TERMINOLOGY 



D. The diameter of the clear opening in the flange and therefore the effective 



diameter of the window. 



D The overall diameter of the window, or diameter of opening on high-pressure 



o 



side of flange (minus clearance). 



P Critical pressure or the pressure at which complete failure of the window 



occurs, resulting in explosive release of pressure from the vessel and frag- 

 mentation of the window. 



t The nominal or exact measured thickness of the acrylic window. 



