A Puget Sound Naval Shipyard & Intermediate Maintenance Facility team comprised of welding engineers and technicians, machinists and others helped conduct explosive bulge testing on steel that may be used in future submarine construction and repairs, at Hawthorne Army Depot, Nevada, in late August.
According to Kiichi Harada, welding engineer, Code 138.3, Weld Engineers & Non-Destructive Test Examiners, PSNS & IMF regularly supports explosion bulge testing for the U.S. Navy.
The most recent iteration of steel preparation and explosive bulge testing was performed on steel that may be used to build Virginia-class and Columbia-class submarines. The required fabrication, welding and testing of 12 assemblies took more than nine months to complete.
“This process takes one welding engineering technician and one welding engineer for the work at PSNS, plus support from Code 1213, Code 134, Shop 31 and Code 135,” said Harada. “For the testing at Hawthorne Army Depot, we need a team of two welding engineers, two welding engineering technicians, one welding engineering branch head, and one Naval Facilities Engineering Systems Command truck driver. We are also supported by Army civilian and contractor personnel from Hawthorne Army Depot and Rock Island Arsenal, Illinois.”
Rick Sheridan, welding engineering division head, Code 138, Weld Engineers & Non-Destructive Test Examiners, said the explosive bulge testing process helps evaluate commercial samples of plate steel, castings, forgings or weld wire provided to the U.S. Navy for potential use in critical submarine hull applications.
After the steel undergoes various strength tests to include impact and tensile testing, samples are prepared for explosive testing by an experienced welding engineering technician, including applying crack starter beads.
“Scott Trammell, our welding engineering technician, has more than 32 years of welding experience and 12 years working on this type of test,” said Harada. “I was fortunate to be trained by Robert D. Thompson, who ran the testing program both before and after its transfer from Mare Island Naval Shipyard, in California.”
Ben McCreary, branch head, Code 138.2, Non-Nuclear Welding Engineering, and Code 138.3, said the team welded test assemblies for more than three months, which were transported to Nevada; while there, they were subjected to a blast from high explosives.
“Once welding has started, the process is continued as long as possible to limit heat cycles on the steel,” explained McCreary. “After more than three months of welding time, Code 135 [Non-Destructive Testing Division] checked the quality of the welds through non-destructive testing methods. Shop 31 Machinists] helped to machine samples from the ‘prolongs,’ and Code 134 [Laboratory Division] performed destructive testing to verify the mechanical properties of the steel and the welds.”
“The welds must be as strong as, or stronger than, the steel,” continued McCreary. “If the welds fail during explosion testing, the evaluation of the steel cannot be completed.”
Sheridan said the process helps push the steel to its limits, helping to determine if it can withstand the rigors of a deep sea environment as part of a U.S. Navy warship.
“Generally, plates are cooled to zero degrees Fahrenheit in a liquid nitrogen bath and then placed on a test fixture,” Sheridan said. “An explosive charge is set above the plate and detonated. This deforms the plate into the test fixture and we track reduction of area of the plate until all test requirements are met. The two-inch flat plate turns into bowl.”
Harada said the explosive Pentolite or an equivalent high explosive is used in the test. All material preparation and explosive testing is conducted in strict accordance with Naval Sea Systems Command Technical Publication T9074-BD-GIB-010/0300.
McCreary said the testing team of Harada, Scott Trammell and Ray James, Code 138.1, Nuclear Welding Engineering Branch; Skeeter Judd, Code 138.2; and Bob Martello, Naval Facilities Engineering Command, worked in 95-degree heat with Army depot personnel to safely conduct the tests.
“After each explosion, the test team goes to work measuring the plates, making stand-off boxes and cooling the plates back down to test temperature for another round of explosions, until specific acceptance criteria is met,” he said.
While the precision of the testing process is challenging, Harada said PSNS & IMF has helped for decades to ensure U.S. Navy submarines can and will perform as expected.
“It is a very unique testing requirement that cannot be replicated with standard mechanical testing methods,” Harada said. “The Navy has been performing this type of testing since the 1960s, and [PSNS & IMF] has been performing this function for the Navy since 1995.”
Sheridan said rigorous testing of all materials used on U.S. Navy warships is important.
“The NSTP-200 and NSTP-300 programs ensure structural integrity of critical plate, castings, forgings and filler metals,” said Sheridan. “This helped allow USS San Francisco (SSN 711) to make it back to port after a collision at sea.”