TENSA Equipment has launched an “off the shelf” vessel motion monitoring system that allows the dynamic loading on cranes to be accurately predicted.

The Dynamic Motion System (DMS) helps remove the risk in transferring offshore loads by measuring vessel motions such as heave velocity allowing dynamics to be calculated.

Also, the device gives the crane operator a visual indication of the real time vessel motions so the difficulties of estimating the vertical motion of a vessel at night or when looking down, and timing lifts are now reduced.

Dynamic load monitoring systems have previously cost in the order of $100,000 to design and install, whereas Tensa’s DMS is budgeted at about a fifth of that cost as it is now offered as a stand-alone device that can be connected to a PC and powered by USB.

By measuring the vertical velocity at the load position, Tensa’s DMS system takes into consideration where on the vessel the loads are positioned – at the stern of a pitching vessel versus the centre for example; and whether the vessel is pitching into a sea or broadside on; as well as whether the waves are fast and steep or long and slow.

The DMS can use two wireless units to give a crane operator the relative motion between the load suspended from his vessel and the deck of the vessel alongside.

Project and rig spread costs can now be reduced if crane capacity is fully utilised.

To take the guesswork out of selecting the dynamic loading and crane curves to use for offshore lifts, DMS can measure the motions of a vessel before deciding to undertake the lift.

The vessel data can be viewed simultaneously by the crane operator, the vessel skipper and any other party with a DMS receiver within the maximum broadcast range of 500 metres, or to onshore PCs via the internet.

The DMS can also be used to monitor vessel motions and locations during other offshore construction phases such as floatovers, and in floating production, storage and offloading vessel connecting operations, using its wireless linked global positioning system.

The system delivers real time heave, pitch, roll, heading speed, course, position, accelerations at the sensor as well as at offset positions such as the bow, stern roller or an overboarding sheave.

DMS has further safety applications as it can measure the vessel motions when personnel transfers are being contemplated and significantly reduce the risk to workers by allowing clear definition of the maximum tolerable conditions for transfer.

Operators now can start making ship to ship personnel transfers by gangway a reasonable option to helicopter transfers when scoping project feasibility – air transport carrying its own inherent risks and cost base.

Another differentiating feature of the system is its powerful data transmission, capture and visualisation system. It can transmit data by wireless or USB and it uses standard Windows interfaces so that virtually no training is needed to get the system up and running.

DMS is a totally portable system consisting of small waterproof modules that communicate by USB or wireless. It can be permanently installed on a vessel or deployed on a project by project basis, with all data being available real time via the internet, which makes it ideal for shore-based monitoring and input.

There are 3 DMS models currently available.

The DMS Max has both wireless connectivity and up to 500 metres of wired connectivity with a long life battery; the DMS Mini has a USB connection only and the DMS Buoy is a portable floating unit with DMS Max functionality.