Section 1 General
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Offshore Units, July 2022 - Part 5 Main and Auxiliary Machinery - Chapter 23 Jacking Gear Machinery - Section 1 General

Section 1 General

Parent topic: Chapter 23 Jacking Gear Machinery

1.1 Application

1.1.1 The requirements of this Chapter are applicable to self-elevating units with machinery of the rack and pinion type used to raise and lower the position of the hull with respect to the legs, or other supporting structure above the surface of the sea.

1.1.2 Machinery for self-elevating units utilising other systems will be specially considered.

1.2 Definitions

1.2.1 The following definitions are applicable to this Chapter:
  1. Normal jacking load. The maximum design elevated weight of the hull, including variable load, to be raised/lowered by the jacking unit, during normal jacking operation.
  2. Pre-load jacking load. The maximum design elevated weight of the hull, including pre-load ballast load, to be lowered by the jacking unit in the event of sudden leg penetration during pre-load operation.
  3. Pre-load holding load. The maximum design elevated weight of the hull, including pre-load ballast, to be held by the jacking unit during the pre-load operation.
  4. Ultimate holding load. The maximum load capable of being held by the jacking unit, in an emergency situation, without causing slippage of the jacking gear machinery braking device.
  5. Storm survival load. The maximum static design load in the leg to be supported by the jacking and/or fixation systems.
  6. Fixation system. The mechanical locking device, with an engaging mechanism, used to provide positive engagement between the hull support structure and the leg chord.
  7. Jacking gear unit. The individual reduction gear assembly, comprising drive motor, coupling, enclosed reduction gearing and main pinion normally attached to the jack-house.
  8. Jack-house. The structure surrounding the leg chord into which multiple jacking units are installed.

1.3 Submission of plans and particulars

1.3.1 The following plans, together with the necessary particulars of the jacking mechanism are to be submitted for consideration:
  • General arrangement of the self-elevating machinery, including a cross-sectional arrangement.
  • Full design details of all transmission gear elements including gear tooth geometry and machining details.
  • Full design details of all transmission shafting, couplings, coupling bolts, interference assemblies, keys, keyways.
  • Bearing details.
  • Enclosed gear casing details and mounting arrangements.
  • All assembly design tolerances are to be submitted, including, where applicable, allowances for wear during normal operation such as rack guides.
  • Prime mover specifications including braking devices.
  • Drawing of main pinion and rack tooth profile showing full geometric details.
  • Full design details of the fixation system, where fitted.
  • A load-time spectrum for the envisaged dynamic operational requirements of the self-elevating machinery for the unit is to be specified.
  • A simulated load analysis for the main pinion/rack tooth mesh during wet/dry tow conditions.

1.4 Material specifications

1.4.1 Specifications for materials for the gearing and other mechanical components giving chemical composition, heat treatment and mechanical properties are to be submitted for approval with the plans required by Pt 5, Ch 23, 1.3 Submission of plans and particulars 1.3.1.

1.4.2 Where the teeth of a pinion or gear wheel are to be surface-hardened (i.e. carburised, nitrided, tufftrided or induction-hardened) the proposed specification and details of the procedure are to be submitted for approval.

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