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Monadelphous and Incitec Pivot Limited

Category six – Best demonstrated healthy and safe work design

Monadelphous are an Australian engineering group who were contracted by Incitec Pivot Limited (IPL) to clean the Tails Gas Stack (stack) at the Mt Isa Acid Plant after the stack had accumulated acidic sulphate-based material with the potential of impacting operations.

In 2020, some complications occurred that prevented cleaning the stack which included:

  • the vacuum truck did not have adequate suction to remove the dense material.
  • the risk of the acidic materials severely deteriorating the vacuum truck
  • segments of 150 x 6-millimetre steel flat bar with the potential of weighing up to 10 kilograms had fallen within the stack.
  • access to the confined space is located 22 metres above grade presenting access and egress challenges.

The Armadillo was designed and developed by Monadelphous to support the safe manual excavation works to clean the stack. With a curved roof structure that is housed on a steel frame, it provides overhead protection when workers are enclosed into the cylindrical stack. An external platform allows workers to safely enter and exit the stack and it also acts as a shield by protecting workers from falling materials and reducing the downtime required when cleaning.

It enhances worker safety and operational efficiency in an environment with acidic sulphate materials.

The development of the Armadillo involved collaboration among engineers, site managers, rigging teams, fabrication experts, and equipment suppliers. They ensured worker safety, precise installation, and the fabrication of a strong structural steel roof plate. The creation of the Armadillo allowed the cleaning process to be more efficient, required fewer personnel, and eliminated the risk of environmental contamination.

RUN TIME: 3 mins 06 secs

My name's Dan Grey. I'm a project manager with Incitec Pivot. So, our problem was we needed to perform a clean of the exhaust stack to the Mount Isa Acid Plant. This stack builds up chemical materials in the basin and had been doing so for the prior 10 years.

And previous attempts to clean out the stack had failed due to a number of safety issues. The prior attempt at cleaning the stack came to the realisation that there were sections of steel plate that were falling down the internal of the stack and impacting the area where our people would be working in the confined space.

If something had a fallen, up to 10 kilos, we were suggesting, worst case scenario, but yeah, absolutely, it would've instantly killed someone. So, Incitec Pivot engaged Monadelphous as a tier-one contractor to provide the service. Through a lot of investigations, site walks, discussing it with the engineering through the client, internally with our engineers on site, a lot of work between all of us just coming up with ideas on how it was going to work and what was going to be most suitable.

So, our critical stakeholder was the workers who were actually going to be inside that confined space and exposed to the risk of, not only the objects falling above them, but the acid that they were manually excavating below. They were involved from the start and had some comments around the design in order to make it more safe and easy to work for them, which required an overhead protection.

The solution to the problem was the concept and design, which ultimately become the Armadillo, which allows safe access into the tiles gas stack for removing the acidic sludge. So, our Armadillo was constructed out of the Bisalloy 80 plate, which was almost three tonnes in weight.

We had to work out a way to instal that from externally to the stack without exposing any people to the risk. We developed a frame and a counterweight to effectively instal that overhead roof from outside of the vessel with a crane.

So, the staff at the Incitec Pivot Mount Isa Acid Plant, and the contractors that were involved in the project appreciated the clear effort that we had made to make this project safe. And I think it was a great example that management were invested in going to any expense to ensure that their workplace was safe.

It's extremely rewarding to be involved in projects that deliver safety, especially when there's high risks involved, because you immediately see the appreciation of the people who have to be working in those environments.