23 July 2003
approval is required for used view port defect criteria. Crazing
and cracks are not allowed in new or used view ports. Chips and
scratches may be allowed in used view ports and the acceptable
sizes of each, if permitted, will depend upon the view port
design. The service life of a view port also depends on the view
port design. For designs that are in accordance with ASME/ANSI
PVHO-1, view port service lives are either 10 or 20 years,
depending upon the view port design.
B.6.4 Hatches/Closures. For Category 1 or 2 materials, all
pressure retaining closures, including hatches, doors, covers,
and caps or plugs for openings should have a demonstrated (by
all hatches and doors should be integral to the pressure vessel
For Category 3 materials, the criteria stated for Category 1 and
2 materials may not be appropriate or adequate. Therefore, the
criteria used must demonstrate the same degree of conservatism as
the criteria for Category 1 and 2 materials and require SCA
The ease and speed with which a closure can be opened or closed,
and whether tools are required to do so, should be a design
consideration. In all cases when these factors are important,
SCA approval of the closure design should be obtained.
B.6.5 Seals. Sealing materials and techniques must be shown to
be adequate for the range of pressures, temperatures,
pressurizing media, vibrations, lubricants, and atmospheric
environments specified for the system. Seals should not be
subject to failure due to the effects of a non-lethal
extinguishable fire inside or outside the system, attack by the
fire extinguishing agent(s) used by the system, or by thermal
shock caused by the application of the extinguishing agent(s).
The effects of ultraviolet light, pressure cycling, stress
concentrations, differential thermal expansion, differences in
moduli of elasticity, tolerances and aging should be considered
when designing seals.
In systems that may contain elevated oxygen concentrations, only
oxygen compatible materials should be used.
FABRICATION DESIGN CRITERIA
Prior to the start of fabrication, the applicant should
demonstrate to the SCA that accepted commercial or military
guidelines are being used during the system fabrication process.
In cases where the applicant desires to use fabrication
procedures developed to commercial specifications, recorded data,
in addition to that required by the commercial specification, may
be required to provide the SCA with assurance that those
procedures have been followed.