As an important transportation facility in the city, the subway has high personnel density and is completely underground. How to make it safe is a problem that every metro construction and operation department must face. However, from the history of the development and operation of subways around the world, various types of fires, including equipment failures, human negligence, and intentional damages, still occur frequently and have a tendency to rise. Therefore, how to do early detection, early detection, early treatment, and orderly evacuation, minimize the risk of possible fires, and minimize fire damage, have become issues that we need to focus on and solve.
First, the lack of traditional fire detection methods
In the subway, the traditional fire detectors are spot-type smoke detectors, radiation detectors and cable temperature detectors. Due to the characteristics of the subway environment and the working principle and installation methods of traditional fire detectors, traditional fire detection methods still have deficiencies:
1. The alarm sensitivity of the point type smoke detector is low, usually 3% - 5% obs/m. The alarm is slow and does not apply to places with high personnel density and requiring early evacuation.
2. Point-type smoke detectors are passive detection with the installation position at the top. Due to air flow caused by air conditioning and vehicle operation, smoke particles are quickly diluted by the air flow and move with the trajectory of the air flow and do not rise to the top during the initial stage of the fire. Therefore, the point smoke detector Does not apply to environments with high air flow, such as the platform area.
3. The operating environment of the subway is highly variable and there is interference of smoke and dust. Since the alarm threshold of the point-type smoke detector is fixed, it is very easy to generate false alarms.
4. Since the point-type smoke detector does not have a self-cleaning function, the detector needs to be sent back to a professional manufacturer for cleaning every 2 years. This increases the operating and maintenance costs of the subway, and during this period, there will be no fire detectors in the protected area and there is a great risk.
5, the on-site smoke detector needs a large amount of visible smoke to block the alarm, its sensitivity is lower than the point-type smoke detector, not suitable for use in early detection of fire, early evacuation sites. In a high space such as a parking garage, due to thermal barriers and deformation of the building structure, the detection effect of the radiation detector will be greatly reduced. In practical use, the lack of cable temperature detector is also very obvious, the response is slow (due to the development trend of the fire, the temperature sense itself is delayed than the response time of the smoke), and the laying of the installation workers is very complicated, especially when the cable needs When increasing or decreasing, a temperature sensitive cable must be laid separately for each cable, which is expensive.
Therefore, how to overcome the deficiencies of traditional fire detection methods and use fire detection and alarming methods with better detection effect, advanced technology, and simpler maintenance to achieve comprehensive protection, early warning, early evacuation, and preventive measures. Better It is particularly important to ensure the normal operation of the subway and the safety of passengers.
Second, the characteristics of air sampling smoke detection alarm system
The air sampling (breathing) smoke detection system is a smoke detection system based on laser scattering detection principle and microprocessor control technology. The working principle of this system is to collect air samples through the sampling pipe network distributed in the protected area and filter the dust through a special two-stage filter device and send it to a special laser detection chamber for analysis. The generated smoke particles are measured to give an accurate smoke concentration value and a multi-level fire alarm is issued based on the smoke alarm threshold set in advance by the system.
The air sampling smoke detection system consists of detectors, sampling pipe networks, dedicated power supplies, filters, pipeline purge valves, and three-way components. It can be connected with the input module of the traditional fire alarm system through the relay that comes with the detector to realize the linkage function with the fire-fighting facilities on site.
The air sampling smoke detection system is designed in the early stage of a fire (overheating, smoldering or initial generation of aerosols, etc.), which provides a fire warning and the alarm time is several hours earlier than traditional smoke detectors. Therefore, early detection and early disposal can be done to minimize the damage caused by the fire. Compared with the traditional fire alarm system, the air sampling smoke detection and alarm system has the following features.
1, high detection sensitivity, alarm threshold adjustment range
The laser source of the air sampling smoke detection system is stable in operation, with a low false alarm rate. The sensitivity is about 1000 times higher than that of conventional point smoke detectors. It can not only detect the conventional fires generated inside the station during the initial stage of the fire, but also discover The tiny smoke particles produced by the softening of the cable insulation due to the overload of the line can be alarmed and handled early and provide valuable time for the orderly evacuation of passengers.
2, multi-level alarm, improve fire alarm system performance
Air sampling smoke detection system provides four levels of smoke alarm (alarm, action, fire 1, fire 2) mode and four air flow alarm (emergency low airflow, low airflow, high airflow, emergency high airflow) mode for low smoke concentration The early stages of fire (such as electrical fires occurring in switchgear) and the rapid increase of smoke (such as deliberate arson) can provide early warning. The alarm thresholds of smoke and air flow at various levels can be manually or automatically adjusted according to different requirements and environments. set up. Through setting the alarm thresholds of the system and setting disaster prevention and relief plans under different levels of alarm modes, the performance of the fire alarm system can be greatly improved, and early warning and early disposal of fires can be achieved.
3, the system has a self-learning function
The air sampling smoke detection system has the smoke and air flow automatic learning function, can continuously sample and analyze according to the learning time set by the user, and finally set the four-level alarm threshold that is most suitable for smoke and air flow, and increase the sensitivity as much as possible. Avoid false alarms from the system.
4, the detector has a fault self-diagnosis function
The detector's fault self-diagnosis function can diagnose system faults in real-time and quickly without professional equipment or computers, facilitating timely maintenance and rapid response.
5, the system pipe network layout is flexible and beautiful
The sampling pipe network of the air sampling smoke detection system is flexible in arrangement. The main pipe can be concealed and installed in a suspended ceiling that is not detected. The sampling hole can be arranged on the subway station platform, the top area of ​​the station hall, and equipment through a capillary channel as required. Corridor top area, stuffy ceiling, air conditioning air return and equipment cabinet. In this way, interception sampling can be performed on the trajectory of smoke movement, and the sampling point can be beautifully integrated into the decoration of the subway station, thereby reducing the damage to the overall decoration effect of the station public area. In contrast, when a conventional point detector meets a local hollow ceiling, in order to meet the fire code requirements, a double-layer detector needs to be arranged within the ceiling and below the ceiling, which increases the cost of the fire alarm system, and because Need to set aside detector maintenance access, and affect the overall decoration effect of the public area of ​​the station hall and platform.
6, system construction is simple and flexible
The installation of air sampling smoke detectors and the construction of pipelines are very simple and flexible. Since there are no electronic components on the sampling pipeline, neither the pre-embedded pipeline nor the wiring is needed, and only the sampling pipeline needs to be fixed (usually a tube card or a suspender). The construction is simple and the time is short.
7, the lower cost of system operation and maintenance
Conventional smoke detectors need to be disassembled and cleaned periodically to ensure that the detectors can be detected with the manufacturer's nominal sensitivity. In contrast, the air sampling sampling system's sampling pipe does not contain any electronic components and is highly adaptable to the environment. It requires only periodic air purging of the sampling pipe network to complete the maintenance of the system without any need for any Disassemble. The air sampling smoke detection system also has its own monitoring capabilities, can actively propose maintenance requirements, and conduct online maintenance. During maintenance, the system can operate normally, which not only reduces the cost of routine maintenance, but also improves the reliability of the system operation.
Third, the system in the subway application
1, application area
In some areas of the subway, replacing the traditional smoke detector with an air sampling early smoke detection system is completely feasible. It is a more effective and more reliable technology choice. According to the characteristics of the early smoke detection system for air sampling, in the subway project, the areas suitable for the early sampling of air smoke detection systems are:
(1) Depot, parking lot. The use of air sampling early smoke detection system can overcome the shortcomings of traditional on-site smoke detectors with low sensitivity, frequent adjustment and calibration due to building deformation and vehicle vibration.
(2) Platforms, halls and public areas and equipment corridors. Using air sampling early smoke detection system can not only overcome the difficulties of traditional detector installation and maintenance, affect the ceiling decoration effect, but also to avoid the impact of subway piston wind on the sensitivity of traditional detectors, so that early warning, early evacuation.
(3) Complete substations and cable mezzanines. The use of air sampling early smoke detection system can overcome the problems of delay, easy error reporting, and inconvenient maintenance of traditional temperature sensing cables.
(4) There are important equipment rooms and management rooms for automatic fire extinguishing systems in the subway. The use of air sampling early smoke detection systems in these rooms enables early warning of fires and avoids unnecessary activation of automatic fire suppression systems.
2, installation method
The air sampling smoke detection alarm system has a flexible sampling method. According to the different environmental characteristics of the application area, different installation methods can be adopted:
(1) In the area with suspended ceilings such as station halls, platform public areas and equipment area corridors, the system sampling pipe can be laid upright along the wall until the top of the protection area is laid horizontally and holes are opened. Concealed capillary tubes are used to perform composite sampling protection on the ceiling area. ;
(2) In cable traps, depots, parking garages, maintenance garages and other ceilingless areas, the system sampling pipe can be applied to the top of the protected area.
With the rapid development of domestic subways, early smoke detection systems for air sampling have been used in subway projects. For example, subway projects in Beijing, Wuhan, Guangzhou, and Kunming have all been used. Domestic developed regions have successively formulated and implemented local specifications for the design, construction, and acceptance of air sampling smoke detection fire alarm systems to promote the popularization and application of this technology. The new edition of the "Fire Automatic Alarm System Design Specification" (GB50166-2013) also specifically added the selection rules and setting regulations for aspirating smoke detectors. It is believed that with the advancement of science and technology and the rapid development of subway construction, early smoke detection systems for air sampling will be widely used in subways.
Hydraulic Support System Seals Kits
Hydraulic Support System Seals Kits
The hydraulic support system used in mines is used to support equipment during the mining process of coal mines or other underground mines.
It mainly consists of hydraulic supports, hydraulic stations, control systems, and sensors.
Hydraulic support is the core component of the hydraulic support system used in mines, which uses hydraulic cylinders as the support force source,
Capable of supporting huge rock weights in underground mines. The hydraulic station provides a hydraulic oil source,
Hydraulic oil is transported to the hydraulic support through pipelines to achieve support function.
The control system is an important component of the hydraulic support system used in mines, which controls and monitors the hydraulic support through sensors and controllers. Sensors can monitor the status of the bracket in real-time, including support force
The controller controls the hydraulic support based on the feedback data from sensors, such as inclination and displacement, to ensure its stability and safety in the mine.
The hydraulic support system used in mines has advantages such as high support force, good stability, and safety and reliability,
Widely used in underground mining industries such as coal mines, metal mines, and non-metallic mines. With the continuous progress of technology and the continuous expansion of applications, hydraulic support systems for mines will continue to play an important role,
Provide strong support for the safe and efficient development of the underground mining industry.