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Graphic illustration of the structure principle of the smoke densitometer
The smoke density tester is mainly composed of a smoke box, a sample holder, an ignition system and a photoelectric system. 1. Smoke box The structure of the smoke box is shown in the figure. The smoke box is composed of a rust-proof metal plate with a size of 300mmX 300mmX 790mm equipped with a heat-resistant glass door. The smoke box is fixed on a base with a size of 350mm×400mm×57mm, and a controller is provided on the base. The inside of the smoke box should have a surface treatment to protect the metal from corrosion. Except for the opening of 25mm × 230mm around the bottom of the smoke box, the rest should be sealed. A 1700L/min exhaust fan is installed on one side of the smoke box, the air inlet of the exhaust fan is connected to the inside of the smoke box, and the exhaust port is connected to the fume hood. If the smoke box is under the smoke collecting hood, it does not need to be connected to the fume hood. At the center positions on the left and right sides of the smoke box door at a height of 480mm from the base, there is a smoke-proof glass round window with an opening diameter of 70mm. At these positions and outside the smoke box, corresponding optical equipment and additional controls are installed. Device. A replaceable white plastic plate is installed on the back of the cigarette box. It is located at the center of the back panel of the cigarette box 480mm from the base. It is 90mm high and 150mm wide. Through it, you can see an illuminated escape sign 'EXIT' in red on a white background. 'The words. The flame, smoke and combustion characteristics of the material can be easily observed on the white background. It is helpful to find the relationship between visibility and test value by observing the safety exit signs. 2. Sample holder The sample is placed on a square frame slot with a side length of 64mm. The square is made up of 6mm×6mm×0.9mm stainless steel grid. The square holder is located 220mm above the base and is equidistant from the sides of the smoke box. The steel wire grid is located in the stainless key frame slot. The stainless steel frame slot is supported by a steel rod handle fixed on the right side of the cigarette box. Installed on the same key rod handle, there is a similar stainless steel 7fimm below the sample holder The key frame slot, which supports a square asbestos board. The asbestos board can collect drips during the test. By rotating the steel rod of the sample holder, the burned sample can be extinguished by falling into the tray with a small amount of water below. 3. The ignition system sample should be ignited by the propane flame produced by the igniter with a working pressure of 276kPa. The fuel gas should be mixed with air. When the fuel gas passes through a hole with a diameter of 0.13mm, use the action of the propane venturi to push the air and pass it into the igniter together. The igniter must be designed to provide sufficient outside air. The igniter under the sample should be able to quickly adjust the position so that the axis of the igniter falls on an 8mm point above the base. The igniter extends diagonally at the back corner of the smoke box and is inclined upward at 45° from the base. The outlet of the igniter should be 260mm from the reference point on the back of the smoke box. The pipe outside the smoke box should be at least 150mm long, and it should be able to introduce air into the igniter. 4. The photoelectric system uses a light source, a photocell with a barrier layer and a temperature compensator to measure the percentage of the light beam after passing through a 300mm smoke layer. The beam path propagates in the horizontal direction, as shown in the figure. The light source is installed in a light source box protruding from the left wall of the smoke box, located at a height of 480mm above the base. The light source is a filament-intensive instrument bulb with a working voltage of 5.8V. The light source is a spherical reflector. Its power supply is provided by an adjustable voltage transformer. A lens with a focal length of 60-65mm focuses the beam on the photocell on the right wall of the instrument. Another box with a photometer is installed on the right side of the smoke box. Photocells with barrier layers should have standard spectral response. A circular grid box should be installed in front of the photovoltaic cell to protect the cell from astigmatism. The grid should be dark and polished. The depth of the opening should be at least twice the width. The current induced by the photocell is displayed on the meter as the absorption rate of light. The photocell decreases linearly as the temperature increases, so compensation should be made. The working temperature of the photocell is not higher than 500℃. The meter should have two ranges. The range can be changed by switching the meter to one-tenth of its sensitivity. When the smoke accumulates to absorb 90% of the beam, it should be changed quickly to reduce the sensitivity of the meter to the basic value. To achieve this, the scale of the meter should be from 90% to 100%, not from 0 to 100%.
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