Patent ID: 8866049

Claim:
A method of heat treating a tubular device, the method comprising: spooling part of the tubular device around a first reel, a first longitudinal section of the tubular device extending from the first reel into a heat treatment chamber comprising bath media and towards a second reel; heat treating the first longitudinal section of the tubular device in the heat treatment chamber to have a first austenitic finish temperature, wherein heat treating the first longitudinal section comprises flowing gas through a heating element and a porous plate and into the heat treatment chamber, the gas fluidizing the bath media; spooling the first longitudinal section of the tubular device around the second reel, a second longitudinal section of the tubular device extending from the first reel into the heat treatment chamber and towards the second reel; heat treating the second longitudinal section of the tubular device in the heat treatment chamber to have a second austenitic finish temperature different than the first austenitic finish temperature, wherein heat treating the second longitudinal section comprises flowing gas through the heating element and the porous plate and into the heat treatment chamber, the gas fluidizing the bath media; spooling the second longitudinal section of the tubular device around the second reel, a third longitudinal section of the tubular device extending from the first reel into the heat treatment chamber and towards the second reel; heat treating the third longitudinal section of the tubular device in the heat treatment chamber to have a third austenitic finish temperature different than the first austenitic finish temperature and the second austenitic finish temperature, wherein heat treating the third longitudinal section comprises flowing gas through the heating element and the porous plate and into the heat treatment chamber, the gas fluidizing the bath media; spooling the third longitudinal section of the tubular device around the second reel, a fourth longitudinal section of the tubular device extending from the first reel into the heat treatment chamber and towards the second reel; and heat treating the fourth longitudinal section of the tubular device in the heat treatment chamber to have a fourth austenitic finish temperature different than the first austenitic finish temperature, the second austenitic finish temperature, and the third austenitic finish temperature, wherein heat treating the fourth longitudinal section comprises flowing gas through the heating element and the porous plate and into the heat treatment chamber, the gas fluidizing the bath media.