The operation conditions of oil storage and transportation system in petrochemical enterprises are relatively “mild” compared with production equipment. Its working pressure is generally below 2.5Mpa, in some cases up to 4.0 Mpa; the working temperature is generally below 100 °C, the highest does not exceed 1809C, only when purged with 1.0Mpa steam, the highest temperature up to about 250 °C. Various oil products-generally no corrosion or only slight corrosion. Production operations of oil storage and transportation, such as oil loading and unloading, reconciliation, and transportation, are generally intermittent corrosion. Production operations of oil storage and transportation, such as oil loading and unloading, reconciliation, and transportation, are generally intermittent operations. Only a few pumps that supply raw materials to production equipment are continuously operated.
The selection of pipes for oil storage and transportation systems in petrochemical enterprises is currently in accordance with the industry standard “General Rules for the Selection of Pipeline Design Equipment for Petrochemical Enterprises” (SH3059-94). The specification for selection of resistance welded carbon steel straight seam steel pipe (ERW pipe): the product whose expansion rate does not exceed 1.5% of the outer diameter after cold expansion should be used in pipes with a design temperature not exceeding 200 °C without cooling The expanded steel pipe can be used for pipes whose design temperature does not exceed 425 °C. It can be seen from this that ERW steel pipes can be used in the oil storage and transportation system. However, in the actual design work, each design unit has more specific pipe selection regulations and some customary practices.
Due to the limitation of historical conditions, there were no ERW steel pipes in China in the 1970s and 1980s, and only high-frequency welded steel pipes that could be used for low-pressure fluids (such as water, compressed air, etc.), that is, according to the national standard “galvanized welded steel pipes for low-pressure fluid transportation” ( GB3091) and “welded steel pipes for low-pressure fluid transportation” (GB3092). There are also spiral welded steel pipes produced in accordance with industry standards “Spiral Seam Submerged Arc Welded Steel Pipe for Pressure Fluid Transport” (XSY5036) and “Spiral Seam High Frequency Welded Pipe for Pressure Fluid Transport” (XSY5038). This kind of steel pipe can generally only be used in non-toxic medium pipes with a design pressure not exceeding 1.0Mpa. Therefore, in the design of oil storage and transportation systems, no matter what the actual production and operating conditions are, only seamless steel tubes can be used. For a long time, the specific pipe selection regulations of various units have specified the use of seamless steel pipes under general circumstances. Only in DN2350 can spiral spiral submerged arc welded steel pipes be used (the main reason is that large-diameter seamless steel pipes need to be imported at the time, the price expensive). Sometimes in order to select materials for production equipment, it is also required to select seamless steel pipes in the oil storage and transportation system.
Since the 1990s, my country has successively introduced ERW steel pipe production technology and equipment from abroad, and has been able to produce DN80-300 ERW steel pipes, with an annual output of up to millions of tons. It can be produced according to API, ASTM, GB/T and other standards. Although the price of these products is much lower than that of seamless steel pipes and can also be adapted to many production occasions in petrochemical enterprises, these products have not been widely used in PetroChina and Sinopec systems due to various reasons.
For the construction of long-distance pipelines, the choice of pipe materials and pipe-making methods is extremely important. It not only affects the construction technology and quality of pipeline engineering, but also affects the safe operation and management of pipelines in the future, as well as the entire project. Investment has a huge impact (in the entire project investment of long-distance pipelines, the Investment generally accounts for about 50%-65%).
The length of the trunk line from Zhenhai Refining & Chemical Co., Ltd. to Xiaoshan Nanyang Oil Depot in Zhejiang is 153KM, and the length of the branch line is 5.3KM. The adopted pipe diameter is 355.6*6.4mm, X42 steel grade, the design working pressure is 6.4Mpa, and the conveyed medium is 90*, 93# unleaded gasoline. 0# light diesel and 3# aviation kerosene and other four oil products. The maximum transmission volume of the designed project in the first phase is 2,232,900 tons/year, while the maximum transmission capacity of the pipeline design is 3.102 million tons/year. Pipeline anticorrosion adopts anticorrosion system combining sintered epoxy powder coating and applied current cathodic protection. The welding method is manual all-position downward welding. The project uses ERW steel pipes in total 7100 tons, calculated at an average saving of 800 yuan/ton per ton (compared to SML steel pipes), the entire project will save 7100×800=568 million yuan for a single steel pipe, which has achieved gratifying economic benefits.
In the history of the world, ERW steel pipes have tended to be mature and perfect in the 1980s. A large number of domestic advanced technologies have been introduced in the 1990s, and they have been promoted. Not only in theory but also in practice, ERW steel pipes can be explained in the field of oil and gas storage and transportation. Reliability and safety of transmission quality and reduce pipeline construction investment. In the future oil and gas storage and transportation projects and pipeline construction, we must break the old habits inherited from the design and vigorously promote the use of ERW steel pipes.