In offshore operations, moving heavy equipment from and to vessels in a seastate can be a tricky business. The movement of the vessels can cause large dynamic loads to be applied to a crane when the load is lifted from the deck.
These loads, however, are not easily predicted with the current technology of ‘guesstimating’ the dynamic load by using the significant wave height (Hsig). Instead, TENSA’s off the shelf vessels motion monitoring system, the Dynamic Motion System (DMS), measures the load velocity directly which then allows the dynamics to be accurately calculated.
Here we list 5 potential applications for TENSA DMS motion monitoring system in the offshore operations to improve safety and efficiency:
TENSA DMS measures the vertical velocity of the load so that the appropriate crane chart for the lift can be selected directly. There is a direct correlation between the measured velocity and the correct crane chart (charts are typically defined by seastate) that should be used. The DMS also offers crane operators powerful visualisation by displaying real time vessels motion, which allows the operators to time the lift on a rising wave and reduce the difficulties of estimating vertical motion of vessels at night or when looking down.
TENSA DMS motion monitoring information can also help measure safe operating conditions for offshore helicopter operations. While DMS doesn’t comply with the current onerous CAP437 requirements, DMS system can be developed to incorporate the Significant Heave Rates and Motion Severity Index data displays required by CAP437 at a fraction of the cost.
Monitoring of towed barges and cargoes
The TENSA DMS can be utilised as an inexpensive tool for fleet owners to assess and reduce their operational risk during towing operations. In particular cargo on towed barges experiences damage due to excessive motions. The DMS can send the barge motions wirelessly to the tow vessel and can log the data.
TENSA DMS can be used to monitor vessel motions and locations during offshore construction phases such as floatovers and in FPSO connecting operations, using its wireless linked GPS and motion sensors. The TENSA DMS motion monitoring system delivers real time heave, pitch, roll, heading speed, course, position, accelerations at the sensor as well as at offset positions which could be the bow, stern roller, crane boom tip or an overboarding sheave on an A frame. Decisions as to whether conditions are suitable for work or whether weather downtime applies can be quantified and the logged data is available for reference. The DMS buoy can additionally be used for measuring wave heights and seastate as well as the other DMS functionality.
The TENSA DMS can measure vessel motions when personnel transfers are being contemplated. The DMS motion monitoring allows clear definitions of maximum tolerable conditions for safe transfer, hence significantly reducing the risk to personnel.
Visit our booth J1 at AOG 2018 to see a demonstration of the TENSA Dynamic Motion System (DMS). The DMS is available in different versions: DMS Max with wireless connectivity and inbuilt 24 hour battery, the entry-level DMS Mini and the DMS Buoy, which is a DMS inside a portable buoy for delivering real time wave data.