Influencing factors and Prevention Countermeasures

Influencing factors and Prevention Countermeasures for the safe operation of urban gas pipe

1 preface

Qinhuangdao gas pipe was put into operation in October, 1993. The pipe adopts the medium low pressure two-stage pressure system, and the medium pressure design operating pressure is 0.07MPa. 72.84 medium pressure pipes have been laid in a clean environment without corrosive media and electromagnetic interference; 6 kilometers, low-pressure pipe more than 280 kilometers

the development of urban gas pipe facilities has become one of the important symbols of urban modernization. However, the following safety problems of gas pipe operation are becoming more and more prominent. Ensuring the safe operation of urban gas pipes has also become an urgent task for the development of gas industry

2.1 building illegal buildings on gas pipelines and facilities

illegal buildings on urban gas pipelines and facilities are killers that threaten the safe operation of pipelines. Once these illegal buildings crush the gas pipeline, resulting in gas leakage, the consequences are unimaginable. In order to expand the floor area, some builders built and expanded various illegal buildings within a safe distance from the regulator station. Some of these illegal buildings are occupied by people, and some are singing halls, restaurants, garages, etc. it is very difficult to clean up because of the weak safety awareness and driven by economic interests

2.2 management of damage to gas in road and building construction

ground subsidence caused by foundation construction of high-rise building projects and damage to gas pipelines; The widening of roads, the construction of urban supporting sewage, new water, electricity, heat, etc., and the phenomenon of digging, shoveling and crushing gas pipelines and their auxiliary facilities are common. A few construction units carried out barbaric construction and destroyed the common faults of the gas pipeline testing machine, and the cleaning and concealment of the faults affected the safe operation of the pipe

2.3 use pipes and fittings with unsatisfactory quality

in a fracture accident of cast iron connecting sleeve, the measured wall thickness of the pipe is 6mm, while the standard wall thickness should be 15 ± 1.8mm, and the comparative value is 54.4%, resulting in its failure to meet the design bearing capacity. When the external force (uneven settlement of foundation, soil collapse, ground load vibration, change of groundwater level, etc.) and internal force (change of gas pressure in the pipeline) exceed the allowable limit, sudden fracture occurs

2.4 the construction and installation are not standardized

the bolts on both sides of the pressure flange of the gray cast iron pipe connecting sleeve are not tightened symmetrically and evenly as required, and the two pressure flanges are not parallel; In order to simply ensure the air tightness, the bolts are tightened excessively, and the local flange is tightly contacted with the connecting pipe, so that the stress on the connecting sleeve is uneven. The flexible connection becomes a rigid connection, and the flexible rubber ring of the connecting sleeve loses the function of absorbing external forces

2.5 changes in the operating environment of the pipeline

uneven settlement caused by long-term ground load, the influence of the dead weight of the buried soil and the vibration of the ground load will increase the external force on the differential position of the cast iron connecting sleeve interface, and it will break when it exceeds the limit. A large number of power cables and communication optical cables, together with new water, sewage, heat and other pipelines, make the underground extremely crowded, and it is difficult to ensure a safe distance between pipelines

2.6 changes in natural environmental conditions

since 1999, 39 connecting sleeve fracture accidents have occurred in our city. From the time period, 76.90% of them are concentrated between April and July every year. During this period, the groundwater level of the pipe foundation often changes. Cause soil disturbance and change of pipe foundation. From the point of view of the location of the accident, the majority are medium pressure gas pipes

3.1 governments at all levels must fully recognize the harmfulness of illegal buildings on gas pipelines, strengthen the demolition of illegal buildings, and improve the safe operation coefficient of gas pipelines

3.2 sign the construction agreement and keep it safe. The construction unit shall apply for the construction permit before construction. For mechanical excavation near the pipeline, the pipeline protection agreement must be signed, and the construction unit is responsible for the safety protection of the pipeline, and the Gas Corporation will conduct random inspection. Establish a construction safety inspection team to ensure that the storage facilities are not damaged

3.3 further strengthen the construction management of gas pipelines, strictly control the construction, material and quality inspection, and hold the first line of defense for the safe operation of gas pipelines. In accordance with the bidding law and the regulations on engineering construction supervision, and the principle of "safety measures are determined in design, guaranteed in construction, checked in acceptance, and implemented in operation", bidding is adopted for engineering design, construction and supervision, and pipe procurement to ensure project quality. The new pipe section must stop using the form of connector socket

3.4 actively adopt new materials. Code for design of urban gas gb50028-93 (2002 Edition) stipulates that "polyethylene pipes, mechanical interface ductile black cast iron pipes, steel pipes or steel skeleton polyethylene plastic composite pipes should be used for medium and low pressure gas pipelines." Grey cast iron pipes are not included in the selection range of medium and low pressure gas pipes in cities and towns in the specification. Grey cast iron pipes have entered the phase of elimination

3.5 non gas users near medium pressure pipelines and some low-pressure pipelines hang alarms. Non gas users found 6 leakage accidents, preventing the expansion of the situation and causing adverse consequences. We will extensively carry out mass prevention work, promote and implement public alarm reward methods, and give material rewards and commendations to those who first discover hidden dangers and leaks

3.6 increase investment and strengthen management. The pipeline patrol personnel shall be equipped with portable gas leak detector, and the line patrol system of fixed line, fixed section and fixed personnel shall be implemented; Inspect the medium pressure pipeline with a trolley twice a year. Formulate external emergency repair and rescue plans, prepare special equipment and technical data, and improve the emergency repair speed and emergency response capacity of gas pipeline leakage

3.7 the factory gas is odorized in strict accordance with national standards, and it is easy to be detected in case of gas leakage

3.8 according to the characteristics of gas pipes, regular safety inspection is one of the important measures to find hidden dangers and plug loopholes. It is also necessary to highlight the key seasonal inspection. For example, in summer, the inspection and protection of flammable, explosive and flood hazardous parts should be highlighted, and in winter, the cold weather will focus on the parts that are easy to cause frostbite and freezing will make the pressure not crack high

3.9 give the gas operation management unit the power to enforce the law and strengthen the supervision of safe operation

gas has become an integral part of urban residents' lives. Ensuring the safe operation of urban gas pipes will be the top priority of the safety work of the gas industry, otherwise it will restrict the development of gas industry