Geelong Port KIS-1 Load Cell Installation
Geelong Port's Lascelles Wharf was in need of replacing load cells that had failed in service on two large mobile ship off loading hoppers at their facility in Geelong. The load cells originally supplied with these hoppers had failed in service, possibly due to the high side loads and shock loads imposed by the crane grab bucket accidentally knocking the hopper on occasion.
Geelong Port required load cells with the ability to withstand large shock loads and sides loads, with good sealing against water and constructed of materials able to cope with the salty conditions at the wharf. Load cells of sufficiently low profile were also required to fit in the existing structure. Control Overload Pty Ltd, representing Vishay Nobel’s excellent range of very rugged and accurate KIS load cells, was approached by Geelong Port for a solution.
The original low profile “hockey puck” style load cells (with no ability to withstand high side load) where replaced by KIS-1 load cells with total immunity to side load.
The KIS load cell is unique in being a “Double Cantilever” shear beam load cell. The strain
gauges are located close together on a very rigid “I” beam. An outer sheath encapsulates the inner I-beam, allowing the load to be placed directly over the strain gauges (neutral axis of the load cell). No bending forces reach the measuring section of the KIS load cell making the KIS able to measure the true weight without being effected by side loads and any thermal expansion of the structure being weighed.
With the KIS load cells, an AST 3P High Performance Weight Transmitter was supplied for each weigh system. Using a large concrete test weight, a dead weight calibration was performed using the crane to lower the test weight in place. The AST 3P weight transmitters have a 4-20mA output, RS-485/Modbus RTU serial output plus 2 x relay outputs for level control. These two relay outputs are used to alert the crane operator of potential hopper overload conditions.
When selecting load cells for a new application, it is important to consider what “real world” forces such as wind load, side load, vibration, thermal expansion are present – forces which can greatly effect the overall weigh system accuracy if the wrong type of load cell is selected for the application.
