A member has reported two incidents involving personnel transfer using the Crew Transfer vessels (CTVs) used in the offshore renewables industry.
Incident 1 – Near miss: use of fall arrest devices during CTV personnel transfer
Whilst transferring personnel to a wind turbine generator tower during the hours of darkness in the winter months, a CTV was pushed onto the boat landing for approximately 10-15 minutes. During this time two persons were transferred safely. As a third person clipped on to the fall arrest device, a rogue wave hit the vessel. It was dark and the wave was unseen and unexpected. It lifted the CTV at least 4 meters up the boat landing. The crewman assisting the transfer instructed the transferee to quickly unclip from the fall arrest device to prevent himself from being picked up off the deck. He was able to do so, and the vessel quickly dropped to its previous level on the boat landing.
The Master immediately notified the company of the incident and stopped transferring personnel until there was an improvement in sea state and/or visibility. In due course the Master was happy that the safe transfers could resume, and operations continued without further problem.
The client issued a safety notice warning of the imminent worsening seasonal weather in their newsletter – this included additional instruction for CTV transfer during marginal weather conditions.
Incident 2 – Manoeuvring in close quarters to other vessels – crew transfer as Simultaneous Operations (SIMOPS)
A CTV was requested to attend a wind turbine generator monopile to transfer some personnel, whilst a construction vessel was nearby in dynamic positioning (DP) mode. The personnel were successfully transferred to the foundation, but as the Master activated astern gear and pulled away from the monopole, the CTV went through the thruster wash caused by the construction vessel (which was in DP mode). This caused the CTV to move in an unpredictable and uncontrollable way – the CTV passed within 4 metres of the construction vessel itself.
Construction vessels holding station using DP are now in common use in the offshore renewable industry; these vessels, which are much larger than crew transfer vessels, operate in DP mode whilst navigating close to a wind turbine generator monopile. It is not always possible for the construction vessel to move further away from the monopiles as they are generally constrained by subsea equipment such as cables, survey gear and construction equipment.
The client required that procedures be reviewed and reconsidered:
- When personnel are not on the wind turbine generator, the construction vessel should maintain a clear distance between itself and the tower of approximately 50m;
- After personnel have safely accessed the wind turbine tower, the construction vessel can then move into position to complete works.