【Haichuan Expands Horizons】Overall lifting and removal of a floating roof with a diameter of 40 meters and a weight of 106 tons

The floating roof removal project for the 20,000 m3 storage tank at Songyi Combined Station is located at Songyi Combined Station in the First Production Area of the Eighth Oil Production Plant. 　　Since 2018, the purification tanks have been unable to function properly due to the aging of their floating roofs, resulting in rising costs for oil storage and transportation year by year. At the end of 2022, the engineering construction company transported 550 tons of crawler cranes from Huaibei, Anhui, to Daqing, making it possible to remove and lift the floating roofs of storage tanks. 　　To this end, the resource sharing center tasked with the lifting operations acts as the main force in oilfield construction, determined to tackle this tough challenge. They selected the best equipment and personnel to form a 30-member lifting team aimed at carrying out large-scale lifting operations. This team is anchored by the 550-ton crawler crane, known as a \"powerful tool for oil fields\", with Li Rukun, a lifting expert with 30 years of experience, and Yan Guo, a young skilled technician who serves as his apprentice, serving as the core of the team.

In the past, for lifting the floating roof of storage tanks, it was necessary to first enter the tank to carry out dredging operations, then cut the floating roof inside the tank using water cutting, and finally use a crane to lift the cut floating roof out of the tank. The biggest challenge in carrying out this project is to safely and smoothly remove the 40-meter-diameter floating roof from the storage tank without performing any cutting. 　　“The thickness of the floating roof panel is only 6 mm, which greatly increases the difficulty of lifting it. To this end, we installed a total of 35 lifting points on the floating roof of the storage tank, using steel wires with a diameter of 32 mm. For the first time, this new method of one-time overall lifting was applied, which not only saved on water cutting costs but also reduced the lifting time and minimized safety risks. ”

　In the initial phase, the construction workers worked in shifts to enter the tank in order to fix the lifting points; they used guide chains to gradually adjust the length of the steel cables, while removing all obstacles inside the tank that could interfere with the lifting process, so as to keep the floating roof at a horizontal level. However, due to continuous rainfall, water accumulated inside the floating vessel, disrupting its float balance. Therefore, to ensure successful lifting, they had to stop the lifting process and drain water every time the lifting capacity increased by 10 tons, then readjust the balance. Under such challenging working conditions, the crew overcame various obstacles such as high temperatures, heavy rainfall, and significant safety risks, and successfully raised the floating roof gradually until it was near the top of the tank, thus preparing everything properly for the trial lifting operation. 　　It is understood that during the trial lifting process, they took into account the weight of sediment and rust, increasing the lifting weight from 82 tons to 99 tons; yet obstruction still occurred when the floating roof was raised to the top of the tank. 　　To identify the problem, Li Rukun, a 57-year-old operator of the 550-ton crawler crane, climbed inside the 15-meter-high storage tank on multiple occasions to carefully observe and find the cause. Ultimately, after extensive research, repeated discussions, and precise calculations, it was determined that the issue was caused by excessive adhesion forces at the bottom of the floating vessel and the bottom of its top plate. It was estimated that the weight of the floating top at the moment it was lifted would be close to 120 tons, which far exceeded the lifting capacity of the cranes available. To address this challenge, they decided to adopt the approach of \"reducing the length of the rods and adding counterweights\" in order to increase the lifting capacity of the crane; at the same time, pipe rows were laid down to enhance the strength of the ground. After another attempt at lifting, success was finally achieved. 　　This lifting operation was, within the relevant industry sector, the first of its kind to involve high-risk activities carried out under unconventional procedures. They implemented ten safety measures, including the use of axial flow fans to expel combustible gases and reduce their concentration, as well as the use of life ropes and restraint ropes to prevent falls, thereby ensuring safe and environmentally sustainable construction throughout the process.

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