Reflex Marine FROG-6 HC6-01 620, User Manual

Page: 22 / 97

User Manual FROG-6
UM-0007-REV.06 Page 22
5.4 Crane Operator Guidance
When landing the FROG-6 on the deck of a heaving vessel the Crane Operator must always release
and maintain line slack to prevent any snatching. This means the FROG-6 will be secure on the deck
and will provide occupants plenty of time to enter and exit the FROG-6. (This landing procedure is
different to the rope basket procedure, which requires the Crane Operator to maintain tension on
the hoist to keep the soft rope basket upright during entry and exit).
Fig 1: Sling Diagram
For the standard 30 ft / 9 m sling provided with the FROG-6, it is generally recommended that
approximately 10 ft / 3 m of slack is paid out once the unit has landed on the vessel. However, the
required amount may vary according to sea state and vessel motion response. The Crane Operator
must pay out sufficient slack to avoid snatching, although, must avoid paying out more than is
necessary as the section of sling hanging could constitute a hazard to crews alighting or entering the
capsule.
It is also recommended that the Crane Operator
slews the boom ‘down weather’ from the capsule.
This will provide more time for the Crane Operator / crews to react in the event of a failure of the
vessel’s station keeping.
5.4.1 Use of Shorter Slings
Reflex Marine Ltd recommends the use of a 30 ft / 9 m sling, however for operations where the 30 ft
sling is not suitable then a 20 ft / 6 m or 10 ft / 3 m sling can be supplied.
It must be noted that using shorter slings increases the risk of snatching. Using the 20 ft / 6 m sling,
10 ft / 3 m of slack will provide a 17.3 ft / 5.3 m allowable offset before the sling becomes taught
from the crane hook weight
– this does not however account for vessel heave. For a 10 ft / 3 m sling,
8 ft / 2.4 m of slack will provide 9.8 ft / 2.7 m (allowable offset).
Using a shorter sling set also increases risks associated with the hook block being in close proximity
to the passengers alighting.
Note: The operating parameters in Section 3.2 are defined for a FROG-6 with a sling length of 30 ft / 9 m. For transfers
using a shorter sling an additional risk assessment combined with dry runs should be performed to establish safe
operation routines and weather conditions.
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