LASSTEC technology is the first to measure the load “where it really happens,” which is directly in the twistlock of the spreader. A specially designed sensor is inserted into the centre line of the twistlock, which measures the elongation of the twistlock shaft when under load. The load data is sent into the crane PLC and is displayed on the monitor in the crane cabin. The system can be installed into new and existing spreaders, and does not require any twistlock or spreader modifications.
The ultimate benefits of the LASSTEC system are:
- Accurate container weighing and load eccentricity determination in single-, twin- and tandem-lift configurations.
- Multiple accident prevention advantages.
- Twistlock and spreader lifecycle monitoring.
Using the spreader twistlock to measure container weights has been tried before with conventional strain gauge technology or with hydraulic load cells. However, excessive torsional and bending forces, as well as dynamic and shock loads prevent these methods from providing consistently reliable and accurate long-term results.
The only area on the twistlock where no torsional or bending forces are present is in the neutral centre line. Fibre optic sensor technology measures elongation of the twistlock and therefore can measure container weights. The advantage of fibre optic over conventional strain gauges is that fibre optics require very little space, are inert to EMI and do not corrode.
The LASSTEC sensor has a diameter of only 3mm and the hole in the twistlock has therefore no measureable effect on its strength. The inserted sensor is encased in steel and the net loss of the cross-section of the twistlock is practically negligible. The patented sensor is of a solid design and totally shockproof. It is bonded into the twistlock with conventional adhesive and cannot be recuperated when the twistlock is replaced. The sensor is therefore conceived as a replaceable item, another feature possible only with fibre optic technology. The accuracy and loadreading repeatability is well within +/-100kg per twistlock. The LASSTEC-developed sensor compensates for the temperature fluctuations of the twistlock.
Making the sensor an integral part of the twistlock allows the lifecycle of each twistlock to be traced. Twistlocks are replaced when they have completed their lifespan and not when the replacement date arrives. Lifecycles are stored and can be retrieved for planned maintenance and accident investigations, if required. Overload situations can be spotted and twistlocks can be replaced to prevent failures.