Case Study – Four Coke Drums Replaced with Mammoet’s SK350 in Texas
The impressive capabilities of Mammoet’s SK350 crane aided in the efficient replacement of four coke drums at a Texas City, Texas refinery located close to the River Mississippi. The replacement of the coke drums was part of a planned turnaround at the refinery’s coker unit.
By utilizing the SK350, a 5,000t class crane, no preparation work was needed as the crane could lift the derrick as constructed. This allowed significant time savings for the client and other third-party contractors since they did not have to make modifications to the derrick for lifting ahead of time.
In addition, the SK350 had more than sufficient capacity to extract the 740t derrick and keep ground bearing pressure low because of its ring design, while also completing all lifts from the same location.
First the 53m (174 ft) tall derrick was removed so the coke drums could be reached. After this, one by one, the old 270t (596,000 lb.) coke drums were removed and replaced with new, 448t (998,000 lb.) coke drums. Once in place, the derrick structure was reinstalled.
Each of the four old and four new coke drums was handled with the SK’s auxiliary hook. Typically, lattice boom cranes have two hook blocks hanging from the boom. The main hook block is the crane’s heavy-duty block that can handle the full lifting capacity of the crane. Hanging in front of the main hook block is the auxiliary or runner hook block, which is typically considered a light duty block. The auxiliary hook block moves up and down much quicker than the main block, hence its nickname “runner”.
The runner is very useful for quickly handling lighter loads for routine job site and crane assembly activities. On the SK, the runner hook on its own has a 600t capacity, making it strong enough to lift a load as heavy as an average coke drum, which would typically require the strength of a heavy-duty main block on most cranes.
Mammoet provided manpower for two 12-hour shifts, allowing for around-the-clock work to complete all ten lifts several days ahead of schedule despite encountering multiple days’ worth of weather including strong winds and heavy fog.
Mammoet Project Manager, Sidney King, states, “Using the world’s strongest land-based crane, Mammoet’s international team comprised of six nationalities led the coke drum replacement project to a successful conclusion. With zero recordables and despite some weather downtime, the SK350 was able to complete all the client’s lifts days ahead of their planned schedule, giving the turnaround an opportunity for an ahead of schedule completion.”