor functions as a DC blocker. >T Instrument indication error = (Indicated value) – (Calibrated value) ； Relative error of the instrument reading = (Error in instrument reading) / (Indicated value) ； Instrument reference error = (Instrument reading error) / (Instrument full-scale value) ； In the various scales of the instrument, the numerator of the percentage representing the largest absolute value of the reference error is the instrument’s accuracy class. t= 7. What are the components of thermal measuring instruments? What is the function of each part? 3 Thermal measuring instruments consist of a sensing element, an intermediate element, and a display element. The sensor is in direct contact with the object being measured, detects changes in the parameters of that object, and converts the signals related to these parameters into signals that are suitable for measurement and display. The middleware transmits the signals output by the sensing element directly to the display element, or amplifies and converts them into signals suitable for the display element. The display element reflects to the observer the value and changes of the parameter being measured. G8, what is the triple point? What is the triple point of water? The Gn~ triple point refers to the temperature and pressure at which three phases of a pure substance coexist in equilibrium. The triple point of water refers to the condition where water, ice, and vapor coexist in equilibrium, at a temperature of 273.16 K (0.01°C) and a pressure of 609.14 Pa. _-@ 9. In the thermal control measurement system diagram, what source measurement points do the following symbols represent? (1) PE; (2) FE; (3) LE; (4) TE; (5) AEW (1) Pressure ； (2) Flow rate ； (3) Liquid level ； (4) Temperature ； (5) Analysis. 10. What functions do the following terms represent in the thermal control diagram? (1) TIT; (2) PDIT; (3) FIC; (4) LIA.q?}k (1) Temperature indication transmitter ； (2) Differential pressure indication transmitter ； (3) Flow indication adjustment ； (4) Level indication alarm. +8 11. What are the components of a self-oscillating oscillator? What conditions must be met for self-oscillation to occur? ),oJ]m A self-oscillating oscillator consists of a basic amplifier, a positive feedback circuit, and a power supply. The conditions for self-oscillation consist of two parts, one of which is the phase condition. The feedback voltage is in the same phase as the input voltage; that is, the total phase shift generated by the amplifier and the feedback circuit is φ=2nπ (where n=0, 1, 2……). Second, to maintain a constant output amplitude of the oscillator, the amplitude of the feedback voltage must be equal to that of the original input voltage, meaning AF=1 (the product of the amplifier’s gain and the coefficients of the feedback network equals 1). &What components does a c 12 sine wave oscillator consist of? Why is a frequency selection network needed? Q A sine wave oscillator consists of three components: a basic amplification circuit, a feedback circuit, and a frequency selection network; in such circuits, the frequency selection network and the feedback network are often the same network. Since a frequency-selective network typically uses an LC parallel circuit, it presents the highest impedance for signals at f=f0, resulting in the highest output voltage at its terminals; this gives the amplifier the ability to select a specific frequency. Without such a frequency-selective network, the output voltage would consist of various harmonics, and it would not be possible to obtain a sine wave of a single frequency. Therefore, a frequency-selective network is essential. anHOP© Happy Forum -- New Air Happy Forum 13: Briefly explain the reasons for errors? The causes of measurement errors include: a) errors arising from the measurement method; b) errors caused by the measuring tools and instruments; c) errors resulting from changes in environmental conditions; d) errors due to the skill level and observation ability of the person performing the measurement; e) errors caused by changes in the object being measured. What is a programmable controller, and what are its main components? A programmable controller is a digital control device based on a microprocessor, and it generally consists of the following components: a central processing unit, memory and expansion boards, I/O interfaces, communication interfaces, expansion interfaces, and a programmer. O 16: Briefly describe the function of a computer’s arithmetic unit and its components? The arithmetic unit is the component that performs arithmetic and logical operations; it is a key part of the central processing unit, and typically consists of an accumulator along with some special registers for storing operands or the results of operations. ' 17. Explain what the instruction list programming notation of a programmable controller is The functions of the following instructions are also explained: LD, AND-NOT, OUT, OR-LD. The -7Ol instruction uses the English abbreviations of the function names as mnemonics to represent the operation commands for various PLC functions; a set of instructions that together can carry out control tasks constitutes an instruction list. A LD: Command for connecting the normally open contact to a wire; command 7_vG AND-NOT; command for the normally closed contact #8'9; command for coil output (h OR-LD); command for parallel connection of program blocks; What are the common calibration methods for Bourdon tube pressure gauges? aAJ4; What are the secondary instruments for temperature measurement using Nk 19 in combination with thermal resistors, and what are the two methods available for comparison: the standard table method and the standard weight method? For two-instrument systems that use n*yvUV in combination with thermal resistors to measure temperature, the available instruments include moving-coil thermometers, ratio thermometers, and automatically balanced bridge thermometers such as the S7R!B. What are the common components used for temperature measurement? There are: thermal resistors, thermocouples, bimetallic thermometers, and expansion thermometers. ~ 21. Briefly describe the structure of a thermal resistor? The structure of a thermal resistor generally consists of a resistive element, a insulating sleeve frame, insulation material, internal leads, a protective tube, and a terminal block (or terminals, junction box), etc. !\ 22. Briefly describe the working principle of a Bourdon tube pressure gauge. #The working principle of the Bourdon tube pressure gauge is as follows: under the action of pressure, the free end of the Bourdon tube moves, and this movement drives the amplification mechanism through a pull rod, causing the pointer to deflect and indicating the measured pressure on the dial. Happy Forum -- New Air Happy Forum 1MmT So, 23. What are the common types of tachometers used in thermal power plants? Commonly used tachometers in thermal power plants include centrifugal tachometers, magnetoelectric tachometers (with a tachogenerator), and electronic counting tachometers. 22Dk 24. Briefly explain the principle of temperature measurement using thermocouples. 3106. Briefly describe the zero-point calibration of industrial mercury thermometers? %`x (1) Obtaining the freezing point: Crush frozen water ice or tap water into flake form, place it in a freezing point cell, add an appropriate amount of distilled water or tap water, then stir and press with a clean glass to darken the surface of the ice. Calibrate using second-class standard mercury, and use it after it has stabilized. (2) During zero calibration, the thermometer must be inserted vertically into the freezing point bath, with a distance of no less than 20 mm from the wall of the bath; readings can be taken only after the indicated value stabilizes. ) 3107: What preparations should be made before putting a pressure gauge into use? The preparatory work that must be carried out before putting the cS&!?+ pressure gauge into use is as follows: (1) Check that the primary and secondary valves as well as the drain valve are closed, that the joint nuts do not leak, that there is an appropriate amount of packing, and that the operation handwheel along with the fastening screws and washers are all present in good condition ； (2) The pressure gauge and fixing clamps should be secure ； (3) The electric contact pressure gauge should also have its signal device section inspected and adjusted. "What are the external factors that affect thermocouple measurements with LH 3108? What methods can be used to eliminate it? (The external factor affecting thermocouple temperature measurement is the cold junction temperature of the thermocouple. Methods for elimination include: constant temperature method, compensation wire method, compensation bridge method, compensation thermocouple method, potential compensation method, and mechanical zero adjustment for high-speed moving-coil instruments. zz 3109: How to conduct on-site inspections of thermal control circuits? All the wiring in the WV7QT control circuit must be inspected to verify that it meets the requirements specified in the drawings, that there are no misconnections, that the insulation between the wires and against ground meets the specified standards, and that the wire connections are in good contact. CSN\ 3110: What are the reasons for needle sticking or jumping in diaphragm pressure gauges? In the transmission mechanism of a diaphragm pressure gauge, rust, wear on the teeth, or the presence of burrs and dirt between the teeth can all cause problems such as the pointer getting stuck or jumping. l{J 3111: How to set the operating value of a pressure switch? When setting the operating value for the pressure-dependent shutdown of RvPpy2, it is appropriate to first use the adjustment screw of the return spring to set the return value of the switch, and then use the adjustment screw of the differential spring to set the operating value of the switch. A 3112: Brief description of the laboratory calibration of the YX—150 model, with a range of 0~1.6 Mpa, 1. Standard instruments and equipment used for 5-grade electric contact pressure gauges. ba:\0 The required standards are as follows: (1) Range of 0~2. 5Mpa, with a precision of 0. 25-grade Bourdon tube standard pressure gauge ； (2) A Class 2 standard piston pressure gauge with a range of 0~6 Mpa. 3113. What are the two adjustment steps for a Bourdon tube pressure gauge? What is the role of each in adjusting these two aspects? The gauge with a spring tube has two adjustment elements; one of them is the adjustable screw on the lever ； Second, the rotating transmission mechanism is used to change the angle between the sector gear and the lever. Adjusting the adjustable screw of the lever allows for different gear ratios, thereby correcting the linear error of the pressure gauge; changing the angle between the sector gear and the lever helps to correct the nonlinear error of the pressure gauge. k, 4114: What issues should be considered when using a piston manometer? hM# (1) The piston and piston cylinder, as well as the load plate and weights, must be used together; they cannot be interchanged with those of other piston pressure gauges ； (2) Corrections to the code knocking must be made based on the local gravity return velocity, for 0. The gravitational acceleration of the 05-grade piston manometer differs from the standard by no more than 0. 005m/s2，0。 The difference at level 2 is not greater than 0. 02 m/s2. This error can be ignored ； (3) The operating temperature for piston pressure gauges is 20 degrees plus or minus 5 degrees, and the viscosity of the pressure-transmitting medium must meet the specified requirements. (4) During measurement, the piston should be rotated continuously at an angular velocity of 30 to 120 revolutions per minute. (5) The pressure transmission medium used shall meet the specified requirements and be filtered. #u 4115: What should be noted when using a precision pressure gauge? (1) The instruments should be properly maintained and kept clean at all times ； (2) When using or handling, avoid severe vibration and impact to prevent damage to the instrument ； (3) When in use, tap the instrument casing gently before taking a reading ； (4) If any doubts arise regarding the instruments, they should be calibrated and repaired ； (5) The operating pressure range of the instrument in normal use should not exceed 70% of the upper measurement limit ； (6) To ensure the accuracy of the instruments, regular inspections and calibrations should be carried out. S: 4116. How to determine the signal error of electric contact pressure gauges? After the electrical contact pressure indication value has passed the calibration, the signal error is checked. The method involves setting the upper and lower limit signal contacts at three or more different calibration points, which should be selected within 20% to 80% of the measurement range. The voltage is increased or decreased gradually until the signal is generated; the error calculated by comparing the actual operating value with the set value should not exceed the allowable error limit of 1%. 5 times. 7n 4117: Briefly describe what aspects are included in the calibration of elastic pressure gauges? How to select the calibration points for elastic pressure gauges? The calibration of uuv pressure gauges includes determining the basic error of the instrument, its hysteresis, zero position, displacement upon tapping, and the stability of pointer deflection (checking for any jumping or sticking issues). The calibration points for elastic pressure gauges should be selected evenly within the measurement range; aside from the zero point, the number of calibration points must be at least 4 for both pressure gauges and vacuum gauges ； For pressure-vacuum (combined) gauges, the pressure scale should have no fewer than 3 divisions, while the vacuum scale should have 1 to 3 divisions. Checkpoints are generally chosen at large-scale marks with numbers. `V2 4118: How to calibrate the XCZ-type dynamic coil meter? kGP#R (1) Check points should be selected at major scale lines and commonly used points, with a minimum of 5 points. (2) Before powering on, adjust the mechanical zero position of the pointer first. (3) After power is applied, a signal is applied to cause the pointer to rise slowly to the end of the scale markings; it remains there for 3 minutes. Then, the signal is reduced to allow the pointer to return slowly to near the starting point of the scale markings. The signal is then disconnected, and the reading is taken after 10 seconds – this value represents the reading when the pointer does not return to the mechanical zero position. The pointer should move smoothly, without any sticking, shaking, or lagging ； (4) When performing upward or downward verification, the pointer should be moved slowly toward the verification point, without going past it and then returning ； (5) When the pointer reaches the center of the scale line being calibrated, read the value indicated by the standard potentiometer. J 4119: What are the procedures for putting steam and water pressure gauges into use? vXFW (1) Open a valve once to fill the conduit with the medium ； (2) When the secondary valve is a tee valve, slowly turn open the drain handwheel; after flushing it clean with the medium to be tested, close the drain handwheel ； (3) Slowly open the secondary valve and install the instrument ； (4) After a pressure gauge for measuring steam or liquid is installed, if the pointer indicates unstably or fluctuates, it is generally due to air in the pressure guide tube. Those equipped with a release valve should be vented ； For those without a vent valve, the secondary valve can be closed, the instrument connection can be slightly loosened, and then the secondary valve can be opened slightly to release the air inside the pipe. After liquid begins to flow from the connector, close the secondary valve tightly, tighten the connector, and resume using the instrument ； (5) After the wind pressure gauges with multiple measurement points are installed, check each point to ensure that the readings are normal ； (6) After the vacuum pressure gauge is installed, a tightness test should be conducted. Under normal conditions, when the valve is closed once, the decrease in the indicated value within five minutes should not exceed 30%. 4120. What are the specific methods for handling the temperature at the thermocouple reference terminal? What issues should be considered when using thermocouple compensation wires? ©Happy Forum -- New Air Happy Forum. Specific method: (1) Thermoelectric potential correction method ； (2) Reference terminal constant temperature method ； (3) Reference terminal temperature compensation method. When using compensation wires, the following points must be noted: (1) The compensation wire must be used in conjunction with a thermocouple of the corresponding type ； (2) When connecting the compensation wire to the thermocouple and instruments, the positive and negative poles must not be connected incorrectly, and the two pairs of connection points must be at the same temperature ； (3) The temperature at the connection point between the compensation wire and the thermocouple must not exceed the specified operating temperature range ； (4) The gauge diameter of the compensation wire should be selected according to the specific requirements of the instruments being used. q_ 4121: What are the common faults in temperature measurement using thermistor thermometers? Common faults in the temperature measurement using uI thermistor thermometers include: (1) short circuits or grounding between the resistive wires of the thermistor ； (2) The resistance wire of the thermoresistor is broken ； (3) Water or dirt accumulation inside the protective sleeve, causing local short circuits ； (4) The wire connecting the resistance element to the junction box is broken ； (5) Poor contact of the connecting wires leads to an increased resistance, or there may be local short circuits, etc. L 4122: How to adjust the linear error of a Bourdon tube pressure gauge? "+Q When the indication error of a Bourdon tube pressure gauge increases proportionally with pressure, this error is called linear error. The main cause of the linear error is a change in the gear ratio; by adjusting the position of the adjustment screw to change this gear ratio, the error can be brought within acceptable limits. When the error of the instrument under test is positive and increases gradually as pressure rises, move the adjustment screw to the right to reduce the gear ratio; when the error is negative and increases gradually as pressure rises, move the adjustment screw to the left to increase the gear ratio. 3| 4123. How to adjust the nonlinear error of a Bourdon tube pressure gauge? /In a QKW* pressure gauge, the reading error varies in a non-proportional manner as pressure increases; this type of error is known as nonlinear error. By changing the angle between the tie rod and the sector gear, it is possible to adjust this nonlinear error. By reducing the angle between the pull rod and the sector gear, the pointer moves faster in the first half and slower in the second half. By increasing the angle between the pull rod and the sector gear, the pointer moves more slowly in the first half and faster in the second half; this adjustment of the angle can be made by turning the movement. The specific adjustment for nonlinear errors must be determined based on the nature of the errors. Normally, the nonlinear error of the instrument should be adjusted to a linear error first, and then the linear error should be adjusted. To this end, in general, adjusting the angle between the tie rod and the sector gear is carried out in conjunction with adjusting the position of the adjustment screw. %38j$ 4124. What is the differential value of a pressure switch? How to adjust? The differential value of the P0/MNZ pressure switch is also known as the dead zone of the pressure switch. After the pressure switch operates, the pressure must be reduced slightly below its operating value for the microswitch to return to its normal state. The difference between the operating value and the reset value is known as the differential value of the pressure switch. Install the pressure switch on the testing device. First, turn the differential knob to zero so that the pressure reaches the operating value. Adjust the control rod, and use the resistance setting of a multimeter to monitor the status of the output contacts; stop adjusting when the contacts just close. Then reduce the pressure to the specified dead zone range, adjust the differential knob so that the contacts break apart precisely, and repeat this verification twice until the operation is accurate. DC6 4125: What should be noted when using a tubular high-temperature calibration furnace? +r’Y (1) Before powering on, it is necessary to check that the temperature controller, as well as the heating power supply, voltage stabilizer, voltage regulator, etc., and the wires connecting them to the electric furnace are properly connected. The furnace housing must be grounded, and all the function knobs or buttons on the temperature controller should be in their correct positions ； (2) The heating current and voltage of the resistance furnace must not exceed the rated power of the furnace ； (3) The heating current must not change suddenly during temperature rise and fall, to prevent damage caused by sudden changes in the furnace temperature ； (4) The resistance furnace used for testing precious metal thermocouples cannot be used to test base metal thermocouples. 5126. What causes friction and sticking problems in the transmission mechanism of diaphragm-type air pressure gauges? How to handle it? ScQ (1) Caused by poor cleaning. The removable parts can be immersed in gasoline and cleaned with a brush ； (2) Issues such as an uneven rotating shaft, burrs on the gears or too small a clearance, damaged hairsprings, friction between components, or overly tight connections of moving parts can be addressed according to the actual situation. {/G+ 5127: How to perform balance adjustment on a diaphragm-type air pressure gauge? The method for balancing a zS diaphragm anemometer is as follows: pressurize the anemometer to 1/2 of its full scale, then tilt it 5 degrees to the left and 5 degrees to the right. If the basic error resulting from this imbalance is less than or equal to half of the allowable error, then the wind pressure is balanced. Otherwise, the following adjustments should be made ； When the right side of the instrument is raised, if the pointer deflects upward, it indicates that the side with the pointer is lighter; in this case, the counterweight should be rotated inward. If the pointer deflects downward, it means the side with the pointer is heavier, and the counterweight should be rotated outward. ;What are the technical requirements for wiring inside BH 5128? The basic technical requirements for wiring within the panel are: construction in accordance with the diagrams and correct wiring ； Secure connection with good contact ； The insulation and wires are undamaged ； The wiring is neat, clear, and aesthetically pleasing. ^ 5129. How should the various piping connections in thermal systems be inspected? The main task is to check whether there are any misconnections, blockages, or leaks in the steam, air, and water pipelines. 9/R0 3130: Outlines the principles for selecting the locations of the measurement points from which wind pressure values are obtained. +-" 4147. What are the interlock conditions for the linked control system of the boiler feed and exhaust fans? & The interlock condition is: (1) When one of the operating exhaust fans (or supply fans) stops, its corresponding inlet guide vane should be automatically closed to prevent air short-circuiting. However, when one operating exhaust fan (or supply fan) or two operating exhaust fans (or supply fans) need to be stopped, their inlet guides must not be closed ； (2) Or when the only induced draft fan in operation stops, the supply fan should automatically stop operating as well. ~N 4148: Brief description of the operating procedures for the first commissioning of a double-ripple differential pressure gauge used for measuring steam flow rate. Answer: (1) Check that the sampling device, valve connections, primary and secondary valves, as well as the drain valves are firmly and tightly connected ； (2) Check the primary and secondary valves; the drain valve should be in the closed position, while the balance valve should be in the open position ； (3) Open the valve slightly to check for any leaks in the pressure guide tube, the valve, and the connections; if there are no leaks, open the valve fully ； (4) Open the drain valve to flush the pressure guide pipe, remove any dirt and air accumulated inside it, and then close the drain valve ； (5) The flow meter can be put into use only after the pressure guide tube is filled with condensed water and cooled down ； (6) The sequence of operations is as follows: First, open the secondary valve on the positive pressure side; loosen the steam vent plugs on both the positive and negative pressure sides respectively. Once the condensate has been drained, tighten the plugs again, close the balance valve, and then open the secondary valve on the negative pressure side. \_For Bsv@ 4149 and DKJ electric actuators, they can only operate in one direction; moreover, when the polarity of the input signal changes, the actuator does not move. Analyze the causes of this fault. Wj~ Answer: (1) Check the wiring from the amplifier to the motor; if one of these wires is broken, this phenomenon will occur ； (2) When the polarity of the input signal changes, alternating pulses should appear in the two flip-flops. If there is no pulse on one side, the possible reasons are: 1. The transistor is broken down ； 2. The single-junction transistor BT31F is open-circuited or broken down; in this case, without a pulse the thyristor will not conduct ； (3) If the outputs of the two flip-flops are normal, the thyristor may be damaged ； (4) The servo motor is damaged. How to perform zero point migration for KqCC+ 3150 and 1151 transmitters? The zero-point migration steps for v0 1151 are as follows: (1) First, adjust the range to the desired value before performing the migration ； (2) Perform zero shift using the lower limit value of measurement; enter the pressure corresponding to this lower limit, and adjust it with the zero adjustment potentiometer so that the output is 4 mA ； (3) Recheck at full scale, and make fine adjustments if necessary ； (4) If the migration amount is large, first switch the transmitter’s migration switch (connector) to the positive or negative migration position (determined by the direction of migration), then apply the lower measurement limit pressure, and use the zero adjustment potentiometer to set the output at 4 mA ； (5) Repeat Step 3. 3151. How is the background voltage of a zirconia probe measured? 8) Heat the probe of the 3C device to 700°C and maintain this temperature for half an hour. Introduce fresh air at a flow rate of 15 L/H through both the test gas port of the probe and the reference gas port. Use a digital voltmeter to measure the output potential of the probe; take the reading once it has stabilized – this value represents the probe’s background electromotive force, which should not exceed ±5 mA. What are the structural similarities and differences between Wq.CO 3152, the monopolar, and the series-pole three impulse feedwater control systems? ut Answer: (1) The similarities are that all of them have three signals: steam flow rate, feedwater flow rate, and water level; the feedwater flow rate signal is used to form a feedback loop, the water level signal forms an external loop, and there is also a feedforward path using the steam flow rate signal. (2) The difference is that a cascade system includes an additional regulator: the main regulator controls the outer loop, while the secondary regulator controls the inner loop. n}eM 3153: How to conduct a test on the output current stability of a DTL regulator? ?j Answer: (1) Set the integration time to its maximum value, the differentiation time to its minimum value, and the proportional band to 100% ； (2) By changing the input signal to make the output take any value, the output jitter range should not exceed 0. 05MA。 3154. How are DKJ actuators tested and inspected? ~0@]" Answer: (1) Connect according to Figure C—3 ； &(1) Turn on the power switch “1K”, place the motor’s handle in the manual position, and turn the handwheel to bring the output to the zero position set at the time of manufacture (at the high point of the cam); at this point, the milliammeter should indicate 4 mA ； (3) Rotate the handwheel to cause the output shaft to turn 90 degrees clockwise; the milliammeter reading should change accordingly from 4 to 20 MA. If it is less than (or greater than) 20MA, the position transmitter cover can be opened to adjust the potentiometer; the output current of the angle and position transmitters should correspond one-to-one ； (4) The output shaft of the control button “2K” should rotate clockwise, while the output shaft of the control button “3K” should rotate counterclockwise; at the same time, the output current from the position transmitter should correspond one-to-one with the angle of rotation. /wKF5> 2155. Briefly describe the composition and measurement principle of ultrasonic flowmeters? An ultrasonic flowmeter is mainly composed of a transducer and a converter; a signal cable and junction box connect the transducer and the converter, while clamped transducers require mounting fixtures and coupling agents. An ultrasonic flow meter measures flow rate by utilizing the fact that the speed of sound of ultrasonic waves changes when these waves propagate through a fluid, as this change is influenced by the properties of the fluid. Kt 3156: What is “alarm deadband handling”? L1G “Alarm deadband handling” is one of the functions of the alarm handling mechanism in the structure of computer applications; it allows for the setting of deadbands for various alarm thresholds, thereby preventing frequent alarms from being triggered when parameters fluctuate around those thresholds and enhancing the stability of the signal system’s operation. aLu^ 3157: Discuss the inspection items for standard orifice plates. Inspection of structural and geometric dimensions, inspection of the open area of the orifice plate, inspection of the sharpness of the orifice plate edges, inspection of the parallelism of the orifice plate, inspection of roughness, and inspection of the discharge coefficient and its uncertainty. The verification of the outflow coefficient can be carried out on a water flow calibration device. The basic error of the device should be less than or equal to 1/2 of the uncertainty in the orifice plate discharge coefficient. kbv% 3158: Describe the methods for checking the arc radius RK at the inlet edge of the orifice plate "Answer 4: (1) Reflection light method: Tilte the orifice plate at a 45-degree angle so that sunlight or an artificial light source shines toward the edge of the right-angled inlet ； When it is 25 MM or more, use a 2x magnifying glass; when D is less than 25 MM, use a 4x magnifying glass to check that there is no reflected light on the edges ； (2) Molding method: Use lead foil to mold the inlet edge of the orifice plate ； After making the replica, RK is measured using a tool microscope, and the results shall comply with the specified requirements. @ 3159. When the amount of water used for temperature reduction has been increased to its maximum and the temperature of the superheated steam is still high, what measures can be taken to lower the steam temperature? N*8w Answer: (1) Adjust the boiler combustion to lower the position of the flame center ； (2) Reduce the excess air volume within the allowable range ； (3) Appropriately reduce the boiler’s evaporation rate. _Nw 3160: What pipeline and fluid conditions are required when using a standard throttling device? ,c2 Answer: (1) The fluid must be a Newtonian fluid; it must fill the pipeline and flow in a continuous and stable manner, without any pulsations in the flow rate. (2) The pipe shall have a circular cross-section, and its diameter shall be within the specified range. The fluid does not undergo phase changes within a certain distance before and after the throttling device; water does not evaporate, and the superheated steam remains in a superheated state, with flow occurring in only one direction. The throttling device is installed between two straight pipe sections of equal inner diameter. The straight pipe sections before and after it must have a certain length (as specified in the regulations) to ensure that the flow velocity of the fluid before passing through the throttling device is parallel to the pipeline axis, with no vortices present. @Dc 4161: Briefly describe the method steps for configuring a computer control system. The steps of the J”@ method are as follows: (1) Determine the type of algorithmic function blocks based on the block diagram of the process control system ； (2) Specify input and output signals for the functional block ； (3) Indicate the method of signal processing ； (4) Enter the parameters required for the function block, etc. D)_'6 4162: Briefly describe the selection principles for standard throttling devices. h_ Answer: (1) The requirements for measurement accuracy must be met ； (2) The pressure loss should not exceed the specified requirements ； (3) The straight sections before and after shall meet the specified requirements ； (4) Under the condition of meeting measurement accuracy requirements, choose throttle devices with a simple structure and low cost as much as possible ； (5) The wear and contamination conditions of the fluid at the installation location on the throttling device must be taken into account ； (6) It should be easy to install on-site. zd1 4163: Briefly list the main reasons for errors that occur when using a balanced container to measure the water level in a steam drum :>