Customer: Europe based Maritime Salvage Company
Loadcell: F317-Z4414 10 tonne submersible load link for sub-sea load monitoring
Generic Type: Cylindrical tension loadcell with integral lifting eyes
Special Features: Completely self-contained and sealed, bright LED display, rechargeable lithium ion battery, non-contact tare function controlled using a magnetic reed switch.

Tension only 'Load links', in comparison to conventional universal loadcells, are often very crudely made items consisting of little more than plate steel, drilled to offer a hole at each end to accept standard lifting shackles. The strain element is also often exposed, save for a liberal coating of a rubberised weather resistant compound, which can adversely affect performance. These devices are readily available from internet only retailers at minimal cost and, as such, Novatech Measurements does not generally offer load links in its standard product catalogue. However, application specific requirements sometimes call for an item that cannot be provided by such online resellers. An example of this is a recent requirement for a fully submersible load link with integrated display.

Heavy-duty tethers were to be attached to bulky items on the sea bed before winching them to the surface. Due to the nature of the winch, the only possible place to position the load link was between the pulleys and the shackles at the end of the tethers. These would be at 25m depth in sea water for the majority of their day to day use and a wired connection and/or telemetry was not viable. The tethers were connected to the items to be hauled to the surface by trained divers with breathing apparatus, who were to stay underwater for extended periods of time and were required to monitor the load on the tethers and relay this to the surface. The display needed to be highly visible even in murky waters and it was critical that the divers could tare the display whilst underwater. The solution was a completely self-contained and IP68 sealed loadcell with a built in battery powered LED display. Large 8mm digits formed with red LEDs were used to avoid dimming by water filtration of light wavelengths. The rechargeable lithium ion battery could last a full 24hrs of continuous use and the tare function was achieved by swiping a magnet across the perspex panel in front of the display, which included a reed switch. The entire loadcell body was sprayed with anti-corrosion coatings for prolonged service life.