In the current situation of dynamic zeroing over the epidemic, timely put forward the decision to stabilize the macro economic market. One of the priorities of stabilizing growth is to increase investment, and the most critical is “comprehensive infrastructure”, which has been raised to the level of national security. “Comprehensive infrastructure construction” still needs to focus on infrastructure. At the same time, there are still many weaknesses in urban infrastructure, especially in cities and towns with rapid population growth in recent years, they still face the contradiction between population growth and inadequate infrastructure. Even in the first – and second-tier large and medium-sized cities, there is still the problem of infrastructure upgrading due to old. Among them, the transformation and construction of urban gas pipeline has become an important power point of infrastructure. On the international front, the war between Russia and Ukraine made Russia cut off the gas supply to many countries of the European Union. In the long run, Russia’s natural gas market pattern will shift from Europe’s center of gravity to China, which will also promote the layout of China’s natural gas urban pipelines in North and East China.

1. Evaluation of the total length of urban gas pipelines in China

How to evaluate the total length of urban gas pipelines? There is a certain proportional relationship between the length of urban gas pipelines and natural gas transmission pipelines. In 2013, the length of oil and gas pipelines in the world was 3.559 million kilometers, of which 2.225 million kilometers were in the United States, accounting for 62.5% of the total length of oil and gas pipelines in the world. Japan, Western Europe and Russia each have about 200,000 kilometers. In 2013, the total length of natural gas pipelines in the world was 2.865 million kilometers, and that of the United States was 1.84 million kilometers, accounting for 69.4% of the total length of natural gas pipelines in the world. Russia’s natural gas pipeline length was 164,000 km, while China’s natural gas pipeline length was only 68,000 km in 2016, 37.8% of that of Russia and 3.1% of that of the US in 2013. In 2018, the total length of oil and gas pipeline was 136,000 kilometers, including 79,000 kilometers of natural gas pipeline. By the end of the 13th Five-Year Plan, the cumulative length of natural gas pipelines is expected to reach 104,000 kilometers. Therefore, according to the ratio of the length of urban gas pipeline to the length of natural gas pipeline is about 6:1, the cumulative length of urban gas pipeline in 2020 is about 600,000 kilometers, which is consistent with the target of the 13th Five-Year Plan of urban gas pipeline network construction to reach a total length of 600,000 kilometers by 2020, among which the total length of steel pipe is about 300,000 kilometers. The total length of other pipes is about 300,000 kilometers.

During the 14th Five-Year Plan period, China built 25,000 kilometers of natural gas pipelines, including 15,000 kilometers of natural gas pipelines and 5,000 kilometers of crude oil and refined oil pipelines.

During the 14th Five-Year Plan period, the layout of China’s long distance natural gas pipelines will be fine-tuned, instead of relying entirely on “west-east gas transmission”. The war between Russia and Ukraine will shift the focus of Russia’s natural gas market from Europe to China. For example, after the opening of the China-Russia Eastern Route, the construction project of Russian natural gas pipeline to China via Mongolia will be promoted, which is scheduled to be completed in detail on November 30 this year. At the same time, Russia is preparing to expand its natural gas exports to China. Natural gas from Sakhalin Island will become the main gas source for the Far East pipeline, and the development work is scheduled to start in 2023. Russia supplies 10 billion cubic meters of natural gas per year to China through the Far East Natural Gas Pipeline under a 25-year contract. This will promote the construction of urban gas pipelines in North and East China.

During the 14th Five-Year Plan period (2016-2020), 2.4 million government-subsidized rental housing units will be built, 53,000 old urban residential areas will be renovated, basic public infrastructure will be strengthened in rural areas, and water, electricity and gas pipe networks and housing renovation projects will be completed.

2. The transformation and construction of urban pipe network has become one of the key points of infrastructure construction during the 14th Five-Year Plan

2.1 Domestic and foreign pipeline safety accidents urgently need to be reformed and updated

Since the 1950s, with the large-scale construction of oil and gas pipelines all over the world, pipeline safety accidents often occur. Statistics show that from 1970 to 1992, there were more than 9000 oil and gas pipeline accidents in the United States, an average of more than 400 a year. From 1981 to 1996, 752 gas pipeline accidents occurred in the former Soviet Union, of which the most disastrous was the 1989 gas pipeline explosion, which killed more than 800 people. Between 1970 and 1990, there were more than 800 pipeline accidents in Canada.

On September 13, 2018, three towns in Massachusetts — Lawrence, Andover and North Andover — experienced the largest series of natural gas pipeline explosions in 10 years. Columbia Gas operates about 8, 000 kilometers of natural gas pipelines in Massachusetts, of which 15 percent are at risk of leaking. On average, more than 1, 200 pipeline leaks a year have to be repaired and expensive to replace.

The pipeline safety situation is also serious. There were more than 200 kinds of pipeline accidents in the southwest of our country in 1976-2006. In recent years, for example, major domestic oil and gas pipeline accidents, on November 12, 2013, the Donghuang pipeline explosion accident in Huangdao, Shandong Province, killed 62 people, injured 136 people and caused an economic loss of 7,517.2 billion yuan. On July 2, 2017, the China-Myanmar pipeline Qinglong gas pipeline in Guizhou Province exploded, killing 8 people and injuring 35 others; A second explosion occurred on June 10, 2018, killing one person, injuring 23 others and causing a direct economic loss of 21.45 million yuan. On March 20, 2019, the Taiqingwei natural gas pipeline in Shandong Province burst into flames and exploded. Fortunately, it did not cause a major accident because it happened in a desert mountain gully.

City gas pipelines are also accident-prone pipelines. For example, on December 22, 2005, the newly installed natural gas transmission pipeline near Maju Bridge, East Sixth Ring Road, Beijing, suffered a natural gas leakage accident due to hydrogen cracking of weld seam three days after it was put into operation. From 2005 to 2007, natural gas leakage accidents occurred in Foshan Gas pipeline and Nanjing Gas pipeline in Guangdong Province. In recent years, especially in Dalian on September 10, 2021, Shenyang on October 21, and especially in Shiyan, Hubei Province, large gas explosion accidents occurred. Among the 28 accidents analyzed by experts, steel pipe quality problems accounted for 39.2%, girth weld problems accounted for 21.43%, corrosion failure problems accounted for 17.86%, excessive deformation problems accounted for 14.29%, and other factors such as third-party construction damage and geological changes accounted for 7.1%.

From above domestic and foreign natural pipeline accidents, the old pipeline urgently need to be reformed and updated, for example Columbia Gas Company of the United States in 2016 to replace hidden danger of leakage pipeline cost about $56 million, our country is also increasing investment in this respect.

2.2 The “accelerator button” is pressed for the renovation and construction of urban gas pipe network

On January 20, 2022, the Director of the Department of Safety Coordination of the Ministry of Emergency Management answered the reporter’s question about the recent gas accidents in some regions of the country at the regular press conference. He pointed out that the scale of the use of gas in cities and towns has grown rapidly, and the population using gas has exceeded 667 million, and the penetration rate of the use of gas in cities and towns has reached 97.87%. As most of the pipelines used are aged and old, built 20 years ago, preliminary statistics show that there are nearly 100,000 kilometers of pipelines in China (including 20,000 kilometers of urban gas pipe network) that are aged in varying degrees and have safety risks. At that time, the construction standard was low, and the daily update, maintenance and maintenance were not timely. The problems have accumulated to now, and the risks and challenges are very great.

The General Office of the State Council issued the Implementation Plan for Aging Renewal and Renovation of Urban Gas Pipelines (2022-2025), and the National Development and Reform Commission and the Ministry of Housing and Urban-Rural Development formulated special implementation plans for the renewal and renovation of aging gas pipelines. Pipeline investment is expected to reach 1.4 trillion yuan, including 60.6 billion yuan in gas pipeline upgrading (including construction).

In Hebei Province, policies have been introduced. From 2022 to 2023, the province will complete the renovation of 3,382.8 kilometers of old urban pipe network. For gas pipe network, the old pipe network of cast iron pipe and galvanized steel pipe whose service life is more than 15 years will be mainly reformed. For example, Guangxi Province will build more than 4,000 kilometers of gas pipelines during the “14th Five-Year Plan” period, and the penetration rate of urban pipeline gas reaches 80% and that of county pipeline gas reaches 45%. Guangdong Province released the 14th Five-Year Plan for urban gas development, speeding up the renovation of old pipelines and building 299.3 kilometers of interconnected gas pipelines. In addition, Zhejiang, Jiangsu, Fujian, Henan, Shanxi and so on have also introduced the urban pipe network transformation, construction of the “14th Five-Year Plan” period.

In order to contribute to the transformation and construction of urban gas pipeline, it is necessary to summarize the new technology and equipment applied in the standard formulation of urban gas pipe network and natural gas long distance pipeline, the high quality development of steel pipe pipe and the new technology of pipe network construction and operation.

3. Comparison of standards of domestic and foreign urban natural gas pipelines and long-haul natural gas pipelines

3.1 Comparison of domestic and foreign urban gas pipeline standards

The pressure of long-distance transportation pipelines and urban gas pipelines in some domestic and foreign cities is shown in Table 1

Table 1 Pressure (MPa) of long-distance Transportation Pipelines and urban Gas Pipelines in some domestic and foreign cities

In the preparation of urban gas pipeline specifications in China, the United States Federal Code No. 49, the federal standard ANSI/ASME B 31.8 and the British Institute of Gas Engineers standard IGE/TD/1 have been absorbed. According to foreign experience and domestic actual situation, urban gas pipeline pressure design is divided into 4 grades and 7 grades, as shown in Table 2.

Table 2 Design pressure grade of domestic urban natural gas pipelines

In the selection of steel pipe, ① pressure P < 1.6MPa, can choose to meet the national standard “welding steel pipe for low pressure fluid transportation” GB/T 3091-2015, (foreign standard: ISO 559), when the pressure P is 1.6-4MPa, the selection of steel tubes should meet the national standard GB/T 9711.1-1996 “Delivery conditions of steel tubes for oil and Natural gas industry Part 1: Class A” or GB/T 9711.2-1999 “delivery conditions of steel tubes for oil and Natural gas industry Part 2: Class B Steel Pipe, (foreign standard: API), and GB/T 8163-2018 Seamless Steel Pipe for Conveying fluids, (foreign standard: EN1026-1:2013). The selection of urban gas steel pipe is mostly HFW high frequency straight welded pipe. When the diameter is more than 711 mm, most of the straight seam submerged arc welding pipe is used. In special cases, seamless steel pipes can also be used, such as crossing rivers, railways, roads and other geological environments.

3.2 Comparison of domestic Foreign gas pipeline standards

The standard of foreign gas pipeline is mainly API Spec 5L; International standards ISO 3183-1, ISO 3183-2, ISO 3183-3, the above ISO are the 1996 version.

After the coordination of the above international standards, the national standard GB/T 9711-2011 “Steel Pipe for Oil and Natural Gas Industry Pipeline Transportation System” has been prepared. Instead of GB/T 9711.1-1996.GB/T 9711.2-1999/, GB/T 9711.3-2005 three standards. This standard considers that there are two basic level technical requirements for pipeline steel tubes, namely PSL1 and PSL2. The steel grade of the national standard is represented by “L”, while the international standard is represented by “A”, “B” and “X”. The corresponding relationship with PSL1 is as follows: L175/A25, L210/A, L245/B, L290/X42, L320/X46, L360/X52, L390/X56, L415/X60, L 450/X65, L485/X70. Domestic commonly used API Spec 5L or GB/T 9711-2011, the two standards are equivalent.

Selection of steel tubes for oil and natural gas long-haul pipelines: spiral submerged arc welded pipes are used in the first and second class areas, and straight seam submerged arc welded pipes are used in the third and fourth class areas.

Now let’s look at the steel grade selection of urban gas steel pipes: when the main line and ring pipe network are under high natural gas pressure, the steel grade is generally between L360-L450; When the pipe network branch pressure is very low, using steel grade generally in L245 can be applied.

Regarding the standard of long distance natural gas pipeline, no matter the international standard (ISO), the American standard (API) or the national standard (GB/T 9711-2011) are the basic requirements. When the user (such as petrochina, etc.) bids, the Technical Annex is often attached, and there are several provisions to supplement the content not included in the national standard. Steel pipe enterprises shall comply. The same is true abroad.

For the construction of the East Route of natural gas between China and Russia, the standards implemented by China and Russia differ from each other. Generally speaking, Russian national standards are more detailed in some technical provisions. The standards for implementing natural gas pipelines in countries along the “Belt and Road” often have their own characteristics. Steel pipe enterprises should communicate well on technical terms in trade negotiations before exporting products.

4. New achievements have been made in new technologies and equipment of long distance natural gas pipelines and urban gas pipelines

4.1 Main new achievements in new technology and equipment of long distance natural gas pipelines: ① Technical progress of oil and gas transmission and pipe. In recent years, taking the China-Russia natural gas East Route transmission pipeline as an example, the application of high-strength X80 class, 1422mm in diameter and large-diameter thick-wall submerged arc welding pipe has increased the gas transmission volume of a single pipe from 15 billion m³/a to 38 billion m³/a in the west-east gas transmission line, realizing the high-pressure large-flow gas transmission. (2) Master the key technologies of X80 large-diameter, thick-wall submerged arc welding pipe manufacturing, one is to ensure the DWTT low temperature toughness requirements, such as the realization of brittle fracture control problem at low temperature (minus 45℃) on the Sino-Russian East line, solve a problem that has plagued the pipeline industry for a long time, the second is steel pipe manufacturing technology, Including pipe forming (spiral welded pipe two-step forming technology, straight seam submerged arc welded pipe UOE/JCOE technology), welding (automatic welding), expanding, water pressure and other process optimization, residual pressure control (including hydrogen cracking) and high precision control of pipe geometry, etc. It has broken through the key manufacturing technologies of high strength (X80), thick wall pipeline steel (spiral welded pipe wall thickness 21.4 mm and straight seam submerged arc welded pipe wall thickness 33.4 mm) and large diameter (diameter 1422 mm), realized batch application, promoted the development of pipeline construction, and reached the international advanced level. (3) The integration degree of informationization and automation in pipe welding production continues to improve, such as the application of artificial intelligence and industrial robots. In the early stage, only Baosteel UOE production line introduced arc extinguishing plate welding robots. At present, the research and development and application of the finished pipe label spraying robot, the pipe end weld grinding robot and the pipe end geometric size automatic laser detection robot have also made great progress. Not only reduce labor, reduce labor intensity, but also improve the production efficiency and manufacturing precision. Some welded pipe enterprises, such as Baoji Petroleum Steel Pipe Company, have implemented ERP, MES, PDM and other information construction, as well as the construction of the Internet of Things information system, improving the digitalization, intellectualization and management level of the whole process of steel pipe production. (4) The construction of long distance natural gas pipelines has risen to a new stage of automation and digitalization. The Heihe-Changling Section of the China-Russia East Route natural gas project is a benchmark of natural gas pipeline engineering. The “Smart Site” has realized real-time remote control monitoring and automatic data collection online during the construction process, and for the first time realized 100% automatic pipeline welding, 100%AUT detection, 100% mechanized anticorrosion patching and the first-pass rate of welding line as high as 95.48%. The engineering quality has reached the international first-class level. This has played an exemplary role in the construction of urban gas projects.

4.2 New achievements in new technology and equipment of urban gas pipelines

① Urban gas pipelines mainly adopt HFW high frequency straight seam welded pipe, and the improvement of HFW welded pipe quality comes from the innovation of manufacturing technology. The manufacturing of high-frequency welded pipe has developed from traditional roll forming to roll forming, and also to FFX flexible forming and the application of equal rigid (URD) frame. Intelligent forming has been realized to a certain extent. The welding and heat treatment power supply has been developed from vacuum tube to all solid state, which saves electric energy and greatly improves the heating efficiency and digital and intelligent control level. Through the high frequency welding technology and heat treatment quality control technology, make the weld performance close to the base material level, through the implementation of the system management mode, the high frequency welded pipe quality control extends to the raw material design and production, thus improving the product performance and quality level of welded pipe, into the ranks of the world’s advanced.

(2) New achievements in the construction, installation, operation and management of urban gas pipelines in terms of new technology and new equipment. When pipelines are laid in a straight line, roads need to be excavated during pipeline construction, maintenance or replacement, thus polluting and damaging the environment. In order to solve such problems, trenchless means are adopted by gas supply enterprises: a. The method of horizontal directional drilling, pipe jacking, separate pipe, shallow buried and hidden excavation (shield) laying is adopted to build new gas pipelines. b. Repair the in-service pipeline by using turning lining technology, PE tube intubation technology, cracked pipe technology, etc. This trenchless construction method is a new green technology and should be widely promoted. The adoption of this new technology in Beijing has greatly reduced the frequent excavation of gas pipelines. The bidding information of gas pipeline projects in Jiangsu and Zhejiang province is concentrated in promoting pipe jacking, directional drilling and CCTV inspection projects. North Dalian China Resources Gas Co., Ltd. 2019 natural gas renovation project — directional crossing project, bidding amount of 4.46 million yuan. Shandong Far-reaching Tongda Pipeline Installation Engineering Company has completed more than 10 directional drilling projects, such as the Xiushan Island directional drilling project of Zhoushan liquefied natural gas (LNG) receiving Terminal pipeline project. Sinopec undertook to build the Lishui River directional drilling project of Xiangxi natural gas pipeline network, with a pipe diameter of 323.8 mm *8.0 mm and a total crossing length of 526 mm.

An important aspect of the operation management of urban gas pipe network is to detect the defects of natural gas pipelines in service operation, so as to ensure the safe and normal transmission of natural gas. The all-directional ultra-high-definition magnetic flux leakage internal detector jointly developed by petrochina and Shenyang University of Technology can detect cracks, welds, mechanical damage and corrosion pits and other defects in the axial direction of pipelines, reaching the international leading level. The intelligent integrated management Corridor in Central New Area of Yunnan Province uses cloud platform, big data, Internet of Things, GIS+BIN technology, and the whole-life-cycle integrated intelligent management and control platform to realize visualization, automatic maintenance, intelligent emergency response, standardized data, global analysis, and precise management and control, thus improving the intelligent management and control level and operation efficiency of the integrated management and control corridor.

There are different understandings at home and abroad about the integration of urban gas pipeline into the integrated pipeline corridor. Integrated pipe gallery is a closed space, when the gas leakage, not easy to spread, prone to fire safety accidents. Japan’s Osaka Gas Company, the total length of its high pressure gas trunk line is about 731 kilometers, among which about 5 kilometers are included in the pipeline corridor, accounting for about 0.68%. France has a long pipeline corridor, more than 2,000 kilometers, but gas pipelines are not included in it.

Due to the global pandemic of Corona, personnel mobility is restricted, and they cannot go to the pipeline construction site to guide the installation, commissioning and training of new equipment. German KRAH company uses network technology to achieve far away from the site to complete the above work, which is worth our reference.

5. Green and intelligent is the development direction of urban gas industry

Urban gas industry from the use of pipeline pressure,≤4Mpa; From the performance of the pipeline, steel grade ≤L450/x65; From the technical level of the basic level of the pipeline, it is positioned as PSL1; In general, it belongs to medium and low pressure fluid pipeline. It is different from the development direction of long-haul natural gas pipeline which pursues high steel grade, high pressure, large diameter and large gas volume. The connotation of high quality development of urban gas pipelines is to ensure safety and reliability. From the manufacturing, construction, installation and operation management of steel pipe, green and intelligent is the development direction, both at home and abroad.

Specifically, long-haul natural gas welded pipes are developing in the direction of large gas transmission. For example, Pavnenkovo-Ucha pipeline in Russia has a diameter of 1420 mm and a pressure of 11.8Mpa, with gas transmission of 58 billion m³/a; Russia’s Nord Stream No. 2 pipeline has a diameter of 1220 mm, a pressure of 22Mpa, and a gas capacity of 55 billion m³/a. The extraction of natural gas resources from the ocean, followed by liquefaction (LNG) and shipping to ports, is the direction of development.

The large-diameter (diameter 219-diameter 630 mm) contact welding process of HFW high-frequency welded pipe saves energy, and its power is about 43%-50% of that of induction welding process. The total weight of shear butt welding machine and spiral looper device 504t is omitted, saving a lot of investment and improving the metal yield.

Urban gas pipeline installation and construction should adopt trenchless method as far as possible; Horizontal directional drilling and pipe jacking operations; For the repair of in-service pipelines, the inverted lining technology should be adopted as far as possible when conditions permit. On the construction site, the model of “smart site” should be adopted. Real-time remote monitoring of the construction process, automatic data collection online, automatic pipeline welding and AUT detection should be promoted to improve project quality.

Urban gas pipeline operation management, to achieve automatic, intelligent, visual maintenance and detection, to ensure safe operation.

6. A little advice

From the administrative point of view, there are three different departments in charge of urban gas industry: urban gas engineering is municipal engineering; Urban gas pipelines shall be in charge of the state construction department; Town gas pipeline special equipment nature of its supervision and inspection authority is subordinate to the market supervision department. How to coordinate the three departments to make the quality assurance system work well.

The quality of urban gas pipeline construction is not easy to control, mainly due to the quality assurance system of construction units out of control. The special equipment supervision department shall urge the construction party to strictly examine whether the municipal engineering unit bidding has the qualification of pressure pipeline installation, and it is forbidden to subcontract the pressure pipeline installation to the unit without the qualification of pipeline installation. At the same time, urge the supervisory and inspection authorities to strengthen the supervision of the operation of the quality assurance system. In short, it is the quality assurance system of the construction unit and the quality assurance system of the supervision and inspection agency under the coordination of the special equipment supervision department, in order to ensure the quality of construction.

Common quality problems in urban gas pipeline installation supervision and inspection often appear in design drawing review, construction scheme formulation, material confirmation, welding process and quality control, non-destructive inspection, pressure test and other key nodes of installation quality control, which directly affect pipeline construction quality. At the same time, the management and technical personnel are required to meet the requirements of professional competence.

1、Alloy steel pipe 2、Stainless steel tube 3、Stainless steel welded pipe 4、Reducing pipe

5、High Pressure Thick Wall Pipe Fitting 6、Elbow 7、Flange 8、Spigot Pipe Fitting

9、Tee 10、Tube Cap 11、Pipe Fitting