(Photo courtesy of BMT Fluid Mechanics Limited)
In these situations the various effects considered in Sections 10.4.3 to 10.4.7 must be considered for the platform complex as a whole. It will normally be necessary for the helideck to be located on the platform corners remote from the other platform(s) in order to comply with 210o obstruction-free sector, and for best aerodynamic performance.
In some cases the platform complex may include more then one helideck, and it will therefore be necessary to assess the design issues for each of these helidecks. However, operational limitations which have to be placed on an individual deck may cause little helicopter downtime if there is an alternate helideck that can be used under these conditions. All such limitations need to be fully investigated, documented, and communicated to the operators to ensure that the various management procedures to control the use of the helidecks are put into place.
10.7.2 Temporary Arrangements
Combined operations also refer to a temporary arrangement where one mobile platform or vessel (e.g. a floatel) is operating in close proximity to another permanent installation. In many cases there may be a gangway in place connecting the two.
Whilst the detailed arrangements for these combined operations may vary considerably from one circumstance to another (see Section 8.1), there are certain aspects of design and platform topsides layout that, if optimised, can minimise the need for helideck restrictions during combined operations.
Certain types of mobile platforms (e.g. flotels) have gangways and/or gangway landing portals, and clearly this defines the side of the mobile platform that will normally be closest to the fixed platform when combined operations are in progress. Consequently the design of the floatel should have the gangway located as far away from the helideck as practicable in order to maximise the available obstruction free sector, and also to ensure that turbulence or hot gas plumes caused by the adjacent fixed platform are as distant from the mobile platform helideck as possible.
Whatever considerations and choices were made at the fixed or mobile platform design stage, when combined operations are to be carried out, a helideck assessment should be conducted to evaluate the effect of one platform on the other, and determine any helideck restrictions that should be imposed. Apart from the physical requirements for an unobstructed 210o obstacle free sector and falling
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