Section 1 General

1.1 Windows, flanges, retaining rings and seals

1.1.1 Acrylic Windows in the hull of pressure chambers used in diving systems for human occupancy require careful design, manufacture installation and maintenance of the windows, flanges, retaining rings and seals.

1.1.2 Before commencement of the manufacture of windows (or viewports) for submersibles and habitats intended to be classed with LR, the Surveyors are to be satisfied with the conditions and processes of manufacture. Plans of Windows are to be submitted for approval, and the Surveyors are to witness the pressure tests defined in Pt 3, Ch 2, 7 Testing and inspection.

1.1.3 Flat acrylic windows shall be renewed every 10 years; for some other type windows may have an extended life depending on shape, construction, geometry and design, for more details reference shall be made to PVHO-1.

1.1.4 The design, materials, manufacturing, inspection and testing of the acrylic windows / viewports are to be as per ASME PVHO-1 latest edition or the edition applicable during order acceptance. Replacements will be as per the code edition as agreed.

1.2 Documentation and markings

1.2.1 The documentation required by Pt 3, Ch 2, 1.2 Documentation and markings 1.2.2 to Pt 3, Ch 2, 1.2 Documentation and markings 1.2.6 is to be supplied by the manufacturer.

1.2.2 A material test certificate from the Supplier for each batch of acrylic plastic giving the minimum values of the physical properties in as cast and annealed condition indicated in ASME PVHO-1. The material acceptance tests are to be documented by a certificate that includes the information required by Form VP-4 in Section 2 of ASME PVHO-1.

1.2.3 A certificate of fabrication for each window indicating all forming, machining, polishing, heat treatment and inspection methods used by the manufacturer. The certificate is to provide traceability of the window through all stages of manufacture and fabrication and is to include the information required by Form VP-1 in Section 2 of ASME PVHO-1.

1.2.4 A certificate of pressure testing indicating test pressure, test temperature, rate of pressurization and duration of pressure test. The certificate is to include the information required by Form VP-5 in Section 2 of ASME PVHO-1.

1.2.5 All windows are to have identification markings corresponding to the suppliers’ certification details. Windows complying with these requirements and those of ASME PVHO-1 are to be identified with the markings required by ASME PVHO-1 preceded by the symbols “LR”. Wherever possible, the marking is to be engraved in the non-load-bearing portion of the window edge.

1.2.6 Design certification is to be provided for each window assembly design. This document is to certify that the design complies with ASME PVHO-1. The certificate is to include the information required by Form VP-2 in Section 2 of ASME PVHO-1.

1.3 Limiting conditions

1.3.1 The requirement of these Rules does not apply to acrylic plastic Windows under the following conditions:

Operating temperatures below minus 18°C and above +66°C;
Where the rate of pressurization or depressurization exceeds 1.0 N/mm² per second;
In environments other than water, sea water, air or gases used in life-support Systems;
Where the number or total duration of pressure cycles during the operational life of the pressure chamber exceeds 10,000 cycles or 40,000 hours, respectively;
Where the underwater operating pressure exceeds 138 N/mm²;
Where the exposure to nuclear radiation exceeds 4 Megarads.

1.3.2 The design life of the windows shall not exceed 20 years for windows that are exposed only to compressive stresses and shall not exceed 10 years for all windows subject to tensile stresses.

1.3.3 LR may give consideration to designs outside these rule requirements.

1.4 Protection

1.4.1 Plans are required to indicate what protection is to be afforded to viewports, etc.

1.4.2 Where acrylic plastics are used, covers are to be supplied to protect them during transport and storage. If these covers are made of polyethylene or similar material they will not, themselves, cause damage to the viewports during fitting or removal.