Stainless bolts

[CC2MC]

Are the bolts in the exhaust risers supposed to be stainless? I removed one to clean some rust off of it to find that some of the threads are a rusted too. I would rather just replace them all with stainless if that is what they are supposed to take.

[Snipe]

Replace them with stainless; then you'll know and have peace of mind.

[JimN]

Originally Posted by CC2MC

Are the bolts in the exhaust risers supposed to be stainless? I removed one to clean some rust off of it to find that some of the threads are a rusted too. I would rather just replace them all with stainless if that is what they are supposed to take.

While they don't need to withstand the stresses of a head bolt, make sure the stainless bolts are hard enough and that the heads won't twist off (shear). I have used stainless screws and marveled at how frequently they broke when I was screwing them into wood, fiberglass or any other hole that wasn't too small. It may be better to use the tri-plated bolts with anti-seize.

They didn't use stainless, just steel.

[Snipe]

Jim, I yield to a greater knowledge. I should have mentioned that the stainless will not have the tensile strength of steel. They will stretch if tightened too much. As you said though, if the torque is not required beyond a good seal, it should be fine. To be on the safe side, the anti-seize may be the better way to go. My bad. I stand corrected.

[JimN]

Originally Posted by Snipe

Jim, I yield to a greater knowledge. I should have mentioned that the stainless will not have the tensile strength of steel. They will stretch if tightened too much. As you said though, if the torque is not required beyond a good seal, it should be fine. To be on the safe side, the anti-seize may be the better way to go. My bad. I stand corrected.

"Greater knowledge", meh. I just got tired of bolts and screws snapping. Steel ones last a long time, even in hostile environments, as long as they're protected.

[MLA]

You can try to pick that bolt up with a magnet, that will tell you if its SS or not. For an exhaust bolt, I would use a grade-8 coated with anti-seize. Dissimilar metals will react together. This will corrode the threads and bind the bolt in the manifold. As soft as SS is, the head will likely snap before the bolt breaks loose. We see this with aluminum towers and SS hardware in the joints.

[Cloaked]

Originally Posted by MLA

You can try to pick that bolt up with a magnet, that will tell you if its SS or not.

For the sake of conversation, I have seen NDE techs do a MT on a 'stainless' sleeve and find flaws. Most stainless has a certain amount of carbon.

Not insinuating you are incorrect, just conversation.

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[Cloaked]

Originally Posted by JimN

"Greater knowledge", meh. I just got tired of bolts and screws snapping. Steel ones last a long time, even in hostile environments, as long as they're protected.

Agreed. In the power generating industry where I have seen many valves and flanges in large-bore and high-pressure steam lines, they typically use carbon bolts where the valve bonnet connects to the body, and in particular where a reactor head bolts to the vessel body.

That is where I saw anti-seize used many years ago. It works like a champ far beyond what the common user may perceive.

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[MLA]

Originally Posted by Cloaked

For the sake of conversation, I have seen NDE techs do a MT on a 'stainless' sleeve and find flaws. Most stainless has a certain amount of carbon.

Not insinuating you are incorrect, just conversation.

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Cheap imported "stainless steel" will likely be poor quality SS or even just be plated in SS. Higher quality SS may not have enough carbon steel to be picked up by a magnet.

[Cloaked]

Originally Posted by MLA

Cheap imported "stainless steel" will likely be poor quality SS or even just be plated in SS. Higher quality SS may not have enough carbon steel to be picked up by a magnet.

Not in my world. Nuclear power plants do not use cheap or poor quality anything. It was a non-pressure retaining sleeve that had four lugs welded inside of it as a pipe guide. It was there by design.

The MT was done by mistake and was irrelevant. A non-conformance report was generated and the corrective action / root cause results were what I was mentioning.


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