Figure 36. Assembled prototype 

 4-inch-ID glass Instru- 

 ment housing for 

 cyclical service to a 

 depth of 1,000 feet. 



from the main body of the pipe and 

 tension resulting from the dragging of 

 the pipe flange across the end plates 

 as the glass pipe diameter is reduced 

 by external pressure. Third ar'e the 

 radial cracks extending from the 

 glass-to-metal contact area up into 

 the main body of the pipe, (See 

 Figure 39.) These cracks originate 

 at the ends and propagate radially 

 along the longitudinal axis of the 

 pipe. These cracks often intercon- 

 nect so that the pipe falls apart when 

 the pressure is relieved, though in 

 many cases the badly cracked pipe 

 may not leak while under increasing 

 or constant pressure. These cracks 

 appear to be the result of stress con- 

 centrations resulting from small 

 protruding irregularities on the pipe- 

 flange face. These irregularities on 

 some of the specimens are large 

 enough to cause the pipe to "rock" 

 when placed on a flat surface. These 

 irregularities can be eliminated by 

 grinding and polishing the pipe 

 flanges. This was not done, however, 

 since one objective of this study was 

 to evaluate off-the-shelf glassware, 

 not custom-finished glassware. 



PREDICTION OF CRITICAL PRESSURES 



Although implosion testing of glass pipes with conical flanges has 

 experimentally determined the critical pressures of various sizes of glass 

 pipes, it is also important to be able to correlate this data with some sort 

 of an analytical expression for the prediction of critical pressures. If the 

 correlation between experimental and calculated critical pressures is good, 

 then such an analytical expression can be used with confidence to predict 

 the critical pressures of glass pipe sizes that have not been tested in this 

 particular experimental program. 



36 



