W

ith the collapse of Silo 20 of State-owned power utility Eskom’s Majuba power station in November 2014, an interim solution to directly feed coal into the power station was implemented, and received the Best Project of the Year award from Eskom at its yearly awards ceremony.

The silo collapse resulted in conveying infrastructure being damaged, thus severing coal supply to the remaining silos and the power station as a whole. In response to the crisis, Eskom implemented a phased recovery plan.

Initially, mobile feeders were used to supply coal directly onto the boiler-incline conveyors from emergency stockpiles. The next phase – the interim solution – was awarded as a contract to turnkey materials handling company Rula Bulk Materials Handling.

The goal of this phase was to quickly implement a silo bypass conveyor system that would reduce the need for the emergency stockpiles and associated vehicles, and provide a reliable coal supply to the generating units.

The project was successfully commissioned in September 2015. Eskom recognised the execution of a technically challenging scope of work, undertaken within budget and on time. The award also acknowledged the key role this project played in restoring the availability of the Majuba coal system.

Rula Bulk Materials Handling’s project scope included the design, supply, construction and commissioning of a 2 250 t/h bypass conveyor to receive coal from one of the existing overland conveyors.

The bypass conveyor discharges into a new 160 m3 steel surge bin with three outlets, each fitted with a 750 t/h feeder conveyor. These convey coal to the three existing boiler-incline conveyors. The surge bin was fitted with a strain-gauge system to allow for bin level control. This was crucial, as the surge bin can accommodate coal delivered in only a few minutes if the bin feed and discharge rates are unbalanced.

As an additional measure to prevent surge bin flooding, the bypass conveyor was fitted with a fixed tripper, thereby facilitating that coal be either conveyed to the surge bin or dumped on an emergency stockpile. In the case of unbalanced surge bin mass flows (typically owing to erratic stockyard reclaiming), the tripper dumps the excess coal, thereby preventing belt trips.

Owing to the urgent nature of the situation, time was a major project constraint. In this regard, Rula Bulk Materials Handling claims its timeous commissioning of the Majuba solution is a result of “doing as much as possible in-house”, making limited use of subcontractors. “This approach was highly successful and allowed the interface problems, which often cause delays, to be avoided,” the company states.

A strong partnership with the Eskom team was also essential to the success of the project, with buy-in from all role-players resulting in a rapid turnaround time on information flow and a supportive, rather than adversarial, client- contractor relationship. This cohesive approach was facilitated through Eskom project managers June Masango and Brand Troskie, working closely with Rula Bulk Materials Handling MD Roelf Odendaal.

Eskom also awarded Rula Bulk Materials Handling the contract for operation and maintenance of the interim solution for two years and three months. This includes contractual plant availability of 85% which, after more than a year of operation, Rula Bulk Materials Handling has consistently exceeded.

Meanwhile, in January last year, Rula Bulk Materials Handling, with its consortium partner, Stefanutti Stocks Civils, was awarded the contract to rebuild the collapsed silo and associated conveying infrastructure.

This project, known as the Permanent Solution, was completed last month. The first conveyor stream was hot-commissioned in December 2016, with hot commissioning of the second stream following in January.