316 stainless steel heat exchanger tube pitting failure (Fenway Frank application)

Dramatic 304-vs-316 substitution case. Original 316 cooker ran 10-20 years with no problems. Replacement parts mis-specified as 304 cracked and rusted within weeks in the high-salt steam environment.

To show you the difference — this is the most dramatic. [Tom holds up a cracked, rusted stainless steel component.] People use 316 all the time because it's weldable, it's got stress corrosion cracking resistance, but you have to be careful — these are all cracked. You can see the cracks in this thing, it's all rusty. This came out of the Fenway Frank hot dog cooker over here in Everett. The hot dog cooker is about the size of this room — it's a big steam oven. They chop up all the types of meat you'd never want to eat, make a slurry out of it, extrude it, put it inside the casing, with a lot of salt — that's why you need chloride resistance. The original hot dog cooker was all made out of 316 stainless steel, had been around for 10 or 20 years no problems. They had to modify some things, it was all specified to be 316, and they put the new stuff in, and within several weeks the new stuff was getting rusty. It was cracking. They called me in, and I actually got to see how you cook hot dogs. Lots of interesting things in this work. They asked me to figure out why. We brought it back, turns out it's 304. Someone used 304 rather than 316. Maybe a harmless mistake, because 40 to 60% of all austenitic stainless steel is 304, and 316 is a lot less in tonnage. Just a mix-up. But that 2% molybdenum went from something that would look stainless for 15 or 20 years or more in this environment, to something that could only last a couple of weeks. That's the most dramatic example I've seen. Plenty of failures where people use 304 rather than 316, but nothing this dramatic.

---