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Improving, optimising classification cones

A cluster of four 380mm dewatering cyclones, originally lined with 12mm alumina tiles, were sent in to wear solutions provider HMA Group for refurbishment. The producer requested HMA propose methods to increase the service life of the items.

The cyclones were lined with HMA’s Alumina/SiTech “hybrid lining” that included the use of engineered alumina tiles in the inlet head and SiTech monolithic linings in the cone sections. SiTech is a fine grain ceramic with a matrix hardness similar to the main ceramic particles, thus providing an extremely hard wearing surface.

Upon first inspection it was noted that one of the four cyclones had suffered a “blow out” at the flange joint between the lower cone and the nozzle (Figure 1). The remaining linings seemed in fair condition with the usual expected wear on the alumina components.

Once disassembled, the cyclone components were examined internally with measurements being taken for existing dimensions and “as new” dimensions.

There was minimal difference between the measured internal dimensions and the “as new” dimensions (apart from the one item that was damaged in transit). The difference between the design measurement and the actual measured items could even be attributed to manufacturing tolerances; this indicated there were no signs of measurable wear in the HMA SiTech components.

The four cyclones had received a total of 5,547,127 tonnes, an increase of around one million tonnes (1mt) without any measurable wear. This is an impressive lifespan increase compared to the original cyclones, especially considering the minimal wear on the HMA SiTech components.

As a direct result, the internal parameters of the cyclones are maintained for a longer period, which provides improved cyclone performance and yield over the same time frame. Improving and maintaining cyclone performance for a longer period is critical to overall plant performance and any downstream processes.

Figure 1. One of the four cyclones (middle) suffered a blow out; the other linings were in fair condition.

Figure 2 shows there was no visible signs of wear at all on the HMA SiTech components, whereas the alumina components were visibly worn with heavy scalloping. Traditionally the inlet head is the component subject to the least amount of wear but there was heavy scalloping on the tile faces, whereas on the lower components where the material velocity was higher, it was actually the gasket joint which had failed, with material chewing through the steel with the ceramic completely intact.

HMA’s recommendation was to remove the nozzle flange joint, lining the cyclone completely from inlet head through to nozzle discharge with HMA SiTech, removing the potential failure point. HMA engineering utilises special joints between SiTech components to overcome fines egress at joints.

The secondary recommendation was the replacement of the inlet head alumina tiles with a one-piece HMA SiTech liner. This would increase the service life of the cyclones, replicating the minimal wear of the SiTech in the lower cone sections into the inlet head. As all cyclones act under centrifugal forces with sliding abrasion on the internal lining, the removal of tile joints provides a smoother surface that leads to less turbulence and improved cyclone performance.

The throughput increase of around 1mt had already achieved a return on investment great enough to cover the cost of the further upgrade.

The expectation is that the frequency of cyclone replacement will decrease even further, enabling each run cycle to handle more throughput than ever before. The benefits from this are that the material cost per tonne reduces, along with a drastically reduced labour cost to replace the cyclones, considerably decreasing their total cost of ownership. 

Figure 2. The alumina components were visibly worn with heavy scalloping (far left), whereas there was no
visible signs of wear on the HMA SiTech components.

Source: HMA Group



















Thursday, 18 October, 2018 05:48am
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