Section 2 Design Principles
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Construction & Classification of Submersibles & Diving Systems, July 2022 - Part 3 Pressure Chambers - Chapter 1 General - Section 2 Design Principles

Section 2 Design Principles

Parent topic: Chapter 1 General

2.1 Compression Chambers

2.1.1 Compression chambers within the Diving system are to be so designed that at least two persons can simultaneously pass in or out through the locks without exposing the other divers in the system to a pressure change.

2.1.2 In diving systems where divers are required to remain under pressure for a continuous period of more than 12 hours, the living compartment of the compression chamber is to be so designed and equipped that:
  1. Persons are able to stand upright in it,
  2. Each diver is provided with a bunk on which he is able to stretch out comfortably.
  3. Inner height of the chambers shall be no less than 2000 mm over the deck plate (measured in the middle of the chamber).
  4. Ensures the divers have a safe and comfortable working environment.

2.1.3 For surface oriented diving operations the main chambers shall have a minimum inner diameter of 1600 mm and 2000 mm length, with possibility of occupants to lie down comfortably. When surface oriented diving with decompression stops are planned, the inside diameter of the chamber shall be at least 1800 mm.

2.1.4 The living compartment of compression chambers and other compression compartments are to be provided with a lock through which provisions, medicines and equipment items can be passed to and from. The lock should be such that provisions are made so the occupants of the chamber are not exposed to a pressure change. Please also refer to Pt 5, Ch 4, 12.11 Medical Lock.

2.1.5 Locks are to be designed to prevent accidental opening under pressure. Suitable interlocks are to be fitted.

2.1.6 Each compression chamber compartment is to be provided with viewports enabling all occupants to be observed from outside.

2.1.7 Wherever necessary, compression chamber windows are to be protected against mechanical damage from inside and outside.

2.1.8 Each compression chamber compartment should be adequately lit, to provide a safe and comfortable working environment. For more details refer to Pt 6, Ch 1, 1.5 Design and construction 1.5.20 of these rules, and NORSOK U-100 or any other recognised code/standard may also be used for guidance.

2.2 Diving bells

2.2.1 Each diving bell is to be so equipped that it is fully protected against excessive working pressures and inadmissible pressure drops.

2.2.2 Each diving bell is to be provided with extra lifting points designed to take the entire dry weight of the bell including ballast and equipment, plus the weight of the persons inside the bell. After release of the ballast weights, the diving bell, at its maximum service weight and with its trunk flooded, must exhibit a positive buoyancy equal to at least 3 per cent of its displacement at maximum operating depth. In these circumstances, the bell should have sufficient stability to maintain a substantially upright floating position.

2.2.3 Close to main lift attachment, the diving bell is to be provided with spare connections for hot water (3/4" NPT female thread) and breathing gas (1/2" NPT female thread), ¼” NPT female (gas analysis) ¼” NPT (depth) and communication and emergency power supply connections as per IMO 808E and IMCA D051 is to be provided. The manifold is to be clearly marked and effectively protected. Where applicable NORSOK U-100 or any other recognised code/standard may also be used for guidance.

2.2.4 Diving bells are to be designed to allow entry and exit even in an emergency.

2.2.5 Diving bells are to be equipped with a device for the recovery of an unconscious diver.

2.2.6 The dimensional design of diving bells shall be such as to provide adequate space for the proposed number of divers and their Seating is to be provided for each diver in the diving bell.

2.2.7 Diving bells are to be provided with viewports.

2.2.8 The lifting and towing points on diving bells are to be designed with a design factor adequate to the accelerations and used in lifting and towing forces defined in Pt 3, Ch 1, 10.1 General 10.1.2/Pt 4, Ch 1, 3 Attachment Points and Pt 4, Ch 1, 4 Alternative Lifting Points. Any doubling pad used in lifting or towing points connection shall be checked for through thickness properties and integrity. Plates shall have an adequate penetration weld within the bell body.

2.3 Doors and access points

2.3.1 Diving bell hatches and mating devices which are not sealed by pressure are to be fitted with a locking mechanism which prevents opening under pressure. The locking mechanism is to be so designed that the correct closure position is clearly apparent before pressure is applied.

2.3.2 Devices are to be fitted to enable doors to be opened from both sides. Hatch trunks are to be fitted with pressure compensating valves.

2.3.3 Doors and hatches for persons are required to have a clear opening at least 600 mm in diameter. For diving bell lockout/-in hatches the clear diameter shall be at least 700 mm. The bottom trunk for the entry into and exit from the diving bell shall have an inner diameter of minimum 800mm.

2.3.4 The trunks are to have a minimum internal diameter of 610 mm (24"). Longer trunks are to be adequately designed and reinforced to ensure stability. They are to be provided with handholds and footholds on horizontal plane for personnel safety.

2.4 Sea transport design requirements

2.4.1 When submersibles and diving systems are stowed on the deck of a ship or floating offshore unit, their cradle or other means of support should be capable of retaining them securely in position without damage or uplift under the following conditions acting simultaneously:
  1. a horizontal (transverse or longitudinal) acceleration of 0,5 gn (This is equivalent to an angle of roll or pitch of 30°)
  2. a vertical acceleration of 1,0 gn
  3. a wind force of 0,00246 N/mm2 (250 kg/m2) on the projected area of the submersible and its cradle.
    Note
    • * (1) Wind force may be applied separately from the acceleration loads defined above.
    • * (2) The accelerations from the actual ship motion analysis can be used in the case where they are more stringent please refer to Pt 5, Ch 1, 2.2 Environmental conditions for environmental loads.
    • (3) For the operational phase please refer to Pt 5, Ch 1, 2.2 Environmental conditions for environmental loads.
    • (4) Handling system loads, hydrostatic test loads and docking/mating loads need also to be considered for permanently installed units.

2.5 Air transport design requirements

2.5.1 British Civil Aircraft regulations specify crash case design requirements as given below for certain items and it is suggested that eye-plates, etc., intended for securing submersibles to their cradles, or their equivalent, be designed to this standard wherever air freighting is a possibility:
  1. 4,5 gn downwards to 2,0 gn upwards
  2. 1,5 gn aft to 9,0 gn forward
  3. zero to 2,25 gn sideways But maximum resultants considered need not exceed 9,0 gn. It is, realized that certain components within a submersible may not be able to survive such accelerations, which are based on crash conditions, but it is considered that the values of acceleration recommended will be an adequate design basis, for all items, for normal flight conditions.
Copyright 2022 Clasifications Register Group Limited, International Maritime Organization, International Labour Organization or Maritime and Coastguard Agency. All rights reserved. Clasifications Register Group Limited, its affiliates and subsidiaries and their respective officers, employees or agents are, individually and collectively, referred to in this clause as 'Clasifications Register'. Clasifications Register assumes no responsibility and shall not be liable to any person for any loss, damage or expense caused by reliance on the information or advice in this document or howsoever provided, unless that person has signed a contract with the relevant Clasifications Register entity for the provision of this information or advice and in that case any responsibility or liability is exclusively on the terms and conditions set out in that contract.