Section 6 Testing and Cleaning

6.1.1 A functional test is to be carried out to verify the satisfactory functioning of the life support systems under normal and emergency conditions.

6.1.2 Indicating and monitoring instruments are to be tested for the accuracy of their readings and their limit value settings.

6.1.3 Automatic control systems are to be checked for satisfactory performance under service conditions.

6.1.4 Normal and emergency communications equipment is to be subjected to a functional test. The effectiveness of the helium speech unscrambler is to be demonstrated for the maximum operating depth of the diving system. Reference is made to modified rhyme test developed by US naval submarine medical centre.

6.1.5 Proof is required of the autonomy of the safety systems.

6.1.6 Details of the proposed method of testing, purging and cleaning of all pipe systems should be submitted for approval.

6.1.7 Arrangements are to be provided for venting and testing all systems while they are being charged with liquids or gases.

6.2.1 All components such as valves and fittings should be cleaned and stored in sealed plastic bags clearly marked `cleaned for oxygen service'. Documentary evidence should normally be provided.

6.2.2 All components used in oxygen systems, including piping, must be thoroughly cleaned and de-greased. Where toxic agents are used for this purpose the system should be thoroughly flushed and cleansed. Care should be taken to ensure that no contamination of the system takes place during the installation process.

6.2.3 Shop air should not be used to blow out component parts after assembly. The use of compressed, oil-free, dry nitrogen is recommended.

6.3.1 As far as possible oxygen systems should be designed so that they may be disassembled for cleaning and testing outside the chambers without the need for separating any permanent or semi-permanent joints, brazed or welded. The number of couplings should be kept to a minimum.

6.3.2 It is recommended that individual components or assemblies be pre-tested before being made up into the complete system. After installation the complete system should be tested to at least 1.5 times the working pressure using water, air or nitrogen. On completion of the above test the system should be thoroughly dried and then pressurised with dry air or nitrogen to the normal operating pressure. The system should then be shut off and the leakage rate measured, where a pressure drop of 0,5 per cent in 12 hours shall not be exceeded, taking into account any temperature change.

6.3.3 Following completion of the leak rate test, the system must be purged and tested to ensure that all traces of test gases, including air or nitrogen, are removed before filling with oxygen to its operating pressure.

6.3.4 All manifolds and connections, complete with supply pipes and fittings, should be pressure tested at least once every four years to 1.5 times the working pressure. The pressure gauges on the system should be tested for accuracy at the same time. The first at four years from the date of build or date of Major Survey for Classification as recorded on the Class Direct website, and thereafter five years from the date recorded from the previous Major Surveys.

6.3.5 At intervals of approximately 12 months, the oxygen storage cylinders are to be visually examined for collected dirt and moisture, excessive corrosion and general condition.

6.3.6 All breathing gas cylinders are to be tested hydrostatically to at least 1.5 times the working pressure every five years. A certificate of test is to be obtained. Additional in service inspections as per IMCA D018 is to be complied with.

6.4.1 After installation breathing gas systems are to be hydraulically or pneumatically pressure tested to 1,5 times the design pressure. It is recommended that individual components or assemblies be pre-tested before installation.

6.4.2 Chambers and breathing gas systems are to be pressurized to the maximum working pressure using normal working gases except that air or nitrogen should be used for oxygen systems or nitrogen with 10% He or addition of suitable halocarbon trace gas to Nitrogen. A leak test should be carried out during which a pressure drop of 0,5 per cent in 12 hours shall not be exceeded, taking into account any temperature change.

6.4.3 Where a suitable halocarbon trace gas is used with air or nitrogen as the test media the system is to be subsequently purged as necessary to ensure that it is halogen free.

6.4.4 Any emergency breathing system which uses a separate gas storage system is to be pressurized and leak tested in a similar manner to Pt 5, Ch 4, 6.4 Gas leak test for all chambers and breathing gas systems 6.4.2 and Pt 5, Ch 4, 6.4 Gas leak test for all chambers and breathing gas systems 6.4.3 and the pressure drop is not to exceed 0,25 per cent in 12 hours