Evaluation of Nitinol Fittings for Joining Titanium Piping for Shipboard Applications.

Basic tests were made of Cryofit heat shrinkable fittings used with C.P. titanium and Ti-3Al-2.5V tube. Tests included flexural fatigue, tensile, burst, torsion and crevice corrosion. Tube sizes of 1.90 in. and 4.0 in. diameter were tested. There were no fitting failures, and flexural life degradation by the fitting was under 10% with Ti-3Al-2.5V tube and less than 20% with C.P. grade 3 tube. The fitting designs were based on 3000 psi aircraft hydraulic system requirements and it is believed even better results might be obtained with designs modified to suit lower pressure Navy systems. The Cryofit fittings can be used with titanium 3Al-2.5V and commercially pure tubing up to 4 in. diameter except in systems of safety significance, i.e., per MIL-STD-882, Class IV or Class III. With further in-depth testing, they could probably be used in any system as original installation or retrofit. (Author)