AGODCO Group

Independently tested and validated primarily at STRESS Engineering in Houston Texas, the Stealth-Lock specimen joints are subjected to high-speed fatigue testing of full-scale pipe specimens to verify the fatigue resistance capabilities of the Stealth-Lock MIF joints during in-service operating conditions.

Resonant Bending Fatigue tests involved applying sinusoidal alternating bending fatigue stresses around the entire pipe circumference to stimulate the pipe specimen to near its resonant bending frequency. With the use of internal pressure in the test samples, a mean axial stress was also imposed.

Generally, tested MIF samples diameters range from 2" to 12" with an average cyclic bending stress range of 5 to 50 ksi (35 to 350 MPa). Cycle rates typically average about 2.5 million per day while alternating fatigue stresses are continuously monitored by a high-speed data-acquisition system. On the Stealth-Lock MIF specimens no leak paths where detected and in all cases of testing to destruction, the pipe wall yielded and not the Stealth-Lock joints tested.