Re

Nov 16, 2023

When Thejo’s filtration division was approached to develop and provide replacement of filter spares for a leading mineral producer in south India, it answered the call.

The south Indian mine’s prime purpose was to utilise the slime deposits generated from its existing seven-million-tonnes-per-annum (Mtpa) screening plant.

To achieve the specified moisture level of nine per cent, a filtration plant of 233 tonnes per hour (TPH) was installed and operated.Filter pressesThe 62 chamber filter presses consisted of 31 polypropylene (PP) membrane plates, 30 PP chamber plates and two PP end plates.The frame was constructed of end cast plates bound together by two metallic side beams on which the moving filter plates were positioned. The opening and closing were operated by a moveable hydraulic unit.A bomb door discharge at the base facilitated the onward loading of cakes onto a discharge conveyor belt.Problematic operationsFrom the plant’s inception, the filter presses were bogged down with problems such as poor performance life of the filter cloth, frequent damage to the PP membranes, leakage of slurry at the mating surface of the membrane and chamber plates, and non-availability of critical spares.These issues hampered the effective functioning of the presses.Unprecedented damages to the PP membranes caused frequent punctures to the filter cloth, resulting in slurry leakage into the chambers and onto the mating surface of the membrane and chamber plates.Due to the construction of the press, the load-bearing side beams were not deflecting in tandem during the closing, locking and pressurising operation of the plates, leading to misalignment of filter plates.This aggravated the damage to the PP filter plates, with the slurry and compressed air under high pressure, causing them to leak through the consecutive plate interfaces and creating deep grooves on the frames of the plate.The leakage of iron ore slurry and compressed air was causing spillage around the equipment in the plant and was a serious safety hazard.Furthermore, the membrane blowouts and repairs were puncturing the expensive filter cloth. The recurring damage to the PP filter plates forced the frequent removal and weld repairing of the same, leading to increased downtimes.Maintaining a large stock of spare plates was not economically viable, so the plant decided to limit operation to one of the two presses and scavenge parts off the other as spares to manage the pressing production requirements.HIPO filtration systems: A sustainable synergetic solutionIn early 2019, Thejo’s filtration division was approached to develop and provide replacement of the filter spares.Based on a detailed study of the presses and plant operations, the engineers from the HIPO filtration division chalked up a detailed proposal with the objective of providing a solution that would:• achieve the optimum output of the plant and equipment• maintain safety and ease of operations• maximise filter cloth life• ensure a high percentage of machine availability for operations• make reliable spares at economic prices• have a long-term sustainable solution, which could deter the client from a major capital expenditure.With these objectives, a detailed proposal for re-engineering and retrofitting project of the two filter presses was submitted to the plant.HIPO combination PP plateA new PP combination plate was designed and developed to replace the alternate chamber and membrane plates of the press.The new plate design fitted a rubber membrane on one side and fielded a chamber on the other.HIPO rubber membraneA custom-designed HIPO rubber membrane was developed for flexibility and durability, while maintaining the rigidity.The rubber formulations provide high tear strengths, high abrasion resistance and high tensile properties, and the replaceable rubber membranes ensured better sealing and higher life of the PP plates.HIPO rubber diaphragms drastically reduced the possibility of any damage to the filter cloth and PP plates, thereby increasing the life expectancy of both these expensive parts.HIPO filter fabricIn collaboration with a global manufacturer, a fabric to meet the life expectancy without affecting the filtration was specifically designed for the operation.The sourcing, manufacturing, inspection and disassembling of the filter presses at the client’s site, along with shipping re-engineered parts, assembling retrofit parts, commissioning the press and establishing production to meet client demands, all coincided with COVID-19 lockdowns of 2020–21 but were nevertheless executed successfully.The project of re-engineering and retrofitting the existing non-performing filter presses with HIPO-SSS system at the client’s plant was a great success.

This feature appeared in the February 2023 issue of Australian Mining.