This standard specifies the definition, principle, equipment, method steps, determination and written procedures for inspection and identification. This standard is applicable to the investigation of the cause of electrical fire, from the appearance characteristics of the copper and aluminum wire melting mark, to identify the relationship between the melting cause and the fire cause. GB 16840.1-1997 Technical identification method for the cause of electrical fire Part 1: Macroscopic method GB16840.1-1997 Standard download decompression password: www.bzxz.net

GB16840.1—1997
The series of standards of "Technical identification methods for electrical fire causes" consists of 4 parts: Part 1 Macroscopic method; Part 2 Residual magnetism method; Part 3 Composition analysis method; Part 4 Metallographic method. This standard is Part 1 of the series of standards of "Technical identification methods for electrical fire causes": Macroscopic method. The macroscopic method is to determine the melting cause and provide samples for microscopic analysis based on the appearance characteristics of the melting mark of copper and aluminum wires and the inner surface characteristics of the molten bead cavity in the fire scene.
This standard consults and refers to the content of the appearance characteristics of the short-circuit melting mark of the wire in the book "Electrical Fire Causes and Identification" compiled by the Tokyo Fire Department of Japan.
This standard is proposed by the National Fire Standardization Technical Committee. This standard is under the jurisdiction of the Sixth Subcommittee of the National Fire Standardization Technical Committee. The drafting unit of this standard: Shenyang Fire Science Research Institute of the Ministry of Public Security. The main drafters of this standard: Han Baoyu, Wang Xiqing, Di Man, Gao Wei. 64
1 Scope
National Standard of the People's Republic of China
Technical determination methods for electrical fire causePart 1 : Macroscopic method
GB 16840.1-1997
This standard specifies the definition, principle, equipment and materials, method steps, determination and written procedures to be followed in inspection and identification. This standard is applicable to the identification of the relationship between the melting cause and the fire cause from the appearance characteristics of the melting mark of copper and aluminum conductors when investigating the cause of electrical fire. 2 Definitions
This standard adopts the following definitions:
2.1 Melted mark
Circular, pit-shaped, nodular, pointed and other irregular micro-melting and full-melting marks formed on copper and aluminum conductors under external flames or high temperatures of short-circuit arcs.
2.2 melted bead
A round bead-shaped melting mark formed on the end, middle or falling part of a copper-aluminum conductor under the influence of external flame or short-circuit arc.
2.3 melted mark due to fire burningA mark left after a copper-aluminum conductor is melted by flame or high temperature in a fire. 2.4 primary short circuited melted markA mark left after a copper-aluminum conductor is melted by its own fault before the fire. 2. 5 secondary short circuited melted markA mark left after a steel-aluminum conductor is charged and the insulation fails due to external flame or high temperature. 2.6 inside carity caused by short circuited melted beadAny melted bead formed at the end of a conductor due to a short circuit has a cavity inside, and the inner surface of the cavity has the characteristics of the environmental conditions at the time when the short circuit was formed.
2.7 Fusion transition
The melting phenomenon that exists within a certain distance from the fusion mark to the conductor is a characteristic of fire fusion marks and secondary short-circuit fusion marks. 3 PrincipleWww.bzxZ.net
Whether copper and aluminum conductors are melted by the heat of fire or the high temperature of short-circuit arc, in addition to being completely burned, residual fusion marks can generally be found, and the appearance of the fusion marks still has the characteristics that can represent the environment at that time. The primary short-circuit melting mark and the secondary short-circuit melting mark are both instantaneous arc high-temperature melting, with the characteristics of fast cooling speed and small melting range, but the difference is that the former short-circuit occurs under the condition of the wire's own fault, and the latter short-circuit occurs under the conditions of fireworks and temperature. The traces of the wire being melted by the heat of the fire, its time and temperature are different from the short-circuit, it has the characteristics of long temperature duration, large burning range, and melting temperature lower than the short-circuit arc temperature. Because different environmental products participate in the whole process of melting mark formation, the respective characteristics of distinguishing the formation of primary and secondary short-circuit melting marks are retained. This has been scientifically verified in terms of appearance, content of different elements, and metallographic microstructure. 4 Equipment and Instruments
4.1 Stereo microscope
Magnification of more than 50 times.
4.2 Lamps
Ordinary lamps with shades, use 60W incandescent bulbs. 4.3 Apparatus
Sampling tools, paper bags for samples, brushes. 5 Methods and Steps
5.1 Sample Extraction
5.1.1 Location
The fusion mark samples used for identification should be taken from the confirmed fire point or fire location. Samples from non-fire locations should not be extracted for identification, but can be used for comparison.
5.1.2 Verification
When extracting samples, it should be verified whether the samples are original or mixed into the fire location due to fire extinguishing, rescue of materials or other reasons. Only after verification can they be extracted as identification samples. 5.1.3 Photographing
Before extracting samples, on-site photos should be taken. Photos are divided into sample extraction orientation and sample close-up. 5.1.4 Extraction
After checking the wire and finding the melting mark, it is advisable to cut the wire and remove it together with the melting mark at a distance of 50~100mm. 5.2 Storage
The extracted sample should be stored in a bag and should not be mixed with other objects. The sample name and extraction location should be marked. 5.3 Sample processing and observation
5.3.1 Removal of dirt
Remove the carbon ash and dirt on the sample with water or solvents such as alcohol and acetone. 5.3.2 Removal of the molten bead
Remove the molten bead at the connection between the wire and the molten bead to expose its inner surface. However, when using the tool to clamp the molten bead, it is not advisable to use too much force to prevent deformation or damage.
5.3.3 Preparation for observation
According to the instrument instructions, remove the cover of the stereo microscope, replace it with the required eyepiece, and prepare for observation. 5.3.4 Observation
Fix the sample and place it on the bottom of a stereo microscope. Observe it under sunlight or incandescent light. The inner surface of a pair of molten beads should be observed for overall gloss, color, number of cavities, carbon traces, and grain traces. It should not be limited to a certain cavity. For the observation of carbon traces, grain traces, and spots, the magnification of the stereo microscope should be adjusted to more than 50 times, and the focus should be on the bottom of the cavity. 6 Determination
6.1 Burning trace
6.1.1 Melt bead
The diameter of the copper wire bead formed by burning is 1 to 3 times the wire diameter, and 1 to 4 times the aluminum wire diameter. The bead is located at the end or middle of the wire. The surface of the bead is smooth, without pits and small pits, and has a metallic luster. 66
6.1.2 Melting transition zone
GB 16840.1-1997
There are traces of melting transition between the wire and the molten bead, and the wire becomes obviously thinner. 6.1.3 Conductor
Copper and aluminum conductors have melted and become thinner, melted and accumulated to become thicker or form melt nodules, pointed melt marks, and small shiny melt beads attached to the conductors.
6.1.4 Pits
Aluminum conductors have a large number of pits formed by melting, and the surface inside the pits is smooth and matte. Copper conductors do not have this feature. 6.1.5 Multi-strand soft wires
Melted beads or pointed melt marks are formed at the ends of multi-strand soft wires. The thin copper wires below the melt marks are melted and bonded together, making it difficult to separate them. 6.2 Primary short circuit melt marks
6.2.1 Melted beads
The diameter of the melt beads of copper conductors is 1 to 2 times the wire diameter, and the diameter of the melt beads of aluminum conductors is 1 to 3 times the wire diameter. The location of the melt beads is at the end of the wire or on one side of the wire end. Some large melt beads are attached to the wires below small melt beads. The surface of the copper molten bead is shiny, while the surface of the aluminum molten bead has a layer of gray aluminum oxide film, pits and burrs.
6.2.2 Melting transition
There is a clear boundary between melting and non-melting between the melting mark and the wire, and there is no melting transition mark. 6.2.3 Wire
Several hemispherical melting marks with cavities are formed on the surface of the copper wire, and their spacing is relatively uniform. Most of them are black, and some are also shiny. Aluminum wires do not have this feature.
6.2.4 Pits
Pits appear on the wire and appear at the corresponding positions of the two wires. The inner surface of the pit is shiny but not smooth, with accumulated molten gold and burrs, and it feels prickly to the touch. Some pits are also stained with tiny molten beads of the same metal. 6.2.5 Multi-strand soft wire
Melting marks are formed at the ends of multi-strand soft wires, and the wires connected to the melting marks have no melting and bonding marks, and the multi-strand thin copper wires can still be separated one by one. Tiny beads of melt appear at the ends of some thin copper wires.
6.3 Secondary short-circuit melt marks
6.3.1 Melt bead
The diameter of the copper wire melt bead is relatively larger than the single short-circuit melt bead, but smaller than the melt bead formed by fire. There are tiny pits on the surface and poor gloss. The surface of the aluminum wire melt bead has a layer of dark gray aluminum oxide film with small pits, cracks and collapse phenomena. The end of the non-melt bead-shaped melt mark is mixed with black carbide.
6.3.2 Melting transition
Within a distance extending from the melt mark to the wire, there are traces of micro-melting and thinning on the wire. 6.3.3 Wire
Several short-circuit points appear on a shorter section of the wire. 6.3.4 Multi-strand soft wire
A melt bead is formed at the end of the multi-strand soft wire, and the wire connected to the melt bead becomes hard or sticks together, and its multi-strand thin copper wire cannot be separated one by one. 6.4 Holes inside the molten bead
6.4.1 Fire molten bead
There are no cavities inside the round bead-shaped molten mark formed by the heat of the fire, but there are gap holes that are not completely melted in the multi-strand soft wire molten bead. 6.4.2 Secondary short-circuit molten bead
There are cavities inside the primary short-circuit molten bead, the number of cavities is small, and most of them are distributed in the middle of the molten bead. The inner surface of the cavity of the copper wire molten bead is dark red, with poor gloss, smooth and with trace carbon traces. Except for a layer of dark gray aluminum oxide film on the inner surface of the cavity of the aluminum wire molten bead, other characteristics are similar to those of the copper molten bead. 6.4.3 Secondary short-circuit molten bead
GB16840.1-1997
There are cavities inside the secondary short-circuit molten bead, the number of cavities is large and distributed at the edge and middle of the molten bead. The inner surface of the cavity of the copper wire molten bead is transparent bright red (ruby color), with strong gloss and more carbon traces. The inner surface of the hollow of the aluminum wire bead has a layer of light gray aluminum oxide film with strong gloss and rough stripes or bright spots. 7 Written procedures to be followed during inspection and monitoring 7.1 When submitting for inspection, the inspection unit should first fill out the application form for technical identification of the cause of electrical fire, which includes the name, address, and contact person of the unit applying for the identification; the name of the unit on fire, the name and quantity of the sample, the sampling location, the sampler, and the purpose of the identification. 7.2 After accepting the identification task, the identification unit should fill out the sample receipt form, task form, reception record, and original record. 7.3 After the identification is completed, the identification conclusion shall be filled in the identification report approval form, signed by the person in charge of the laboratory, and submitted to the leader for approval after the quality review is correct.
7.4 The original of the approved identification report shall be handed over to the inspection unit, and a copy shall be kept for filing and inspection. 68
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