Problems needing attention in the renovation of clean room

The height of the general old factory buildings is about 3m, and the area and shape are quite different from the actual needs. Usually, it is not possible to install air ducts, technical interlayers and special air-conditioning systems in accordance with the routine. According to the basic principles of air purification, in practice, we have explored a very practical method for technological transformation of clean rooms, especially suitable for the technological transformation of small and medium-sized clean rooms. It is introduced as follows:

1. Structural Pattern

The schematic diagram of using ordinary air conditioners to directly send cold air to the mainstream air area to transform the dust-free workshop. The dust-free workshop is built in the old factory building with a room height of 3m. The top of the dust workshop is a fan room with a height of about 0.6 m, which is equipped with a fan box. All sides of the fan room are closed, and there is a medium-efficiency filter air inlet for inward ventilation. The fan is installed in the fan box, and the lower part is the static pressure box and the filter. There is no return air primary filter on the lower side of the clean room, and the outside of the clean room is a return air channel, which is connected to each other, and there is at least one split air conditioner. The air conditioner can be an ordinary cabinet-type split air conditioner first. The air outlet is equipped with a shroud and a cold air duct, and the other end of the cold air duct is installed in the fan room. Under normal circumstances, the blower of an ordinary air conditioner can send the cold air to a distance of 15 m, which can basically meet the use of ordinary small and medium-sized dust-free workshops. When the air supply distance is long, a fan can be installed on the cold air duct to increase the air supply pressure.

It should be noted that the shroud and the cold air duct must be insulated. The thickness of the indoor unit of an ordinary cabinet-type split air conditioner is generally 0.25m~0.35m. Considering the width of the shroud, the width of the return air passage can be made 0.5m~0.7m. When a wall-mounted air conditioner is selected, the width of the return air channel can be reduced, and the width of the other return air channels can be made 0.1 m. In this way, the design of the clean room can utilize the building space.

2. Air circulation mode

The airflow is sent to the static pressure box by the wind, enters the clean room through the filter, and then enters the return air passage from the return air primary effect filter. In the fan room, the other part of the return air flow directly enters the air inlet of the air conditioner. After cooling, the air enters the fan room through the shroud and the cold air duct. After the two partial flows are mixed in the fan chamber, they are sent to the static pressure box by the fan through the medium-efficiency filter on the fan box, and then enter the dust-free workshop through the filter to form an air circulation system. It can be seen from the circulation of the air flow that a good three-stage filtration state has actually been formed. Therefore, the air quality of the clean room is reliably guaranteed. On this basis, by adjusting the structure and layout of the air outlet of the filter, with the corresponding air volume, the clean form and cleanliness of the clean room can be determined to meet different needs.

Ultra-clean bench filter for DOP leak test

Why do DOP leak test for ultra-clean bench filters?

1 Overview

If the filter and its installation are defective, such as the filter itself has small holes or the installation is not tight to form tiny cracks, it will lead to the failure to achieve the intended purification effect. Therefore, after the filter is installed or replaced, it is necessary to check the filter and the installation connection for leaks.

2. Purpose of leak detection

By testing the filter for leaks, defects in the filter and its installation are identified so that remedial action can be taken.

3. Leak detection range

Clean areas, laminar flow benches, and filters on equipment, etc.

4. Leak detection method

The commonly used leak detection is the DOP method (that is, the DOP solvent is used as the dust source, and the aerosol photometer is used for leak detection), and the dust particle counter scanning method can also be used for leak detection (that is, the atmospheric dust is used as the dust source, and the particle counter is used for the detection. leak). Since the particle counter readings are cumulative readings, it is not conducive to scanning, and the inspection speed is slow; in addition, on the windward side of the tested filter, the atmospheric dust concentration is often low, and it is easy to find leaks only after additional smoke is generated. DOP method can make up for these deficiencies, so DOP method is widely used in foreign countries for leak detection.

5. DOP leak detection

5.1. How it works

DOP aerosol is emitted as a dust source on the upwind side of the tested filter (DOP is dioctyl phthalate, molecular weight is 390.57, and the particles are spherical after spraying), and the collected air samples are sampled with a photometer on the downwind side. Through the diffusion chamber of the photometer, the scattered light generated by the dust-laden gas through the photometer is converted into electricity by the photoelectric effect and linear amplification, and is quickly displayed by the microammeter, and the relative concentration of the aerosol can be measured. What the DOP test actually measures is the penetration rate of the filter.

5.2. Materials and Instruments

① Dust source (DOP solvent);

② DOP generator [is a device for generating smoke, after the DOP solvent is poured into the generator container, aerosol smoke is generated under certain pressure or heating conditions and sent to the upwind side of the filter (heating the DOP liquid to form DOP steam, the steam in Under specific conditions, it condenses into tiny droplets, removes too large and too small droplets, leaving only particles of about 0.3 μm, and the misty DOP enters the air duct);

③ Aerosol photometer (the instrument for measuring and displaying aerosol concentration should indicate the validity period of calibration, and it can be used only after passing the calibration and within the validity period);

④ Nitrogen;

⑤ Epoxy silica gel;

⑥ Spare filter of desired type

5.3. Working procedure of leak detection test

5.3.1. Preparation for leak testing

Prepare the equipment required for leak detection and the layout plan of the air supply ducts of the purification air conditioning system in the area to be tested, and notify the purification air conditioning equipment company to be present on the leak detection day to perform operations such as glue application and filter replacement.

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