The Design Temperature of Tees Used in Stations of China-Russia East Pipelines
Posted: 12/11/2022 12:02:22 Hits: 6
The China-Russia East Natural Gas Pipeline Project is a major project for CNPC to build China's four major energy transportation channels. The starting point of the China-Russia East Pipeline is located in Heihe City which is at the border between China and Russia, passing through 9 provinces, including Heilongjiang, Jilin, Inner Mongolia, Liaoning, Hebei, Tianjin, Shandong, Jiangsu, and Shanghai, and the end is Shanghai, with a total length of 3371km. It is the first cross-border long-distance natural gas pipeline project with the largest single-pipeline transmission capacity in the world using steel pipes with 1422 mm super-large diameters, X80 high-grade, and high pressure of 12MPa. The natural environment along the pipeline is complex, and the extreme minimum temperature of some stations in winter reaches -48.1°C, which puts forward higher requirements for the low-temperature toughness of above-ground steel pipes and pipe fittings, and brings great challenges to China's basic industries such as iron and steel smelting, pipe making, and equipment manufacturing.
Determination of design temperatures
Comparing the definitions and regulations on design temperature in China, the United States, Russia and Canada (Table 1), the definition of the minimum design temperature in each standard is essentially the same, that is, the minimum design temperature is used to determine the low-temperature performance index of the material, and the minimum design metal temperature value is adopted. The working condition with the lowest expected metal temperature is the pipeline running under pressure, and the construction and other working conditions are generally not considered. However, the wall temperature is affected by the external environment and the fluid in the pipe, especially the above-ground pipeline, which is affected by conditions such as ambient temperature, wind speed, sunlight radiation, and fluid in the pipe. The minimum design temperature of each project is different.
Table 1 Requirements and standards for the minimum design temperature in long-distance pipelines
Determination of design temperatures
Comparing the definitions and regulations on design temperature in China, the United States, Russia and Canada (Table 1), the definition of the minimum design temperature in each standard is essentially the same, that is, the minimum design temperature is used to determine the low-temperature performance index of the material, and the minimum design metal temperature value is adopted. The working condition with the lowest expected metal temperature is the pipeline running under pressure, and the construction and other working conditions are generally not considered. However, the wall temperature is affected by the external environment and the fluid in the pipe, especially the above-ground pipeline, which is affected by conditions such as ambient temperature, wind speed, sunlight radiation, and fluid in the pipe. The minimum design temperature of each project is different.
Table 1 Requirements and standards for the minimum design temperature in long-distance pipelines
| Standards | The definitions of design temperatures |
| GB 50251-2015 “Codes for Design of Gas Transmission Pipeline Engineering” | The minimum temperature that the pipe wall or element metal may reach under the corresponding design pressure in the normal working process of the pipe. |
| ASME B31.8-2018 " Transmission and Distribution of Gas Piping Systems" | The minimum expected temperature of the material during operation |
| TOCT P 55989-2014 " Basic Requirements for Main gas transmission pipelines with pressure above 10MPa” | The minimum temperature that the pipe wall may reach during the use of the pipeline should be determined according to the temperature of the conveyed product, soil and external air, wind speed, solar radiation, and the thermal interaction between the pipeline and the surrounding environment. |
| CSA-Z662-2015 "Oil and Gas Pipeline Systems" | Minimum expected metal temperature for steel pipes operating at pressure tests and design conditions with circumferential stress exceeding 50MPa |
Regarding the minimum design temperature of the pipeline, since the requirements of each standard are consistent, it is important to analyze and summarize the minimum pipe wall metal temperature according to different environmental conditions and different transmission medium conditions. When the pipeline is shut down, the temperature of the pipe wall will eventually drop to the ambient temperature. Even if insulation measures are taken, the increase in the metal temperature of the pipe wall will not be obvious; According to the relevant standards and research on the design temperature, for ground pipelines whose ambient temperature is lower than that of the conveying medium, the minimum design temperature depends on the local minimum ambient temperature. However, how to choose the minimum ambient temperature, each standard or regulation is not the same.
At present, there are no relevant regulations on the value of the minimum ambient temperature in the standards of the oil and gas pipeline. The minimum ambient temperature specified in TSG D0001-2009 " Safety Monitoring Regulations of Pressure Pipelines - Industrial Pipelines", GB 150-2011 "Pressure Vessels" and other standards is the lowest value of the monthly average minimum temperature over the years. DEP 01.00.01.30-1995 "Definition and Determination of Temperature and Pressure Level", DNV-OS-F101-2013 "Subsea Pipeline Systems", SAES-D-001-2016 "Design Standards for Pressure Vessels". The lowest daily average temperature over the years is adopted for the minimum ambient temperature in BS EN 14015-2004 "Specifications for the design and manufacture of on-site construction, vertical, cylindrical, flat-bottomed, above-ground welded steel storage tanks for storage of liquids at ambient temperature and above" and other standards. For the determination of the minimum design temperature, the extreme minimum temperature is taken for projects such as the Second West Pipeline and Central Asia, and the project of the Third Shaanxi Pipeline and Moda Pipeline is based on the historical minimum temperature. The lowest value of the average minimum temperature in the coming month is adopted. According to the results of benchmarking and domestic engineering analysis, the minimum design temperature of pipe fittings on the China-Russia East Pipeline station is taken from the minimum design metal temperature, and the minimum design metal temperature is taken from the lowest daily average temperature of the station site over the years. The minimum daily average temperature of each station along the pipeline is -41.5°C for China-Russian Eastern Pipelines. Considering a certain design margin, the minimum design temperature of the pipe fittings in the stations of the China-Russia East Pipeline is determined to be -45°C.
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