Modern Mining October 2021

Kwatani innovates to keep screens well isolated

Screens vibrate more when starting and stopping, often causing unexpected dam- age to buildings and reducing the lifespan of the machine. Kwatani has applied cost- effective isolation solutions that include both torsional and coil springs. According to Kwatani’s chief operat- ing officer, Kenny Mayhew-Ridgers, the company has achieved considerable improvements in many screening applica- tions by selectively fitting torsional springs alongside coil springs. “It is well known that the vibrating motion of a screen impacts on the build- ing and structural accessories around it,” says Mayhew-Ridgers. “This vibration is addressed by fitting isolators between the screen and the plant floor, and by construct- ing the plant building to certain minimum structural specifications.” However, the focus is often on the fre- quencies that the screen generates in its steady-state phase – or the normal running phase – rather than during the transient phases when the screen is starting up or

slowing down to a stop. He highlights that it is during these tran- sient phases that the screen’s movement becomes amplified and potentially most destructive. Isolators between the screen and the floor – common among which are coil springs and rubber buffers – are meant to absorb vibrations and prevent damage to surrounding infrastructure. However, the transient phases, especially when stopping, can generate considerable sideways move- ment of the screen, which must be avoided. “Traditional isolators like coil springs usually perform well in controlling the up- and-down movement of the screen,” he says. “Our experience is that the sideways movement, which is induced most strongly when the machine stops, can be better controlled by torsional springs.” However, he notes that coil springs retain the advantages of being cost effec- tive and providing a good linear isolation of the screen from the building structure. In this respect, their isolation characteristics

are generally better than rubber buffers which rather excel in terms of their damp- ing qualities. “The torsional spring provides the best of both worlds, giving a good linear range for compression during operation while also becoming non-linear like the rubber buffer during stopping,” he says. Using its years of experience observing screens operating in the field, Kwatani has developed and trialled various solutions in its dedicated testing centre at its headquar- ters in Kempton Park.  One of Kwatani’s smaller screens used in diamond mining fitted with torsional springs.

October 2021  MODERN MINING  39