BAE Systems March 2008 Signature newsletter reports that the British Ministry of Defence has approved the use of LOKRING Pipe Fittings for safety-critical piping connections on its Astute Class Nuclear Submarines. The approval was won after an extensive test program conducted on LOKRING Fittings in accordance with the relevant Defence Standard, including gas and air pressure testing, thermal cycling, shock, and fire tests.
More than 80 LOKRING pipe fittings (12, 16, and 20mm 70/30 copper-nickel pipe at greater than 280 bar, 4,061 psi) were tested in a pilot program aboard the submarine Ambush, the second Astute Class boat. According to Mr. Lee Halliday, BAE Systems Senior Production Engineer, “The fittings were submitted to the full cycle of pressure testing that would form the normal system test path during commissioning and every one of the 160 connections passed without leakage.”
Most of the testing, including high pressure fire tests on Air and Nitrogen lines, simulating an on-board fire and accelerated vibration/pressure impulse testing to ensure the LOKRING couplings perform effectively for the whole life of the submarine, were conducted by The Submarine Machinery Installation Testing Establishment (SMITE) within the BAE facility at Barrow in Furness. Shock testing to simulate the effects of underwater explosions was conducted by QinetiQ at their Rosyth facility.
Mr. Halliday believes that the installation savings, compared to welding, on first level pipe connections could be as much as 75 percent. He also stated that “With a socket weld, you have to use gamma radiation on board the boat to check for cracks on both welds. It takes six and a half hours to perform NDE on the sleeve, during which time nobody else can work in that unit.”