Section 1 Towing winch emergency release systems - goal-based framework
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Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Ships, July 2022 - Part 7 Other Ship Types and Systems - Chapter 16 Towing Winch Emergency Release Systems - Section 1 Towing winch emergency release systems - goal-based framework

Section 1 Towing winch emergency release systems - goal-based framework

Parent topic: Chapter 16 Towing Winch Emergency Release Systems

1.1 Goal-based framework

1.1.1 The purpose of this Section is to present a goal-based approach to the requirements for towing winch emergency release systems provided on towing winches that are used for towing ships within close quarters, ports or terminals, including those ships normally not intended for towing operation in the transverse direction.

1.1.2 The goals, functional requirements and performance requirements listed herein relate to design, construction and testing of the emergency release system.

1.1.3 The list of goals is as follows:

  1. The towing winch emergency release system is designed, constructed and tested through life to release loads safely, if necessary, in the event of an incident.
  2. The towing winch emergency release system is designed, constructed and tested in accordance with appropriate documented requirements.

1.1.4 The list of functional requirements is as follows:

  1. The emergency release is to operate under all normal and reasonably foreseeable abnormal conditions.
  2. The towline load is to be released in a controlled manner
  3. Control systems are to function in a safe manner in all foreseen operational conditions.
  4. Activation of the emergency release shall not expose the crew to any additional hazard.
  5. Towline load is to be released quickly enough to prevent capsize of the tug.
  6. The release system is to operate across the full range of possible towline loads, fleet angles and ship heel angles.
  7. The emergency release control system is to be designed to ‘fail-safe’, see Pt 6, Ch 1, 2.5 Control systems, general requirements 2.5.3.
  8. Necessary information and instructions to maintain and test the emergency release system are to be available.
  9. Emergency winch release is to be tested to demonstrate functionality and correct operation at appropriate intervals.

1.1.5 The list of performance requirements is as follows:

  1. The emergency release is to operate at 100 per cent of the maximum design load.
  2. Where additional sources of energy are provided, to effect emergency release of the towlinein the event of a black out, they are to be sufficient to allow for at least three attempts to release the towline and/or hold the brake open for sufficient time to release the full length of the towline or five minutes, whichever is lesser.
  3. Towline load required to rotate the winch drum once emergency release has been activated is to be no greater than:
    • the lesser of five tonnes or five per cent of the maximum design load when two layers of towline are on the drum; or
    • 15 per cent of the maximum design load where it is demonstrated that this resistance to rotation does not exceed 25 per cent of the force that will result in listing sufficient for the immersion of the lowest unprotected opening.
  4. The towline release is to be controlled to prevent the towline from becoming jammed.
  5. Control systems are to provide all necessary alarms to alert the crew in the event of failure affecting capability of the emergency release system.
  6. Arrangements of emergency release system controls are to prevent accidental or non-deliberate activation of the release system.
  7. Operation of the emergency release is to be possible from the bridge and from safe locations on the deck.
  8. The load is to be released within a maximum of three seconds.
  9. A weak link or similar arrangement is to be provided connecting the towline to the winch drum.
  10. All locations from where the emergency release can be operated are to have a full view of the towing winch and surrounding area.

1.2 LR accepted solution for towing winch emergency release systems in satisfying the goal-based framework

1.2.1 For LR accepted solutions to satisfactorily meet the goal-based framework see Pt 7, Ch 16, 2 Towing winch emergency release systems - scope and definitions to Pt 7, Ch 16, 4 Validation of requirements for emergency release systems.

1.2.2 The application of the prescriptive content in this Chapter in its entirety is considered to satisfy the functional and performance requirements of this chapter as applied to towing winch emergency release systems.

1.2.3 Alternative proposals for meeting the goal-based framework of this Section will be specially considered.

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