would be rejected, new plates would be selected from the warehouse, and 
the material quality control tests repeated. 
The acrylic plastic plates chosen for the machining of EDU windows met 
(Table 2b) the NCEL specification for man-rated acrylic plastic windows 
and the plates were released for machining of windows. 
Window Performance Evaluation 
The aim of window performance evaluation tests was to establish the 
fact that the combination of window dimensions, window material and 
window flange chosen for EDU hyperbaric chambers is adequate for the 
service to which the windows are to be subjected. The evaluation tests 
chosen for a series of EDU windows selected at random from the lot of 
windows supplied by Swedlow Inc. were: (1) Short-term tests, (2) Long- 
term tests, and (3) Cyclic tests. 1 
Short-term tests were identical to those performed previously 
during exploratory evaluation of acrylic plastic flat disc windows. 
The objective of the short-term hydrostatic tests performed at this 
time was (1) to confirm the validity of the t/D; vs De (where P, denotes 
catastrophic failure pressure) curve for Swedlow 350 acrylic plastic 
established in previous NCEL tests with Plexiglas G acrylic plastic 
windows, and (2) to establish the effect of 120°F ambient temperature 
on p, established previously at 70°F ambient temperature. 
Long-term sustained hydrostatic tests had the objective of establish- 
ing that (1) the catastrophic failure of flat disc acrylic plastic windows 
under long-term sustained hydrostatic loading is predictable, and that 
(2) the window system chosen for EDU chambers is adequate to withstand 
any unforeseeable single sustained hydrostatic loading. Proving the first 
point would permit extrapolating into the future the results of few tests 
of less than a month's duration. Proving the second point would assure 
the operators of the hyperbaric chambers at EDU that even if the divers 
remained inside the chamber for a period of one year, the windows would 
not catastrophically fail due to visco-elastic creep. 
Cyclic hydrostatic tests had the objective of (1) establishing that 
failure of flat disc acrylic plastic windows under cyclic pressure loading 
is predictable, and to (2) determine the cyclic fatigue life of the window 
system selected for EDU chambers. Proving the first point would permit 
extrapolating into the future the results of few tests of less than a 
month duration. Establishing the cyclic fatigue life of windows in EDU 
chambers would permit the chamber operators to establish a window replace-— 
ment schedule with an adequate margin of safety. 
Product Assurance 
To assure that each window was indeed safe for operation under 
stated service conditions all windows were to be subjected for 1 hour 
to a 50 percent hydrostatic overload proof test at 120°F ambient tempera- 
ture. After the test, each window was to be carefully inspected for 
