I. Introduction
XTRM series remote temperature monitor was first applied to cement production monitoring system. In the early 1990s, Shanghai United Cement Plant's technical upgrading project used the Spanish government's mixed loan to import the key equipment of the main production system from the Danish Smith Company, and built a kiln decomposition production line with a daily output of 2,000 tons of clinker. The plant uses ABB's ASEA MASTER distributed control system for production management and control. The operating information of domestic equipment is also required to be centralized and monitored by the system. However, the instrument at the time and the computer system are difficult to match. Therefore, new products must be developed for Shanghai Industrial Automation. The related personnel of the Instrument Research Institute, Shanghai United Cement Plant, and Nanjing Cement Industry Design Institute jointly proposed the relevant requirements by jointly investigating the signals of field instruments, computer interfaces, and domestic equipment introduced by the plant. Shanghai Institute of Industrial Automation Instrumentation specially established the XTRM instrument project team led by the senior engineer of the display room, Jin Jianmin. After hard work, the company completed the development of XTRM series multi-loop temperature remote transmission monitor and successfully signaled the domestic equipment. The matching of the control system improved the centralized control of the entire plant and achieved very good practical results. This new product is particularly suitable for the monitoring of the cement production process. Therefore, the product has been widely used in the design and production of large-scale and medium-scale dry cement plants throughout the country.
The output signal of the XTRM instrument is directly input into the analog input interface of the computer system, monitored in the central control room, and displayed on the instrument panel at the same time. The analog pointer instrument or the LED digital display meter is used for display.
According to the needs of users, indicator instruments, recording meters, regulators, etc. can be connected in series with the power supply in the output circuit of the XTRM meter. The output current is proportional to the temperature change and used as a temperature indication, recording or adjustment. The user can also refer to the temperature of the corresponding circuit one by one through the membrane selection button installed on the panel.
Second, XTRM series of multi-loop remote temperature monitor working principle
XTRM instrument is a two-wire multi-loop temperature transmitter. It is used with multi-point thermal resistance or thermocouple sensors to display and transfer the temperature of solids, liquids, and gases in various production processes. (The functional block diagram is shown in Fig.1.) The XTRM instrument is installed near the object to be measured, and the temperature measurement signal of each loop's thermal resistance or thermocouple sensor is connected to the independent preamplifier of the instrument by a shielded cable. The preamplifier will Weakly change the signal amplification and send it to the comparator input circuit (select high temperature signal) or select the input circuit for signal selection. The selected loop signal is processed by a voltage/current conversion unit to convert the output voltage of the preamplifier into a DC 4-20 mA current signal output. If you select the temperature range 0 ~ 150 °C, it corresponds to DC 4 ~ 20mA output.
Figure 1
Third, examples of XTRM instrument application in cement production monitoring
(I) XTRM instrument for temperature measurement of coal dust collectors and large pulverized coal tanks
Let us first discuss some design conditions of the field instrument in the cement plant, such as coal dust collectors, and coal deposits at the bottom of the dust collector, as shown in Figure 2(a). The large pulverized coal silo for kiln head and calciner for pulverized coal is shown in Fig. 2(b). In order to prevent pulverized coal from spontaneous combustion, explosion-proof and ensure the safety of equipment, such equipment must be equipped with multiple temperature monitoring. There is a temperature display on site, and the patrolling personnel can understand the internal conditions of the equipment; the central control room displays and high temperature alarms, which are managed as important parameters. Coal mill electric dust collector, large-scale pulverized coal bunker the most common three kinds of field instrument design plan, as shown in Figure III.
Figure II
Figure 3
Solution one: As shown in Figure 3 (a), each thermal resistance sensor is equipped with a two-wire temperature transmitter, which is respectively led to the computer's standard analog interface with a two-core shielded cable and monitored in the central control room.
Scheme 2: As shown in Figure 3 (b), each thermal resistance sensor is respectively led to a computer thermal resistance interface with a three-core shielded cable and monitored in the central control room.
Solution 3: As shown in Fig. 3(c), four thermal resistance sensors are connected to the XTRM instrument in the field, and a two-core shielded cable is used to lead to the computer's standard analog interface and monitored in the central control room.
1. The common features of the first two programs are that each temperature measurement point forms an independent circuit and is displayed on the screen of the central control room. This brings about more cables and more interfaces, and there is no temperature display on the site. Job tips.
2. The maximum number of transmitters in the first site of the program increases installation and routine maintenance.
3. The second scheme saves the transmitter, but since the coal dust collector and the coal ash bin are often far away from the workshop control station, the signal of the thermal resistance is very weak, and the long-distance information transmission is not very reasonable. The more important is the applied computer interface circuit, which is not the general 4-20mA DC standard analog interface circuit for general pressure transmitter and temperature transmitter current transmission, and is a dedicated thermal resistance interface circuit, which is expensive and poor in versatility. Using it, it makes the hardware and software of the computer system complicated, and brings more work to the system installation, debugging and maintenance.
4. Compare three options. The third option is the simplest. With an XTRM-4 instrument, not only can the temperature of the four RTD sensors be displayed in the field, but also passed to the highest temperature point of the four signals monitored in the central control room, which is unique to the XTRM instrument. Because the operator does not need to know the temperature distribution in the coal dust collector or coal ash bin, but must know the maximum temperature in the equipment? Do you exceed the critical temperature? Such as the pulverized coal bunker, no matter what the temperature is greater than 70 °C, should be high temperature alarm, the temperature is greater than 80 °C, not only the alarm but also interlocking, to ensure safety, sent to the scene after the alarm, can also query the temperature of each point, Judging the accident situation. Therefore, a high temperature alarm signal can be set in the central control room of the same device. Obviously, this scheme is the most provincial meter, provincial cable, and provincial computer interface design. This design scheme has been widely adopted in the design of large and medium-sized cement plants at home and abroad.
Based on the above comparison, it can be concluded that if the same device needs to set up multi-point temperature monitoring (such as 2 to 4 points) and uses the same temperature measurement element (such as platinum resistance), the same measurement range (such as 0 to 150 °C), the use of XTRM instrument design is the most reasonable program, and it is the most provincial investment program.
(b) XTRM instrument for measuring various bearing temperatures
1. A cement factory often has many large-scale motors, such as 2440KW motor for raw material grinding, 2800KW motor for cement grinding, etc. There are many large-sized fans, such as raw material grinding circulating fans, kiln exhaust fans, and kiln cooling fans. Workers are most concerned about their bearing temperature, and they hope to have a display beside the machine and the central control room can monitor it. XTRM-2 type instruments are generally used for such equipment.
2. Measurement of the bearing temperature of a large mill. Such as raw material mill, cement mill, coal mill, mill feed inlet, discharge port bearings are generally configured with two thermal resistance sensor temperature measurement, the general choice of XTRM-2 type instrument.
3, roller press bearing temperature measurement. Such as cement grinding roller press, per hour through 145 tons of material, the bearing is equipped with four platinum resistance sensors, should use XTRM-4 type instrument, when the bearing temperature T> 47 °C alarm in the central control room, when T> 50 Alarms are interlocked at °C to ensure equipment safety.
4, rotary kiln Roller Bearing temperature measurement. Φ3.75 × 57M rotary kiln, there are three sets of supporting wheels, each set of supporting wheel is equipped with four platinum resistance sensors, XTRM-4 type instrument monitoring should be selected.
(C) XTRM meters are used to measure the winding temperature of high voltage motors.
There are many large-scale high-voltage winding motors in cement plants, such as the above-mentioned mills and fans. In the manufacture of motors, there are stator temperature measuring elements (two per phase), which must be monitored when the motor is running, when the winding temperature is greater than 120 Alarm at °C. XTRM meters are also used for many temperature measurements such as flue gates, gearboxes, etc., which are not listed here.
Fourth, the main features of XTRM instrument
1. The XTRM meter has the characteristics of multiple input, one-way high-selection output. It can measure multiple temperature points at the same time, and automatically display the value of the highest temperature point among multiple measured points to 4~20mA. The standard current signal output. At the same time it has a selection button, the user can use the loop button to view the temperature of the corresponding temperature measurement point when needed.
2. The key components of the XTRM instrument are imported from abroad. The design of the whole machine is reasonable and has high stability and reliability. (The long-term use of the technical upgrading project of the Shanghai United Cement Plant for more than ten years has not been damaged so far.) Instrument sealing performance Well, it is suitable for high-temperature and multi-powder cement plant environment.
3, a wide range of operating voltage. Because the XTRM instrument has a special power supply unit inside, it can self-adjust in the range of 13 to 36 volts of the external power supply to ensure that the instrument can work normally under the harsh industrial and mining power supply conditions.
4, has a good anti-radio frequency interference performance. In the XTRM instrument design, a number of anti-radio frequency interference technologies were adopted. According to the test and test of the Shanghai instrumentation automation system, the test of GB18268-2000 "Electromagnetic Compatibility Requirements for Electrical Equipment for Measurement, Control, and Laboratory Use" was conducted at 10V/m ( Its variation range is less than 0.3% under the field strength of 80 MHz to 1000 MHz. Therefore, it can effectively suppress radio frequency interference such as walkie-talkies from the scene.
V. Conclusion
XTRM instrument is a novel instrument, energy-saving instrument, instrument worthy of promotion. Although widely used in the production of cement plants, there are very few in the field of metallurgy, chemical industry, electric power and other industries. Therefore, this article is written to show technical exchanges, and to promote and improve in the application.
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