Overhead Crane Load Measurement Systems

One of the main difficulties encountered by crane owners, with many existing crane load monitoring systems, is the difference between the load displayed on the indicator and that actually hanging on the hook during the lifting and lowering operations. Controlled tests have demonstrated changes in load reading of up to and exceeding 20% between lifting and lowering the load. These errors are frequently caused by friction losses on in sheave bearings on multi-sheave cranes. Our experience and knowledge in resolving these issues provides the confidence in promoting effective solutions to these challenges.

There is a distinct difference between a Crane Overload Protection Device (COPD) and a Crane Load Monitoring System (CLMS, and therefore the equipment to fulfill these applications can be significantly different if both requirements are to be met.

The COPD is there to provide either an alarm or control interlock that trips when a preset load is exceeded. It does not have to display hook load or undertake any other function on the crane described above. A simple CLMS or below-the-hook load measuring device can consist of a portable load measurement device such a strain gauged load link or shackle that is positioned between the crane hook and the load.
The CLMS has a function to display load information to the user for real time operational decisions to be taken or to calculate crane operating performance that is used in inspection and maintenance programs.

More comprehensive CLMS systems consist of a range of sensors/transducers to measure; load, angle, slew and payout all connected to an integrating instrument that calculates load information plotted against component position and crane body. This system is frequently called Crane Safe Load Indicator (SLI).

For clients wishing to utilize the data collected for determining crane usage and inspection criteria, we offer an array of sensors with a data collection package that enables the user to gain access to this information either in close proximity to the crane or at remote locations.

Note: Water Weights supplies integrated measurement systems for electric overhead traveling cranes. Each system is custom designed to suit the precise requirements of the crane. A simple, low cost, system can comprise of a load measurement transducer positioned at point within the crane rigging and instrument incorporating relay cut off which is set to operate in the event of a crane overload. Other devices can be added to these systems such as; large scoreboard displays, analogue and serial outputs to interface with other equipment and wireless transmission of load information to portable hand held display instruments through to a visual graphics display providing real time information and data storage of the cranes movements within defined operating periods.