SummaryHospitals, as public venues with dense buildings and a concentration of people, particularly vulnerable groups such as patients, can suffer significant property damage and loss of life in the event of a fire. Among the various factors that can lead to hospital fires, electrical fires stand out due to the unique functions of hospital buildings compared to other structures. Proper analysis of the factors, scenarios, and equipment that can lead to electrical fires in hospitals is crucial for preventing such incidents before they occur, thereby effectively preventing and reducing the occurrence of fire accidents.
KeywordsHospital Electrical Fire; Cause; Prevention
Introduction
Due to the high volume of traffic in hospitals, there is a concentration of large-scale inspection equipment, with a significant number of flammable and explosive items such as pressure vessels, chemical reagents, bedding, and paper. This results in numerous fire hazards, which, when ignited, can cause widespread fires with profound impacts and substantial losses. For instance, the operation of pressure vessels such as boiler rooms, supply room sterilizers, and high-pressure oxygen chambers must be standardized and regulated; safety valves should be inspected regularly as required. Flammable items in laundry rooms, uniform centers, ward storage rooms, radiology film storage rooms, medical records rooms, and library rooms must be managed properly. Similarly, flammable chemical reagents like ethanol, methanol, acetone, ethyl ether, and turpentine in operating rooms, pathology, and laboratory departments, as well as anesthetics used in operating rooms, require standardized management. Chemical reagents used daily in biochemical testing and laboratories, along with open flames such as alcohol and gas lamps, as well as electric heating equipment like electric stoves and ovens, must also be managed in accordance with standardized procedures. With the development of hospital modernization and the strict management of fire prevention departments at all levels, as well as the increased awareness and understanding of hospital management departments and medical staff, the level of prevention and attention to these fire hazards has risen. As a result, potential fire hazards are now a high priority for hospitals, and a comprehensive set of management methods and measures has been established.
Electrical fires are characterized by their widespread, persistent, and concealed nature of fire hazards. In hospitals, medical equipment, power lines, power sources, and various switchgears that can trigger electrical fires are often difficult to detect early on due to their widespread distribution, long-term continuous operation, and the fact that electrical wiring is usually concealed (such as in ceilings and cable trenches). As a result, it is crucial for medical staff to place a high priority on preventing electrical fires.
Causes of Electrical Fire Incidents
1.1 Short Circuit
A connection formed between two or more points in a circuit that are normally at different voltages, either accidentally or intentionally, through a relatively low resistance or impedance. Short circuits are categorized into phase-to-phase and phase-to-ground types: the former occurs when phase wires touch each other; the latter happens when phase wires come into contact with the neutral wire, grounding conductors, or the earth directly. When electrical equipment is operating, a massive current flows through it when an abnormal connection (short circuit) occurs between the power supply's phases or between phases and ground. Due to the reduced impedance of the power supply circuit and the transient process during a sudden short circuit, the current in the short-circuit loop increases many times. For instance, if a short circuit occurs at the output transformer end of electrical equipment, the short-circuit current can reach 10 to 15 times its rated current. Since the heat generated by the current is proportional to the square of the current, it causes the circuit temperature to rise sharply, leading to sparks or arcs at the short-circuit points, which can destroy equipment and cause fires or explosions.
The primary cause of electrical short circuits is:
The selection, installation, and usage environment of electrical equipment did not comply, leading to the insulation material being damaged under high temperatures, humidity, and acidic or alkaline conditions.
(2) Electrical equipment, when used beyond its lifespan, may experience insulation aging and become brittle.
Improper use and long-term operation with malfunctions have expanded the scope of the fault.
Overvoltage leads to insulation breakdown.
(5) Incorrect operation or directing power to a faulty circuit.
1.2 Overload
Operations of electrical equipment exceeding normal full-load ratings or conductors exceeding their rated current-carrying capacity. If such operations persist for an extended period, they can damage the equipment or lead to dangerous overheating, igniting surrounding combustible materials.
The primary causes of equipment overload include:
Improper selection during design and installation resulted in the electrical equipment's rated capacity being smaller than the actual load capacity.
(2) Improper installation of equipment or wiring, resulting in increased load and operation beyond capacity.
(3) Delayed maintenance and repairs have led to equipment wires operating in a substandard condition for an extended period.
Overload converts electrical energy in conductors into heat. When the conductor and insulator become locally overheated to a certain temperature, it can cause a fire. Many of the old ward and outpatient buildings in hospitals were not designed with sufficient consideration for the rapid development of electrical equipment. As medical equipment and other electrical appliances continue to be added, it reveals that the electrical equipment specifications were too small and the wire cross-sections were too thin, with actual loads exceeding their safe current carrying capacity. Additionally, sudden increases in load, such as when equipment driven by motors lacks lubrication, can lead to increased frictional resistance and jammed transmission mechanisms. Furthermore, due to the need for temporary construction or other purposes, excessive power or too many electrical devices are connected to the circuit, exceeding the load capacity of the distribution lines.
1.3 Poor Contact
Contact resistance refers to the resistance that occurs between the conductor surfaces in contact, or at the contact interface. It is composed of contraction resistance and surface film resistance. Contraction resistance arises when the current contracts at the point of contact between conductors, reducing the effective conductive area. Surface film resistance is due to chemical or electrochemical reactions and environmental contamination that form a surface film at the contact interface upon contact with the surrounding medium. The size of contact resistance is related to the conductor material, the surface roughness of the conductor, and the type and pressure of contact, with the resistance value decreasing as pressure increases. In electrical equipment connection points, the contact resistance is negligible when the contact is normal. However, when the contact is abnormal, the contact resistance significantly increases, producing a large amount of heat, which can cause metals to change color or even melt, ignite the insulation layer of the electrical circuit, and nearby flammable materials.
The primary causes of poor contact include:
Surface contamination of electrical connectors increases contact resistance.
(2) The electrical connector has been in long-term operation, resulting in the formation of an oxide layer that hinders conductivity, which was not promptly removed.
(3) Electrical connectors are subject to loosening due to thermal action.
(4) At the copper-aluminum junction, due to the presence of approximately 1.69V potential difference, electrolysis occurs in damp conditions, leading to aluminum corrosion and poor contact. Poor contact can result in localized overheating, creating a potential ignition source.
Improper selection of electrical equipment or use of counterfeit products
Electrical appliances are not providing protection, control devices are not effectively controlling, and protective measures have not been added to areas requiring them. Consequently, when automatic switches, contactors, gate switches, welders, and other equipment are in use, the resulting electric sparks or arcs can ignite flammable materials in the vicinity.
1.5 Friction
Equipment containing generators and electric motors, such as when stators collide with rotors, or bearings experience poor lubrication leading to dry friction due to drying, or even when lubrication is normal but high-speed rotation occurs, can all cause fires.
1.6 Thunderstorms
Lightning can produce discharge voltages ranging from several million to tens of millions of volts, with discharge currents reaching several hundred thousand amperes. The hazards of lightning include the mechanical forces, high temperatures, intense arcs, and electric sparks generated during discharge, which can damage buildings, transmission lines, or electrical equipment, leading to fires and explosion accidents.
1.7 Static Electricity
The occurrence of static fire is due to the gradual accumulation of static charge formed by various factors such as friction, contact, separation, splashing, electrostatic induction, and charged bodies, which results in high potential. Under certain conditions, the surrounding air medium is punctured, causing discharge on metal and producing a spark discharge with sufficient energy. The spark discharge process primarily converts electrical energy into heat energy, which ignites or explodes flammable mixture using the heat energy from the spark.
Fire Prevention Measures for Electrical Equipment and Appliances
2.1 Proper Selection and Installation of Power Equipment
Hospitals have high demands for power reliability. In operating rooms, emergency departments, intensive care units, hemodialysis rooms, delivery rooms, nurseries, CT and MRI scanning rooms, and blood matching rooms, power outages can greatly impact medical work and even lead to medical accidents, threatening patients' lives. Therefore, these power loads are classified as level one, requiring dual power sources to supply electricity simultaneously. In the event of a fault in one power source, the other must continue to supply power to ensure reliability. For locations with even higher reliability requirements, such as fire control centers and computer rooms, a two-way power supply should be used, with power drawn directly from both sides of two transformers at the substation to the power consumption point. When laying the two cables in the bridge, they should be placed in separate bridges or equipped with fire isolation panels within the bridge to ensure the reliability of the dual power supply.
In facilities where a sudden power interruption poses significant medical risks, it is advisable to use an IT (Insulated Ground) power supply system. This system should be equipped with a dedicated isolation transformer, with the secondary winding of the transformer providing the IT system's power source to prevent the generation of ground fault currents. The IT system should be introduced into operating rooms and emergency rooms, with a distribution box installed inside the room. Inside the box, a leakage detection device (insulation monitoring device) should be set up. When a single-phase grounding fault occurs (usually when the system's insulation level is below 0.5MΩ), a fault alarm is triggered. Since the fault current during a single-phase grounding fault is only a small amount of ground capacitance and current from a short section of circuit within the medical facility, the potential differences within the facility are minimal. Under the condition of ensuring patient safety, power supply does not need to be cut off, and surgery can continue.
2.2 Enhance the installation quality of electrical equipment
For issues such as loose connecting screws and insufficient tightness in neutral line installation, regular inspections should be enhanced. Particularly when the complete set of electrical products in the new ward building are installed and powered on, strict checks should be conducted. Regular maintenance and care should be performed after operation.
2.3 Electrical wiring renovation for the old ward and outpatient building
In recent years, due to the development needs of hospitals, a large number of medical equipment has been introduced. Especially during the summer, the extensive use of split air conditioners highlights the issue of insufficient electrical wiring cross-sections and low design capacity in the old ward and outpatient buildings, leading to frequent tripping of circuit breakers. More seriously, the long-term overloading of electrical lines has caused insulation degradation, posing a difficult-to-address fire hazard. Therefore, it is advisable to renovate the wiring when conditions permit.
When modifying wiring, be mindful of:
(1) Select the right wire based on environmental characteristics, considering factors such as moisture resistance, heat resistance, and corrosion resistance.
Wiring should be standardized, and wire passages through walls should be protected with conduits to prevent damage to the wire's insulation.
Ensure wire connections are secure to prevent oxidation at the joints.
(4) Enhance fire prevention measures for temporary electrical lines and strictly prohibit unauthorized connections.
(5) Ensure the safety protection of low-voltage power distribution lines
(6) Common protective electrical appliances, such as automatic switches and fuses, offer protection against overloads and short circuits. It's crucial to select the correct trip mechanism value and fuse specifications based on the load size, and ensure they match the cable cross-section.
Fire Prevention Measures for Electrical Equipment
- Properly selecting the power supply and wiring for medical equipment typically requires a power supply capacity greater than the equipment's power by about 10%. Medical equipment should be kept at least 1 meter away from flammable materials and should not be installed on combustible surfaces. The outer shells of medical equipment and their power supply units should be properly grounded.
- Dryers, sheet spreaders, washing machines, and other electric heating equipment should be powered by a separate electrical circuit. The wiring should use fire-resistant and insulating materials, and protective devices such as fuses should be installed. In locations where electric heating equipment is used, necessary fire-fighting equipment should be provided to extinguish fires in the early stages.
- Commonly used low-voltage switchgear in hospitals includes automatic door switches, iron case switches, contactors, control relays, etc. Automatic switches should be installed in dry, well-lit areas that are convenient for maintenance and ensure construction safety, and should not be placed in flammable, explosive, vibrating, humid, high-temperature, or dusty locations. The operating mechanism, the current setting value of the release mechanism, and the timing limit should be checked regularly, and dust and carbon deposits on the inner walls and ceiling panels should be regularly cleared to maintain good working conditions; the knife switch should be selected rationally based on actual usage, with the rated current of the contacts typically being more than 2.5 times the calculated current of the line. The knife switch should be installed in a switch box outdoors or in a dedicated electrical room in areas with chemical corrosion, dusty, or humid conditions, and should be installed and used correctly as per regulations. If contact looseness, severe oxidation, small contact area, or melting wire breakage is found, repairs or replacements should be made promptly; the iron case switch is a safe and reliable switchgear with a long service life, capable of preventing electrical sparks, arcs, and high-temperature particle splashes, with a wide range of applications. To ensure safety, in addition to selecting the iron case switch correctly, its casing should be well grounded, and it should not be used for long-term overload. If mechanical interlock devices or cover damage, or insertion-type fuses are found to be damaged, they should be repaired or replaced promptly; contactors are common control electrical equipment, and the spring pressure of the contactor contacts should not be too low, ensuring good contact to prevent excessive contact resistance, overheating, or burning of the coil. It is also necessary to ensure that the arc extinction device is intact and undamaged.
2.5 Enhance Management, Focus on Key Monitoring
Daily fire inspections are a crucial measure to ensure hospital fire safety. Key areas such as hyperbaric chambers, pathology labs, operating rooms, and pharmacies are subject to intensive monitoring. Non-explosion-proof switches and plugs in the operating room should be turned on and properly inserted before anesthesia is administered. After the surgery is completed and the ether vapor has been fully eliminated, the plugs may then be disconnected or removed. Effective prevention of electrical fires in hospitals also requires continuous improvement of management systems. Only by clearly defining policies, ensuring adequate facilities and equipment, and assigning management responsibilities can fire accidents be effectively prevented and minimized.
Ankorri Electrical Fire Monitoring System
(1) Overview
The Acre1-6000 Electrical Fire Monitoring System, developed by Ankoer Electric Co., Ltd. in accordance with the current national standards, is a fully digital, independently operated system. It has passed the fire product test certification by the National Fire Product Quality Supervision and Inspection Center and has also passed stringent EMC electromagnetic compatibility tests. This ensures the safe and normal operation of the product series within low-voltage power distribution systems. The system is now in mass production and widely used across the country. By collecting and monitoring signals such as residual current, overcurrent, overvoltage, temperature, and fault arcs, the system enables early prevention and alarm of electrical fires. It can also disconnect the over-standard distribution circuits detected with residual current, temperature, and fault arcs upon necessity. Additionally, it can meet user requirements for data exchange and sharing with the AcreIEMS Enterprise Microgrid Management Cloud Platform or fire automatic alarm systems.
(2) Application Scenarios
Applicable to intelligent buildings, high-rise apartments, hotels, restaurants, commercial complexes, industrial and mining enterprises, key fire protection units, as well as the fields of petrochemicals, culture and education, healthcare, finance, and telecommunications.
(3) System Architecture
(4) System Features
The monitoring equipment can receive residual current and temperature information from multiple detectors. When an alarm is triggered, it emits both audio and visual alarm signals. Simultaneously, the red "ALARM" indicator light on the device illuminates, the display indicates the location and type of the alarm, records the alarm time, and the audio-visual alarm persists until the "RESET" button on the device or the "RESET" key on the touch screen remotely resets the detector. The audio alarm signal can also be manually silenced using the "Mute" key on the touch screen.
When the monitored loop alarms, the control output relay closes to control the protected circuit or other equipment. Once the alarm is cleared, the control output relay releases.
Communication Fault Alarm: When a communication failure occurs between the monitoring equipment and any connected detector, or when the detector itself fails, the corresponding detector on the monitoring screen displays a fault alert, the yellow "Fault" indicator light on the device illuminates, and an alarm sound is emitted. Power Supply Fault Alarm: In the event of a failure in the main power supply or the backup power supply, the monitoring equipment emits an audible and visual alarm signal, displays fault information, allows access to a corresponding interface for detailed information, and can deactivate the alarm sound.
When residual current, over-temperature alarms, communication, or power failures occur, the alarm location, fault information, and alarm time are stored in the database. Similarly, records are made when alarms are lifted and faults are rectified. Historical data offers various convenient and quick search methods.
(5) Configuration Solutions
Reference
- "Fire Safety Regulations and Fire Prevention Standards: Prevention and Investigation of Fire Accidents" [M]. Jilin Electronics Publishing House, 2004, 2.
- Ankorri Enterprise Microgrid Design and Application Manual, 2022.5 Edition
- Du Shouliang, Case Analysis of Fire Cause Investigation at Liaoyuan Central Hospital [J], Fire Science and Technology, 2007, 26(1)
- Zhang Shisong. "Practical Handbook on Operation, Maintenance, and Safety Standards of Medical Electrical Equipment" [M]. Beijing Library Press, 2003, March.
- Shi Yongmei, "Comprehensive Practical Handbook of Electrical Equipment Installation, Testing, Maintenance, and Operation," China Energy Industry Press, 2005, March.
- Wang Haoki, Li Song, discuss the causes and prevention of electrical fires in hospitals.
