Appendix A 

 DISCUSSION OF WINDOW MOUNTINGS 



INTRODUCTION 



Variables Investigated 



In conjunction with the experimental program investigating the relationship 

 between the t/Dj ratio of flat acrylic windows and their critical pressure, an explor- 

 atory study was initiated to investigate several window-mounting variables which 

 probably influence this relationship. The variables investigated were: (1) the 

 relationship between the overall diameter (D^) of the window disk and the effective 

 diameter (D|) of the window's unsupported viewing area as defined by the supporting 

 shoulder of the window flange; (2) the method of making a pressure-tight seal between 

 the window and the flange; and (3) the effect of radial clearance between the window 

 and the flange. For these preliminary investigations, several test arrangements were 

 devised and a number of windows were tested using each arrangement (Table A-1). 



Experimental Methods 



For the evaluation of the effect of the D /D; ratio of windows on their critical 



O' I 



pressure, two different flanges were fabricated that had the same Dj but different Dq 

 openings (Figures A-la, A-lc, and A-2). Windows (Figures A-3a and A-3c) of the same 

 thickness, but with a Dq that matched the Dq of the flanges were tested in these 

 flanges. 



To evaluate the influence of the sealing method on the critical pressure of 

 flat windows, two different types of seals were used in both the large and the small 

 Dq/D; ratio windows. The two types of seals used were an O-ring seal (Figures A-3b, 

 A-3d, and A-4) under radial compression located around the circumference of the 

 window, and a grease, surface-to-surface seal (Figures A-3a, A-3c, and A-5) 

 between the window's low-pressure face and the flange's facing (Figures A-la and 

 A-lc). If the collapse pressure of windows tested in them remained the same regard- 

 less of the seal used, it could be postulated that the two methods of sealing were 

 equivalent, and exerted no influence on the collapse pressure of windows. Collapse 

 pressures of different magnitude resulting from the use of different sealing systems 

 would, on the other hand, be indicative of seal's influence on the collapse pressure, 

 and thus the collapse pressure of windows would have to be evaluated for each 

 different kind of sealing method. 



