An Analysis of the Fire in the Elderly Apartment of Luhe Park in Siping City in 2014

With the rapid economic development, all kinds of electrical equipment and electrical products are widely used in social production and life. Due to factors such as careless use of electricity, use of substandard electrical products, failure of electrical lines, etc., fires caused by electrical causes frequently occur every year. The fire caused by this accounted for more than 30% of the total number, causing losses to the lives and property of the people. Electrical fires have become the main disaster-causing factors affecting the fire safety of the society. The author through the investigation of the cause of an old apartment fire accident, starting from the accident investigation process, analyzes the causes of electrical fault fire, identify the main points, and put forward the prevention measures of electrical fire.

1 Basic situation of fire

At 21:56 on December 22, 2014, a fire broke out in the old apartment at the Green Hee Garden in Tiexi District, Siping City. The burned area was 780m2. The interior decoration, furniture, clothing and other items were burnt, causing 2 deaths and 1 serious injury. The direct property loss of fire was 84,000 yuan.

2 Fire investigation work

After the fire broke out, leaders at all levels attached great importance and quickly organized experts in various fields to set up a joint investigation team for fire accidents, conducted repeated inspections of the fire scene, and conducted investigations and inquiries with related personnel.

2.1 Site inspection

The fire building is a single-story accommodation for the elderly apartment, brick-concrete structure, a fire-resistant grade building, construction area of ​​about 800m2, from east to west about 88.6m, north and south depth of about 9m. The north wall of the building has three exits. The easternmost side is two independent warehouses. The exits are located on the east side of the external wall. The corridors in the building are east-west and the rooms are distributed on both sides of the corridor. The north side has 20 rooms. West is 218, 217 until 201, there are two unnumbered staff quarters; there are 24 rooms on the south side, from east to west 122, 121 up to 101, and two unnumbered staff quarters.

There were no signs of excessive fire on the external wall of the building. The roof of the steel structure was overheated and the steel beams and steel frames deformed. The degree of discoloration gradually decreased from east to west, and the residual roof tiles gradually increased from east to west. There were bricks on the top of the external walls of the two separate warehouses and 122, 218 rooms, accompanied by smoked traces that faded from east to west. The rooms with the most serious indoor burning conditions were concentrated in the two easternmost independent warehouses and rooms 122 and 218. The rest of the rooms were basically in good condition. Among them, 122 rooms and 218 rooms are located on the south and north sides of the corridor, and are adjacent to the two independent depots on the east side. 122, 218 The height of the roof at the end of the eastern corridor outside the room is obviously higher than other positions in the corridor, and the collapse level is the same as the two rooms.

2.2 Identification of Fire Points

After on-site inspection and investigation, it was determined that the fire site was located at the ceiling of the corridor between 122nd chamber and its adjacent warehouse and the south side of Room 218 and its adjacent warehouse on the south side, and between 122 and 218 rooms.

(1) There is no trace of smoke on the north wall of the 218-room apartment, there is a small amount of smoke marks on the south wall, there are obvious smoke marks on the door, and smoke marks gradually reduce from top to bottom.

(2) The degree of bending of the iron frame at the northern side of the warehouse is lighter than that of the south and the southern wall of the warehouse has obvious traces of smoke.

(3) The iron scaffolding on the south side of the warehouse has all slumped. The bending is heavy. There are heavy smoke marks on the surrounding walls. The stone bricks on the top of the south side of the window roof have turned grayish, gradually reducing from the westward to the top. Smoke marks cracked at the top of the partition wall at 122 rooms on the west side.

(4) The wall around 122 rooms had obvious signs of excessive smoke and smoke. The door of the room was burned badly. The traces of smoke on the steel windows were heavy. The glass on the wall was cracked. The inside of the glass was heavy with smoke, and most of the wall peeled off. The frame was heavier, the automatic fire alarm probe was burned, the bottom of the wooden bed in the room was charred, and there was no trace of excessive quilts on the bed. The floor coverings were cleaned layer by layer. From top to bottom, tiles, clay, sampan plates, and ceilings were placed in order. (Silicon calcium plate).

(5) Convex accumulations in the corridors of rooms 218 and 122 are evident, and the traces of the ceiling lines are gradually reduced from east to west.

(6) Fire alarm detectors are installed in the rooms and corridors of fire building. The probes in the hallway are set every 4m. According to the alarm sequence, it can be inferred that the fire point is located in the area.

(7) It was confirmed by witnesses at the scene that the area where smoking was first found was consistent with the above-mentioned area.

2.3 Determination of the cause of fire

Through on-site inspections, investigations, inquiries, and inspections and appraisals, it was determined that the cause of the fire was caused by a fault in the electrical lines inside the stuffy roof on the eastern side of the old apartment building and ignited the surrounding flammable materials causing a fire. The following causes of fire can be ruled out:

(1) Overhead electric lines and chimneys are not installed outside the old apartment buildings, and lightning strikes and chimney fires may be eliminated.

(2) The Public Security Criminal Investigation Department has issued a report. The on-site inspection work centered on the internal fire scene of the Green Hee Garden Senior Citizen Apartment. The detailed exploration work was carried out. The scope of the investigation was up to the whole wall of the old apartment of the Green Hee Garden and the entire Green Hee. The old apartment in the park was all included, and it was ruled out that people could set fire to it.

(3) No pyrophoric substances were found in the fire room, and the ignition of spontaneous combustion was excluded.

(4)122 The indoor rice cookers and refrigerators are in the non-energized state, excluding the possibility of fire caused by electrical equipment failure.

(5) There is no flammable liquid residue and flammable gas source in the fire room, and flammable liquids, gases, etc.

3 Analysis of causes of fire caused by faults in electrical lines

3.1 Short Circuit Causes Electrical Fire

Once the electrical circuit is short-circuited, its current increases rapidly, and the increased current is all added to the line. Excessive current will generate high temperature after exceeding the rated value of the wire, and the instantaneous temperature may reach thousands of degrees, causing the wire to strike an arc and catch fire. , Combustibles around the ignition line eventually led to fire. The causes of fire caused by short circuit are: the electrical line is in disrepair, and the insulation skin is damaged; the wire that meets the specifications is not selected according to the specific environment, resulting in the insulation loss of the insulation under the negative environment; the insulation layer of the voltage over the ambassador is broken down; improper management , Poor maintenance caused a short circuit.

3.2 Overloading causes electrical fire

Overload means that the current of the electrical circuit exceeds the rated value or the specified allowable value. When the load current of the electrical circuit exceeds its rated safe current-carrying capacity, the wire will generate heat. The more the safe current-carrying portion, the higher the heat production. , which led to overheating of the fire line. The causes of electrical fire caused by overloading include: electricity equipment or personal access to power equipment, power cord load, overloading the power cord; inappropriate wire selection, cross-section is too small, so that the wire load is too large.

3.3 Electrical fire caused by overheated contact resistance

Poor contact leads to excessive contact resistance at the line connector, causing the contact site to overheat and cause a fire. If the contact of the electrical line is loose or the contact is impregnated with impurities, the voltage between the contacts is sufficient to break through the air gap to form an arc, and the spark is ignited to ignite the nearby flammable material to form a fire. Poor contact leads to poor connection between the wire and the wire, poor connection between the wire and the electrical equipment, poor contact between the plug and socket, and poor contact between the wire and the switch terminal. The causes of electrical fire caused by contact resistance heat are: violation of wiring specifications and connection methods, poor installation quality; when copper and aluminum are mixed, the joints are handled improperly; the connecting parts of the wires are oxidized and corroded under a harsh environment for a long time.

3.4 Electric sparks and arcs cause electrical fires

EDM is a strong flow column during breakdown discharge between electrodes, and a large amount of electric sparks converge into an arc. The temperature of EDM is as high as several thousand degrees. It can not only directly cause the burning of combustibles, but also melts and splashes the metal, forming a secondary fire source. Electrical sparks or arcs may occur when the insulation of an electrical circuit is subjected to overvoltage breakdown, short circuit, fault grounding, and disconnection of wires or loose connections. Thunder discharge, electrostatic discharge, and electromagnetic induction discharge may also produce sparks. If the arc falls on flammable or inflammable materials, it may cause fire.

4 Identification of causes of electrical fire

After the on-site inspection and investigation and inquiry, the fire and fire points were determined, and other fire factors were excluded. When the analysis identified as electrical causes of fire, it was firstly confirmed that the occurrence of electrical faults or the use of electrical equipment had to occur before the fire broke out. In addition, the following conditions should also be met:

4.1 In the event of fire or within the effective time before the fire, electrical circuits and electrical equipment are powered on

Electrical fires can occur only when the electrical circuit is energized. If the electrical circuit is not energized during a fire or during the effective time before the fire, it is generally assumed that the fire has nothing to do with electricity. It is also necessary to pay attention to the following conditions when determining the energization status: The switch controls the lighting line at the neutral line, and the phase-to-ground short-circuit fire or electric leakage fire can still occur when the light is turned off; the residual heat of electrical equipment can also cause fire, such as the use of electric irons and electric furnaces. After that, the residual heat can still ignite flammable substances; the thermal energy released by the electrical fault causes smoldering flammable substances, and it spreads into a fire after a long period of power failure. If the electrical wiring on the ceiling produces electrical sparks, the electrical spark igniting the insulation material or other flammable materials needs a long smoldering process, and the open flame will cause an open flame after a period of time.

4.2 There are electrical lines and electrical equipment heating points at the fire point or fire area

In the case of an electrical fire, it must be possible to find electrical barriers, electrical equipment, roadblocks, or heating or ignition components at the point of ignition or ignition, otherwise it cannot be deemed as an electrical fire. Of course, exceptions cannot be found due to limitations of objective conditions. Sometimes there is a certain distance between the point of fire and the point of failure, which requires careful investigation to find

4.3 Heating points of electrical lines and electrical equipment must generate enough energy to ignite nearby combustibles

A short circuit point of the electrical circuit, electrical equipment, or electrical circuit must be able to generate enough energy to ignite nearby flammable materials before it can be used as a source of ignition for identifying electrical fires. If the spark generated by the short circuit, the temperature can reach more than 2 000 °C, but the instant is fleeting, sometimes can not ignite flammable substances, so it is not necessarily a short circuit will inevitably catch fire. Whether or not a short circuit can cause a fire depends not only on the size of the short-circuit current, but also on the positional relationship between the short-circuit point and the combustibles and the combustible properties of the combustible material.

4.4 Standards extract evidence, scientific application of the identification of the conclusion of the role of

In the practice of fire investigation work, there are often cases where it is suspected that a power line may cause a fire. However, in the process of fire investigation, there are neither investigation materials supported by relevant evidence nor melting traces found on electrical lines. The actual situation to develop fire evidence identification (experimental) program, according to the identification of the identification of the identification of institutions, comprehensive analysis to determine whether the physical evidence of the possibility of fire caused by the final identification of electrical fires to provide important technical support.

5 Cause Analysis and Preventive Measures of Electrical Fire

5.1 Cause Analysis of Electrical Fire

Electrical fire accidents are caused by a variety of reasons. There are problems with inadequate supervision and management of management departments, and problems with units failing to implement fire safety responsibilities and fire safety education, as well as unqualified product quality and poor maintenance of equipment. The illegal operation, illegal construction and other reasons.

5.1.1 Electrical Circuits

One is improper selection of electrical lines. The selection of electrical cables is not compatible with the environmental conditions of the places where they are used. The diameter of the core, the flame retardancy of the outer insulation layer, and the withstand voltage level cannot meet the requirements of the existing national fire protection technical specifications. Second, the laying and protection measures of the electrical lines are weak. Distribution lines are laid directly on flammable materials or in suffocating roofs or suspended ceilings, and fire protection measures such as wearing non-flammable or flame-retardant conduits or closed metal tanks are not adopted. Third, the design and laying of temporary power supply lines did not meet the requirements. Temporary power supply line design, construction units and technicians do not have corresponding qualifications. Electrical cable products cannot meet national product standards. Line laying methods and protection measures cannot meet the relevant technical standards of the state and industry departments.

5.1.2 Daily Management and Use

First, there is no official electrician or the employment of non-qualified electricians in the management and use units, the maintenance and repair of electrical lines is in the form of some, and some of them are connected to the electrical lines by themselves or install temporary circuits at will, resulting in rough electrical wiring of civil buildings and insecure connections. The internal electricity management system is generally not in place. When a fire occurs, the fire-fighting power is turned off illegally, causing the fire-fighting facilities to not play their due role and causing tragic consequences. Second, some units have unqualified electrical products, poorly maintained equipment, illegal electrical installations, and illegal construction. Some companies have illegally installed electrical equipment and lines, and cables have been applied without protection, and major accidents have been buried. Hidden danger. Thirdly, the work duties of the staff of the safety supervision department are unclear, the daily supervision is arbitrary, the safety supervision and inspection of the unit is in a form, and there is a lack of supervision on the special work personnel holding certificates, and the units are not carefully supervised and urged to carry out thorough investigation and treatment of potential safety hazards.

5.2 Preventive measures

(1) Further implement the firefighting work responsibility system and improve self-management capabilities. China's fire safety laws and regulations system has been increasingly perfected, further clarifying the main role of the unit in fire safety work, and clarifying fire safety responsibilities of the unit's fire safety personnel, fire safety managers and all employees. We will implement a step-by-step fire safety responsibility system, meet regularly for deployment, and carry out inspections, especially inspections and patrols of electrical equipment and electrical lines, and identify problems in a timely manner.

(2) Good quality from the source. Manufacturers of electrical products must strictly comply with the national standards for production and ensure product quality; design units must strictly follow the relevant specifications for the design; construction units must adopt qualified products and perform construction according to design drawings to ensure project quality and eliminate hidden dangers at the source. Prevent the occurrence of electrical fires.

(3) Further standardize the internal electricity safety management system of the unit. From the plan design, construction, installation, selection of products, to acceptance, use, emergency handling and other aspects are further defined responsibilities. The relevant law enforcement agencies must also strictly observe various approval and review procedures.

(4) Strengthen the publicity and education of the society and raise the awareness of fire safety. Taking firefighting propaganda as one of the important contents of propaganda and education work, using all means of propaganda and education, intensifying the popularization of general knowledge of electrical safety and improving the self-prevention and self-rescue capability of the whole society.

(5) Strengthen the standard management of electrical special work types. As one of the special types of work, electricians are required to obtain two kinds of qualification certificates in accordance with the relevant regulations. One is the “Electrical Network Access Permit” issued by the electricity supervision department, and the second is the “Special Operation Operation” issued by the safety production supervision and management department. certificate". Relevant departments should increase the training and examination of the two kinds of qualification certificates, and increase the inspection and assessment of the operational capabilities of special operators.

This article is from Fire Science and Technology, January 2017, Vol. 36, No. 1.