economic development and improvement of living standards, the current in
the electronics, pharmaceutical, food, bio-engineering, medical and
other areas of the increasingly clean room requirements, clean
technology also developed. It combines the technology,
construction, decoration, water supply and drainage, air purification,
HVAC and other aspects of technology. In accordance with
the standards of the People's Republic of China GBJ73-84 "clean plant
design specifications", and air conditioning system related to the main
I、Specification for clean room air conditioning systems
1, Air cleanliness: grade per M3 air ≥ 0.5 micron dust particles per M3 air ≥ 0.5 micron dust particles:
100 level ≤35×100
1000 level ≤35×1000 ≤250
10000 level ≤35×10000 ≤2500
100000 level ≤35×100000 ≤25000
2, clean room air conditioning system specifications temperature and humidity:
(1) to meet the production requirements;
(2) the production process without temperature and humidity requirements, the clean room temperature is 20-26 ℃, humidity less than 70%;
(3) staff cleaning room and living room temperature is 16-28 ℃.
3, clean room pressure:
Clean room must maintain a certain positive pressure. Different levels of clean room and clean area and non-clean area between the static pressure difference should be not less than 4.9Pa, clean area and outdoor static pressure difference should not be 9.8 Pa. In addition, there are technical requirements for air volume, wind speed and so on. In short, the indicators of cleanliness are very strict. Therefore, it is necessary to make precise control of it.
II、The meaning of clean room air conditioning control:
In modern commercial and industrial buildings, air-conditioning system equipment more automated management is to make it safe and good operation of the important guarantee. At the same time, air-conditioning energy consumption in general accounts for more than 40% of total energy consumption, energy saving is an important means of energy saving. For cleanliness, it is even more so. The use of air conditioning products, will produce the following series of benefits:
First of all, because the air conditioning system to achieve automatic monitoring, you can make the system more secure operation, and maximize the comfort level. For clean rooms, it is necessary to ensure the production of the necessary conditions.
In addition, due to the realization of automated monitoring, you can meet the safe operation of the system and ensure that the system of various technical indicators at the same time, the maximum realization of energy-saving control, in line with increasingly prominent energy and environmental protection needs. The data show that the use of air conditioning automatic control system, air conditioning system can save the annual operating costs of 10%. More optimistic estimate that up to 15% -30%. While the investment in air conditioning control products accounted for less than 0.5% of the total investment in the whole building or plant, and the investment recovery time is short. At the same time, due to the automatic control and management of equipment, personnel maintenance can be reduced, personnel costs, improve the level of integrated management, reduce the occurrence of sudden accidents and equipment damage, which brings potential benefits.
III、Clean room air conditioning control system function brief introduction:
Excel 20 Chinese version of the controller is the United States HONEYWELL company advanced Excel 5000 controller family members. Especially for the clean room, such as the operating room, clean room air conditioning control, in accordance with the "clean room construction acceptance", "clean plant design specifications should be", "ventilation and air conditioning design specifications" and other national standards, and taking into account the above The internal relationship between the system, we have to Excel 20 as the core to build a more complete clean room air conditioning control system, which has the following characteristics:
1, constant temperature and humidity ratio integral control; 2, indoor remote start and stop air conditioning; 3, indoor temperature setting; 4, critical fault (fire) alarm and interlock; 5, non-critical fault (filter plug / Alarm and interlock; 6, summer to prevent air condensation / winter antifreeze; 7, boot sequence and interlock; 8, custom start and stop time procedures.
IV、Air conditioning control system equipment configuration:
To achieve air-conditioning automatic control system equipment, controllers, sensors and actuators. As before, the mainstream control system has been transformed from
analog control to computer control. Here, the DDC control device is
mainly introduced for direct digital control.
(1), DDC controller: power: 24; power consumption: 45 protection standards: backup battery: 3V lithium battery; LCD display: 4 lines × 16 An Fu. EPROM in the standard program; Excel capable DDC controller, is the Chinese national standard DCP intelligent sub-station. The programming of each controller is stored in its own memory. Excel20 contains 16-bit microprocessors i80186 can control 16 physical points, (that can be connected to 16 detectors, switches, actuators). (AL): 7 points, 0 ~ 1VDC, 2 ~ 10VDC, 420MA; Analog output module (AL): 7 points, 0 ~ 1VDC, 2 ~ 10VDC, 420MA; Analog output module (AL): 7 points, 0 ~ 1VDC, 2 ~ 10VDC, 420MA; Analog output module (DI): 4 points, 210VDC; digital input module (DI): 2 points, dry contact; digital output module (DI): 4 relay output switch start / stop through the time schedule to control when Start and stop. Flexible time plan up to 1 year.
(2), temperature sensor: indoor temperature transmitter T7412, set point adjustable, effective temperature range: -20 ℃ to 50 ℃, the maximum transmission distance: 200 meters; NTC20K. Environmental requirements: - 35 ℃ to 60 ℃, 5% RH to 95% RH, electrical wiring: 2X 1.5MM2, should be shielded with the line power supply, outdoor temperature sensor C703F, the effective temperature range: -20 ℃ to 50 ℃; Distance: 200 meters, NTC20K, environmental requirements: -35 ℃ to 60 ℃, 5% RH to 95% RH, electrical wiring: 2 × 1.5MM2, should be shielded with the line power supply, duct temperature sensor C7031C, effective temperature range : -20 ℃ -50 ℃, the maximum transmission distance: 200 meters.
(3), hot and cold water valve and drive, proportional integral electric valve: which includes: valve V5011, equal percentage characteristics, electric valve actuator ML7984 or M7421, matching different valve body for chilled water, hot water medium, DN25 -150 grid for choice.
(4), steam heating / humidification valve and drive: valve V5011, linear characteristics, electric valve actuator M7421, matching different valve body, for steam media, DN25-150 specifications to choose from.
(5), electric damper: electric new air valve ML6184, damper actuator ML6XXX, ML7XXX, ML8XXX, for 0.75M2-15M2 area of the throttle, a switch type / intermittent / continuous type to choose from.
(6), air pressure switch: DPS400, pressure range: 40-400Pa, protection level: IP54, switching capacity: 1.5A / 250VAC.
(7), air pressure meter and differential pressure transmitter: 1. Micro differential pressure table 2000 Series: Field display: pointer display; Measuring range: the smallest section 0-60 Pa; 2. Micro differential pressure transmitter MODT30: Measuring range: min 0-25 Pa Output signal: 4-20MA Input signal: air pressure, working power: 10-35VDC;
(8), other detection, calibration equipment: 1, portable digital temperature / humidity table 485-1 / 2: range: temperature -30-85 ℃; humidity 0-100% RH; accuracy: temperature ± 0.5 ℃; temperature ± 2, portable digital pressure / pressure gauge 477 type (with temperature display); range: the smallest 0-1000Pa; operating temperature: 0 (1), the power supply: 9V alkaline battery; probe length: 219mm (485-2 type) -50 ℃; accuracy: 50% FS; power supply: 9V alkaline batteries; 3, portable digital anemometer 471 (with temperature display): range: minimum 0-1000 Pa; operating temperature: 0-40 ℃; 3% FS; power supply: 9V alkaline battery; 4, portable digital particle counter: hand-held, battery operation; 0.1FM (cubic feet / minute) to calculate 0.3 or 0.5 micron particles; 5, the calculation mode; storage data: Group; RS232 / RS485 output; display: 4-line LCD display, 7-bit calculation results.
V、Clean room air conditioning control system to achieve:
1, air purification: the general clean room space system, the air treatment using air filters. Under
normal circumstances, the installation of early effects filter and the
effect of the filter, the air cleanliness can reach 10000 level. And for the clean requirements of the clean room should also be installed high efficiency filter. In this way, air cleanliness can be higher (such as 100 or even higher). When
the filter is used for a long time, the dust on the filter will slowly
increase, which will increase the airflow resistance and affect the
operation of the whole air conditioning system. Therefore, the project should be on the filter air resistance to force the automatic detection and alarm. Usually used to measure the differential pressure before and after the
filter before the pressure Pd, and the differential pressure signal
display and according to set the differential pressure limit alarm for
timely cleaning or replacement.
2, the temperature control: (1), a heating control: air heating, also known as preheating, is used to heat the new wind or fresh air and a return air mixed air. A heating is generally used only in cold winter areas, to prevent fresh air and a return air after mixing to achieve saturation, resulting in water mist or ice. A heating is also used in a mix of non-allowable changes in the ultra-clean air-conditioning system. When the use of steam or hot water for heating, the general use of steam or hot water control valve opening to achieve temperature control; when using electric heating, through the thyristor power controller, to control its heating power to achieve temperature control. (2), secondary heating and three heating control: air secondary heating is usually set in the surface cooler or after the second return air mixing section. The purpose of secondary heating is to have the relative humidity requirements, in order to ensure the air supply temperature or air conditioning room temperature. Its control mode and a heating situation is basically the same. (3), three times heating and then fine heating, usually in the high-precision temperature control, for the temperature fine-tuning and set the heating section. Its control should be based on specific circumstances with reference to the above principles.
3, humidity control: (1), humidification treatment and control: clean room air conditioning works, humidification operation is generally in the winter or the transition season when the air dry. Air humidification methods are more. Usually using steam humidifier and electric humidifier switch control or power adjustment. Steam humidification, according to the humidity control requirements, through the solenoid valve for bit control or the use of two-way control valve to achieve continuous adjustment. (2), dehumidification (drying) treatment and control: air cooling and drying treatment commonly used to complete the surface cooler. Table cold on the air treatment of wet and wet two kinds of treatment process. When using the surface cooler for humidity control, it is achieved by adjusting the flow rate of refrigerant (such as chilled water) in the surface cooler. When the humidity is higher than the required value, you can increase the opening of the cold water valve to increase its flow to achieve dehumidification (ie drying) treatment; the contrary, reduce the flow to achieve humidification.
It should be noted that, due to the physical properties of air, the humidity control is relatively complex, more methods. Moreover, the temperature and humidity of the air two parameters in the adjustment process and mutual influence. For some reason, the indoor temperature is raised, causing the saturation of the water vapor in the air to change, in the case of absolute moisture content will change the relative humidity will be reduced. Therefore, when one of the parameters of the adjustment, it will cause another parameter changes. For example, in the summer with a surface cooler for dehumidification adjustment, open the cold water valve, the humidity back to normal, but also to reduce the temperature. Therefore, in the process design and automatic control program design should take full account of this feature.
4, positive pressure control: China's national standards, different levels of clean room should be greater than 4.9Pa, clean area and should be greater than 9.8 Pa. Clean room structure and other basic to determine, in the course of running, to maintain positive pressure can be controlled by the amount of fresh air or air to achieve. That is, by controlling the opening of the new damper or return valve to achieve.
5, other control and air conditioning energy: the clean room, in addition to the above must ensure that the technical indicators that there are some security and energy and other aspects of the requirements. Combined with years of engineering practice, mainly in the following areas. (1), fan failure alarm: by detecting the air flow of the fan to determine whether the normal operation of the fan. If the motor burns or the belt loosening and other reasons cause the fan to stop, should immediately report the alarm. <BR> 3.5.2 fan frequency control In order to keep the clean room stable positive pressure or a certain fresh air / return air ratio, Machine (motor) frequency conversion frequency control. Practice has proved that the frequency control than the simple throttle opening adjustment control effect is better, and can save a lot of power consumption. Because in the air conditioning system, the new wind / back to the transport of electricity accounted for the largest proportion of electricity consumption. The throttle control is actually through the throttle device (ie, the damper) to achieve airflow changes. (2), the pump frequency control: in a pump on a regulatory system, the use of frequency control (pump speed) to achieve flow control than the use of throttle devices (ie, control valve) is better. This approach is not only reflected in the control effect is better, at the same time reflected in the substantial savings in power consumption. (3), energy-saving program: the application of computer control systems, so that energy-saving control become a reality. In addition to the above-mentioned characteristics of the implementation of the energy-saving air-conditioning system control means, the computer control can also be achieved such as enthalpy control, night cycle, night wind purification, the best start and stop, zero energy area. Of course, for a particular clean room, its energy-saving procedures should be based on the specific circumstances of the preparation, in order to achieve the best energy-saving effect.