New class notation for seismic vessels

The new notation focuses on increased availability of vessels during critical phases of seismic operations. Besides vessel operators, DNV has consulted seismic-handling and high-pressure equipment suppliers to ensure that all current and future industry challenges are comprehensively dealt with.
The maintenance of propulsive power is a key issue. The class notation has therefore taken the DNV concept for redundant propulsion one step further so that any failure on board will not lead to loss of more than 50% forward trust, the classification society said. This is sufficient to maintain a minimum speed of a few knots and will protect any high cost air guns and streamers deployed.
Seismic vessels typically operate for many months continuously without seeking harbour. The class notation requires a deck arrangement that facilitates side-by-side transfer for crew and resupply from a seismic support vessel.
Beyond this, it also sets a requirement for the bridge arrangement to ensure good view to the streamers and any workboats that are close by during normal operation. High-pressure systems are also addressed to ensure that deck operations can be carried out safely by the crew.