High-pressure natural gas pipelines
High-pressure natural gas pipelines have become an integral part of our modern society, providing a reliable and efficient means of transporting this valuable resource. These pipelines are designed to withstand immense pressure, ensuring the safe and efficient delivery of natural gas from production sites to distribution centers. High-pressure natural gas pipelines have the advantages of transporting large quantities of gas over long distances. This allows for the optimization of resources, as gas can be sourced from remote locations and delivered to areas with high demand. Furthermore, these
pipes are highly cost-effective compared to alternative transportation methods such as trucks or ships.
Safety is a paramount concern when it comes to high-pressure natural gas pipelines. Rigorous engineering standards and regular inspections ensure that these pipelines are built to withstand extreme conditions and prevent leaks or ruptures. Advanced monitoring systems are also in place to detect any anomalies in pressure or temperature, allowing for prompt intervention if necessary.
However, despite these safety measures, accidents can still occur. The explosion at San Bruno in 2010 serves as a stark reminder of the potential dangers associated with high-pressure natural gas pipelines. Pipeline operators must remain vigilant in their maintenance efforts and invest in state-of-the-art technology to minimize risks. As we strive for a sustainable future, we must continue investing in the development and maintenance of high-pressure natural gas pipelines while prioritizing safety above all.
For oil pipelines, it is required to have good weldability and can be welded without preheating at the pipeline construction site. Pcm should be less than and equal to the range between 0.20 and 0.25, plus sufficient strength and toughness. In addition to the above requirements, welded pipes for natural gas pipelines transporting corrosive media are also required to be resistant to corrosion caused by stress. Among them, the main ones are corrosion caused by hydrogen sulfide and corrosion caused by stress due to chloride ions and carbonic acid.
The main forms of corrosion in
high-pressure natural gas pipelines are corrosion caused by stress, hydrogen sulfide embrittlement and hydrogen-induced cracking. The steel pipe wall of corrosion caused by stress is rapidly thinned, while hydrogen sulfide embrittlement develops very fast usually within hours to several days after the completion of the pipeline. Hydrogen-induced cracking (HIC) develops relatively slowly and usually takes a period or even several decades. In general, the corrosion of steel caused by hydrogen sulfide is predicated on the presence of water. If water can be kept below 0.0005%, the impact of hydrogen sulfide on steel pipes will be negligible. However, this is generally difficult to do, so attention must be paid to the pipe material.
Corrosion caused by stress is a general term for damage caused by various factors other than hydrogen sulfide. At present, corrosion caused by stress is a major cause of accidents in gas transmission pipelines abroad. It has been found that corrosion caused by stress is mainly caused by corrosion of soil. It can also develop in acidic, neutral, and even alkaline environments. Therefore, corrosion inhibitors do not work. Foreign countries believe that the main measure to prevent this kind of corrosion caused by stress is to improve the quality of the outer packaging and isolate the corrosion of the pipe body from soil. From the perspective of reducing residual stress of welded pipes, there are no reports on this in China. Corrosion caused by hydrogen sulfide is generally controlled by using corrosion inhibitors and controlling the hardness of pipeline steel plates and welded joints can reduce hydrogen sulfide embrittlement (SSC). However, this principle is not working, especially when there is welding stress. Therefore, the requirements for the welding process of gas pipelines are stricter than those for oil pipelines. Hydrogen-induced cracking (HIC) can even develop in very mild steel. This is a type of damage caused by hydrogen that has not yet been solved in China from the perspective of gas pipeline steel.
The improper use of welded pipes not undergoing stress relief annealing after welding and causing corrosion due to hydrogen sulfide is the main factor for accidents. Of course, if this pipeline can be strictly dehydrated and kept dry during operation, there will not be so many accidents.
Among the causes of accidents, the quality of steel plates and welded pipes used in pipelines accounted for 83% of the causes of accidents. If 10% of the factors caused by corrosion and thinning of the pipe wall are added, 93% of the causes of the accident are factors related to the material of the welded pipe. Comparing the statistical results of Canadian pipeline companies, it can be seen that the material of China's gas pipelines should be paid attention to. It can be seen that even in foreign countries, corrosion caused by stress mainly occurs in gas transmission pipelines.
