The Beast! Introducing Schenck’s New Screen Model SLK4390WXFS

The Beast! Introducing Schenck’s New Screen Model SLK4390WXFS

Schenck Process has designed, built and commissioned the largest double deck flat screen in their range.  Doug Teyhan, the “Product Expert in screening” for Schenck Process, said the screen model SLK4390WXFS is made for wet processing the largest of mine throughputs with extreme fatigue strength and ability to resist huge loads.  The project goal was to supply vibrating screens to withstand the SAG mill discharge of 5,500 tonnes per hour (6,000 tons US per hour) plus 4,000 cubic metres per hour (140,000 cubic feet per hour) of water.

The model is approximately 5.5 metres (18 feet) wide, 10.5 metres (35 feet) long and 6.5 metres (21 feet) high and is driven by the four DF704 exciters, mounted in pairs on two exciter beams, with a dual drive arrangement of twin 90 kW (120 HP) motors and variable speed controllers.  The screen uses continuous vibration to process 3,500 tonnes per hour (approximately 3,800 US tons per hour) of dense slurry or 9,000 tonnes per hour (approximately 10,000 tons US per hour) of dilute slurry into three sizes.

With an installed mass of 120 tonnes (135 tons US), a vibrated mass of 72 tonnes (80 tons US) and exciters producing over 4.5g acceleration that generate a combined force equivalent to fourteen Boeing 747 jet engines at full thrust, there is no surprise the screen has been nicknamed “The Beast”.

A machine of this size has the potential to impair the rest of the plant due to the vibrations transmitted into the support structure.  This risk has been addressed by the use of a tuned vibration absorber called an Isolation Frame so that, in operation, less than 0.4 per cent of the exciter force will be transmitted into the building structure.

The entire assembly, including the vibration isolation frame, transport trolley (which carries the motors, built-in water spray system, and fines chute), is equipped with a jacking system and wheels to allow rollout to expedite screen change out when maintenance is due.  Only the electrical supply cables and water supply piping requires disconnection before the trolley assembly is moved.  And while the screen weighs 72 tonnes (80 tons US), the entire assembly results in an installed mass of 120 tonnes (135 tons US).  The trolley allows the combined screen, isolation frame, and ancillary equipment to be lifted using an overhead crane as a single 120 tonnes (135 tons US) assembly.

Typical Project Application

This is the era of large open-pit copper and gold mines in many districts and countries.  It is typical that these mines use “40 foot” Semi-Autogenous Mills (SAG mills) to process the ore, often in more than one production line.  Many of these projects will process on multiple parallel lines and use two, three or four screens in producing many thousands of tonnes of copper, gold, molybdenum, and other metals to satisfy the world’s demand for manufactured products.

Teyhan said that “Schenck Process application knowledge was vital to get this right; understanding how the infeed material behaves as a mixture of rocks, clays, and water, and manipulate this to achieve the goal of separating the fractions into different streams comes from the combined years of experience of the Schenck Process application and engineering team”.

The screen is equipped with a multi-channel ‘CONiQ® Monitor’ condition monitoring system that is “cross connected” to all four exciters;  Its purpose is to detect and evaluate phase defects, check and record the bearing and gear vibrations, operating oil temperature, and gross machine motion in six (6) degrees of freedom (three translational and three rotational).

Schenck Process, our clients and their engineering teams, are all engaged and focused on producing an optimum screen installation.  Schenck Process has a global footprint in the design, engineering, manufacture and testing of vibrating equipment for the mining, mineral processing and aggregate industries.