d. The STCP of a window accepted for service in pressure vessels for
human occupancy should not be less than
STCP = (CF x P)
where CF and P are the conversion factor and design pressure respectively.
(1) For flat disc windows, shown in Figure 3-11, use conversion
factors from Table 3-3 and short term critical pressures from Figures 3-12
and 3-13. Figure 3-12 should be utilized for determination of critical
pressures in the 0 to 7,250 psi (50 MPA) range, while Figure 3-13 should be
used for 7,250 to 43,500 psi (50 to 300 MPA) range. Short term critical
pressures may be also experimentally determined according to procedure inc
above. For more detailed information on the design of flat disc windows see
Reference 4, Stachiw, Flat Disc Acrylic Plastic Windows, Technical Note
N-1127.
(2) For conical frustum windows, shown in Figure 3-11, use
conversion factors from Table 3-4 an short term critical pressures from
Figures 3-14 and 3-15. Figure 3-14 should be utilized for determination of
critical pressures in the 0 to 7,250 psi (50 MPA) range, while Figure 3-15
should be used for the 7,250 to 43,500 psi (50 to 300 MPa) range. Short term
critical pressures may be also experimentally determined according to
procedures above. For more detailed information on the design of conical
frustum windows, see Reference 3, Stachiw, Conical Acrylic Windows, 1966).
(3) For double bevelled disc windows, shown in Figure 3-11, use
conversion factors from Table 3-4 and short term critical pressures from
Figures 3-14 and 3-15, Figure 3-14 should be utilized for determination of
critical pressures in the 0 to 7,250 psi (0 to 50 MPa) range, while Figure
3-15 should be used for the 7,250 to 43,500 psi (50 to 300 MPa) range.
However, only 50 percent of the overall thickness should be utilized in
calculation of short term critical pressure according to Figures 3-14 and
3-15.
e. When selecting the conversion factors from Tables 3-3 and 3-4 the
temperature ranges must be chosen on the basis of highest ambient sustained
temperature expected during operation of the chamber at the design pressure.
If the interior of the chamber is illuminated by externally mounted
incandescent lights shining through the windows, the 150 deg. F (66 deg. C)
temperature range must be mandatory in selection of conversion factors for
all windows. For chambers not illuminated with externally mounted lights,
the
temperature ranges must be chosen on the basis of environment temperature
where the chambers reach design pressure. If the design pressure is reached
when:
(1)
only submerged in water, use ambient temperature of water at
that depth;
(2) only in air, use the average of maximum ambient external and
internal air temperatures;
(3) either in air or water, use the average of maximum ambient
external and internal air temperatures.
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