Removing industrial ducting from tall silos requires careful planning, the right crane, and riggers experienced in work-at-height operations. When RCL Foods needed to remove three stainless steel ducting pipes from their concrete silos in Pietermaritzburg — each pipe measuring 50 metres in height — Reef Rigging developed an approach that safely completed the operation in a single day. Here is what the safe removal of silo ducting at height actually involves.
What Equipment Is Needed to Remove Ducting from Tall Silos?
For the RCL Foods project, the following equipment was mobilised: a 150-tonne mobile crane (providing the reach and capacity needed to suspend a man cage and support the ducting during removal), a crane truck for receiving and handling the removed ducting sections at ground level, certified man cage, rigging tackle, qualified riggers, and fitters with cutting and unbolting equipment for disconnecting the ducting from its brackets. The man cage was the critical component — providing the riggers with a stable, safe working platform at 62 metres from which to access the bracket locations on the silo walls.
Why Was a Man Cage Used Instead of a Scaffold?
Installing a conventional scaffold at 50 to 62 metres on the outside of a cylindrical concrete silo is significantly more expensive, time-consuming, and difficult to manage than using a crane-suspended man cage. The man cage allowed the team to access the exact bracket positions around the circumference of each silo quickly and in sequence, with the crane repositioning the cage laterally between each bracket location. The approach reduced the project duration from what would have been several days with scaffolding to a single 12-hour operation.
What Safety Measures Apply When Removing Silo Ducting at Height?
Safe removal of ducting at height requires a formal fall protection plan for all work-at-height activities, a certified man cage with a current load test certificate, full fall arrest harnesses for all cage occupants, continuous two-way radio communication between the cage team and the crane operator, a wind speed limit and monitoring procedure (operations must be suspended in high winds), and an exclusion zone at ground level below the work area to protect personnel from any dropped objects or falling debris during the removal process.
How Are Ducting Sections Lowered Safely?
Once the riggers in the cage have unbolted the ducting from its silo wall brackets and the crane has taken the weight of the section, the ducting is lowered in a controlled manner to ground level. The crane operator manages the lowering speed, with the banksman at ground level confirming when the section is clear of any obstructions and guiding it to the landing area. For long ducting sections, the centre of gravity must be identified before the rigging is released from the wall, and the crane must be positioned to allow the load to be lowered vertically without swinging.
Reef Rigging provides specialist work-at-height rigging services across South Africa. Contact the team to discuss a silo ducting removal, high-level steel dismantlement, or other work-at-height rigging project.
Frequently Asked Questions: Removing Silo Ducting at Height
What crane capacity is required for man cage operations at 50–60 metres?
The crane capacity required depends on the weight of the man cage and its occupants, the weight of the ducting or other load to be handled, and the boom radius required to reach the work positions on the silo wall. At extended radius and height, a large crane is typically needed. For the RCL Foods project, a 150-tonne mobile crane was deployed. As always, the specific crane requirements must be calculated based on the actual loads and geometry of each project.
Are there height limits for crane-suspended man cage operations in South Africa?
There is no specific legal height limit for man cage operations in South African law. However, the crane used must be capable of providing a stable, controlled hold at the required height without excessive sway, and the operation must comply with all applicable fall protection, man cage certification, and work-at-height regulations. Practical and safety constraints — particularly wind sensitivity at height — increase with elevation, and wind speed monitoring is especially important for operations above 30 metres.