Section 9 Pressure, Temperature and Humidity Control
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 5 Main and Auxiliary Machinery, Systems and Equipment - Chapter 4 Life Support Systems - Section 9 Pressure, Temperature and Humidity Control

Section 9 Pressure, Temperature and Humidity Control

Parent topic: Chapter 4 Life Support Systems

9.1 General Requirements

9.1.1 The submersible unit and chambers should be equipped with a suitable system of valves, gauges and measurement instrumentation equipment as is necessary to:
  1. Monitor the pressure, temperature and humidity of the atmosphere and the oxygen and carbon dioxide levels within each compartment;
  2. Control the pressure and the temperature and humidity within the chambers; and
  3. To release any overpressure from within the chambers before opening the hatch.

9.1.2 The system should be designed as far as is possible to avoid high relative humidity’s in association with high temperatures in view of the deleterious effects on personnel, equipment and materials in the submersible. However all vital pieces of equipment in the craft and chambers should be designed to operate in a 100 per cent relative humidity environment.

9.1.3 If automatic temperature and humidity control systems are used, manual overrides of critical functions should be provided. The set point of the system should be manually adjustable.

9.2 Pressure

9.2.1 A pressure gauge should be fitted so that the submersible unit may be maintained at atmospheric pressure by regulation of the oxygen supply as the carbon dioxide is absorbed. It is recommended that this be an aneroid barometer with a pointer and should be accurate to within 2.5 per cent.

9.2.2 The compartments (chambers) shall be fitted with a safety valve or a visual and audible overpressure alarm alerting the operators at the control station.

9.3 Temperature

9.3.1 Means should be fitted in each manned compartment to measure internal temperature. Temperature can be measured by any appropriate means but mercury thermometers are not acceptable.

9.3.2 The use of a temperature gauge to measure external temperature is also recommended. This may take the form of a thermometer fitted outside the submersible craft and visible through a viewport or by an internal gauge with an external sensor.

9.4 Diver heating

9.4.1 Means are provided for:
  1. External body heating of the diver at depths in excess of 50 m for air diving system and at any depth for saturation diving.
  2. Respiratory gas heating in addition to means of external body heating of the diver for diving in depths in excess of 150 m. When the means of heating is by hot water it is recommended that a main and secondary hot water supply be provided. The use of electrically heated undersuits will be the subject of special consideration.
  3. Suitable safety features are to be provided to prevent overheating by the heating system.

9.5 Chamber heating

9.5.1 Submersibles and compression chambers should have sufficient power and/or hot water available for diver heating, under the emergency conditions.
Note Designers should bear in mind that helium atmospheres have a faster heat transfer rate than the normal constituents of air.
9.5.2  Bells shall have emergency means of preventing excessive heat loss by the divers for a period of 24 hours at dmax and shall be independent of the main umbilical.
Note This can be achieved by heating the bell environment, the divers directly by heated suits, or by passive thermal insulation as well as heating the divers' breathing gas by active or regenerative methods.
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