INTRODUCTION 
The Supervisor of Salvage, USN, requested the Naval Civil Engineer-— 
ing Laboratory to design, fabricate, evaluate and deliver flat disc 
acrylic plastic windows for replacement of glass windows currently 
utilized by the EDU (Experimental Diving Unit) at Washington, D. C. 
In view of the fact that the pressure vessels into which the windows 
were to be installed are man-rated, the windows also had to be subjected 
to a sufficiently exhaustive testing program that would justify man- 
rating them. This report is a brief summary of the systematic window 
and material testing program to which the acrylic plastic windows for 
the EDU chambers were subjected to insure their acceptability for man- 
rated service in a USN installation. 
DISCUSSION 
Since the main objective of an evaluation program for windows 
applicable to man-rated service is establishment of confidence in the 
installed windows, all the phases of the evaluation program had to 
contribute to the attainment of this objective. Thus, confidence had 
to be established in the design, material, fabrication, quality control 
and service life of such windows under stated operational condifions}3 
450 psi maximum pressure and 120 F ambient temperature. 
Design 
The design of the windows was based on the destructive short-term 
hydrostatic tests performed previously by NCEL in 75°F ambient environ- 
ment on flat disc acrylic plastic windows. Since the short-term 
loading conditions are distinctly different from long-term sustained 
or cyclic pressure tests, a conservative conversion factor had 19 be 
used in applying the short-term test data to the design of windows for 
the more severe sustained and cyclic pressure operational service 
conditions at 120°F temperature. The conversion factor chosen was 12, 
considered to be sufficiently large to take into account not only the 
difference in loading conditions (short-term vs. cyclic and long-term 
loading) but also the need for a safety margin of at least 300 percent. 
Using the conversion factor of 12, the t/D; (thickness to ffange 
opening diameter ratio) was found*™ to be 0.325. This value gave the 
When the 450 psi operational pressure is multiplied by the conver- 
sion factor of 12, the result is 5400 psi. Using Figure 10 in NCEL 
Technical Report TR-527, one finds that a t/D; (thickness to flange 
opening diameter) ratio of about 0.325 is required in order for windows 
to fail at 5500 psi under short-term loading conditions at 75°F. 
