Wireless Load Monitoring

31 Oct

The latest development in proprietary support systems is the ability to equip struts with integrated wireless load monitoring capability. This fully automated service is a huge leap forward in the field of excavation monitoring and offers engineers instant access to the real-time performance of their temporary works schemes by simply logging onto a website and accessing the data. 

Monitoring loads in struts or ground anchors is by no means a new concept, however the convenience, simplicity and accuracy of this particular pre-assembled load monitoring system is a major step forward.

In terms of the monitoring hardware itself, we at Groundforce have taken on board the advantages in the latest breed of wireless telemetry technology to develop an integrated system within the prop itself that can, on demand, transmit the real-time load in the prop and the respective ambient temperature.

The heart of the system is a load sensing pin with integrated strain gauges that is located within the end swivel connection of the prop. The pin (which by its very nature replicates standard zero moment end conditions), together with it’s anti-rotation/protection plate are assembled within the strut prior to delivery to site. To ensure the greatest accuracy, the load pins are pre-calibrated off site in a test rig before each use and come accompanied with all the necessary certification.

Each of these load pins is connected to a specific acquisition/transmission module via a short length of cable which is then housed away from potential damage within the strut casing, adjacent to the hydraulic ram. The battery powered acquisition module draws the information on demand from the pin and then transmits the live load data on to one of two available viewable receiving sources. Yet again, this part of the setup is completed in the Groundforce depot prior to delivery so that once the strut is installed within the excavation, it is immediately on-line, delivering instant and accurate data to the pre-determined destination.

Two options are available for collection and viewing of the load data. In its simplest form the receiver is a hand held device which will pick up data from any of the struts at a range of up to approximately 50m. Once turned on, the handheld device activates all of the acquisition modules within range enabling the user to scroll through and manually record the data on each prop. The readings are displayed in tonnes, meaning that no further conversion calculations are necessary.

The second option is a lot more comprehensive and introduces a fully automated monitoring service that can be tailor made to suit specific customer requirements. This involves locating a weatherproof GPRS sampling device and battery pack at a convenient location on-site within range of the pins. This unit automatically gathers data at pre-set intervals, and transfers this via the GPRS network. There is the potential to set the destination for the data as text message, e-mailed data file, or both, which then enables the information to be easily compiled in graphical format for simple comparative purposes.

There is a warning trigger system that runs in parallel with this general data collection system, which uses up to 20 pre-programmed warnings keeping the user up to date with any substantial load increases without having to continuously keep an eye on the data. If measured loads in any of the props exceed any of these pre-set levels, the unit will in turn trigger either an automatic email or a text message to be sent to (the perhaps unlucky) nominated recipients.

The system despite extensive trials is in its relative infancy, we now have several sites using this equipment and we plan to use one of these as a case study in a forthcoming blog entry. 

Tony Gould
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