Part 4 of 4 on Qualifying Casing Connections for Underground Hydrogen Storage
Part 3 laid out the importance of selecting appropriate full-scale connection specimens for testing.
This final installment in the series, Part 4 presents several key considerations in safely conducting full-scale connection tests.
Full-scale connection testing requires the application of a complex series of tensile and compressive loads, bending deformations, internal pressure cycles and, in some cases, temperature to simulate the full life cycle of and underground storage wells. These procedures are complicated further for underground hydrogen storage since hydrogen should be used as the testing media instead of the traditional use of nitrogen.
To manage the safety aspects of full-scale tests with high pressure hydrogen, a secondary containment structure such as C-FER’s Special Environments Chambers (SEC) is required. The secondary containment system protects against sudden specimen failure as well as any fugitive leaks from the testing system itself.
Care must be taken during the application of load, bending, pressure and temperature to ensure that the stresses on the pipe body remain within the load envelope developed based on results from the small-scale material characterization tests (See Part 2 of this series).
A precision leak detection system is required to monitor leaks across each of the connection seals under test. Each step in the test program should be maintained for at least 15 minutes to all sufficient time for leaks to develop across these seals. Hydrogen flux sensors should also be installed on the body of the specimen to ensure that hydrogen permeation has stabilized at each stage of the test.
Pass/fail criteria for hydrogen leakage across a premium connection seal is set at 1 mL of gas leakage per 15 minutes, but this is based on testing with nitrogen. No specific criteria has been published for testing with hydrogen so it is up to the evaluator and end user to specify a pass/fail criteria for connection leakage.
