Light Pipes. Light pipes have been designed in many variations
for installation in new chamber penetrations and existing penetrations. The
light pipe pressure containing window, shown in Figure 9-4, has an acrylic
rod and is mounted in a metal housing. The metal housing is sealed to the
chamber hull by O-ring and held in place by an external nut. The heat is
dissipated by the outside light source over the acrylic rod which transmits
the light into the chamber. This is ideal for recompression chambers or
low-pressure vessels. Figure 9-5 shows the design preferred for
high-pressure hyperbaric chambers. Here the pressure is contained by the
viewport window to which a separate acrylic rod interfaces. This design has
a disadvantage in that there is a 10% light loss due to constant interference
between the rod and window; the advantage is that if the acrylic rod is
damaged or broken, it can be replaced from the outside without endangering
chamber occupants or stopping the mission.
Submarine navigation lights may be replaced with safer
(1) Hull-mounted submarine navigation light is replaced by an
acrylic light pipe and adapter plate, as shown in Figure 9-6.
(2) Stuffing tube type submarine navigation light is replaced by
an acrylic light pipe rod as shown in Figure 9-7.