Laboratory ventilation design standard

Laboratory ventilation system is one of the systems with large scale and wide influence in the whole process of laboratory design and construction. Whether the ventilation system is perfect or not has an important impact on the laboratory environment, the health of laboratory personnel, the operation and maintenance of experimental equipment and so on.

The problems such as excessive negative pressure in laboratory, gas leakage of fume hood and noise in laboratory are always the problems that perplex the laboratory staff. These problems have caused serious physical and psychological injuries to the staff working in the laboratory for a long time, even to the management and logistics personnel working around the laboratory.

A scientific and reasonable ventilation system requires good ventilation effect, low noise, simple operation, energy saving, and even the indoor pressure difference and temperature and humidity can keep the human body comfortable.

I. design standard

1. Code for design of heating ventilation and air conditioning (GB 50019-2003);

2. Code for acceptance of construction quality of ventilation and air conditioning engineering (GB 50243-2002);

3. Code for safety of power supply and use on construction site (gb50194-93);

4. Code for construction and acceptance of fan, compressor and pump installation engineering (GB 50275-2010);

5. Code for construction and acceptance of low voltage electrical appliances in electrical installation engineering (GB 50254-1996);

6. Integrated emission standard of air pollutants (GB16297-1996);

7. Ambient air quality standard (GB3095-1996);

8. Environmental noise standard for urban areas (gb3096-2008);

9. Code for fire protection design of buildings (GB50016-2006);

10. Design standard for energy efficiency of public buildings (gb50189-2005);

11. Concise ventilation design manual;

II. Design principles

1. According to the structural characteristics of the building, air shaft shall be set up nearby to divide the exhaust and make-up air system. The pipeline system shall be "short, flat, smooth and straight" to reduce system resistance and system noise;

2. The exhaust and supplement air system shall reach the air volume balance, maintain the negative pressure of - 5pa - 10Pa in the room, prevent the dispersion and overflow of harmful gases, and ensure the physical and mental health of the laboratory personnel;

3. Cool air in summer and warm air in winter to ensure the normal indoor temperature and humidity;

4. Adopt the intelligent frequency conversion control system to achieve the purpose of convenient operation, energy saving and noise reduction;

5. Considering all factors comprehensively, adopt mature technology with less investment, stable operation, low operation cost and good operation effect;

6. The selected process must meet the site conditions, the plane layout is simple, compact, less land occupation, and convenient for production, operation, maintenance and repair;

7. The non-standard equipment shall conform to the relevant national or industrial specifications, and ensure stable performance and beautiful appearance;

8. Noise, odor, etc. shall be fully considered in the design to prevent secondary pollution and avoid new pollution to the surrounding environment;

9. The treatment facilities shall have impact load capacity to ensure that the exhaust gas can meet the discharge standard.

III. design parameters

1. The wind speed in the branch pipeline is 6-8m / s, and that in the main pipeline is 8-14m / S;

2. Design air volume of ventilation equipment:

Air speed on the face of the ventilation cabinet: 0.3-0.8 M / s, design air volume of a single 1200 * 800 * 2350 ventilation cabinet: 1500 m3 / h, design air volume of a single 1500 * 800 * 2350 ventilation cabinet: 1800 m3 / h, design air volume of a single 1800 * 800 * 2350 ventilation cabinet: 2200 m3 / h, design air speed of the universal air extraction hood: ≥ 0.35 M / s, exhaust air volume of the universal air extraction hood: 150-350 m3 / h, air speed of the atomic absorption hood: ≥ 0.35 M / s, exhaust air volume of 350-600 m3 / h.

3. Air change times:

Air changes in general chemistry laboratory: 8-12 times / hour

4. The terminal noise of ventilation system is ≤ 62db.

5. The fan adopts corrosion-resistant centrifugal fan and the system adopts frequency conversion control to achieve the purpose of energy saving and noise reduction.

IV. technical parameters of fume hood

(I) ventilation cabinet 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 kept at 0.5m/s, the actual exhaust air volume shall not be greater than 5% of the calculated exhaust air volume (calculated exhaust air volume = width of the moving door * opening height of the moving door * 0.5m/s * 3600 seconds) within the range of exhaust air volume specified in technical standard JB / t6412-1999 of exhaust cabinet.

2. Surface wind speed

2.1 under the condition that the working opening height of the moving door is 0.5m and the surface wind speed is kept at 0.5m/s, the exhaust air volume is unchanged, and when the opening height of the moving door changes, the surface wind speed can meet the following requirements:

2.2 the opening height of the mobile door is fully open, and the average surface wind speed is greater than 0.3m/s;

2.3 the opening height of the mobile door is 0.15m, and the average surface wind speed is less than 0.7m/s;

2.4 uniformity of surface wind speed (with low wind speed detector);

2.5 the surface wind speed of the exhaust cabinet shall be evenly distributed. Under the condition that the opening height of the sliding door is 0.5m and the surface wind speed is 0.5m/s, within the opening area of the sliding door, take a point every 0.3m up, down, left and right, and the deviation between the Zui big value, Zui small value and the arithmetic average value is less than 15%.

3. Resistance of fume hood

When the moving door of the exhaust cabinet is opened to the Zui high position, the resistance of the exhaust cabinet shall be less than or equal to 70pa under the condition that the exhaust air volume and surface air speed specified in the technical standard of exhaust cabinet (JB / t6412-1999) are maintained at 0.5m/s.

4. Other functional requirements

The control system of fume hood operation panel shall be LCD (safer and more convenient for users). High temperature alarm function in the cabinet; for example, kfj-17 type surface wind speed monitoring audible and visual alarm (high and low wind speed alarm function) is selected; automatic delay protection device can exhaust residual corrosion, harmful and toxic gas; any adjustment function within the voltage range of 0-220V; step air valve performs any adjustment function of the system.

(II) ventilation cabinet of VAV system

1. According to the American ANSI z9.5-2003 standard, if the air speed on the face of the ventilation cabinet is higher or lower than 0.5m/s, harmful gases may escape. If the air speed is too low, harmful substances can not be effectively captured. If the air speed is too high, turbulence and eddy current will form in the air flow in the ventilation cabinet, harmful substances may escape. In order to ensure the ventilation effect, VAV variable air volume control mode is adopted for the fume hood, and the wind speed on the fume hood surface is required to be stable at 0.5m/s ± 5%;

2. The direct wind speed measurement and control system can ensure the wind speed of the ventilation cabinet quickly and effectively, so as to ensure the safety of laboratory staff. In order to avoid the influence of ambient temperature and humidity on the reference point drift of ordinary wind speed sensor, the control system of ventilation cabinet uses hot wire type wind speed sensor to measure the real wind speed; the wind speed sensor is equipped with a unique self-cleaning filter, which has the function of preventing dust blockage;

3. When the wind speed sensor detects the change of the surface wind speed, the controller sends a signal to the actuator, and changes the opening of the VAV valve to make the surface wind speed return to the set value. The system response time is required to be less than 3 seconds;

4. The wind speed sensor of the fume hood monitors the real face wind speed in real time. When the face wind speed is not within the set range, the monitor will give an audible and visual alarm after 15 seconds delay;

5. The monitor has the functions of Zui high air volume and Zui low air volume. In case of an emergency, press the Zui high air volume button to fully open the exhaust valve. When you want the fume hood to operate with low air volume (for example, at night), press the Zui low air volume button to operate the fume hood with low air volume;

6. The monitor also has a low wind speed operation button. Press this button to make the surface wind speed setting value 70% of the normal value, which is used to reduce gas emissions and save energy. (it is not recommended to use when there are high-risk substances in the fume hood).

V. ventilation system control

(I) 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 induced static pressure into a 0-10V electrical signal input frequency converter according to the number of open ventilation equipment, so as to automatically adjust the fan frequency, so that the fan's exhaust volume matches the actual exhaust volume, so as to ensure the exhaust effect and achieve energy saving The effect of noise;

2. Each fume hood is equipped with an electronic air volume regulating valve. Its control switch is linked with the frequency conversion control system and the fan to realize the control of single or multiple ventilators under different working conditions. The air volume control valve adopts the electronic air volume control valve with digital display adjustable angle, and has the memory function (that is, it can remember the adjustment angle this time, and still adjust to the design angle the next time it is opened).

3. The system air valve is interlocked with the fan as a whole to realize the orderly flow of air flow, balance the air volume of the system, and prevent the air flow from being reversed.

(II) 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 electrical signal input frequency converter according to the number of ventilation equipment opened, so as to automatically adjust the fan frequency, so that the fan's exhaust volume matches the actual required exhaust air volume, so as to ensure the exhaust effect and achieve the effect of energy saving and noise saving;

2. Each fume hood is equipped with a venturi VAV valve. Its control switch is linked with the frequency conversion control system and the fan to realize the control of single or multiple ventilators under different working conditions. The VAV regulating valve adopts the venturi valve with digital display adjustable angle, and has the memory function (i.e. it can remember the adjusting angle this time, and still adjust to the designed angle the next time it is opened).

3. The system air valve is interlocked with the fan as a whole to realize the orderly flow of air flow, balance the air volume of the system, and prevent the air flow from being reversed.