Southern African heavy lifting and plant relocation solutions provider Vanguard was contracted by engineering and construction firm SNC Lavalin to install two cold boxes as part of a second oxygen plant at a mining operation, in Namibia.
Owing to confined spaces on site, Vanguard developed a unique solution for its strandjacking system, which would provide horizontal manoeuvrability and stability at heights of over 30 m.
“Space on site was very constrained, providing only enough room for both cold boxes to approach the plinth at one point. It was also necessary to position the column cold box and heat exchanger cold box directly next to each other.
“Coupled with this, no crane was available in Namibia that could perform this type of lift and, transporting the required crane to site, would have proved too costly,” says Vanguard project engineer Roland Cumings.
To perform the lift, Vanguard used two strandjacks, each configured to 50 t, which were placed on a header beam secured to 30 m lattice tower sections. A travelling framework was developed by the company for the header beam to enable the strandjacks to move horizontally to position the cold boxes.
A top and tailing method was used to lift each cold box. The strandjack reeled in cables, which were connected to the top end of the boxes, to provide vertical lift, while a standard 170 t crane was used to secure and manoeuvre the bottom end.
Once vertical, the boxes were moved horizontally – with the help of the unique travelling system, turned 90°, and then lowered onto their final locations.
“Strandjacking provides a very controlled and engineered lift, offering precision and safety. “This was necessary for placing the second cold box and heat exchanger directly next to each other. “We were able to design the unique solution and complete the project within budget and the prescribed timelines,” says Cumings.
Vanguard was also responsible for the transport of all additional items for the oxygen plant, which were shipped to Walvis Bay, to the site.
It also lifted and installed five additional items on site, including a storage vessel, a water wash tower, two mulsive vessels and a chill tower.