Application of the hottest intelligent instrument

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Application of intelligent instruments in production measurement

Abstract: This paper introduces the principle, characteristics and performance of intelligent instruments such as intelligent transmitter and mass flowmeter, as well as their practical application combined with DCS in factory production and energy measurement

keyword: decentralized control system; Hart manual operator; The first polyester plant of Coriolis Chemical Fiber Co., Ltd. mainly produces polyester chips and polyester fibers, and DCS is used in the production unit. Because the production capacity of capacity expansion and transformation has been greatly improved, in order to ensure the stability of the production process, the control system has been technically transformed, and the key measurement and control points of production and energy measurement and statistics instruments have also been updated. The combination of intelligent instruments and DCS is used for production control, management, measurement statistics and various data report printing. The following mainly focuses on flow instruments, and discusses the examples of the combination of intelligent instruments and DCS in energy measurement and statistics, production process measurement and control

1 application of intelligent instruments in energy measurement and statistics

the gateway meter of the plant is an instrument that counts the instantaneous amount and cumulative total flow of medium and low-pressure steam, nitrogen, compressed air and other energy media entering the plant, and is an important basis for plant energy accounting. The gateway meter originally used 1151 differential pressure transmitter for flow measurement. Due to large pressure fluctuations, high humidity, large changes in ambient temperature and other factors, the commissioning rate is low, which can not guarantee the long-term stable provision of accurate data, resulting in the problem that the planned accounting often exceeds the standard. In view of this phenomenon, a transformation scheme combining intelligent 1151 and DCS is proposed. After investigation, four 1151alphaline and one 3051C smart transmitter from Rosemount were finally selected (3051C transmitter is used for the flow measurement of 3.5Mpa steam)

1.1 working principle and characteristics of smart transmitter

1) 1151alphaline smart transmitter is the same as ordinary type δ Room sensor, and code s intelligent circuit board. The conversion circuit board adopts special integrated circuit and surface packaging technology to receive the digital signal of the sensor and carry out correction and linearization processing. The configuration data is stored in the nonvolatile eee-rom memory on the transmitter circuit board. Even if the transmitter is powered off, the data can still be saved. Process variables are saved in the form of digital data, which can be accurately corrected and converted into engineering units

2) 3051C smart transmitter adopts a new coplanar sensing membrane head, which has high flexibility. The sensor is far away from the process flange and moved to the neck of the electronic housing, thus realizing mechanical isolation and thermal isolation. The sensing film head also carries out temperature measurement to compensate for temperature effects. The data and correction coefficient during the factory test are stored in the memory of the sensing film head, which is easy to use. When replacing the circuit board, there is no need to re calibrate or remove the independent prom that stores the correction coefficient. The sensing membrane head inner Xuan circuit board is used to directly convert capacitance signals and temperature signals into digital format signals that can be further processed by the conversion circuit board

1.2 smart transmitter and DCS form a measurement loop

Figure 1 shows a simple schematic diagram of a measurement loop composed of big differences between smart transmitter and DCS companies

originally 1151 was powered by 24VDC from the on-site distribution box, but now it is powered by DCS in the control room. The power supply unit safety barrier is used for power supply isolation. Then these signals form AI fuel efficiency increase by 36%, and sent to DCS for display. DCs also needs to configure the flow accumulation to carry out pressure compensation, so as to complete the real flow display and flow accumulation. The flow field display is changed to CRT display in the central control room

nbsp; The flow equation is as follows

2 application of mass flowmeter in flow control

five kettles are used in polyester production in this plant. With the further improvement of domestic scientific and technological strength, the continuous reaction production process is adopted. The output. China's broad market demand for polyurethane insulation materials has attracted great attention from foreign manufacturers, which responds to the harsh production conditions. 10fq-0034 flowmeter is used to measure the flow of ethylene glycol from 10v-04 (eg feeding tank) to 10v-01 (slurry mixing tank) of raw material preparation for polyester production. It is one of the main control points. Whether it can operate normally and stably directly affects the esterification rate of polyester, and then affects the quality of products. In order to produce stably for a long time, the flow of 10v-04 to 10v-01 is normal and stable. According to the requirements of polyester production process, the eg flow transmitter ft-0034 in key parts requires high measurement accuracy, can truly reflect the measured value, accurately alarm, low failure rate and convenient maintenance. After investigation, the mass flowmeter produced by e+h company is finally selected. The process flow diagram is shown in Figure 2

2.1 composition of the control system

the process requires that EG is the main material and PTA is the slave material, and the molar ratio of PTA to eg is unchanged. In order to meet the above requirements, the eg flow measurement is required to be very accurate, and the mass flowmeter is selected. A double closed-loop variable ratio regulation system composed of wfqrc-0039, fqrc-0034 and dr-0047 is designed, and its block diagram is shown in Figure 3. SP is the given value of EG flow constant value regulation system. The flow regulator fc-0034 controls the opening of control valve fv-0034 according to the difference between SP and eg actual flow value measured by flow transmitter ft0034, so as to regulate eg flow. The measured signal of EG flow is used as the given value of PTA feeding regulation system after the ratio calculation of comparator wf-0039. The ratio coefficient in the comparator is adjusted according to whether the slurry density measured by densimeter dt-0047 deviates from the normal value. Thus, the given value of wc-0039 is changed to return the slurry density value to the normal value. The whole system control part is realized by DCs, and the details will not be detailed. The measurement part consists of PTA, wt-0039, eg flow transmitter ft-0034 and y-ray densitometer dt-0047

2.2 working principle of mass flowmeter

mass flowmeter works according to Newton's second law and Coriolis force

e+h mass flowmeter is different from general mass flowmeter in that

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