【 Weak current College 】 cold fire cause and fire system design

A brief introduction, cold storage

Cold storage is used in low temperature preservation of the architectural complex of cargo. Including Treasury, ammonia compression engine room, distribution, and its subsidiary building (construction) construction.

(A) mechanical cold storage works in sound insulation in buildings, equipped with a mechanical refrigeration warehouse unit, uses gasification temperature very low liquid (refrigerant) that would enable it in low pressure gas evaporation becomes so absorb heat, and cooling purposes. And on the basis of the storage temperature, humidity and ventilation requirements for cold storage systems for regulation and control.

(Ii) the classification of the purpose and cold storage

1. purpose: cold storage is mainly used for food, medicine, mechanical processing of frozen and refrigerated.

2. classification: (1): according to structure forms: civil cold storage built single-layer or multi-layer, body structure and use of underground loading structure, its maintenance of reinforced concrete structural walls are made of brick. Prefabricated cold storage (active cold storage): body structure (columns, beams and roof) are using light steel structure, with the support structure of the wall with precast composite insulating Board group. Insulation materials with rigid polyurethane foam and rigid polystyrene foam, etc. This type of cold storage can also be called a modular combination of cold storage, refrigeration storage and mounting cold storage, refrigeration storage fabricated activities. (2) the nature of use: productive cold storage; distribution of cold storage; retail freezer. (3) size: large freezer: cold storage capacity is 10000t above. Medium cold storage: cold storage capacity in 10000-1000t. Mini refrigerator (small freezer): freezing capacity in 1000t. (4) press the refrigeration equipment selection of refrigerants, refrigeration storage can be divided into: ammonia refrigeration storage: use ammonia as a refrigerant. Freon refrigerator: freon as refrigerants. (5) by using the library temperature requirements, cold storage room can be divided into: high temperature freezer: L-+ 5 ° c-5 ° c. Cold storage temperature:-10 ¡æ d-18 degrees centigrade. Low temperature freezer: J--23 ℃-28 ℃. Cryogenic cold storage: ≤-30 degrees centigrade, it is used for frozen foods and industrial test, medical and other special-purpose refrigerated cold storage: keep the library temperature 4 ° C to 2 ° C. Quick-freezing cold storage: also known as tunnel freezer. Used for quick frozen foods. (6) by using the storage features, cold storage room can be divided into: constant cold storage: storage of goods in temperature and humidity have precise demands of cold storage. Air conditioning cold storage: it is capable of regulating library within the temperature, humidity, and control library in oxygen, carbon dioxide and other gases. The oxygen concentration from 21 percent to 3 percent to 5 percent.

(3) cold storage building features cold storage building and general industry, civil construction, it has its own unique structure. Cold storage room sound insulation structure allows you to keep the freezer unit manufacture of cold in the refrigerator within less disclosure, on the contrary, is to reduce the heat to a cold cold storage-internal leakage, which is cold and general housing major differences. Its walls, floor and roof are laying a certain thickness of the insulation material to reduce cold heat from the outside world. To reduce the absorption of solar radiation energy cold facade surface, usually painted white or light color. Cold storage building to prevent vapour diffusion and air permeability, moisture-proof insulation needs to be set so that the cold has good sealing and dampproofing geqi. Low temperature freezer floor in addition to effective insulation, insulation layer down must also be addressed to prevent soil freezing. Cold storage floor to dump large quantities of goods, and to access a variety of loading and unloading, transport machinery and equipment, on the flat roof is also equipped with refrigeration equipment or pipeline. Therefore, its structure should have a larger capacity. Low-temperature environment, particularly in the periodicity of freezing and thawing circulation process, building structures sensitive.

(4) of the refrigeration system and the impact of fires

1, refrigerants refrigerants and refrigeration, is the work of the refrigeration cycle, using the media with refrigerant heat of phase transition to delivery, the current material cannot be used as a refrigerant and 80 species, the most common is ammonia, freon, water and a handful of hydrocarbons, etc. This article focuses on ammonia as a refrigerant. Ammonia vapour colorless, have a strong smell of stimulation. Ammonia on the human body have greater toxicity, when ammonia liquid splash into the skin will cause frostbite. When the air volume of ammonia vapor 0.5-0.6% may cause an explosion. Ammonia at room temperature, not combustion, but when heated up to 350 ° c, the decomposition of nitrogen and hydrogen, hydrogen and oxygen in the air is extremely prone to explode after mixing. The above characteristics, fire suppression process if not taken measures, will science on fire suppression incalculable losses. 2. refrigeration mechanical refrigeration machinery mainly include compressors, water-cooled condenser, thermostatic expansion valve, evaporator and some auxiliary equipment. In the cold store to use several systems in a consolidated form a freezer, refrigerated display cases, the primary air fan, water cooled condensing unit, piston-type compressor group. Use prefabricated cold store refrigeration equipment is mainly made of metal, sealing materials, plastics, coating and drying filter cores, etc. A cold-insulation uses materials and pipeline outer attracts the attention of firemen. Some insulation with burning speed, product toxicity, combustion smoke characteristics (such as Korea lichuan cold storage is a carbamate blowing jobs and raise the fire explosion occurred); pipeline outer wrapper is combustible. 3. ventilation system design specifications "of the cold store for use purposes taken into account in the requirements of the" into the cold room should be fresh air cooling (or heat), "cold outside air is difficult to directly into cold storage. Cold storage of ventilation design maximum limits for direct exchange of gas inside and outside. Whether natural or mechanical ventilation, ventilation in the specification of requirements for air duct (cement) diameter should be 25-30 cm, while the window is not mandatory. So, cold storage internal fires often ventilation difficulties; whereas thermal insulation layer around the fire caused when connected, forming a good ventilation environment. 4. fire safety design in accordance with the norms requirements of cold storage, cold construction of fire rating I, II and III are available, single-layer and multi-layer cold fire partitions between 3500 and 2000 respectively. At present, China's cold storage for a fire-resistant building II, a few small refrigerator. In accordance with the architectural design of the fire prevention regulationsVan on freezer alarm system installed is not a mandatory requirement for automatic water sprinkler system installation specifically provides, with the exception of the "cold." Smoke devices in low-temperature environment effects can get some play, thermal device in cold storage at the beginning of the fire could not afford to good effect, but rather cold storage's own temperature control system adequate to respond to the initial fire emits heat. Cold storage in the event of fire, in addition to early detection, or wait until the fire forces arrived at the scene, basic has formed stable combustion.

(5) other refrigeration system is a diversified system, others such as electrical systems, piping systems, refrigerant water tower, various kinds of high-voltage instrument also for the entire refrigeration system work played an important role.

II. cold fire characteristics

In General, cold storage building is its stringent insulation and sealing dampproofly geqi, frost resistance of soundness and to guarantee the quality of the building. The above construction characteristics and capabilities determine their fire with large-span steel structure, multi-tiered storage, chemical goods, people, centralized place even underground construction and so on many kinds of fire characteristics. When the fire broke out, smoldering, open fire, explosion and other combustion forms may coexist and interact.

(A) the spread of fast, easy to form a solid fire. For the cold chain industry rapid development needs, our cold storage room is large and cluster model. Isolated single freezer gradually reduced, with comprehensive functionality of gradually increasing. Cold storage of large-span space, causing stocks rise and insulation material consumption increased, as the fire spread rapidly and provides the Foundation. Despite the cold storage of supplies most of the combustible substances in combustion and embarrassed, but cargo package often combustible or flammable materials. Coupled with low temperature freezer burns smoldering time long after the disastrous fire is very difficult to control. Multilayer freezer floor, floors, roofs, walls are massive use of insulation materials. To ensure that the cold store load, thermal insulation materials are mostly use rice husk, Cork, polystyrene foam, polyurethane foam and other materials, the fires spread quickly and easily to form solid combustion.

(Ii) the combustion conditions a concealed, complex, difficult to extinguish. Early Burns, smoldering fire in wall concealed the up direction of the development department or parallel, external keylogger. The fire was increased, the various types of electrical systems, refrigerants and refrigeration machinery in fire situations will produce many complex changes, often accompanied by leakage, explosion, and the freezer's internal cargo rack range in fire detection, it is difficult to find accurate fire as soon as possible. The fire development strongly, span, big space or a multiple-level work surface in the implementation of the fire, and it is difficult to attack, the attack is limited because of the offensive line, often fighting to live, not live fire flame.

(C) of the aerosol, high temperature, low visibility, the difficulties in the attack. Because entrances, burn calories hard to disseminate, store temperature has risen dramatically, causing slow, internal temperature of the exhaust system. Fire into cold storage channel, and also the high temperature smoke and flame from the hole, it is difficult to close water gunman; multiple layers of cold storage settings in the voices of the stairs, in the formation of solid combustion, water gunmen in smoke and flames of difficult to attack along the stairs; cold storage for insulation, the entrances are often set 2 door, water gun Jet does not accurately hit fire point; cold storage fire after internal visibility, construction or container (cage) in fire location unknown, after attack staff often long time in one location shooting water but ineffective, road trips to overcome (feet unknown), drop (drop from above), trapped (no exit), and other difficulties, slightly inadvertently brings casualties.

(Iv) how the toxic gases, there is a danger of explosion. Use of cold fire, air, fire, carbon monoxide is very high. Acute lethal concentrations of carbon monoxide only 0.5%, colorless and tasteless, and activity of extremely strong, personal protection such as firefighters are not in place, vulnerable to acute poisoning. Use polystyrene foam and other chemical blowing agents for insulation of cold storage, caught fire after easy release a lot irritating poison gas, causing poisoning. This class of substances the combustion and a characteristic, the products of combustion are toxic dust particles of black, very easy to float attachment in offensive personnel face mask, so that this is not high visibility even lower. Cold storage in ammonia pipeline rupture of an ammonia leak that gave off a large number of ammonia, except for personnel have poison, where open flame is an explosion. In addition, not emptying pipe ammonia and the formation of explosive mixture of oxygen, the case of jobs open flame will explode. Liquid ammonia vaporization heat absorption when large numbers could easily cause frostbite. The explosion caused by a fire are often prone to cold storage building or maintenance, such as Korea cold fire, according to lichuan fire authorities for investigation, accident location is in the basement mechanical rooms. At that time, welders are welded air-conditioning piping. Machinery rooms surrounding messy piled up many comparative, carbamate and flammable substances. A few days ago, in the walls and roof insulation jobs so that 10 cm of carbamate foam insulation to rapid solidification, construction personnel use gasoline, resulting in a basement full of oil vapour. Electric welding sparks and oil vapour, explosion, and other flammable substances in the basement of a continuous explosion, 7140 m2 in the basement (the equivalent of four football pitches) suddenly between is filled with poisonous gas and fire.

(5) fire range, a variety of fire characteristics, high dispatch requirements. Total area of cold storage, Korea lichuan 3.583 million square meters, 2 floors above ground, 1 floor under ground; China's Qingdao qianwan new port area of cold storage, building area of 5.5 thousand square meters; the construction of Dongguan credit, international agricultural trade city cold storage project of new building area is 2.23 million square meters. Large refrigerator or freezer group covers an area of large, multi-tier cold floors feature is not a complicated process. Despite the overall cold fire is unlikely, however, regardless of the point on the fire, will definitely affect the freezer this man-made and external conditions different independent systems. In fighting process commander must have excellent comprehensive quality and access to comprehensive and accurate information, and provide to the main points of the firefighters, the Commander has to take into account the main points of the battle, but also to consider external largePrevent the spread, but also to take account of toxic gases, explosion, collapse, visibility, etc.

(Vi) prone to collapse. To save costs, steel combined large freezer more and more people of all ages, while the steel structure in the temperature reached 350 ° c and 500 ° c and 600 ° c, its intensity decreased 1/3, 1/2, 2/3, in high temperature condition of its internal stress can also be changed so that the steel bearing system problems. At full load, the steel structure out of balance and stability of the critical temperature of 500 ° c, average temperature of the fire are 800 ℃-10 ℃. As mentioned previously, refrigerator fire found late, fighting hard, a long time, when the fire has developed to a certain scale, steel structures due to high temperature after the loss of bearing capacity, it is easy to collapse.

Third, the large cold fire suppression methods

(A) enhancing the first come and do a fire detection. 1. after receiving the alarm, first flown. Large tonnage tank cars should be first out of power. On the one hand, face the refrigerant (primarily means ammonia refrigerants) combustion and leakage; on the other hand, ready to attack through the roof, shell. 2, in the rush to the scene of the way, once the external reconnaissance found the fire under control, to congresses at cannot immediately up one level command requested reinforcements and reports compiled at the battle. 3, arrived at the scene, to elect competent personnel and technical staff reconnaissance unit detailed and meticulous fire detection. (1) identifying any casualties and was trapped, if so, determine the casualty severity and causes. (2) clarify the freezer use status (construction or in use), the nature and have no refrigerants ammonia gas explosion, leakage, frozen warehouse storage types and quantity of goods. (3) there is no collapse may detect. (4) reconnaissance is the insulating layer of fire, or the Treasury internal articles leaked combustion or ammonia. (5) where combustion fire investigation of the nature, quantity and combustion area, internal combustion and spread. (6) to detect the structure, the cold storage internal layout and container (frame) of a substantial, distribution. (7) reconnaissance ammonia and ammonia tanks of compressed room control valve position, pipeline leak location. (8) reconnaissance coffers lighting circuits and power supply in the form of trend, whether the power down. (9) other reconnaissance.

(B) adhere to save first principle, take many forms to rescue and evacuation were trapped. Determine who was trapped, to ensure safe, according to the fire situation, the scientific potential. You can save lives, fire-fighting; can also be assured of the following acts, edge fire; if trapped workers have no risk and must be fire when opening lifesaving, or you can take to save lives by fighting to achieve the purpose.

(C) rational use of military force, the science that put out the fire.

1, library materials fire within. Fighting methods and similar general warehouse fire, taking advantage of topographical features, play equipment, you must implement the storm. (1) cooling protection of steel structures, prevent collapse. Attack before full cooling fire building steel structure to prevent the collapse. (2) in the library, set the position to intercept the fire, covering of attack. Use of high-tonnage vehicles, large water tank car, covering the water into the reservoir area in tapping the gunmen fire. (3) make full use of the freezer door, organize an effective attack. If it is safe, refrigerator door is the best offensive way. (4) if necessary, you can use the breaking tools open up new offensive line. When it is difficult to close the library door to the appropriate location in the cold room flanking breaking hole reduce pressure, at the entrance of pyrotechnics and the Organization of new external attack or a front position. (5) attack, attack, alternating between inside and outside the clip, fight fire storm. Organization of two battle group, accompanied by Qi protective equipment, common access to the scene, a group attack, another group cover observation; within a few minutes after the attack, two groups of Exchange.

2. insulating layer of fire. Cold storage insulation fire clear fire and smoldering in two ways, and they are likely to exist simultaneously on different points, fire detection, suppression and always should permeate the prevent trigger library material caught fire and refrigerant leakage, explosion. (1) fully expand fire detection, identified fire point location. Available from smoke movement in fire sites to determine which side of the cold store. Watch the warehouse walls there are no changes in color or touch the wall temperature, can be broadly identified smoldering parts. In General, the temperature is high, the colors change parts of the fire point. (2) upper Jet flow, lower breaking the interposer board or opening fire. Extinguish smoldering fires, when the insulation layer is closed, you can number in the upper panel, opened from the upper part of the spray of water, control the fire development; after determining the smoldering parts, fire below breaking the interposer board or opening, edge waterjet edges out clear insulating layer of material, to meet the elite lording it over the fire.

3. ammonia compression engine room fire. This type of fire occurs, ammonia has hazardous; as a result of ammonia leakage after the explosion may cause ignition, pipe insulation and other fuel, thus affecting the entire cold storage systems. Handling difficult, the Suppression time be ever so careful. (1) put out the fire. Ammonia easily soluble in water, can be directly controlled with water or fire, the fire extinguished cannot stop shooting water. (2) close the valves off source. Flame control or fight, engineering and technical personnel, implementing the closing valve fault source. In addition, the cold store design code of request: in the pipeline system, consideration should be given to any one device (container) in ammonia pumped out, such as fighting objects meet this condition, you may consider relying on other devices reduce the burning area stock of ammonia as a refrigerant. (3) diluted explosion-proof. Set the water gun positions, leak-proof, and await the dilution.

(5) active evacuation supplies. Evacuation route is frozen warehouse door or new open channel. Evacuate personnel to wear gas masks, in the Shui gunmen carried out under cover of the evacuation. The evacuation of the goods to safety and strengthening.

(6) a comprehensive fire. The above three fires seldom occur simultaneously, but a form of fire, if the fight is taking too long or disposed of improperly, has aroused the other or both of the fire. Commanders in the face of this situation, you should follow the fighting methods, science develop firefighting strategy, differentiation, and properly processed.

4. very early discovery of fire

Over the years, ICAM aspirating smoke detection system (ASD) has been widely used for protection of cold storage facilities. Currently, at low temperature used in most fire technology can provide early detection and alarm, and easily the forklift and other damage to the equipment. ICAM detectors for very early warning capabilities means that it can detect elementary (smoldering) fire, and the primary fire could lead to property damage, business interruption and thoroughly endanger personal security. ICAM air sampling smoke detection system is designed to be flexible, you can add ICAM air sampling smoke detection system as preaction fire extinguishing systems (including gas fire suppression and extinguishing system) automatically fire equipment.

Cold storage facilities in daily stockpiled items many are flammable materials, which are strongly airflow, air is very dry, fire risk is greatly increased. Fire in cardboard, plastic packaging, oily materials, food raw materials and wooden pallets spread rapidly between. Therefore, the earlier you detect fire hazard exists, the better.
Refrigerated or frozen goods in storage facilities and many are easily spoiled, under any circumstances to prevent the increase in temperature, it is very important. In case of fire, flame heat generated or freezer system downtime and results in an increase in temperature will make inventory spoilage and loss of profit. In such an environment, even if they're junior fire, if not early detection and to take measures that will result in significant losses. Inventory long exposure at a low concentration of smoke will be polluted.

Good system design can give full play to the ICAM air sampling smoke detection system of other advantages, its performance is reliable, is not subject to condensation phenomenon or freezing room air flow generated by the strong impact.

Many international norms and standards had been aware of the other traditional detection technology in the limitations of low-temperature environment, so in its provisions against the ambient temperature is below 0 ° C (32 ° F), use traditional detection equipment [10]. Line sexy temperature cable allows use in cold environment, but the temperature sensor cable can easily be forklift and other common workflow is damaged. And ICAM detector is installed in a protected area, only sampling network exposure in sub-zero conditions. Sampling of the mezzanine below or to the ceiling suspended ceiling, is not easy to be damaged.

Note: with the FM sector ICAM air sampling smoke detection system of certification, the line was already clear sexy temperature cable can be used to start the install preaction fire
Reset, but it cannot provide very early smoke detection alarm, and very early warning to avoid the release of fire-extinguishing system.

5. considerations

(A) the safety and health must always fight through the fire and rescue operation.

1, security

(1) entry into cold store personnel must carefully check the personal protective equipment, and strict enforcement of air respirator use registration system. After entering the scene, the inspector must always pay attention to internal attackers use of air ventilator, the time and location of the person's position and to prevent accidents. In particular, into the air conditioned library jobs, air breathing apparatus should be repeated checks. (2) into the library personnel must carry the lead rope, communication and lighting appliances, grouped into that single shall enter in the fire. Outside the library may randomly change to library within the hose lines. (3) the Commander, the battle fronts, group leader in the access number, when the inventory and the AMS staff at any time to master. (4) in case of disposal of hazardous chemicals should an air breathing apparatus, overalls, anti-static underwear, tighten belt, pants and cuffs, preventive measures and frostbite. (5) sets the security officer, observation of measuring building fire, prevent collapse hurt.

2. medical

(1) trauma care (2) poisoning (3) Frostbite treatment (4) counseling (5) long time operation of medical security

(B) determine the exact inner fire points, attack. Fighting a cold fire, the blind in attack is very dangerous; only identify fire point to implement effective fire fighting attack.

(3) the discreetly breaking. Breaking the hole to fit, to select the right location, both for the fire, without affecting the architectural structure.

(4) the reasonable choice of fire extinguishing agent. Some meat freezer, in the fight to select good fire extinguishing agent. No forbidden extinguishing foam, so as not to increase the loss.

(5) of the exhaust gas. Cold fire suppression difficult, a large part of the smoke. Extinguishing process attaches great importance to smoke.

(6) power off source. Cut off power supply, cooling system stop in the fire fighting; close the valve or down moves the refrigerant, avoid chain disaster and loss.

(VII) to prevent the smoldering fire fighting. Cold store clips wall insulation fire was put out, to check whether there is smoldering fire source. Fire after leave certain power monitoring fire and prevent recurrence.