Testing waters: load cells and load testing in marine environments
It’s not just our cars and boilers that need an annual MOT or service; marine lifting equipment and cranes all require regular safety tests to ensure they are in good working order and capable of lifting their safe working loads.
Load cells and lifting
Most dockyard and marine lifting equipment requires an accredited inspection and load testing once a year, and this is often achieved by test lifting of large waterbags. Load cells placed at strategic points on the crane and in the hoist for the bag will measure the force exerted as well as the precise weight of the bag.
Using wifi-enabled load cells and a handheld wireless display gives the inspector an accurate readout of the forces registered by the various load cells, while maintaining a safe distance from a large swinging bag of water. Data can also be relayed to a PC or tablet for storage and further software analysis if required. All types of marine cranes can be tested in this way quickly easily and efficiently, and the water bags can be simply emptied in between jobs, for easy transport.
Load cells in Liverpool
The newly opened Liverpool 2 Docks caught the media’s attention for the impressive high cranes that now tower above the skyline. However, one ‘unsung’ job really caught our eye. Back in January 2015, a 100 tonne U tube was installed to carry services from one side of the dock to the other. Two cranes lifted it onto a third floating, which then sailed 1 mile down the dockside before lifting the u tube into position. The whole operation was monitored using specialist load cells, as contractor Lifting Projects UK explained in a blog:
“This involved 9 legs of wires at around 50metres per leg and specialist load cells used to monitor the exact weight each leg was responsible for; thus ensuring the lift was carried out in a safe manner.”
Load cells in Cross Rail construction
Load cells have also helped deal with water issues during the construction of the Cross Rail Connaught Tunnel in London’s Docklands. Load cells were installed 3 metres underwater to measure the load on the ties for a cofferdam while working at the Royal Albert Docks. (A cofferdam is “A structure that retains water and soil that allows the enclosed area to be pumped out and excavated dry. Cofferdams are commonly used for construction of bridge piers and other support structures built within water.”)
Load cells and offshore oil platforms
Underwater load cells are nothing new in terms of testing, but few have to be as robust as those used to monitor deepwater mooring systems used to secure oil platforms. While load cells are certainly the most established form of monitoring, an article in Offshore Magazine highlights the issues:
“Accuracy, reliability, and robustness are major concerns with this (load cell) approach, especially underwater, where access to the mooring line and instrumentation is extremely limited. … The introduction of in-line load cells housed in protective casing and transmitting data via acoustic transmitter offers improvements to the traditional approach.”
The article examines the alternatives – inclinometers, global positioning systems (GPS) and an integrated monitoring system used in association with a forecast system. It’s a fascinating glimpse into the challenges in effective monitoring of moorings, and the pros and cons of each method.
It’s well worth a read if you need to secure something in salt water for any length of time, and we’ll be happy to quote for any waterproof load cells you might require for your own projects.
