2.4 Systems
Clasification Society 2024 - Version 9.40
Statutory Documents - IMO Publications and Documents - Circulars - Maritime Safety Committee - MSC/Circular.981 – Guidelines for the Design, Construction and Operation of Passenger Submersible Craft – (29 January 2001)Amended by MSC/Circ.1125 - Annex - Guidelines for the Design, Construction and Operation of Passenger Submersible Craft - Chapter 2 - Design and Construction - 2.4 Systems

2.4 Systems

 Systems should be designed, installed and tested in accordance with the requirements of a recognized organization to the satisfaction of the Administration.

Parent topic: Chapter 2 - Design and Construction

2.4.1 Penetrations

2.4.1.1 Piping

 Any piping system penetrating the pressure hull should be equipped with a manual shut-off valve mounted directly on the inner side of the hull. Where this is not practicable, short and strong stub pieces capable of withstanding anticipated mechanical and pressure loads may be fitted between the valve and hull.

2.4.1.2 Electrical penetrations through pressure boundaries

  2.4.1.2.1 Penetrating devices conveying electricity through pressure boundaries should be designed, manufactured and tested to standards acceptable to the Administration. The penetrating devices should be capable of maintaining the watertight integrity of the hull if the cable is cut.

  2.4.1.2.2 Electrical conductors within the penetrating device should be of solid material.

  2.4.1.2.3 The positive and negative conductors from a power source are not to pass through the same penetrating device unless:

  • .1 it can be shown that there is little risk of short circuiting or 'tracking' between conductors; and

  • .2 the voltages and currents are of such an order that, in the event of failure in any way of the conductor insulation, the integrity of the penetrating device's water block is maintained.

  2.4.1.2.4 Electrical penetrating devices should not have any pipes or other system passing through them. This would not preclude having different types of penetrating devices passing through a common plate.

2.4.2 Mechanical systems

2.4.2.1 Piping

  2.4.2.1.1 Systems, fittings and equipment subject to internal or external pressures or a combination of both should be suitable for this purpose. All piping which may be exposed to the sea pressure should be able to withstand the design depth of the hull.

  2.4.2.1.2 Means should be provided for valves or cocks to indicate open and closed positions. When such an arrangement is not practicable an equivalent method/procedure may be accepted.

  2.4.2.1.3 Piping passing through spaces inaccessible for maintenance should consist of continuous length pipe.

  2.4.2.1.4 Piping which may be susceptible to mechanical damage should be adequately protected.

  2.4.2.1.5 For piping systems penetrating the occupied pressure hull and open to the sea pressure a non-return valve or shut-off valve should be provided in addition to that provided in accordance with paragraph 2.4.1.1.

  2.4.2.1.6 Taper cocks should not be used.

2.4.2.2 Hydraulic systems

 To protect the hydraulic system from over pressurization, a closed circuit safety valve should be fitted to the pressure line. The liquid discharged through safety valves should be returned into the system.

2.4.3 Electrical systems

 All power sources and electrical equipment should be designed for the environment in which they will operate to minimize the risk of fire, explosion, electrical shock and emission of toxic gases to personnel and passengers, and galvanic action of the passenger submersible craft.

2.4.3.1 Power

  2.4.3.1.1 Each passenger submersible craft should have a separate main and an onboard emergency source of electrical power.

  2.4.3.1.2 If the main source of electrical power is from an external support facility, the capacity of that source is to be adequate for its intended usage.

  2.4.3.1.3 The main source of electrical power should have a reserve capacity beyond the normal mission time to supply, where and as appropriate, the following systems for a period of time consistent with the emergency rescue plan but in no case less than 24 h:

  • .1 emergency lighting;

  • .2 communication equipment;

  • .3 life-support systems;

  • .4 environmental monitoring equipment;

  • .5 essential control systems; and

  • .6 other equipment necessary to sustain life.

  2.4.3.1.4 The onboard emergency source of electrical power should have the capacity to supply the systems listed in paragraph 2.4.3.1.3 .1), .2), .4), .5) and .6) plus the emergency life support system, if electrically supplied, for 1.5 times the time required for emergency ascent or 1 h, whichever is greater, unless approved otherwise by the Administration on the basis of special operating conditions.

  2.4.3.1.5 Passenger submersible craft should be fitted with emergency lighting which is switched on automatically in the event of failure of the main power supply.

  2.4.3.1.6 The emergency source of electrical power should be located so as to ensure its functioning in the event of fire or other casualty causing failure to the main electrical power source.

2.4.3.2 Electrical arrangements

  2.4.3.2.1 Power cables should be provided with short circuit and overload protection. The device fitted to power cables passing through a pressure boundary should have response characteristics which will ensure watertight integrity of the electrical penetrators. Protection devices located in the battery compartment should not, under any circumstances, provide an ignition source for the hydrogen gas.

  2.4.3.2.2 Adequate precautions should be taken to eliminate all potential sources of ignition within battery compartments. The use of a rigid interconnecting links between batteries should be avoided.

  2.4.3.2.3 Electrical equipment should be suitable and safe for its intended use. Consideration should be given to pressure and pressure cycling, humidity, moisture, temperature, oxygen concentration, cable combustibility and water absorption characteristics.

  2.4.3.2.4 Arrangements and procedures should be in place to avoid the potential hazards arising from hydrogen accumulation. Hydrogen gas concentrations within the pressure boundary should be monitored and maintained at a level below the lower explosive limit in order to allow the craft time to take corrective action.

2.4.4 Life support

  2.4.4.1 The passenger submersible craft should be provided with systems and equipment necessary to ensure adequate life support during normal and emergency conditions.

  2.4.4.2 A separate main and an on-board emergency life-support system should be provided for maintaining the oxygen content of the breathing gas between 18% and 23% percent by volume and the concentration of CO2 below 0.5% by volume under normal conditions and 1% percent under emergency conditions.

  2.4.4.3 The capacity of the main life-support system should be sufficient for the design mission time plus a period of time consistent with the emergency rescue plan, but in no case less than 24 h. The capacity of the on board emergency life support system is to be sufficient for 150% of the time normally required to reach the surface or 1 h, whichever is greater. The Administration may consider a reduced duration for the emergency system based on special operating conditions.

  2.4.4.4 For the purpose of calculating the required capacities of main and emergency life-support systems, the consumption of oxygen should be assumed to be 28.3 litres per hour per person and a CO2 production rate of 0.0523 kg per hour per person.

  2.4.4.5 Where oxygen containers are located inside the pressure hull, the volume of a single container should be limited such that the complete release of its contents will not increase the pressure by more than 1 atmosphere nor raise the oxygen level above 25% by volume. The allowable pressure increase may be further limited by design and safety considerations.

  2.4.4.6 When the pressure containers for oxygen are stored outside the pressure hull, they are to be arranged in at least two banks with separate penetrations entering the craft. The pressure containers are to be designed for an external pressure differential not less than the rated pressure of the passenger submersible craft.

  2.4.4.7 In view of the hazards associated with oxygen systems, special consideration should be given to the selection of materials, equipment, installation, cleaning and testing procedures. Ball valves should not be used in oxygen systems.

  2.4.4.8 The pilot or a crew member should be able to monitor O2 and CO2 concentrations, humidity, temperature and pressure of occupied spaces.

  2.4.4.9 Means should be provided and/or operational procedures implemented to notify of a malfunction of the life-support systems.

  2.4.4.10 Consideration should be given to the possible need for thermal protection, sanitary facilities, food and water, consistent with the mission time and the emergency rescue plan.

2.4.5 Fire protection

  2.4.5.1 The general construction of the passenger submersible craft should be such as to minimize hazards of smoke and fire. All materials and equipment within the craft should be non-combustible within the range of O2 levels envisaged. Toxicity of burning materials and low flame-spread characteristics should be taken into account.

  2.4.5.2 Passenger submersible craft may be fitted with fire/smoke detectors to alert the crew as may be required by the Administration. Consideration should be given to the size of the passenger submersible craft, usage of unoccupied spaces and the ability of occupants to detect fire/smoke in advance of an on-board detector.

  2.4.5.3 Passenger submersible craft should be fitted with a suitable means of fire extinguishing. This may consist of a permanently installed system and/or portable extinguishers. The design of the system and selection of the extinguishing medium should consider type and location of fire anticipated, hazards to human health and the effects of increased pressure. Carbon dioxide and seawater are generally considered to be unsuitable.

2.4.6 Navigation

  2.4.6.1 Passenger submersible craft, when engaged in surface navigation, should be provided with means and/or procedures to enable the craft to be navigated safely. Autonomous craft should be provided with such visibility on the surface as will enable the craft to be navigated safely.

  2.4.6.2 Provisions are to be made for the pilot to assess the situation in the area in which the craft is intended to surface.

  2.4.6.3 Means are to be provided to render the passenger submersible craft, while on the surface, readily visible to other vessels.

  2.4.6.4 Passenger submersible craft should be provided with navigational equipment to enable safe operations under all design conditions. Equipment may include, but not be limited to, directional indicator, depth indicator, depth sounder, clock, trim and heel indicator, underwater location device, speed and distance device and Sonar. Navigational equipment should be located in the pilot’s work area.

  2.4.6.5 Passenger submersible craft equipped with propulsion systems should be provided with adequate controls and indicators to enable safe operation under all design conditions.

  2.4.6.6 Where a releasable location system is used, the release arrangement may be manual or hand-hydraulic. It should not depend on electrical power for its operation and should be able to operate at all anticipated angles of heel and trim. The size of the float and length of line should be such that expected currents acting on the line do not prevent the float from coming to the surface.

  2.4.6.7 Passenger submersible craft should have two independent instruments for registration of its depth. At least one of these instruments is to be a pressure gauge capable of functioning also in an emergency situation. If both are pressure gauges, they should not have a common inlet. Passenger submersible craft operating in areas where the sea-bed depth is greater than the rated depth should have a depth alarm set at no greater than the rated depth of the craft.

2.4.7 Communications

  2.4.7.1 Passenger submersible craft should be provided with such equipment as is necessary for the craft to communicate with the support facility when on the surface and when submerged.

  2.4.7.2 Surface communications

Passenger submersible craft should be equipped with at least one two-channel transmitter/receiver, one of the channels of which must operate on safety channel 16-VHF, while the other is used as a "working channel" for communication between the passenger submersible craft and its support facility.

  2.4.7.3 Underwater communications

Passenger submersible craft should be equipped with at least one single channel side-band underwater telephone system. Such system should as a minimum requirement enable communication to be maintained with the support facility when it is at a distance equivalent to twice the nominal depth of passenger submersible craft.

  2.4.7.4 Provisions should be made for easy and reliable communication between the crew members and to passengers.

  2.4.7.5 Where passenger submersible craft have more than one compartment, intercommunication should be provided.

  2.4.7.6 Passenger submersible craft should be fitted with a radar transponder if they are not clearly visible on a radar screen.

  2.4.7.7 Passenger submersible craft should be fitted with an emergency acoustic pinger compatible with surface support facilities or with sonar reflector. Buoys may be additionally provided. These means should remain operational in the event of loss of main power.

2.4.8 Control and instrumentation

  2.4.8.1 The arrangements for blowing ballast tanks should be such that damage to the tanks due to overpressurization is not possible.

  2.4.8.2 Adequate indications should be available to the pilot to enable effective monitoring of conditions affecting the safety of the passenger submersible craft and its occupants. The equipment provided should be consistent with the design operating and emergency conditions and procedures. Indications should be provided for at least the following:

  • .1 water leakage into the main pressure hull, battery pods and other compartments as may be deemed necessary;

  • .2 indications of available power (fuel, electrical, etc.);

  • .3 amount of ballast water;

  • .4 ground/earth fault monitoring; and

  • .5 voltage of, and current from, each electrical source of power.

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.