Figure 16. Typical end closures used to evaluate the effect of end-closure 

 material on short-term critical pressure of 4-inch-ID x 6-inch- 

 long glass pipe with flanged ends. 



Since the purpose of this series of experiments was to enhance the 

 usefulness of the glass pipe in terms of numbers of use cycles and depth 

 limits, an arbitrary minimum acceptable short-term collapse pressure of 

 3,000 psi was adopted. Systems which failed at pressures less than this 

 were not further tested to determine what their maximum depth rating 

 would be for cyclical service. 



The gasl<et systems tested were as follows: 



1 . Soft (60 durometer) 3/32-inch cross section 0-rings were placed 

 in the grooves in the glass pipe flanges, lubricated with silicone grease and 

 then compressed between the glass pipe flanges and the steel end plates by 

 tensioning the tie rods holding the assembly together. (See Figure 17.) 



In each test assembly the 0-ring acted as a wedge and sheared off 

 the external flange lip from the pipe (Figures 18 and 19). This occurred 

 during the first cycle to 3,000 psi for each pipe. Thus the maximum useful 

 depth rating for 3/32-inch 0-rings is not known. Substitution of thinner 

 0-rings may eliminate the wedge action, as was shown subsequently in the 

 successful light housing design (Figures 33 and 34). 



