How do alternative access options measure up to the challenge?

Currently the dominant method of turbine access is by step based transfer.  It is simple and low cost, but is not considered robust in harsher environments as the risks to personnel (and the turbine and vessel) increase substantially.   The first question to ask is “what does an access system need to do?” we can then identify the key features of any access option.

Does the access system perform safely in harsh sea states (> 1.5m Hs)?

Most offshore development locations under planning have extended periods of significant wave height above 1.5m but below 3.0m Hs.  An access system that performs safely and reliably across this range will meet most year round access demand.

Does the access system present undue risk to personnel, vessel or turbine?

Have the risks been quantified and is this tolerable or minimised under the principles of ALARP?   It is a fair observation that the offshore wind industry experience is still in the early stages and safety statistics to date are probably not a reliable indicator for the future industry as a whole.

Does the access system allow evacuation of an injured person? 

An access system should be available that allows transfer of injured people including stretcher cases.  A ladder fall could easily render a operator incapable of using a ladder or bridge.

Does the access system support the transfer of adequate spares and equipment?

Unplanned events are also likely to require the lifting of replacement components and tools possibly up to 2 Tonnes or even higher.  There appears to be little benefit in transferring maintenance personnel without the ability to transfer the desired equipment at the same time.

Is the access system costly to install or operate? 

Capex and Opex should be economically judged against the cost of failure to access (economic losses) , or the cost of incident during access (insurance and reputation loses).

There are four principle categories of access options, ‘step based’, the traditional boat landing and ladder access; ‘bridge based’, where a temporary link is established with the installation; ‘lift based’, where a turbine or vessel based winch is employed to provide a lift access, or ‘air based’ where in emergency situations hoist type access may be granted.

Reflex Marine scored the relative performance of each access options against the criteria discussed.  Overall a ‘lift based’ system scored well in most categories of evaluation. Uniquely this option provides dual capability for the lifting of equipment and people in harsh conditions and also provides a safe and secure route for the evacuation of personnel in stretchers.