When a client has an urgent breakdown is when Robtek performs at their best. Tanga Cement is a long-standing customer of theirs and the company was only happy to assist, when the client’s kiln shell ripped apart for three quarters of its circumference and the plant was immediately stopped end March 2021.
On a breakdown basis, 60mm steel plate had to be sourced, procured, prepped and rolled. Due to abnormal road transport constraints through to Tanzania, the shell sections had to be fabricated in SA in 2 halves. While this was being done the Robtek team packed and prepped their tool and equipment containers. They were loaded onto the first available truck and the team set off on the long trip up to Tanzania.
Once the kiln shell was fabricated it was set up for machining – this needed to be done on both sides of the kiln shell section. Chair plates which fit between the shell and riding ring tyre were also required for the replacement. These plates required machining to the correct thickness and to be rolled and cut to size, followed by drilling and tapping.
Due to abnormal road transport constraints, the kiln shell sections had to be fabricated in two halves in SA and assembled on site in Tanzania. Image credit: Robtek Plant & Engineering Services
Once the kiln shell sections were completed, they were loaded onto a second truck for transport. Crates containing kiln chairs, retainers, blocks, erection steel and consumables were also loaded on the truck and made their way up to Tanzania.
While the trucks were making their way to site, A 250t crane required for the lift was arranged and began making its way to site for establishment.
On the 30th of April 2021, Robtek dispatched its first kiln installation team to commence the stripping and removal work to gain access to the kiln shell. Their team got to work on a kiln support tower and began stripping where possible. When the first truck carrying tools and equipment arrived on the 6th of May, the team got to work, removing the old part of the shell that needed replacing.
Once the kiln shell was fabricated it was set up for machining on both sides of the kiln section. Image credit: Robtek Plant & Engineering Services
They were then also able to remove the old shell piece from the tyre. Truck 2 carrying the shell section reached Tanga cement on the 11th of May and the team got right to work to commence joining the section halves which entailed bracing and aligning in preparation for submerge arc welding.
The section halves were welded at the longitudinal splits on the outside, back gouged, ground, weld tested with dye pen and then welded on the inside as well. With the new completed section, the existing tyre could be positioned onto the new shell. The complete assembly was then rigged into position.
Erection steel was installed inside new and old sections so that the seams could be temporarily joined and aligned. The remaining chair plates were then installed and the first set of alignment runouts could be taken. Shell seam measurements were recorded, runouts calculated and adjusted accordingly. Once the runouts met specification and were accepted for welding the manual root welding could commence. Once the root welding was complete, the submerge arc machine could be set up on the first joint seam. Preheating of the seam commenced and submerge arc welding was underway.
When both external seams were complete, the internal erection steel could then be removed and internal weld preparations could commence. This entailed gouging and grinding a weld prep for internal welding. After dye pen cracking tests were complete, sub-arc welding completion could then be done from the inside.
3rd Party NDT testing was then carried out and Robtek’s highly efficient team achieved a 100% pass. The kiln could now be handed over back to the plant for refractory installation. Final fit up of chairs and shimming was completed and discharge seals refitted. All temporary supports and scaffolding were then removed, the area cleaned up and site de-establishment could commence.