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Design Requirements |
Primary Design
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Triple5 – Primary Design Requirements
In developing the Triple5 hook there were a central
set of Primary requirements, these are outline
below.
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Off-Load Safety with On-Load
Functionality
Off-load release hooks were used in
lifeboats for many years. These were
replaced when a requirement for On-load was
deemed desirable.
Off-load hooks are less likely to fall from
their davits due to operator or equipment
error as they will not release when the
weight of the boat is on the hooks. However
off-load hooks do not provide an ability to
release under load on the occasions when
that may be necessary.
On-load hooks have the ability to release
under load using the weight of the boat to
open the hooks. However conventional
twin-fall on-load hooks have been prone to
accidents due to accidental release when the
boat is in the air.
Both off-load and on-load capabilities are
desirable. The design goals were to design
an Off-load hook (less prone to accidental
release) which has On-load functionality
when required.
Based on SSI’s Current Hook (25 Year Safe
History)
SSI developed their own On-load/Off-load
release mechanism for use in its single
cable capsule equipment. This release
mechanism has been in operation since 1982
without a single incident or injury. The
twin-fall hook solution was developed based
on this proven design.
The Weight of the Boat Holds the Hook
Closed
To ensure that the boat does not release in
the air the design should be such that the
weight of the boat will keep the hooks
closed.
Weight of Boat Not Used to Open Hook in
On-load Release
Related to the previous requirement the
weight of the boat should not be used to
open the hooks, therefore limiting the
chance of accidental release in the air.
Inherently Stable Hook: meets “Fail to
Safe” Criteria
Should something go wrong with the operation
of the hook system it will “Fail to Safe”
i.e. it will remain in a safe position and
will not drop the lifeboat.
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Detail Sections: |
Primary |
Secondary |
Operator Interface |
Maintenance Interface |
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