Coarse screens are the protective equipment of a screening system. Their task is not removing the incoming screenings from the water flow, but coarse screens are used to protect downstream finer screening systems (or machine technology in general) in the event that massive amounts of coarse material or extreme-size debris occur. Such unusual events in the operation of a screen include the occurrence of large-volume flotsam (e.g. tree trunks, tyres, etc.), man-sized screenings rolls, suddenly occurring huge quantities of screenings or large debris and sediment loads at the channel bottom. Such disturbing material can - provided that no coarse screen is available - severely impair or interrupt the operation of screening systems and also lead to damage to the respective machines.
The art is to select the right coarse screen for the application in question so that the screen reliably detects and removes the impurities from the channel during operation.
With the HUBER Multi-Rake Bar Screen RakeMax® and the HUBER Coarse Screen TrashMax®, HUBER has two screening systems on the market that cover most of the requirements of common coarse screen systems. But what to do if there are applications and/or channel and structure dimensions where these machines reach their limits?
The answer to this question is the new HUBER Grab Screen TrashLift, whose functional principle is really simple:
A solid stainless steel shell acts as an "excavator bucket" to clean the channel bottom as well as the bar rack section. This excavator bucket is operated cyclically by a winch system.
With this functional principle it is possible to realize channel widths up to 6 m and channel depths up to 40 m with a 90° installation. In order to ensure maximum operational safety and service life of the machine, the HUBER Grab Screen TrashLift is characterised by the following features:
- Detection of blockages of the bucket carriage in the up and down movement (overload and slack rope detection of the load winches)
- Long rope service life due to directly acting load ropes / control rope on the bucket and winch drum, no unnecessary rope deflections
- Safe transport of the flotsam and screenings, even in 90° position, thanks to the active bucket closing mechanism
- Safe flotsam/screenings discharge through a scraper and swivel mechanism of the bucket at the discharge point