Section 4 Other components
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 3 Pressure Chambers - Chapter 2 Acrylic Windows - Section 4 Other components

Section 4 Other components

Parent topic: Chapter 2 Acrylic Windows

4.1 Windows, flanges

4.1.1 Window flanges are to be designed to meet the reinforcement requirements for pressure chamber penetrations and in addition the following minimum requirements should be met. Also refer to ASME PVHO-1.

4.2 Window seats

4.2.1 Radial deformation of the window seat at the internal or external design pressure shall be not more than 0,002Di (Di = as shown in Figure 2.4.1 Seat cavity requirements (Also refer to ASME PVHO-1)).

4.2.2 The angular deformation of the window seat shall not exceed 0,5 degrees at the design pressure. Specifications for some standard flanges are given in Figure 2.4.1 Seat cavity requirements (Also refer to ASME PVHO-1).

Figure 2.4.1 Seat cavity requirements (Also refer to ASME PVHO-1)

4.3 Impact protection

4.3.1 Large viewport windows are to be provided with impact protection capable of absorbing a 1,0 m/second collision between the diving system and a rigid flat wall. Windows of thicknesses ≥ 90 mm are considered to be acceptable without special impact protection.

4.4 Seals - Refer to ASME PVHO-1

4.4.1 The sealing arrangement of acrylic windows shall satisfy the requirements of Pt 3, Ch 2, 4.4 Seals - Refer to ASME PVHO-1 4.4.2 to Pt 3, Ch 2, 4.4 Seals - Refer to ASME PVHO-1 4.4.4. Also refer to ASME PVHO-1.

4.4.2 A primary seal of soft elastomer gasket material resistant to damage by ozone is to be fitted between the retaining ring and the window on the high pressure side. This seal shall be of sufficient thickness to permit an initial compression as specified in Pt 3, Ch 2, 4.5 Retaining rings - Refer to ASME PVHO-1 without permanent set.

4.4.3 In the case of flat disc windows a secondary support is to be fitted between the window and the sealing surface correctly bonded with contact cement to the metal flange seat and of thickness not exceeding 3.0 mm. The hardness of this seal should be less than 80 Shore hardness A.

4.4.4 Sealing ring grooves are not allowed in any bearing surface of the viewport unless the cyclic fatigue life of the assembly is determined by testing at the required design pressure and temperature and is greater than 10000 pressure cycles. The test details are to be submitted for approval.

4.5 Retaining rings - Refer to ASME PVHO-1

4.5.1 Retaining rings shall provide the following minimum initial compression of the seals (also refer to ASME PVHO-1):
  1. Conical frustum windows:
  2. Spherical sector windows:
  3. Flat disc windows (0.01 (t) + 0.05) mm, t=thickness of window

Where n is given in Table 2.4.1 Operational pressure gauge.

Table 2.4.1 Operational pressure gauge

n Operational pressure gauge, in N/mm2
1 1 – 17.2
2 17.3 – 34.5
3 34.6 – 51.7
4 51.8 – 69

4.6 Dimensional tolerances and surface finish - Refer to ASME PVHO-1

4.6.1 Dimensional tolerances and surface finish are to meet the requirements of Pt 3, Ch 2, 4.6 Dimensional tolerances and surface finish - Refer to ASME PVHO-1 4.6.2 to Pt 3, Ch 2, 4.6 Dimensional tolerances and surface finish - Refer to ASME PVHO-1 4.6.11. Also refer to ASME PVHO-1.

4.6.2 The minimum window thickness shall be equal to or greater than the nominal value determined using the maximum operating conditions.

4.6.3 The major diameter of the conical bearing surface on a window shall be within +0/-0,002Do of the nominal value. Where Do is shown in the Figure 2.4.1 Seat cavity requirements (Also refer to ASME PVHO-1).

4.6.4 The included conical angle of the windows must be within +0,25/- 0 degrees of the nominal value.

4.6.5 The included conical angle of the window seat in the flange must be within +0/0,25 degrees of the nominal value.

4.6.6 The major diameter of the conical seat cavity in the flange must be within +0.002Do/- 0 of the nominal value.

4.6.7 The spherical surfaces of a window shall not differ from an ideal spherical sector by more than ± 0,5 per cent of the specified nominal external spherical radius for the given standard CF values.

4.6.8 Tolerances on a flat disc window diameter are to be in accordance with Figure 2.4.1 Seat cavity requirements (Also refer to ASME PVHO-1) or ASME PVHO-1.

4.6.9 All seating surfaces of windows and flanges are to be machined to a finish of 1,3 μm. RMS

4.6.10 Viewing surfaces shall be polished to satisfy ASTM D702 Optical Clarity requirement.

4.6.11 All other surfaces shall be finished to 2,5 μm RMS minimum. Saw cut finish is not acceptable on any window surface.

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.