Engaged by Stefanutti Stocks Oil & Gas Division in the construction of the largest air separation train ever built, Johnson Crane Hire has been providing heavy lift services as well as a range of smaller lifts at Sasol’s Secunda complex.
This milestone plant under construction for Air Liquide, which is the 17th train to be built at this site, will have a total capacity 5 000 tons of oxygen per day.
The contract for the project’s heavy lift scope was won by Johnson Crane Hire’s Heavy Lifts Project Division on a fixed value basis, according to Peter Yaman, executive – sales, while the smaller crane work was serviced through the company’s Trichardt branch near the Sasol Secunda site. At the heart of the plant is the argon column, which presented Johnson Crane Hire with its heaviest lifts.
According to Grant Parker, project ma-nager - Heavy Lifts Pro-jects Division, the lower section of this column weighed 287 tons, and was lifted by the company’s main lift crane, a Liebherr LR1750.
This 750 ton lattice boom crawler crane was configured initially with 84 metre boom length, which was later in the project extended and re-configured at 112 metres.
“An interesting aspect of the contract was that most of the large components – such as the columns – were lifted in an almost fully assembled state,” says Parker.
“The upper sections would then have to be accurately positioned on the lower sections, with tolerances less than 1 millimetre per metre. For the large argon column, this meant a tolerance of less than 10 millimetres.”
The tall structures meant that verticality had to be carefully addressed in the lift planning, with the use of tailing cranes – mainly the Liebherr LTM1500-8.1, a 550 ton telescopic mobile unit.
Close attention to planning and safety procedures is always key to the smooth implementation of lifting pro-jects undertaken by the company, says Yaman, so Johnson Crane Hire placed a CAD technician permanently on site to create twodimensional and threedimensional plans for all lifts over five tons – which the customer would also sign off before execution.
“This planning allows us to position the cranes in exactly the right locations to facilitate the coordination between the main crane and the tailing crane, and to ensure the cranes don’t work against each other,” says Parker.
“As the column nears the vertical, for instance, the weight transfer between the one crane and the other can occur very quickly. With the HP/LP column, another of our heavier loads, this transfer took place over an angle of just two degrees.”
A 400 ton lattice boom crawler crane was also brought to site for additional tailing capacity in the big package lifts, as well as a support crane in the form of a 100 ton Liebherr LTR1100 telescopic boom crawler crane. A particular challenge was the wind resistance created by the installed panelling on the columns, which could delay work if the wind strength exceeded a certain level.
Once lifted, the upper section would have to be held in place for extended lengths of time while being secured to the lower section – sometimes overnight.
“Space is also often at a premium on construction sites like this, and it is important that all contractors collaborate closely,” he said.