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The best solution to the AUTOMATIC CONTROL SYSTEM OF CLEAN AIR-CONDITIONING UNIT in clean workshop

The best solution for the AUTOMATIC CONTROL SYSTEM OF CLEAN AIR-CONDITIONING UNIT in clean workshop. In general clean space system, air filter is used for air treatment. Usually, after installing air filter, the air cleanliness can reach 10000 grade. For the ultra-clean requirements of the clean room should also be installed air filtration. In this way, the cleanliness of the air can be higher (100 or higher, for example) . When the filter is used for a long time, the dust deposited on the filter material will gradually increase, which will increase the air resistance and affect the operation of the whole air conditioning system. Therefore, the air flow resistance variable force of the filter should be automatically detected and alarmed in engineering. The differential pressure method is usually used to measure the differential pressure PD before and after the filter, and to display the differential pressure signal and alarm according to the set differential pressure limit value in order to clean up or replace it in time. Clean Room must maintain a certain positive pressure. The static pressure difference between clean rooms of different grades and clean and non-clean areas shall not be less than 4.9 PA, and the static pressure difference between clean areas and outdoor shall not be less than 9.8 PA. . In addition, there are technical requirements for wind volume, wind speed, etc. . In short, the cleaning room of the indicators are very strict, so it is necessary to carry out precise control The best solution for the AUTOMATIC CONTROL SYSTEM OF CLEAN AIR-CONDITIONING UNIT IN CLEAN WORKSHOP 1. The related standard of clean air-conditioning system with the development of economy and the improvement of living standard, at present, in electronic, pharmaceutical, food, biological engineering, medical and other fields of clean room more and more high requirements, clean technology has also developed. It integrates technology, architecture, decoration, water supply and drainage, air purification, HVAC and other aspects of technology . According to the Chinese Standard Gbj73-84"Clean Workshop Design Code" , the main technical indexes related to the air conditioning system are as follows: A, air cleanliness grade ≥0.5 micron particle number per M3, ≥0.5 micron particle number per M3,100 grade ≤351001000 grade ≤351000 grade ≤25010000 grade ≤3510000 grade ≤25010000 grade 100000 grade ≤35100000 grade ≤25000

B, temperature and humidity (1) meet the production requirements; (2) when the production process has no temperature and humidity requirements, the temperature of the clean room is 20-26 °c and the humidity is less than 70% ; (3) the temperature of the clean room and the living room is 16-28 °C. C, clean room positive pressure, clean room must maintain a certain positive pressure. The static pressure difference between clean rooms of different grades and clean and non-clean areas shall not be less than 4.9 PA, and the static pressure difference between clean areas and outdoor shall not be less than 9.8 PA. . In addition, there are technical requirements for wind volume, wind speed, etc . In short, the cleaning room of the indicators are very strict, so it is necessary to carry out precise control In modern commercial and industrial buildings, there are a lot of air-conditioning systems. Automatic management is an important guarantee for their safe operation and good operation. At the same time, the energy consumption of air conditioning generally accounts for more than 40% of the total energy consumption, so energy conservation of air conditioning is an important means of energy conservation. Especially in a clean room . There are a number of benefits to be derived from the introduction of air-conditioning automation products. First, the automation of the air-conditioning system enables the system to operate more safely and maximize comfort . For a clean room, it is also a necessary condition to ensure production . In addition, the automatic monitoring system can meet the safety operation of the system and ensure the system's various technical indicators, while maximizing the realization of energy-saving control, in line with the increasingly prominent energy-saving and environmental protection needs. Relevant information shows that the use of air-conditioning automatic control system can save 10% of the annual operating costs of air-conditioning system equipment. A more optimistic estimate is 15 to 30 percent . The investment of air-conditioning automatic control products accounts for less than 0.5% of the total investment of the whole building or plant, and the recovery time is short. At the same time, the realization of automatic control and management of equipment can reduce personnel maintenance, save personnel costs, improve the level of integrated management, reduce the occurrence of accidents and equipment damage, thus bringing potential benefits.

Introduction of air-conditioning Control System in clean room Excel20 Chinese version controller is a member of advanced Excel5000 Controller family of Honeywell Company. It is especially suitable for air conditioning control in clean rooms such as operating rooms and clean workshops, in accordance with national standards such as "code for construction and acceptance of clean rooms" , "code for design of Clean Rooms" , "code for design of ventilation and air conditioning" , etc. , considering the internal connection of the above-mentioned systems, we take Excel20 as the core to construct a more complete air-conditioning automatic control system of the clean room, it has the characteristics of constant temperature and humidity proportional integral control, indoor long-distance start-stop air-conditioning, indoor temperature setting, critical fault (fire) alarm and interlock, non-critical fault (filter blockage/air supply overheating) alarm and interlock, preventing air supply condensation in summer/freezing in winter, starting sequence and interlock, and self-defined start-stop time program.

The composition of the automatic control system of the air conditioner in the Clean Room 1. The automatic control of the analog control instrument because of its mature theory, simple structure, low investment, easy adjustment and other factors, in the past, it has been widely used in air conditioning, cooling and heating source, water supply and drainage system. General Analog Controller for electrical or electronic, only the hardware part, without software support. Therefore, in the adjustment, put into operation process is relatively simple. Its composition is generally a single loop control system, can only be applied to small-scale air-conditioning systems. From the development trend, has been less used, do not make further explanation here. 2. Computer Control System with the development of computer technology, control technology, communication technology and image technology, the application of microcomputer control technology in refrigeration and air-conditioning automatic control is becoming more and more popular. After the introduction of the microcomputer, the traditional control system can make full use of the powerful functions of the computer such as arithmetic, logic, operation and memory. The control and management of controlled parameters, such as data acquisition and data processing, can be realized by executing these programs. The computer control process can be summarized as three steps: real-time data acquisition, real-time decision-making and real-time control. These three steps repeated repeatedly will make the whole system in accordance with a given law of control, regulation. At the same time, the controlled variables and equipment operation status, fault monitoring, over-limit alarm and protection, record historical data. It should be said that the computer control in control functions such as accuracy, real-time, reliability and so on is the simulation control can not match the control. What's more, the enhancement of management functions (such as alarm management, history record, etc.) brought about by the introduction of computer is impossible to be realized by analog controller. Therefore, in recent years, in the refrigeration air conditioning automatic control application, especially in the large and medium-sized air conditioning system automatic control, the computer control already occupied the dominant position.

Direct digital control (DDC) the so-called on-line digital control is the direct input of the output signals of sensors or transmitters in the system to the microcomputer without the aid of analog instruments, on the basis of microprocessor mobility, direct Digital Control (DDC) is the Control mode of Direct drive actuator which is calculated and processed by the microcomputer according to the pre-programmed program. This kind of computer is called Direct Digital Control (DDC) . The CPU in the DDC controller is very fast and has as many input and output ports (i/0) configured. Therefore, it can control multiple loops at the same time, equivalent to multiple simulation of higher price ratio characteristics. Distributed Control System Total Distributed control System abbreviation for TDS. Compared with the traditional computer control method in the past, its control function is as decentralized as possible, and its management function is as centralized as possible. It is connected by the central station, the sub-station, the spot sensor and the communication channel. The substation is the aforementioned microprocessor-based DDC controller. It is distributed in the field of the controlled equipment of the whole system, directly connected with the sensors and actuators of the field to realize the detection and control of the field equipment. Central Station realizes centralized monitoring and management functions, such as centralized monitoring, centralized start-stop control, centralized parameter modification, alarm and record processing, etc. . It can be seen that the centralized management function of dcs is accomplished by the central station, while the control and regulation function is accomplished by the sub-station or DDC controller.

The realization of automatic control system of clean room air conditioning 1, air purification in the general clean room system, air filter is used for air treatment. In general, the installation of primary and intermediate filters, the air cleanliness can reach 10,000 grade. For the ultra-clean requirements of the clean room should also be installed high-efficiency filter. In this way, the cleanliness of the air can be higher (100 or higher, for example) . When the filter is used for a long time, the dust deposited on the filter material will gradually increase, which will increase the air resistance and affect the operation of the whole air conditioning system. Therefore, the air flow resistance variable force of the filter should be automatically detected and alarmed in engineering. The differential pressure method is usually used to measure the differential pressure PD before and after the filter, and to display the differential pressure signal and alarm according to the set differential pressure limit value in order to clean up or replace it in time.

2, temperature control a, a heating control of the air a heating, also known as pre-heating, is used to heat fresh air or heating fresh air and a return air mixture. One-time heating is generally used only in very cold winter areas, to prevent fresh air and a return air mixed to reach saturation, produce water mist or ice. One-time heating is also used in one-time mixing is not allowed to change the ultra-clean air conditioning system. When steam or hot water is used for heating, the temperature is controlled by the opening of the regulating valve which controls the steam or hot water, and when electric heating is used, the temperature is controlled by controlling the heating power of the thyristor electric controller. B, the second heating and the third heating control air second heating is usually set after the surface cooler or the Second Return Air Mixing section. The purpose of the secondary heating is to ensure the supply air temperature or the temperature in the air conditioning room under the condition of relative humidity. The control mode is basically the same as that of a single heating. Three-time heating into fine heating, usually in high-precision temperature control, for temperature fine-tuning and set up the heating section. The control shall be carried out according to the above-mentioned principles in accordance with the specific conditions.

3. Humidity control a, humidification treatment and control of air conditioning in clean spaces, humidification operations are generally carried out in winter or transition season when the air is dry. There are many ways to humidify the air. Usually use steam humidifier and electric humidifier switch control or power regulation. When the steam is humidified, according to the requirement of humidity control, it can be realized by the position control of the solenoid valve or the continuous regulation of the two-way Valve. B, dehumidification (drying) treatment and control of air cooling drying treatment commonly used surface cooler to complete. Table Two processes of equal humidity cooling for cold air treatment. When the surface cooler is used for humidity control, it is realized by adjusting the flow rate of refrigerant (such as frozen water) of the surface cooler. When the humidity is higher than the required value, the flow can be increased by increasing the opening of the cold water valve to achieve dehumidification (that is, dry) treatment, and conversely reduce the flow to achieve humidification treatment. It should be noted that, due to the physical nature of the air, its humidity control is relatively complex, methods are more. Moreover, the two parameters of air temperature and humidity influence each other in the process of regulation. If some reasons make indoor temperature rise, cause the change of saturation partial pressure of water vapor in the air, the relative humidity will be reduced under the condition of constant absolute humidity. Therefore, when one parameter is adjusted, another parameter will be changed. For example, the use of table cooler in summer dehumidification regulation, open large cold water valve, the humidity in the normal, but also reduce the temperature. Therefore, this characteristic should be fully taken into account in process design and automatic control scheme design.

4. Positive pressure control China's national standards, the different levels between clean rooms should be greater than 4.9 PA, clean area and between should be greater than 9.8 pa. The structure of the clean room is basically determined. During the operation, the positive pressure can be maintained by controlling the amount of fresh air or return air. That is, by controlling the opening of the fresh air door or return air door to achieve. 5, other control and air conditioning energy-saving for the clean room, in addition to the above-mentioned technical indicators must be guaranteed, there are some safety and energy-saving requirements. Combined with many years of engineering practice, the main aspects are as follows. A, Fan failure alarm. Judging whether the FAN is working normally by testing the state of air flow of the fan. If the motor burns down or the belt loosens and so on causes the fan to stop to turn, should immediately alarm. B, Fan frequency control to maintain a stable positive pressure in the clean room or a certain fresh air/return air ratio, the machine (motor) can be the implementation of frequency control. The practice proves that the frequency conversion control is better than the simple air door opening control, and it can greatly save the power consumption. Because in air conditioning system, fresh air/back to the transmission of the largest proportion of electricity consumption. The throttle control is actually through the throttle device (that is, the throttle) to achieve the change in airflow.

C, pump frequency control in a pump-to-regulation system, frequency control (pump rotation) to achieve flow control than the use of throttling device (that is, the control valve) is better. This kind of way not only manifests in the control effect to be better, simultaneously manifests in the large scale saves the electricity consumption. D, energy-saving program as a result of the application of computer control system, make energy-saving control become a reality. In addition to the above-mentioned energy-saving control measures for the process characteristics of air-conditioning system, computer control can also achieve such as enthalpy difference control, night cycle, night air purification, the best start-stop, zero energy zone. Of course, for a specific clean plant, its energy-saving procedures should be based on its specific circumstances, in order to achieve the best energy-saving effect. The equipment configuration of the air-conditioning control system the equipment of the air-conditioning automatic control system includes controller, sensor and actuator, etc. . As the former mainstream control system has already changed from analog control to computer control, this paper mainly introduces the DDC controlled equipment which realizes direct digital control. DDC Controller Power: 24 power consumption: 45 Protection Standard: BACKUP BATTERY: 3V LITHIUM BATTERY LCD DISPLAY: 4 Lines 16 amperes

EPROM is hosted with Standard Program Excel DDC controller, which is an intelligent DDC substation specified in the national standard of China. The programming of each controller is stored in its own memory. Excel20 contains 16-bit microprocessor I80186 can control 16 physical points, (that can connect 16 detectors, switches, actuators) . It is based on the basic CPU module and Power Module, and the following function modules are installed by the software according to the actual needs: analog input and input module (Al) : 7 points, 0 ~ 1VDC, 2 ~ 10VDC, 420MA; analog output module (Ao) : 3 points, 210VDC; Digital Input Module (Di) : 2 points, dry contact; digital output module (DI) : 4 relay outputs; switching on/off can be controlled by a time schedule; flexible time schedule up to 1 year.

Temperature sensor effective temperature range:-20 °C to 50 °C maximum transmission distance: 200 M Environmental Requirements:-35 °C to 60 °C, 5% RH to 95% RH electrical wiring: 21.5 MM2, should be shielded with line power 3, hot and cold water valve and driver proportional integral electric valve. These include: Valve V5011, equal percentage characteristics, electric valve actuator ML7984 or M7421, different valve body for cold and Hot Water Media, DN25-150 grid options. Steam heating/humidifying valve and drive valve V5011, linear characteristics, electric valve actuator M7421, various body options, suitable for steam medium, DN25-150 various specifications for choice, 4.6 electric air door driver, electric fresh air valve ML6184, air door actuator ML6XXX, ML7XXX, ML8XXX, air door suitable for 0.75 m2-15 M2 area, with on-off/off/continuous type for choice.

5. AIR DIFFERENTIAL SWITCH DPS400 pressure range: 40-400PA protection class: IP54 SWITCHING CAPACITY: 1.5 a/250VAC6, air differential meter and differential transmitter micro differential meter 2000 series: Field Display: Pointer display; measuring range: Minimum Section 0-60Pa; Micro-differential pressure transmitter MODT30 measuring range: minimum 0-25Pa output signal: 4-20MA INPUT SIGNAL: air differential working power supply: 10-35VDC air cooling drying processing common table cooler to complete. Table Two processes of equal humidity cooling for cold air treatment. When the surface cooler is used for humidity control, it is realized by adjusting the flow rate of refrigerant (such as frozen water) of the surface cooler. When the humidity is higher than the required value, the flow can be increased by increasing the opening of the cold water valve to achieve dehumidification (that is, dry) treatment, and conversely reduce the flow to achieve humidification treatment. It should be noted that, due to the physical nature of the air, its humidity control is relatively complex, methods are more. Moreover, the two parameters of air temperature and humidity influence each other in the process of regulation. If some reasons make indoor temperature rise, cause the change of saturation partial pressure of water vapor in the air, the relative humidity will be reduced under the condition of constant absolute humidity. Therefore, when one parameter is adjusted, another parameter will be changed. For example, the use of table cooler in summer dehumidification regulation, open large cold water valve, the humidity in the normal, but also reduce the temperature. Therefore, this characteristic should be fully taken into account in process design and automatic control scheme design.



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