Laboratory ventilation system is one of the largest and most influential systems in the whole process of laboratory design and construction. Whether the ventilation system is perfect or not will directly affect the laboratory environment, the health of the experimenters and the operation and maintenance of the experimental equipment.
Laboratory excessive negative pressure, ventilator gas leakage, laboratory noise and other issues have always been a difficult problem for laboratory staff. These problems have caused serious physical and psychological harm to the staff who have been working in the laboratory for a long time, even to the management and logistics personnel who work around the laboratory.
A scientific and reasonable ventilation system requires good ventilation effect, low noise, simple operation, energy saving, and even requires indoor pressure difference and temperature and humidity to maintain human comfort.
I. Design Standards
1. Design Code for Heating, Ventilation and Air Regulation (GBJ19-87-2003).
2. Standards for Quality Inspection and Assessment of Ventilation and Air Conditioning Engineering (GBJ304-2002).
3. Concise Ventilation Design Manual (GB50194-2002).
4. Code for Construction and Acceptance of Installation Works of Compressors, Fans and Pumps (JBJ29-2002).
5. Code for Construction and Acceptance of Low Voltage Electrical Appliances for Installation Works of Electrical Devices (GB50254-96)
6. Comprehensive Emission Standards for Atmospheric Pollutants (GB16297-1996).
7. Environmental Air Quality Standard (GB3095-1996).
8. Urban Regional Environmental Noise Standard (GB3096-93).
9. Code for Fire Protection in Architectural Design (GB50016-2006).
10. Standards for Energy Conservation Design of Public Buildings (GB50189-2005).
11. Relevant information of the company and relevant information provided by Party A.
II. Design Principles
1. According to the structural characteristics of the building, air wells are set up nearby, and exhaust and supplementary air systems are divided. Pipeline systems are "short, flat, smooth and straight", reducing system resistance and system noise.
2. The exhaust and supplementary air system can balance the air volume, maintain the negative pressure of - 5Pa - 10Pa indoors, prevent the spillover of harmful gases, and ensure the physical and mental health of the experimenters.
3. Make up cold air in summer and warm air in winter to ensure the comfort of indoor temperature and humidity.
4. Intelligent frequency conversion control system is adopted to achieve the purpose of convenient operation, energy saving and noise reduction.
5. Considering all factors comprehensively, the mature process with less investment, stable operation, low operation cost and good operation effect is adopted.
6. The selected process must satisfy the site conditions, the layout is simple, compact, less space occupied, and it is convenient for production operation and maintenance.
7. Non-standard equipment should conform to the relevant national or industry specifications, and ensure stable performance and beautiful appearance.
8. Fully consider noise and odor in the design to prevent secondary pollution and avoid new pollution to the surrounding environment.
9. The treatment facility has shock loading capacity to ensure that the exhaust gas meets the discharge standards.
3. Design parameters
1. The wind speed in branch pipeline is 6-8 m/s and in trunk pipeline is 8-14 m/s.
2. Design air volume of ventilation equipment:
The ventilation hood surface wind speed is 0.3-0.8 m/s, the design air volume of a single 1200*800*2350 ventilation hood is 1500 m3/h, the design air volume of a single 1500*800*2350 ventilation hood is 1800 m3/h, the design air volume of a single 1800*800*2350 ventilation hood is 2200 m3/h, the ventilation speed of a universal exhaust hood is (>0.35 m/s), the exhaust air volume of a universal exhaust hood is 150-350 m3/h, and the air speed of an atomic absorption hood is: More than 0.35 m/s and 350-600 m3/h of exhaust air.
3. Frequency of ventilation:
Gas exchange rate in general chemical laboratory: 8-12 times per hour
4. Ventilation system uses terminal noise less than 62 db.
5. The anti-corrosion FRP centrifugal fan is used in the fan, and the frequency conversion control is used in the system to achieve the purpose of energy saving and noise reduction.
IV. Technical parameters of ventilators
(1) Ventilator of constant air volume system
1. Exhaust air volume
When the opening height of the moving door is 0.5m and the surface wind speed is 0.5m/s, the actual exhaust volume should not exceed 5% of the calculated exhaust volume (calculated exhaust volume = width of the moving door * opening height * 0.5m/s * 3600 seconds) within the range of the exhaust volume specified in the Technical Standard JB/T6412-1999 of the Ventilation Cabinet.
2. Surface wind speed
2.1 When the working opening height of the moving door is 0.5 m and the surface wind speed is kept at 0.5 m/s, the exhaust air volume remains unchanged and the opening height of the moving door changes, the surface wind speed can meet the following requirements:
2.2 The opening height of the moving door is fully open, and the average surface wind speed is greater than 0.3m/s.
2.3 The opening height of the moving door is 0.15m, and the average surface wind speed is less than 0.7m/s.
2.4 wind speed uniformity (with low wind speed detector);
2.5 The surface wind speed of the exhaust hood should be evenly distributed. In the case of 0.5m height of the moving door and 0.5m/s of the surface wind speed, within the opening area of the moving door, at 0.3m intervals from top to bottom, a point should be taken to measure the surface wind speed. The deviation between the maximum and minimum values and the arithmetic average values is less than 15%.
3. Ventilator resistance
When the moving door of the exhaust hood is opened to the highest position, the resistance of the exhaust hood shall be less than or equal to 70 Pa when the exhaust volume and surface wind speed specified in the Technical Standard JB/T6412-1999 are maintained at 0.5 m/s.
4. Other functional requirements
The control system of the operation panel of the ventilator should be LCD (the user can operate safely and conveniently). High temperature alarm function in cabinet, such as KFJ-17 surface wind speed monitoring acoustooptic alarm (alarm function of too high and too low wind speed); automatic delay protection device, which can completely empty residual corrosion, harmful and toxic gases; arbitrary regulation function in voltage range of 0-220V; arbitrary regulation function of stepping air valve execution system.
(2) Variable Air Volume System (VAV) Fume Cabinet
1. According to ANSI Z9.5-2003 standard, the ventilator surface wind speed above or below 0.5m/s may lead to harmful gas escape, too low surface wind speed can not effectively capture harmful substances discharged, too high surface wind speed causes turbulence and eddy current in the air flow inside the ventilator, which may also lead to harmful substances escape. In order to ensure the ventilation effect, VAV variable air volume control mode is adopted in the ventilation cabinet, requiring the ventilation cabinet surface wind speed to be stable at 0.5m/s (+5%).
2. The use of direct wind speed measurement and control system can quickly and effectively ensure the ventilation cabinet surface wind speed, so as to achieve the purpose of ensuring the safety of laboratory staff. In order to avoid the influence of ambient temperature and humidity on the base point drift of common wind speed sensors, the hotline wind speed sensor is used in the control system of the ventilator to measure the real face wind speed, and the wind speed sensor is equipped with a unique self-cleaning filter, which has the function of preventing dust clogging.
3. When the wind speed sensor detects the change of the surface wind speed, the controller sends a signal to the actuator. By changing the opening of the VAV valve, the surface wind speed can return to the set value, requiring the response time of the system to be less than 3 seconds.
4. The wind speed sensor of the ventilator monitors the real face wind speed in real time. When the face wind speed is not within the set range, the monitor sends out sound and light alarm after 15 seconds delay.
5. The monitor has the function of maximum air volume and minimum air volume. In case of emergency, it can press the button of maximum air volume, and the exhaust valve can be fully opened. When the fan is expected to run at a small air volume (e.g. at night), it can press the button of minimum air volume, and the ventilator can run at a small air volume.
6. The monitor also has a low wind speed operation button. Pressing this button can set the surface wind speed to 70% of the normal value, which can be used to reduce gas emissions to save energy. (It is not recommended to use when there are high dangerous substances in the ventilator.)
V. Ventilation system control
(1) Constant air volume system control
1. The system adopts the static pressure sensor automatic frequency conversion control (or PLC programming control). The static pressure sensor automatic frequency conversion control can change the static pressure to 0-10V electric signal input frequency converter according to the number of opening ventilation equipment, so as to automatically adjust the frequency of the fan and make the exhaust volume of the fan phase with the actual exhaust volume. Matching, so as to ensure the exhaust effect, achieve the effect of energy saving and noise saving;
2. Each ventilator is equipped with an electronic air volume regulating valve, whose control switch, frequency conversion control system and fan linkage can realize the control of one or more ventilation equipment under different working conditions. The air volume control valve uses digital adjustable angle electronic air volume control valve, and has memory function (that is, the angle of this adjustment can be remembered, and it will be adjusted to the design angle when it is opened next time).
3. The whole interlock of the system air valve and fan can realize the orderly flow of air, balance the air flow of the system, and prevent the reverse series and reverse flow of air flow.
(2) VAV control
1. The system adopts the static pressure sensor automatic frequency conversion control. The static pressure sensor automatic frequency conversion control can change the induced static pressure into 0-10V electric signal input frequency converter according to the quantity change of the opening ventilation equipment, so as to automatically adjust the frequency of the fan, so that the exhaust air volume of the fan matches the actual exhaust air volume, so as to ensure the exhaust air volume. Wind effect, to achieve energy saving and noise saving effect;
2. Each ventilator is equipped with a Venturi VAV air valve. Its control switch, frequency conversion control system and fan linkage can realize the control of single or multiple ventilation equipment under different working conditions. Variable air volume control valve uses a digital adjustable angle Venturi air valve, and has memory function (that is, you can remember the angle of this adjustment, the next time you open it, still adjust to the design angle).
3. The whole interlock of the system air valve and fan can realize the orderly flow of air, balance the air flow of the system and prevent the air flow.
