Introduction
1. The composition of the course work
2. Choice technical means measurements
3. Explanations for the graphic part
4. Explanations for the calculation part
4.1 Calculation of the narrowing device
4.2 The order of calculation of the throttle device
4.3 Orifice design
4.4 Calculation of the measuring circuit of the automatic potentiometer
4.5 Calculation of the measuring circuit of the automatic bridge
Literature
INTRODUCTION
The decisive role in solving the problems of ensuring production efficiency, reliability and safety of operation of technological equipment belongs to automated process control systems (APCS). The basic system of any modern automated process control system is an automatic control system that allows obtaining measurement information about the regime parameters of technological processes. The issues of organization of measurements, selection of measuring instruments and measured parameters are closely related to the specifics of technological processes and must be resolved at the design stage of the corresponding technological installations, i.e., a heat power engineer participating in the design of a technological installation must have appropriate knowledge of methods for measuring various physical quantities and the skills to use them.
Future specialists studying in the specialty 140104 "Industrial Heat Power Engineering" receive this knowledge when studying the discipline "Heat Engineering Measurements". The course work, provided for by the work program of this discipline, contributes to the consolidation, deepening and generalization of the knowledge gained by students during the training, and the application of this knowledge to the integrated solution of specific engineering problems for the development of schemes for thermal control of heat power plants.
Course work includes the development of a measuring channel for monitoring one of the parameters of a process unit, the choice of measuring instruments, the calculation of a narrowing device or a measuring circuit of a secondary device, depending on the task option.
1. COMPOSITION OF COURSE WORK
Coursework on the design of a measuring channel for monitoring a physical parameter technological process consists of an explanatory note and a graphic part.
Text part ( explanatory note) course work includes the following main sections:
Introduction;
Choice of technical means of measurement;
Calculation of the error of the measuring channel;
Calculation of the narrowing device (measuring circuit of the secondary device);
The graphic part of the work includes:
functional diagram of the developed measuring channel;
drawing of the narrowing device (assembly drawing of the installation of the primary converter on the process equipment).
2. CHOICE OF TECHNICAL INSTRUMENTS OF MEASUREMENT
This part of the explanatory note includes a description of the technological process and the rationale for choosing a method for measuring a given physical parameter. Main design solutions are accepted on the basis of the analysis of the technological process and the current state and industry regulations.
Specific types of measuring instruments are selected taking into account the characteristics of the technological process and its parameters.
First of all, they take into account such factors as fire and explosion hazard, aggressiveness and toxicity of the environment, the range of information signal transmission, the required accuracy and speed. These factors determine the choice of methods for measuring technological parameters, the required functionality of instruments (indication, recording, etc.), measurement ranges, accuracy classes, type remote transmission etc.
Devices and transducers should be selected according to reference literature, based on the following considerations:
To control the same parameters of the technological process, it is necessary to use the same type of measuring instruments, mass-produced;
With a large number of identical parameters, it is recommended to use multi-point devices;
The accuracy class of instruments must comply with technological requirements;
To control technological processes with aggressive media, it is necessary to provide for the installation of special devices, and in the case of using devices in their normal version, they must be protected.
The most common types of industrial secondary devices included in the State system of industrial devices and automation equipment (GSP) are presented in table 1.
Table 1
PV devices are secondary devices of the "Start" pneumatic system and are used to measure any technological parameters previously converted into compressed air pressure (unified pneumatic signal).
KSP automatic potentiometers, KSM balanced bridges, KSU milliammeters are used to measure and record temperature and other parameters, the change of which can be converted into a change in DC voltage, active resistance, DC current.
KSP-4 potentiometers, depending on the modification, can work either in a set with one or more (if the device is multipoint) thermocouples of standard calibrations, or with one or more DC voltage sources.
KSM-4 balanced bridges work with one or more standard calibration resistance thermometers, and KSU-4 milliammeters with one or more DC signal sources.
Secondary KSD devices work together with primary measuring transducers equipped with differential transformer sensors.
Each type of instrument mentioned above is available in various modifications, differing in size, measurement ranges, number of input signals, availability of auxiliary devices, etc.
When choosing one or another device on the basis of functionality, it is necessary to combine the simplicity and cheapness of the equipment with the requirements for monitoring and regulating this parameter. The most important parameters should be controlled by self-recording instruments, which are more complex and expensive than indicating instruments. The adjustable parameters of the technological process must also be controlled by recorders, which is important for adjusting the settings of the regulators.
When choosing secondary devices for joint operation with the same type of sensors of the same calibration and with the same measurement limits, it should be taken into account that KSP, KSM, KSD devices are produced with a number of points of 3,6,12. AT multipoint devices there is a switch that automatically and alternately connects the sensor to the measuring circuit. The printer, located on the carriage, prints points on the chart with serial number sensor.
When choosing the type of unified signal of the communication channel from the sensor to the secondary device, the length of the communication channel is taken into account. With a length of up to 300 m, any unified signal can be used if the automated technological process is not fire and explosion hazardous. In case of fire and explosion hazard and a distance of no more than 300 m, it is advisable to use pneumatic automation equipment, for example, devices of the "Start" system. Electrical measuring instruments are characterized by much less delay and surpass pneumatic instruments in terms of accuracy (accuracy class of most pneumatic instruments is 1.0, electrical - 0.5). The use of electrical means simplifies the introduction of computers.
When choosing sensors and secondary devices for joint operation, attention should be paid to matching the output signal of the sensor and the input signal of the secondary device.
For example, with a current output signal of the sensor, the input signal of the secondary device must also be current, and the type of current and the range of its change for the sensor and the secondary device must be the same. If this condition is not met, then you should use the intermediate converters of one unified signal to another available in the GSP (Table 2).
table 2
The most common intermediate GSP converters
|
Converter type |
Input signal |
Output signal |
|
thermocouple emf |
DC current 0...5 mA |
|
|
Electrical resistance |
DC current 0...5 mA |
|
|
thermocouple emf |
DC current 0...5 mA |
|
|
Electrical resistance |
DC current 0...5 mA |
|
|
DC voltage 0...2 V |
DC current 0...5 mA |
|
|
DC current 0...5 mA |
Compressed air pressure 0.2 ... 1.0 kgf / cm 2 |
The intermediate converter NP-3 is used as a normalizing converter for converting the output signal of a differential transformer converter into a unified current signal.
Converter EPP-63 carry out the transition from the electric branch of the GSP to the pneumatic one.
When choosing sensors and instruments, one should pay attention not only to the accuracy class, but also to the measurement range. It should be remembered that the nominal values of the parameter must be in the last third of the measurement range of the sensor or device. If this condition is not met, the relative measurement error of the parameter will significantly exceed the relative reduced error of the sensor or device. Thus, it is not necessary to select a measurement range with a large margin (it is enough to have an upper measurement limit no more than 25% higher than the nominal value of the parameter).
If the measured medium is chemically active with respect to the material of the sensor or device (for example, a spring pressure gauge, a hydrostatic level gauge, a differential pressure gauge for measuring flow using the variable pressure method), then its protection is carried out using separating vessels or diaphragm seals.
The developed measuring channel is depicted in the figure in the form of a functional diagram, made in accordance with GOST 21.404-85. measurements and appliances. - M.: Energoatomizdat, 1984. - 232 p. ...
Thermotechnical boiler control
Coursework >> Industry, productionThe course project must be completed thermotechnical control of the boiler unit En- ... devices are selected according to the necessary data thermotechnical control. Preliminarily completed... .300 TO 5. Murin R.P. Thermotechnical measurements M., Energy 1979 6. Secondary...
METHODS AND MEANS MEASUREMENTS TEMPERATURES. ADVANTAGES AND DISADVANTAGES OF EACH METHOD. METROLOGICALLY
Coursework >> State and LawV.P. Thermotechnical measurements and appliances. M.: Energy, 1978, - 704 with Chistyakov S. F., Radun D. V. Thermotechnical measurements and appliances. ... M.: graduate School, 1972, - 392 measurements in industry: Ref. ...
Types of thermotechnical quantities. Types of measuring instruments for heat engineering quantities.
Terminology in the field of temperature measurement. Classification of temperature measuring instruments. Types and methods of temperature measurements. Measurement errors. The choice of measuring instruments to ensure the required measurement accuracy.
Ensuring the uniformity of temperature measurements
General concepts verification of temperature measuring instruments: preparation for verification, verification operations and registration of verification results. Requirements for premises for verification of temperature measuring instruments.
Instruments for measuring the physical and chemical composition and properties of substances
Terminology in the field of measuring the physical and chemical composition and properties of substances. Units of measurement. Methods of technical analysis: chemical, physical, physico-chemical, electrochemical, optical. The essence of direct and indirect measurement methods. Classification of instruments and auxiliary equipment for physical and chemical measurements.
Ensuring the uniformity of measurements of the physical and chemical composition and properties of substances
General concepts of verification of measuring instruments of physical and chemical composition and properties of substances: preparation for verification, verification operations and registration of verification results. Requirements for premises for verification of measuring instruments for the physical and chemical composition and properties of substances.
QUESTIONS FOR THE STATE EXAMS ON THE DISCIPLINE "METHODS AND INSTRUMENTS OF MEASUREMENT, TESTING AND CONTROL" FOR THE SPECIALTY 27.03.02 "QUALITY MANAGEMENT"
measurements
The concept of measurement.
Classification of measurements: according to the characteristic of accuracy; by the number of measurements in a series of measurements; in relation to the change in the measured value; by expression of the measurement result; according to the method of obtaining information; depending on the metrological purpose.
The concept of the measurement area. Classification of measurements by areas of measurements.
Measuring instruments: concept and classification
Types of measuring instruments: measures, measuring instruments, measuring transducers, measuring installations, measuring systems, auxiliary measuring instruments.
Classification of measures: unambiguous, multivalued, set of measures. Classification of measuring instruments by device: comparating, indicating, self-recording, integrating. Classification of measuring transducers: primary, intermediate, transmitting, scale. Classification of measuring instruments according to their purpose: initial working standards, working standards, working measuring instruments.
Error and accuracy of measuring instruments. Metrological characteristics of measuring instruments
Errors of measuring instruments: basic and additional, statistical and dynamic. Ways of expressing the limits of permissible errors. Classes of accuracy of measuring instruments and categories of working standards.
Metrological characteristics of measuring instruments: concept and types; standardization of metrological characteristics.
Tests
The concept of testing. Test classification. Test tools. Metrological assurance of the testing process.
Control
The concept of control. Classification of control. Means of control. Metrological support of the control process.
Measurement principles. Techniques (methods) of measurements
Measurement principles: concept and classification.
Measurement methods: concept and classification.
The concept of measurement methods, structure, regulatory support. Purpose, methods, procedure and content of metrological certification of measurement procedures.
Measuring instruments for geometric quantities
Terminology in the field of measurements of geometric quantities. Classification of measuring instruments for geometric quantities. Types and methods of measurement of geometric quantities. Measurement errors. The choice of measuring instruments to ensure the required measurement accuracy.
Ensuring the uniformity of measurements of geometric quantities
General concepts of verification of measuring instruments of geometrical quantities: preparation for verification, verification operations and registration of verification results. Requirements for premises for verification of measuring instruments for geometric quantities.
Measurement was the first control function to be automated. A measuring device with an indicator replaces the human senses, provides fast and fairly accurate measurements. If necessary, a recording device (RP) can be connected to it, which records the dynamics of changes in technological parameters (Fig. 1.1). This data can be used to analyze the flow of the technological process (TP), and the diagram recorded by the registrar serves as a reporting document. The functions of the operator (O) with automatic indication are reduced to determining the control error, as well as the implementation of the regulatory action.
Small technical improvements have made it possible to move from automatic indication to automatic control. In this case, the operator receives information about the deviation of technological parameters from the specified values. The automatic control system, in addition to the meter and indicator, contains a comparison device (US) and a master (ZD) - a device that remembers the value of a process parameter. The division of functions between the operator and the control system is shown in fig. 1.2. Thus, the task control(from French contr?le- checking something) is the detection of events that determine
Rice. 1.1.
automatic indication automatic control
course of a process. In the case when these events are detected without the direct participation of a person, such control is called automatic.
the most important integral part control is the measurement of physical quantities characterizing the course of the process. Such quantities are called process parameters. Technological processes in engineering systems are characterized by the values of such physical quantities (parameters) as humidity, pressure, temperature, level, flow rate and quantity of liquid and gaseous media.
by measurement called finding the value of a physical quantity empirically with the help of special technical means. ultimate goal any measurement is to obtain quantitative information about the measured value. In the process of measurement, it is established how many times the measured physical quantity is greater or less than a qualitatively homogeneous physical quantity, taken as a unit.
If a 0 - a measured physical quantity, - a certain size of a physical quantity taken as a unit of measurement, c- numerical value (7 in the accepted unit of measurement, then the measurement result (7) can be represented by the following equality:
( 1. 1)
Equation (1.1) is called the basic measurement equation. It follows from this that the value c depends on the size of the selected unit of measure }
