1.1.1 LR does not lay down any strict environmental or pressure differential
loadings in these Rules (except as in Pt 4, Ch 1, 1.1 General 1.1.2 to Pt 4, Ch 1, 1.1 General 1.1.4). The designer is, however, to satisfy LR that the
loadings used are satisfactory and the Class will be based in those conditions used.
1.1.2 Tanks forming an integral part of a submersible are generally to be
suitable for a hydraulic test pressure of 1,5 times the maximum differential
pressure for which they are designed to be used in service.
1.1.3 Hull structure which does not form part of the pressure hull or other
pressurized system is to be designed with a load factor of not less than 2 against
failure under the worst combination of loading during service operations. Failure,
in this context, is assumed if the component has fractured, collapsed or distorted
to an extent rendering it, or associated components, inoperable or dangerous to
operate in the designed manner.
1.1.4 Where practicable, the outer fairing, other non-pressurized structure or
equipment attachment to a submersible, should be designed so that in the event of
shock from collision or similar accident, local collapse can occur sufficient to
avoid acceleration in excess of 3g for the unit as a whole, without causing the loss
of the unit. A clearance of not less than 150 mm between the fairing and critical
life-support components should be arranged, where practicable, in the areas most
susceptible to damage. Fairing or other protection should be arranged in way of hull
penetrations; especially of umbilicals, to minimize damage (e.g. being sheared
off).
1.1.5 Diving baskets are to be provided with adequate mechanical protection to
protect the divers and to prevent damage to the critical components of the basket
during handling operations and other normal or emergency operations. The lower
section of the basket is to be provided with a platform enabling the divers to stand
safely. Baskets are to be provided with internal handholds to support the divers and
gates or chains to prevent the divers from falling out.
1.1.6 For the purpose of the design calculations the un-factored acceleration
of the submersible from the point of view of collisions should be generally assumed
to be not less than 3g in the horizontal direction. The vertical acceleration,
including those during launch and recovery of the unit, should be assumed to be not
less than 2g. Generally the sea state for manned submersible handling systems should
not exceed Sea State 4. Special consideration will be given to cases where diving
operations service in more severe sea state is envisaged for manned diving
operations.
1.1.7 The effect of loads due to launching and recovery together with wave
impact should also be examined. Particular attention should be paid to the strength
of the lifting point attachment to the submersible.
1.1.8 The Builder shall supply material and welding specifications including
procedure tests required for the fabrication. Procedure qualification tests are to
be carried out using representative materials and thicknesses. These tests are to be
witnessed by the LR Surveyor and are to be to the Surveyor’s satisfaction. The
Builder shall maintain a complete record of procedure qualification test
results.
1.1.9 Calculations used to establish the adequacy of the exostructure should be
submitted for approval at an early stage. The calculations should take account of
the hydrostatic loads due to submergence together with loads due to manoeuvring and
underwater tasks to be undertaken. In addition forces due to collision with
underwater obstructions should be taken into account.
1.1.10 The design methods used to establish the adequacy of the exostructure,
including buoyancy/ballast tanks, may follow any recognized engineering practice and
may be performed using a specialist software program for structural analysis and
design. The maximum pressure differential, wave slam and similar loadings are to be
adequately catered for.