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CC2MC 12-21-2013 11:06 PM

Stainless bolts
 
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.

http://i1053.photobucket.com/albums/...psicytwsb2.jpg

Snipe 12-22-2013 07:27 AM

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

JimN 12-22-2013 07:35 AM

Quote:

Originally Posted by CC2MC (Post 1000137)
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.

http://i1053.photobucket.com/albums/...psicytwsb2.jpg

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 12-22-2013 08:06 AM

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 12-22-2013 08:55 AM

Quote:

Originally Posted by Snipe (Post 1000158)
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 12-22-2013 08:57 AM

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 12-22-2013 09:03 AM

Quote:

Originally Posted by MLA (Post 1000178)
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 12-22-2013 09:08 AM

Quote:

Originally Posted by JimN (Post 1000177)
"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 12-22-2013 09:24 AM

Quote:

Originally Posted by Cloaked (Post 1000179)
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.

.

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 12-22-2013 09:35 AM

Quote:

Originally Posted by MLA (Post 1000183)
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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