< Previous | Contents | Next >
Section 4 Principles of Manufacture and Construction
401. Treatment
1. Treatments applied to materials are to be properly carried out. Materials whose characteristics have been impaired by hot or cold forming are to be suitably heat treated.
2. Materials are to be so marked as to enable them to be identified and correlated with their re- spective test certificates even during and after the fabrication of the pressure hull.
3. The requirements separately provided are to be complied with in the manufacture and machining of acrylic windows.
4. The pressure hull is to be exhibit no compression against 1.5 times the maximum permissible working pressure
402.Welding
1. Companies wishing to undertake the fabrication of pressure hulls for submersibles are to have been approved by the Society with regard to their facilities, welding personnel and professional supervision.
2. Before welding work is commenced, the properties of the joints to be welded are to be proved by welding procedure qualification tests at the manufacturer's works.
3. All butt welds in the pressure hull are to be performed as full penetration, multipass welds exe-
cuted from both sides. In addition, the work is to be performed in such a way that it
signed a weld factor V of 1.0.
can be as-
403. Cutouts and viewports
1. Cutouts causing a weakening of the pressure hull are to be suitably strengthened. The reinforcement is to form an integral part of the pressure hull or connecting piece. Set on reinforcing rings are not permitted. Openings and cutouts, e.g. pipe, cable and mechanical linkage penetrations in bulk- heads and web frames, are to be rounded.
2. In the design and construction of viewport flanges, account is to be taken of the fact that the
acrylic windows make no
contribution to reinforcing the cutout in the shell of the pressure hull.
Where the inside diameter of viewport flanges is greater than 350 ŶŶ , more stringent requirements are to be applied to the permissible radial deformation and angular deformation of the window
seats, and these are to be
agreed with the Society in each case.
3. The window seat in the viewport flange is to be designed to give the window sufficient support at the maximum operating pressure. The seat dimensions for various standard windows are separately provided by the Society.
4. For flat windows having a right angled edge and an O-ring seal, the seat diameter in the viewport flange shall be within +0.25 - 0.00 mm of the nominal value, or within +0.75 - 0.00 mm where flat gasket seals are used.
5. For spherical windows with a conical bearing surface, the major diameter of the conical seat in the viewport flange shall be within + 0.002 Do / -0.000 mm of the nominal value. The included con- ical angle of the window seat in the viewport flange shall be within +0.000-0.25 degrees of the nominal value.
6. The surface roughness of the window seat shall not exceed 1.5 mm.
7. The window seat is to be permanently protected against corrosion (e.g. by overlay welding using corrosion resistant filler metals).
8. A soft gasket material can be used for the primary seal of standard windows. This seal is to be sufficiently thick to enable it to absorb a reasonable degree of deformation without experiencing permanent set.
9. In the case of flat windows with a right angled edge, a second seal is required which is bonded to the flange seat with contact cement. The second seal also acts as a supporting gasket for the win- dow and may not be more than 3 mm thick.
10. Sealing ring grooves are not allowed in the window bearing surface or the metal flange seat.
11. Retaining rings are to be able to provide the necessary initial compression of the window seals.
12. When fitting acrylic plastic windows, care is to be taken to ensure that all bearing surfaces are thoroughly cleaned. Where cleaning agents, window seat greases or adhesives for the window seals are used, these are to be tested for compatibility with acrylic plastic prior to use.
404. Ends
The movement of the rims of dished ends shall not be inadmissibly restricted by mechanical re- straints of any kind, e.g. retaining plates, stiffeners etc.
405. Pipe connections and flanges
1. The wall thickness of pipe connections are to be so dimensioned that they are fully able to with- stand additional external loads. The wall thickness of socket welded pipe connections shall be com- patible with the wall thickness of the part into which they are welded. Pipe connections and flang- es are to be socket welded in such a way that the weld configuration includes the whole wall thickness of the pressure hull.
2. Pipe connections in accordance with Pt 5 of Rules for the Classification of Steel Ships are to be provided for the connection of pipes.
