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GB/T 40237-2021 English PDF (GBT40237-2021)

GB/T 40237-2021 English PDF (GBT40237-2021)

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GB/T 40237-2021: Test method for ignitability of foamed plastic - Welding spark method

This document specifies the test method by using welding spark to impact the horizontally placed foamed plastic samples to measure its ignitability under laboratory conditions. This document applies to all kinds of rigid foamed plastics and flexible foamed plastics, such as polystyrene, polyethylene, polyurethane, phenolic aldehyde and other materials.
GB/T 40237-2021
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 13.220.40
CCS C 80
Test method for ignitability of foamed plastic -
Welding spark method
ISSUED ON: MAY 21, 2021
IMPLEMENTED ON: DECEMBER 01, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the PEOPLE Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms and definitions ... 4
4 Test principle ... 5
5 Instruments and apparatuses ... 5
6 Test sample ... 10
7 Conditioning ... 11
8 Test procedure ... 11
9 Optional procedures ... 13
10 Test result judgments ... 14
11 Safety protection ... 14
12 Test report ... 15
Test method for ignitability of foamed plastic -
Welding spark method
1 Scope
This document specifies the test method by using welding spark to impact the horizontally placed foamed plastic samples to measure its ignitability under laboratory conditions.
This document applies to all kinds of rigid foamed plastics and flexible foamed plastics, such as polystyrene, polyethylene, polyurethane, phenolic aldehyde and other materials.
2 Normative references
The contents of the following documents constitute the indispensable clauses of this document through normative references in the text. For dated references, only the version corresponding to that date is applicable to this document; for undated references, the latest version (including all amendments) is applicable to this document.
GB/T 2918-2018, Plastics. Standard atmospheres for conditioning and
testing
GB/T 5117, Covered electrodes for manual metal arc welding of non-alloy and fine grain steels
GB/T 5907.1, Fire protection vocabulary - Part 1: General terms
GB/T8110, Wire electrodes and weld deposits for gas shielded metal arc
welding of non alloy and fine grain steels
3 Terms and definitions
Terms and definitions determined by GB/T 5907.1 and the following ones are applicable to this document.
3.1
Welding spark
20 ?€? electric welding ignition system.
Figure 1 ?€? Schematic diagram of the electric welding spark test device
5.2 Combustion box
5.2.1 The combustion box shall meet the following requirements.
a) It is made of a stainless-steel plate; a heat-resistant glass window whose size is 570 mm ?? 970 mm is installed at the front, to facilitate the test operation and observation from the front of the box.
b) The inner space of the combustion box is 800 mm ?? 800 mm ?? 1 000 mm. c) The combustion box is fixed on a base whose size is 880 mm ?? 880 mm
?? 50 mm; a controller is provided on the base.
5.2.2 The combustion box is naturally ventilated through the opening at the bottom of the box. There are 3 vents, and the opening size is 25 mm ?? 430 mm. 5.2.3 The flue gas that is generated by combustion is removed through the exhaust hole whose diameter is 250 mm on the top of the combustion box. 5.2.4 The combustion box shall be placed under the fume hood; the fume hood shall be closed during the test, and shall be opened immediately after the test, so as to eliminate potentially toxic combustion products.
5.3 Electric welding ignition system
5.3.1 The electric welding ignition system includes a carbon dioxide gas shield welding machine, a welding wire, a welding gun, a low-carbon steel plate, and a micro-motor, where the carbon dioxide shield welding machine is located on one side of the combustion box and placed in a small stainless steel box. The stainless-steel box and the combustion box are welded together.
5.3.2 The carbon dioxide shield welding machine includes welding power
source and wire feeding mechanism. The welding power source is provided with an arc voltage adjusting knob and a welding current adjusting knob. Adjust the arc voltage and welding current to make the welding machine in normal working condition. In general, there is an optical matching value for the arc voltage and welding current, which can be adjusted according to the actual use. 5.3.3 The wire feeding mechanism is located on the upper part of the welding power source, which can send the welding wire in the wire reel to the outlet of the welding gun, and adjust the wire feeding speed of the welding wire. 5.3.4 This test method uses ER50 rolled carbon steel welding wire whose diameter is 1.0 mm. The material and performance of the welding wire shall meet the requirements of the standard GB/T 8110.
5.3.5 The welding gun is connected to the positive electrode of the welding power source and shall meet the following requirements.
a) The welding gun passes through the opening on the side wall of the box and is placed on the upper part of the combustion box.
b) The welding gun can adjust the extension length of the welding wire. The extension length of the welding wire is usually about 10 times the diameter of the welding wire.
c) The welding gun uses the heat that is generated by the high current and high voltage of the carbon dioxide shield welding machine to gather at the welding gun terminal to melt the welding wire.
5.3.6 The low carbon steel plate, which is used as the base material to simulate the welded workpiece, shall meet the following requirements.
a) The low carbon steel plate is connected to the negative electrode of the welding power source.
b) The low carbon steel plate is located directly above the welding gun; the size is 250 mm ?? 150 mm ?? 10 mm.
c) The low carbon steel plate is fixed on the metal clip of the micro motor through the screw holes on the four corners; the micro motor drives the movement of the low carbon steel plate.
d) During the test, the low carbon steel plate moves at a constant speed relative to the welding gun.
5.3.7 There are two micro motors that control the operation of the low carbon steel plate; one controls its left and right movement, and the other controls its forward and backward movement. The following requirements shall be met
during operation.
a) First, a micro motor drives the low carbon steel plate to run from the left end to the right end; then, another micro motor drives it to change the line, so that the low carbon steel plate runs from the right end to the left end; then, it changes to another line and runs line by line.
b) The motion trajectory that is formed by the welding wire on the low carbon steel plate is shown in Figure 2.
5.4.4 The timing device can continuously record the test time and display it to the second with an accuracy of 1 s.
5.5 Sample holder
5.5.1 The sample holder is a square stainless steel frame slot, whose size is 610 mm ?? 610 mm. The steel wire grid is located in the stainless-steel frame slot and is composed of a 6 mm ?? 6 mm ?? 0.9 mm stainless steel grid.
5.5.2 The sample holder is located above the base and equidistant from the sides of the combustion box. The sample holder is supported by a steel rod handle that is fixed on the right side of the combustion chamber; the upper and lower distance can be adjusted by the knob on the handle, so as to ensure that the lower surface of the low carbon steel plate and the upper surface of the sample maintain a distance of (600??50) mm.
5.6 Tray
5.6.1 The tray is a stainless-steel collection tray; the tray is tapered, and located directly below the sample holder; it is used to collect drips generated during the test.
5.6.2 Absorbent cotton is placed in the tray. The area of the absorbent cotton is 550 mm ?? 550 mm. It is used to observe whether it is ignited by dripping during the test.
6 Test sample
6.1 Requirements
The test samples shall be prepared according to the following requirements. a) The sample shall be taken from a sample that is large enough to represent the product.
b) The sample shall be a rectangular parallelepiped. The standard sample size is (600??5) mm ?? (600??5) mm ?? (50??2) mm. If the thickness of a single sample is less than 50 mm, the thickness can be superimposed up to 50
mm; other thicknesses can also be used; but the thickness shall be stated in the test report.
c) Determine the fire surface according to the actual use of the sample; keep the fire surface when cutting.
d) The sample can be processed by mechanical cutting and grinding; the
surface of the sample is required to be smooth and flat, free of flash and burrs.
6.2 Quantity
The number of test samples in each group is 3 pieces. The deviation of the density of any sample from the average density of 3 samples in the same group shall not be greater than 5%; otherwise, a new sample shall be replaced until it meets the requirements.
7 Conditioning
7.1 Before the test, the sample shall be conditioned, in accordance with GB/T 2918-2018, in an environment where the temperature is (23 ?? 2) ??C and the relative humidity is (50 ?? 10) %, for at least 88 hours.
7.2 The test shall be carried out under standard laboratory conditions where temperature is 15??C ~ 35??C and the relative humidity is 45% ~ 75%, unless there are other conditions specifically specified.
8 Test procedure
8.1 Test preparation
8.1.1 Turn on the power switch of the base and adjust the welding current and arc voltage of the carbon dioxide shield welding machine.
8.1.2 Place the welding wire reel in the wire feeding mechanism; one end of the welding wire passes through the welding gun; send the welding wire out of the gun nozzle through the adjusting knob of the wire feeding mechanism and the control switch of the welding gun; adjust the wire feeding speed and extension length of the welding wire. The wire feeding speed shall be compatible with the arc voltage, so as to ensure that there will be no wire jacking or arc breaking. 8.1.3 Place the low carbon steel plate under the metal clip of the micro motor; use 4 screws to fix it.
8.1.4 Set the angle between the welding gun and the low carbon steel plate. Adjust the welding gun, so that the welding gun is obliquely upwards, at an angle of (45??5) ?? with the low-carbon steel plate, so as to ensure that the generated electric welding sparks are vertically downward. The relative position of the welding wire and the low carbon steel plate is shown in Figure 3. 8.1.5 Set the speed of the micro motor to keep the operating speed of the low carbon steel plate relative to the welding gun between 5 mm/s ~ 10 mm/s. 8.1.6 Set the ignition time to 60 s; if other ignition time is used, it shall be noted in the report.
8.2.7 There is strong light radiation during the test, and it shall not be directly observed with the naked eye; a video recorder or camera can be set to record the test process; the video recorder or camera shall be placed so that the shooting range includes the panoramic view of the flame impact area when the spark ignites the sample; the time shall be displayed in the area where the image is recorded, and the timing shall be accurate to the second.
8.2.8 60 seconds after ignition, turn off the test switch, and the welding spark stops. If there is still flame burning, the flame burning time shall be recorded continuously; if smoldering occurs, the smoldering time shall be recorded. 8.2.9 Until the flame burning or smoldering is completely extinguished, the test is over, and the flame burning time or the smoldering time ends. Record the smoldering time, which shall not exceed 24 h. Open the heat-resistant glass window and turn on the external exhaust fan to exhaust the flue gas in the combustion box.
8.2.10 Take out the test sample and clean the sample drips in the sample holder and tray.
8.2.11 Carry out 3 tests according to the above steps.
8.2.12 If the safety of test personnel and equipment is threatened during the test, the test shall be terminated immediately.
9 Optional procedures
9.1 For the test device, carbon steel welding rod can be selected to replace welding wire; the carbon steel welding rod shall be an E43 series welding rod. 9.2 The diameter of the carbon steel welding rod is 2.5 mm; the length of the welding core is 300 mm. The chemical composition and mechanical properties of the welding rod shall meet the requirements of GB/T 5117.
9.3 The welding current and arc voltage of the welding power source in the test device shall be set according to the normal operating conditions of the welding rod.
9.4 Before operation, place the welding rod in the clamping mechanism of the special welding gun and fix it. Adjust the angle of the welding gun, so that the welding rod and the low carbon steel plate are at an angle of (45??5) ??. An additional micro motor can be added to the test device to control the movement of the welding gun.
9.5 The operation mode of the low-carbon steel plate remains unchanged; the welding rod moves at a uniform speed under the drive of the welding gun; the

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