Section 3 Control and Supervision

3.1.1 The compartments of compression chambers are to be fitted with pressure and temperature gauges which can be read from inside. Diving bells are to be equipped with instruments indicating the internal and external pressure and the pressure of the independent gas supply. In addition, the diving bell is to be equipped with an autonomous unit for monitoring the oxygen and CO2 levels.

3.1.2 Means are to be provided to maintain atmospheric pressure by regulating the oxygen supply as the carbon dioxide is absorbed, an atmospheric pressure gauge is to be fitted to indicate that atmospheric pressure is being maintained within the chamber.

3.1.3 Provision is to be made for the automatic release (with manual override) of accidental pressurization in order to limit ‘high internal to low external chamber’ differential pressure to two atmospheres. Account is to be taken of the delay time for the operation of the release.

3.1.4 Simple analysers of the chemical gas absorption type are to be carried as spot check devices for atmosphere sampling on service voyages.

3.1.5 Pressure gauges connected directly to the compression chamber system are to be fitted with a shutoff valve.

3.2.1 All chambers which have variable pressure control are to be provided with means to change their internal pressure from the outside of the chamber. Where necessary, means to change their internal pressure may also be provided within the chamber and/or from adjacent compartments.

3.2.2 Where dual controls are fitted for changing the chamber pressure the external control is to override any internal controls.

3.2.3 In the case of airlocks the pressure controls are to include the selection of the correct gas mixture within the chamber at any time.

3.2.4 For safety interlocks associated with the prevention of unintentional or uncontrolled loss of pressure via mating systems, food and equipment locks and sewage systems, see Pt 5, Ch 6, 2.1 General 2.1.10.

3.2.5 In addition to the instrumentation required for isobaric chambers a means of determining the rate of change of pressure is also to be provided. On submersibles where decompression schedules require the use of pure oxygen, the oxygen dump system is to be adequately instrumented to enable proper control of partial pressure to be maintained.

3.3.1 Where the life-support systems of a submersible or chamber can be controlled from more than one chamber a full set of the instrumentation required by Pt 6, Ch 2, 3.3 Life-support systems 3.3.2 to Pt 6, Ch 2, 3.3 Life-support systems 3.3.4 is to be provided in each chamber.

3.3.2 Pressure gauges are to be fitted showing the pressure drop across pressure reducing valves, filters and absorbers, together with the pressure within all gas storage bottles, or within the discharge rail where two or more bottles are on line.

3.3.3 A pressure recorder is to be provided in the life-support systems to divers.

3.3.4 Means of ascertaining the humidity and temperature of all chambers is to be provided.

3.3.5 A wide-band toxic contamination level indicator is to be available, and is to be used during trials to check that there is no buildup of toxic vapours in any chamber. With the exception of chambers used for welding it need not be carried on normal service voyages. The toxic contamination limit (threshold limit value) is to be in accordance with National Regulations.

3.3.6 The make-up of breathing gases within hyperbaric chambers is to be regularly monitored and the content of all relevant breathing gas constituents is to be displayed in the diving control room. Means are to be provided to enable the diving control room superintendents to verify satisfactory performance of the analyser.

3.3.7 Throughout the entire operating period, the oxygen analysing system must give a reading accurate to ± 0,015 bar partial oxygen pressure or equivalent to 0.1% full scale reading surface equivalent.

3.3.8 Throughout the entire operating period the CO2 analysing system must give a reading accurate to ± 0,001 bar partial CO2 pressure or equivalent to 1% full scale reading surface equivalent.

3.3.9 In addition, autonomous instruments for monitoring the oxygen and CO2 levels are to be provided in diving bells and the living compartments of compression chambers.

3.3.10 Where gases other than air, helium-oxygen mixtures or He/N2/CO2 mixtures are used for diving operations, the instrumentation required shall be agreed with LR in each case.

3.3.11 A system is to be provided for analysing the chamber atmosphere for impurities such as CO, NO, NOx and hydrocarbons. Test tubes may be recognized for this purpose.

3.4.1 Navigational equipment is to be at least in accordance with the 1982 International Maritime Organisation Publication 979 82.07E Performance Standards for Navigational Equipment.

3.4.2 For underwater navigation, heading information is to be provided at the steering position by means of a magnetic compass or a gyro compass.

3.4.3 In addition to watches carried by the crew and divers, a clock with movable segments showing the working time and operational time remaining available is to be fitted. This clock is to be self-contained and not reliant on the electrical supply.

3.4.4 A depth indicator accurate to ± 1,0 per cent at target maximum diving depth is to be provided. The indicator is to be graduated in meters to the maximum operating depth plus 20 per cent. In built test facilities or shut off cocks for easy replacement and testing are to be provided. A quick-read table for conversion of the scale for density and temperature correction is to be available. The depth indicator is not to be affected by pressure changes within the chamber.

3.4.5 The instrument indicating the pressure in the compression chambers and diving bells must be accurate to ± 0,25 per cent of the whole scale with a maximum deviation of 30 cm water column. All other pressure reading shall be accurate to ± 1 per cent of the whole scale.

3.4.6 Where a hazard analysis required by Pt 1, Ch 2, 3.2 New Construction Surveys, demonstrates that the submersible may be required to operate in waters deeper than its maximum operating depth a second independent depth indicator complying with Pt 6, Ch 2, 3.4 Navigational equipment 3.4.4 is also to be provided. In addition a depth alarm is to be fitted and arranged to operate before the maximum operating depth is exceeded.

3.4.7 A speed and distance indicator is to be provided for mobile submersibles.

3.4.8 Suitable heel and trim or attitude indication is to be provided.

3.4.9 Suitable meters are to be provided to indicate the state of charge of the submersible’s batteries.

3.4.10 Where an echo sounder is used in more than one role, e.g. for obstacle avoidance in the ahead, upward or downward zones, clear visual indication of the direction of the beam is to be given. If of the recording type, the direction is to be recorded.