With the rapid development of urban construction and economic construction, the general improvement of people's living standards and the development of petrochemical industry. There are more and more users and units using natural gas, and the scope is wider and wider. In recent years, with the large-scale development and exploitation of natural gas in northern Shaanxi, the users and units of pipeline natural gas in xi city have reached a certain number, and the promotion and use of natural gas will surely become the main domestic and production gas in this city. In addition to residential users, hotels, restaurants and production enterprises, there are ComDress natural gas vehicles (CNG vehicles). Because the main component of natural gas is methane (CH4), which is generally above 95%, its characteristics are: ① high calorific value (average calorific value is 8000 kcal/m3) and stable combustion; ② High safety. The explosion concentration range of natural gas is 5%- 15%, while that of gas is 4%-35% and that of liquefied petroleum gas is 4%-24%. Therefore, natural gas has always been favored by people. The composition of natural gas determines that it is a combustible gas with great fire risk and belongs to the first-class combustible gas. A slight carelessness in the supply process, or a broken pipeline will escape into the air, and fire and explosion accidents may occur when encountering a fire source, even causing heavy casualties. Therefore, it is necessary to strengthen the fire safety management in the process of natural gas supply. L, fire risk of natural gas Natural gas is a general term for hydrocarbons and a small amount of non-hydrocarbon mixed gases mined from underground through gas wells. It is generated and migrated under different geological conditions, and stored in the underground structural layer at a certain temperature and pressure. The main component of natural gas is methane (above 95%), and contains hydrocarbons above ethane, propane, butane and pentane, as well as a small amount of non-hydrocarbon components such as carbon dioxide, hydrogen and hydrogen sulfide. At the same time, with the gradual popularization and use of CNG vehicles, its unsafe accidents also occur constantly. (1) For example:1On August 2, 995, the CNG filling station of Mianyang Local Natural Gas Company exploded and caught fire because the dehydration treatment of gas cylinders was not clean when they were inflated. ② On September 29th, 1995, the CNG filling station of Zigong Fushun Huayou Company exploded due to cylinder leakage and combustion, causing great economic losses and casualties; ③1On June 7th, 1995, Suining CNG filling station was burned due to the quality problem of gas cylinders, and the flame column was more than 20 meters high, resulting in direct economic loss of180,000 yuan. The main reasons why CNG places and their gas cylinders are prone to combustion and explosion are as follows: 1. CH4 medium itself is a first-class combustible gas, which has Class A fire hazard. The explosion concentration limit is 5%- 15%, the minimum ignition energy is only 0.28 MJ, the specific gravity to air is 0.55, and the diffusion coefficient is 0. 196. It shows that it is easy to burn and explode, with strong diffusion ability and fast fire spread. Second, the gas is under high pressure. CNG technology requires that the compressor of filling station must be pressurized to above 25MPa before CH4 can be compressed into the cylinder, which is the highest pressure combustible gas storage container in China at present. If the quality of gas cylinders or pressurization equipment fails to meet the basic technical requirements, an explosion or fire accident may occur with slight negligence. Third, operators and users violate the rules. Both natural gas and gas are transported to users through pipelines, and accidents have the same characteristics. The causes of natural gas and gas accidents in pipelines are mostly caused by leakage. For example, 1 1 On March 30, 1994, an overhead gas pipeline crossing the road in Maanshan City, Anhui Province was knocked off by a dumper, and the gas quickly spread in a large area, and the people living nearby were deeply poisoned. ②199517: 5310. On 3rd October, the underground power cable trench of Heping Road in Jinan City was broken due to the medium-pressure gas pipeline located at the western end of the cable trench, and the leaked gas flowed into the cable trench with a distance of113m parallel to the gas pipeline through the soil and the wall of the cable trench. As a result, the 2.2-kilometer-long sidewalk and part of the road surface were damaged to varying degrees, and the windows of buildings facing the street in serious sections were blown up, resulting in 13 deaths, more than 40 injuries and direct property losses of 429 1 10,000 yuan; ③1996 65438+12: 0510. On October 6th, a fire broke out in Building No.3 of a family hospital of a company in the middle section of Xi 'an Hanguang Road, and suddenly there was a loud noise. Several walls on the northwest side of four units on the first floor collapsed instantly, and the indoor gas pipeline was seriously broken, causing a fire, causing three people to die on the spot. 13 people were injured: ④ 1996 65438+ 10/9, 2 1 day and night, pipeline gas leakage accidents occurred continuously in Hongqiao town, Yueqing City, Zhejiang Province, and four households were poisoned by *** 15 people. Failing to operate according to the operating rules for safe production, failing to inform the user in advance when stopping gas and resuming gas at night, failing to operate according to Safety Instructions for Gas Use, being negligent when stopping gas, and going to bed without turning on the switch of the cooker and the valve in front of the gas meter. ⑤199965438+On the morning of February 8, an underground cable trench burst accident occurred in the west section of Xi 'an Anlian Lake. The reason is that the seal at the flange joint of natural gas pipeline near the explosion point fails, which leads to a large amount of gas leakage and enters the cable trench and telephone trunk well with insufficient safe distance from it. During the construction of Litong Telecom Engineering Company of Xi 'an Telecommunications Bureau, the operators did not carry out gas detection, and went down the well to work, and the blowtorch ignited natural gas to cause an explosion. The accident caused a large-scale power outage in this area, resulting in direct economic losses of more than 3 million yuan, injured 15 people and seriously injured 3 people. ⑥199965438+February 1 1N, at10/23 am, a natural gas leakage and explosion accident occurred in Building 8, Gaoxin Park, Hi-tech Development Zone, Xi City. Natural gas leakage and explosion occurred in four households on the first floor of Unit 2 of Building No.8 1 Unit 2, which damaged the indoor facilities and caused the kitchen floor to burst to the deepest place. The blown glass and things flew to the Rose Building not far from the opposite side, and the Icm thick glass was also shattered, causing injuries to more than 10 residents, pedestrians and nearby migrant workers. ⑦ At about 9: 30 a.m. on October 5, 2000/KLOC-0, the natural gas pipeline under South Second Road of Henan Road in Urumqi suddenly exploded, completely interrupting the water, electricity and heating in this area. Two manhole covers were blown off at the explosion point, one of which was higher than the five-story teaching building next to it. A section of concrete pavement about 60 cm long on Naner Road was cracked and dislocated, and a section of pavement about 20 meters long was lifted up. 2. Common fire causes of natural gas 2. 1 Buried pipelines or outdoor pipelines are corroded, vibrated or frozen, which leads to pipeline rupture and leakage, and gas rushes into the room through soil layers or sewer pipes, and contacts with open flames to cause fire or explosion. 2.2 Due to improper closing of the indoor valve on the air inlet pipeline, the valve stem and thread are damaged and fail, the valve does not meet the safety and quality requirements, or the valve is opened by mistake, natural gas escapes, and it burns or explodes in case of open flame. 2.3 The distance between natural gas metal furnace or furnace tube and combustible buildings and articles is not enough, and the valve is not properly adjusted, which makes the furnace and chimney burn red, baking combustible buildings or articles, causing fire accidents. 2.4 The heating kang and fire wall with natural gas will take too long, the kang surface will be overheated, and baking bedding, clothes or other items will cause fire. 3. Fire prevention measures for natural gas 3. 1 Natural gas pipelines should not be laid underground, but should be laid overhead. Pipeline installation should be carried out by professionals, and non-professionals are not allowed to pull and connect randomly. 3.2 The valves of the pipeline must be complete and easy to use, and no leakage is allowed in any part. It is forbidden to use other valves instead of needle valves. 3.3 Both ends of natural gas loading conduit must be fixed firmly. The conduit shall be an oil-resistant and pressure-resistant wire-clamping hose. 3.4 An oil-water separator should be set at the appropriate position of the user's inlet pipeline, and the separated light oil and water should be discharged regularly. When the cooker is found to be leaking oil or water, it is necessary to stop the fire immediately and drain the oil and water before using it. 3.5 Natural gas stoves and pipelines should be inspected frequently. When the gas leaks or smells, it is forbidden to use open flames and switch the electric switch. Doors and windows should be opened quickly for ventilation. If the leak cannot be found, contact the gas supply department immediately. 3.6 The flue of stoves, fire pits and firewalls that use natural gas for heating should be unblocked. If the fire suddenly goes out, it should be lit every few minutes to prevent explosion. The distance between the mouth of the metal chimney and the combustible structure should not be less than 1 m, and a neck should be installed to prevent the flame from blowing out against the wind. 3.7 The maintenance of natural gas pipelines and valves must be carried out when the gas is stopped. When stopping or turning off the gas, the user must be informed in advance. Installed pipes, valves, etc. It can only be used after passing the pressure test and leakage test. 3.8 In case of fire accident, don't panic. Immediately close the main valve and put out the fire with blankets and bedding. You can also use carbon dioxide, dry powder and other fire extinguishers to extinguish the fire, and report to the fire department in time. 4. Technical and administrative means to prevent pipeline natural gas, in addition to mastering the fire characteristics, fire causes and fire prevention measures of natural gas and gas, it is also necessary to strengthen management and supervision from the technical and administrative aspects, discover and rectify hidden dangers in time, and strengthen law enforcement. Municipal planning, public utilities, public security and fire control, labor safety, municipal supervision and other relevant functional departments must work together to participate in the prevention and disposal of natural gas accidents and strive to eliminate such hidden dangers. 4. 1 Set the safety monitoring and protection system. (1) Establish a manual monitoring system for natural gas and a regular inspection system for gas leakage in pipelines; (2) Develop and adopt self-operated or gas over-flow self-closing valves. When the natural gas pipeline suddenly breaks due to external factors, the natural gas leakage is often sudden, and the gas over-current self-closing valve has the protection function of automatically and effectively closing when a large amount of gas is ejected; (3) Gradually study the computer-controlled urban natural gas pipeline leakage monitoring, remote centralized display and remote locking system, and gradually realize the central control room to control and monitor the leakage of key parts of the pipe network, and close the valves upstream of the leakage parts in time when leakage is found. 4.2 Strictly abide by gas safety regulations. The Regulations on Urban Gas Safety jointly promulgated by the Ministry of Construction, the Ministry of Labor and the Ministry of Public Security (199 1 implemented since May of 1 year) and the Measures for the Management of Urban Gas in Xi promulgated by the Xi Municipal Government on April 25th, 1996 are all technical regulations and administrative regulations related to gas safety. Natural gas and gas pipeline network is very extensive, involving many departments and units, but also related to every household and ordinary people. The wider their safety knowledge is, the better. For some typical gas accidents, only through in-depth interviews and reports on radio, television and newspapers, and analysis of reasons, responsibilities and lessons, can we receive the expected educational effect. In a word, ensuring the safety of pipeline gas is not only a matter for gas companies, but also requires the cooperation and support of all sectors of society and the care and efforts of every ordinary person. Although gas pipeline accidents are common in our lives, don't be afraid of doctors. We should learn to master and understand the dangerous characteristics and safety precautions of gas, treat pipeline gas well, and make it truly an "angel" in our life.