Design Of Laboratory Ventilation System Engineering

- May 12, 2018 -

Design of laboratory ventilation system engineering

The laboratory ventilation system is one of the largest and most influential systems in the design and construction of the entire laboratory. The perfection of the ventilation system,

It has a direct impact on the laboratory environment, the physical health of experimental personnel, and the operation and maintenance of experimental equipment.

Excessive negative pressure in the laboratory, gas leaks from the fume hood, and laboratory noise have always been problems that have plagued laboratory workers. These problems give long-term

People working in the laboratory, even the management and logistics staff working around the laboratory, caused serious physical and psychological harm.

A scientific and reasonable ventilation system requires good ventilation, low noise, easy operation, energy saving, and even requires indoor pressure and temperature and humidity

Keep your body comfortable.

First, the design standard

1. "Code for the design of heating, ventilation and air conditioning" (GBJ19-87-2003).

2. "Quality Inspection and Assessment Standards for Ventilation and Air Conditioning Engineering" (GBJ304-2002).

3. Concise Ventilation Design Manual (GB50194-2002).

4. "Code for construction and acceptance of compressor, fan and pump installation engineering" (JBJ29-2002).

5. "Code for construction and acceptance of low-voltage electrical installations for electrical installations" (GB50254-96)

6. Integrated Air Pollutant Emission Standard (GB16297-1996).

7. Ambient Air Quality Standard (GB3095-1996).

8. "Urban area environmental noise standard" (GB3096-93).

9, "Building Design Fire Protection Code" (GB50016-2006).

10. "Energy-saving Design Standards for Public Buildings" (GB50189-2005).

11. The company's relevant information and relevant information provided by Party A.

Second, the design principle

1. According to the structural characteristics of the building, a ventilation shaft is set up nearby to divide the ventilation system and make-up system. The piping system is “short, flat, smooth, straight” and reduces system resistance.

Reduce system noise;

2. Exhaust air and air supply systems achieve air volume balance, maintain indoor -5Pa - -10Pa negative pressure, prevent spillage of harmful gases, and ensure the physical and mental health of experimenters;

3, cool air in the summer and warm air in the winter to ensure the comfort of indoor temperature and humidity;

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

5, comprehensive consideration of various factors, the use of less investment, stable operation, low operating costs, the effect of a good mature process;

6, the selected process must meet the site conditions, the layout of the plane is simple, compact, less land, and to facilitate the production operation and maintenance;

7, non-standard equipment should meet the national or industry-related norms, and to ensure stable performance, beautiful appearance;

8. Take full consideration of noise and odor in the design to prevent the occurrence of secondary pollution and not cause new pollution to the surrounding environment;

9. The processing facility is equipped with impact load capacity to ensure that the exhaust gas meets the emission standards.

Third, the design parameters

1. The wind speed in the branch pipe is 6~8m/s, and the wind speed in the trunk pipe is 8~14m/s;

2, ventilation design air volume:

Ventilation counter wind speed: 0.3~0.8 m/s, single 1200*800*2350 fume hood design air flow 1500m3/h, single 1500*800*2350 fume hood

Design air volume 1800m3/h, single 1800*800*2350 fume hood design air volume 2200m3/h, universal suction hood surface wind speed: ≥0.35 m/s, universal

Exhaust hood exhaust volume 150 ~ 350 m3 / h, atomic absorption hood wind speed: ≥ 0.35 m / s, exhaust capacity 350 ~ 600 m3 / h.

3. Air changes:

Number of air changes in general chemical laboratories: 8-12 times per hour

4. The ventilation system uses terminal noise ≤ 62db.

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

Fourth, the technical parameters of the fume hood

(I) Constant air volume system fume hood

1, the amount of exhaust

When the moving door is at a working opening height of 0.5m and the surface wind speed is maintained at 0.5m/s, it shall be in the row specified in the Technical Standard of the “Fume Hood” JB/T6412-1999.

Within the range of air volume, the actual amount of air exhausted shall not be greater than 5% of the calculated air flow (Calculation of exhaust air volume = sliding door width*moving door opening height*0.5m/s*3600 seconds).

2, surface wind speed

2.1 When the working opening height is 0.5 m and the surface wind speed is kept at 0.5 m/s, the exhaust air volume does not change and the moving door opening height changes.

The surface wind speed can meet the following requirements:

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

2.3 The moving door opening height is 0.15m, the average surface wind speed is less than 0.7m/s;

2.4 Surface wind speed uniformity (with low wind speed detector);

2.5 The surface wind speed of the exhaust hood should be distributed evenly. When the sliding door opening height is 0.5m and the surface wind speed is 0.5m/s, within the sliding door opening area, up and down

Every 0.3m, take a point, the measured surface wind speed, its maximum, minimum and arithmetic average deviation is less than 15%.

3, fume hood resistance

When the moving door of the exhaust hood is opened to the highest position, the exhaust volume and surface wind speed specified in the technical standard of "Fan Cabinet" JB/T 6412-1999 are maintained.

Under conditions of 0.5m/s, the resistance of the exhaust cabinet should be less than or equal to 70Pa.

4, other functional requirements

The fume hood operation panel control system must be a liquid crystal display (users operate more safely and conveniently). High-temperature alarm function in the cabinet; for example, KFJ-17

Profile speed monitoring sound and light alarm (wind speed too high, too low alarm function); automatic delay protection device, can completely evacuate residual corrosion, harmful,

Toxic gas; any adjustment function within the voltage range of 0~220V; step air valve performs any adjustment function of the system.

(2) VAV hood

1, according to the United States ANSI Z9.5-2003 standard, the ventilation cabinet surface wind speed higher or lower than 0.5m / s may lead to harmful gas escape, too low surface wind

Speed does not effectively capture harmful emissions. Excessive surface wind speeds cause turbulence and turbulence in the air flow in the fume hood. It may also lead to harmful substances.

Escape. In order to ensure the exhaust effect, the ventilation cabinet uses VAV variable air volume control method, which requires the air speed of the fume hood to be stable at 0.5m/s ± 5%;

2. The direct wind speed measurement and control system can quickly and effectively ensure the wind speed of the fume hood so as to ensure the safety of laboratory workers.

purpose. In order to avoid the impact of ambient temperature and humidity on the reference point drift of common wind speed sensors, the fume hood control system uses a hot wire wind speed sensor opposite

The actual wind speed is measured; the wind speed sensor is equipped with a unique self-cleaning filter that is resistant to dust plugging;

3. When the wind speed sensor detects a change in the surface wind speed, the controller sends a signal to the actuator, and the wind speed is returned to the surface by changing the opening of the variable air volume valve.

The set value requires the system response time is less than 3 seconds;

4. The wind speed sensor of the fume hood monitors the true surface wind speed in real time. When the surface wind speed is not within the set range, the monitor sounds after 15 seconds delay.

Light alarm

5. The monitor has the function of maximum air volume and minimum air volume. When an emergency occurs, the maximum air volume button can be pressed and the exhaust valve can be fully opened.

When you want the fume hood to run at low air volume (for example, at night), you can press the minimum air volume button. The fume hood operates with a small air volume.

6, the monitor also has a low wind speed operation button, press this button, you can make the surface wind speed setting value is 70% of the normal value, used to reduce the gas

Emissions are energy-saving (not recommended 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 sensing automatic frequency conversion control (or PLC programming control), and the static pressure sensing automatic frequency conversion control can be based on the opening ventilation equipment.

The amount of change, the static pressure of its induction into a 0-10v electrical signal input frequency converter to automatically adjust the fan frequency, so that the fan's ventilation

The quantity matches the actual required exhaust volume to ensure the exhaust effect and achieve the effect of energy saving and noise reduction.

2, Each fume hood is equipped with an electronic air volume control valve. Its control switch and frequency conversion control system and fan linkage can realize single or multiple channels.

Wind equipment and other conditions under control. The air volume control valve adopts an electronic air volume control valve with a digitally adjustable angle and has a memory function (that is,

Keep in mind the angle of this adjustment, and when it is opened next time, it is still transferred to the design angle).

3. The system air valve and the fan are interlocked as a whole to achieve an orderly flow of air and balance the air volume of the system so as to prevent reversed flow and reverse flow.

(II) Variable Air Volume System (VAV) Control

1. The system adopts the static pressure sensing automatic frequency conversion control, and the static pressure sensing automatic frequency conversion control can change the amount of the ventilation equipment according to the opening and induce it.

The static pressure reached is converted into 0-10V electric signal and input to the inverter to automatically adjust the fan frequency, so that the amount of air drawn by the fan matches the actual required amount of exhaust air.

Matching, to ensure the effect of exhaust, to achieve energy-saving effect of noise reduction;

2. Each ventilating cabinet is equipped with a venturi variable air damper. Its control switch, frequency conversion control system and fan linkage can realize single or multiple units.

Ventilation equipment and other conditions under control. VAV control valve adopts Venturi air valve with digitally adjustable angle and memory function

In order to remember this adjustment, the next time it is opened, it will still be adjusted to the design angle.)

3. The system air valve and the fan are interlocked as a whole to achieve an orderly flow of air and balance the air volume of the system so as to prevent reversed flow and reverse flow.

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