Thermal-shock tests of 6-in pipe-and-valve assemblies, representing both austenitic and ferritic steels in 80 and 160 schedules, are described. The shock-testing procedure was devised to simulate conditions resulting from carryover of boiler feedwater into main steam lines operating at 900 or 2000 psi pressure, 1050 F temperature. Other test procedures described include cyclic deflection tests of full-size mock-ups consisting of 160 schedule pipe and valves for simulating expansion bends. Results are reported for mock-ups of both austenitic and ferritic materials which were tested at 2000 psi pressure, 1050 F temperature. Each assembly was subjected to 4000 or more deflections corresponding to expansion cycles that would obtain on heating up a piping system from room temperature to 1050 F once every 2 days for approximately 20 years.