MH/T 6040-2017Test method for smoke density generated by aircraft materials (English PDF)

4.1 Smoke density tester

4.1.1 Composition

The composition of the smoke density tester is shown in Figure 1.

4.1.2 Smoke density box

As shown in Figure 1, the dimensions of the cavity width, depth, and height of the smoke density box are (914±3) mm, (610±3) mm, and (914±3) mm, respectively.

The material of the smoke density box should be enamel steel plate or stainless steel plate to prevent chemical corrosion and easy to clean regularly. The front of the box should be equipped with Door with glass observation window. The vertical light path passes through the left side of the smoke density box. The bottom and top plates of the box are inlaid with two corresponding plates of glass.

It is a light window so that the vertical parallel beam can pass through the smoke box. The box shall be equipped with air inlet, exhaust port, sampling port, mixed gas inlet, pressure relief port and and pressure measuring ports, etc., the door on the box body and the surroundings of all openings should be sealed to ensure that during the test, when the door is closed, the inside of the box the substance does not leak and may generate a small positive pressure to remain in the box. Explosion-proof plates should be provided at appropriate positions on the box wall.

4.1.3 Radiant furnace

The radiant furnace uses an electric furnace with an opening diameter of 76 mm and a power of about 650 W. The specific structure is shown in Figure 2.The electric stove should be located in the box the center line of the front and rear walls is equidistant, the opening end is 305 mm from the right box wall, and the furnace center line is 195 mm higher than the bottom of the box. Stability after closing the door in the state, the radiant furnace control system should maintain the heat at (2.50±0.05) W/cm2.The control system should have an autotransformer or AC control equipment.

4.1.4 Power supply

A stable power supply should be configured according to the requirements of the components of the smoke density analyzer. If the voltage fluctuation exceeds 2.5% of the rated value, it should also be equipped A voltage regulator.

4.1.5 Sample box

The sample box is shown in Figure 3.The exposed area of the sample should be (65.0±1.5) mm×(65.0±1.5) mm, and the sample box frame should be fixed separately the backing plate, spring leaf and stop rod of the sample.

4.1.6 Specimen backing

Use a heat insulation board as the backing of the sample and the blank sample. The heat insulation board shall be cut into (74±1) mm×(74±1) mm×(13±1) mm.

4.1.7 Insulated lead frame

The insulated lead frame is used to support the test lead. Its material is stainless steel. The structure and dimensions are shown in Figure 4 and Figure 5.

4.1.8 Support for radiant furnace and sample box

The brackets of the radiant furnace and the sample box should be assembled according to Figure 6.The distance between the end face of the furnace mouth of the radiant furnace and the exposed surface of the sample should be (38±1) mm.

4.1.9 Optical measurement system

4.1.9.1 The light measurement system is composed of a light source and a photodetector. The photodetector is used to measure the light emitted by the test material in the vertical direction.

Changes after the smoke is put. The position of the system in the smoke density box is shown in Figure 7, and the structure is shown in Figure 8.

4.1.9.2 The light source should be an incandescent lamp, installed in an airtight opaque cover at the bottom left of the smoke density box, with optical devices in the cover to shape the parallel beam passes through the smoke box. The light source should work in a constant voltage circuit, and the color temperature should be (2200±100) K.

4.1.9.3 The photodetector is a photomultiplier tube with a dark current less than 10-9 A. The photomultiplier tube is installed on the top of the box corresponding to the light source in the airtight opaque cover, there are corresponding optical devices in the cover to focus the parallel light beam passing through the smoke box into the light window of the photomultiplier tube.

4.1.10 Heat flow meter

There should be an air-cooled or water-cooled heat flow meter to calibrate the output of the radiant furnace.

4.1.11 Pressure regulator

The pressure regulator should consist of an open bottle filled with water and a tube with a length of no more than 305 cm and an inner diameter of 25 mm to 30 mm. tube One end is connected to the port in the box (the port is located within 152 mm from the top of the smoke density box), and the other end is 102 mm below the horizontal plane in the bottle Place.

4.1.12 Smoke density box wall thermocouple

The smoke density box wall thermocouple is used to monitor the temperature of the smoke density box wall. The thermocouple should have an insulating cover plate and be installed on the inner surface of the back wall of the box.

Where in the center.

4.1.13 Pressure gauge

The pressure gauge is used to monitor the pressure change in the tank, and a water pressure gauge with a measuring range of 152 mm water column should be used.

4.1.14 Smoke exhaust device

The smoke exhaust device is used to remove the residual gas and smoke in the test box after each test.

4.1.15 Burner

4.1.15.1 General requirements

The burner is composed of six combustion branch pipes and a mother pipe, as shown in Figure 9 and Figure 10.The six combustion branch pipes should have an outer diameter of 3.2 mm and an inner diameter it is made of (1.4±0.025) mm stainless steel pipes, all connected to a stainless steel mother pipe with an outer diameter of 6.4 mm and a wall thickness of 0.9 mm. Mother tube One end should be closed, and the other end should be connected to the gas source connection joint at the bottom of the box. The burner should be centered and placed parallel to the front of the sample box.

The centerline of the nozzle of the tube is located (6.4±1.5) mm above the bottom edge of the exposed surface of the sample, and (6.4±1.5) mm from the surface of the sample, as shown in Figure 9, 10 shown. The burner should be detachable so that different burners can be used for different tests. In addition, if there is a sample dripping in the nozzle hole Objects or residues should be removed in time with spring steel wire or other effective methods to avoid affecting the test results. The combustion tube of the burner can see the flame length the degree should be 6 mm, and the inner flame length should be 3 mm.

4.1.15.2 Standard burner

The nozzles of the six branch pipes of the standard burner (as shown in Figure 9) and the exposed surface of the sample form an angle of 0°, 45°, and 90° respectively, with two in the middle the angle between the nozzle and the exposed surface of the sample is 45°, the two nozzles on both sides form an angle of 90° with the exposed surface, and the other two have an angle of 0° with the exposed surface.

4.1.15.3 Straight tube burner

The nozzles of the six branch pipes of the straight-tube burner (as shown in Figure 10) are at an angle of 90° with the exposed surface of the sample. The burner is used to insulate wires Smoke density test.

4.1.16 Gas

The gas used by the burner is a mixture of filtered oil-free air and propane with a purity of at least 95%, and then is sent to the burner.

Each gas is passed through a calibrated flow meter. The mixture of air and propane is flowed at standard temperature and pressure.

(500±20) cm3/min of air and (50±3) cm3/min of propane. The pressure of compressed air flowing to the flowmeter is (0.14±0.03) MPa, the propane pressure is (0.1±0.02) MPa.

4.2 Pretreatment tank

The pretreatment chamber is used to process the samples. The samples should be kept at a temperature of (21±3) °C and a relative humidity of (50±5)%.

4.3 Other equipment

Other equipment refers to some auxiliary equipment used in the test process, such as recorders, computer data acquisition systems, etc.

5.1 Dimensions

The length and width of the sample should be (73 ± 2) mm, and the thickness should not be greater than 25 mm. The uncut surface should be the exposed surface.

5.2 Sample orientation

If the surface of the test sample has obvious texture or anisotropy, the sample should be sampled in two or more directions and all test results should be reported.

As a result, take the maximum value in the report and report the orientation direction of the sample, and the wire only tests the vertical direction.

5.3 Number of samples

At least three samples should be prepared for each material, product, structure or component.

5.4 Sample preparation

5.4.1 Sampling

The sample should be sufficiently representative of the tested material or component and be prepared in accordance with the specified procedures. Should be in the same thickness and same composition plane Partial rather than curved surface, molded surface or special part sampling. If either side of the tested material may be exposed to the flame, then the two sides both should be tested, and two sets of samples should be prepared accordingly.

5.4.2 Sample installation

5.4.2.1 All specimens shall be coated with 0.04 mm thick aluminum foil on the fire-back surface and surrounding edges, and the specimen shall be contacted with a matte surface. In package During the coating process, the aluminum foil should not be pierced or cause unnecessary wrinkles. After the sample is installed, the excess aluminum foil should be trimmed.

5.4.2.2 A spring plate and a stop rod are used to fix the sample and the backing plate. For samples with a thickness of 16 mm~25 mm, the thickness of the compressible sample should not be Deformed to be lower than normal thickness.

5.4.2.3 When installing the wire sample, for wires with a diameter of 1.29 mm or smaller, the wires should be wound around the insulated lead frame shown in Figure 4 A on. Pass one end of a 2.5 m long wire through a hole in the sample frame, and then wrap it in the groove on the frame one by one.

After one turn, put the end on the other hole of the sample holder to prevent loosening. For wires with a diameter of 1.29 mm~1.63 mm, the wires should be wound around

Figure 5 shows the insulated lead frame B. For wires with a diameter greater than 1.63 mm, the wires should be cut into 75 mm long wire segments, and then

Are arranged in front of the sample holder.

5.4.2.4 Wrap the sample with aluminum foil, put the sample, the backing plate and the spring sheet into the sample box in turn, and fix it so that the wire is vertically fixed in the test box.

The front of the inspection box is shown in Figure 11.

Figure 11 Fixing diagram of wire with diameter greater than 1.63 mm

7.1 Protection of radiant furnace

Prepare a blank sample composed of (13±1) mm thick asbestos plates. In order to ensure the stability of the heat flow radiated by the radiant furnace, the test is not carried out.

During inspection or calibration, place the blank sample in front of the radiation furnace.

7.2 Regular calibration steps

7.2.1 Optical measurement system

The optical system should be calibrated with a set of neutral filters or equivalent at least every two months.

7.2.2 Radiant furnace

Use a calibrated heat flow meter to monitor the heat generated by the radiant furnace. Install the heat flow meter on the horizontal rod of the radiant furnace bracket and slide it or move the blank sample box to accurately locate the relative position of the heat flow meter and the radiant furnace opening. Adjust the setting of the radiant furnace control system so that the heat is (2.50±0.05) W/cm2.When the heat reaches the specified requirements and is stable for at least 5 minutes, take out the heat flow meter from the box and place the blank sample box Move to the radiant furnace mouth.

7.2.3 Leak test of cabinet

The smoke density box leakage test should be carried out at least once a month. The test steps are as follows.

a) Close the intake valve and the box door;

b) Pressurize the tank so that the pressure in the tank is not lower than the atmospheric pressure 76.2 mm water column;

c) Monitor the pressure in the tank and confirm that the pressure leak in the tank is less than 50.8 mm water column within 2 minutes.

7.2.4 Total system

A test should be performed at least once a month to check the entire system. The test material should use a stable, maximum smoke density value (4Dm) within 4 minutes Standard samples between 150 and 220.

8.1 Preparation before the test

8.1.1 Clean the inner wall of the test box, the electric furnace and the support, and clean the upper and lower light windows of the light measurement system.

8.1.2 Position the burner and the test position accurately, and then place the blank sample in the test position (only in the calibration of the radiation furnace and the test Move away from that position when the time comes).

8.1.3 Turn on the main power supply, adjust the temperature of the inner wall of the box to (35±2) °C through the heating power supply and exhaust fan, adjust the voltage of the radiant furnace, and make the test the surface heat of the sample reaches (2.50±0.05) W/cm2.

8.1.4 Perform zero adjustment and 100% adjustment on the optical measurement system respectively.

8.1.5 Adjust the propane gas and air flow to (50±3) cm3/min and (500±20) cm3/min respectively, and ignite the six flames of the burner Ensure that the flame meets the requirements of 4.1.15.1.

8.2 Test

8.2.1 Fix the sample on the sample box, place the sample box in the test position, start the timer and close the door immediately.

8.2.2 During the test, the pressure in the box should be checked. When negative pressure occurs, the air inlet should be slightly opened; when positive pressure occurs, attention should be paid to the pressure difference change;

When the pressure difference is too large, the exhaust valve should be opened to prevent explosion or other accidents.

8.2.3 During the test, carefully observe the burning condition of the combustion tube. when.

a) When testing insulated wires, at the beginning of the test (within 5 s), if the flame of the burning branch pipe goes out, the test should be stopped.

Re-ignite and perform the test again; if the flame of the burning branch pipe is extinguished within the first 10 minutes, the test should be invalid and a new sample Re-test; if the flame of the burning branch pipe goes out after 10 minutes, the test should be continued, and the number of flames extinguished and Extinguishing time

b) When testing other samples, pay attention to the four combustion tubes perpendicular to the surface of the sample and at an angle of 45° to the surface of the sample.

If any one of the combustion tubes has been extinguished for more than 3 s, the test shall be deemed invalid, and the test shall be retested with a new sample;

c) When performing flameless combustion, the burner should be removed before starting the test.

8.2.4 The test time for insulated wires is 20 min, and the test time for other samples is 4 min. After the test, replace it with a blank sample box for the sample box, open the exhaust valve to completely remove the smoke in the box and prepare for the next sample test.

8.2.5 After each test, the glass light window, observation window, cabinet wall, and sample box of the optical measurement system should be cleaned.

8.3 Test record

8.3.1 The light transmittance in the test box shall be recorded continuously until the end of the test.

8.3.2 Detailed records of various phenomena during the test, such as shrinkage, melting, delamination, dripping, and sinking of the sample.