Need Ideas for cracked and fatigued 316 SS

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I'm working on repairing some cracks in a 316 stainless pressure vessel (84" ID, 1/4" shell thickness).   We have been successful in the past with a simple groove and fill with GTAW and 317" filler, but this particular vessel is fighting us every step of the way.   Some of the cracks have spidered and are bad enough to warrant large patches be cut out and welded in with fresh material.  I have tried low heat with 1/16" rod, runnign thin stringers, stitch welds layered up, even boxing the bad area with good weld, then slowly overlaying rod onto the parent meterial.  It will continuously show small hairline cracks otuside of the HAZ after Dye-penetrant.     I need ideas to help stop the cracks.   I've tried a lot, but interested in what some of you experienced folks have come up with over the years.    I cannot use any other rod, strictly 316/317 alloys.  This is an FDA-regulated unit.  What I don't need is input on telling me to scrap it.   $3million dollars on a new unit and 2 years of FDA testing says nope unless all hope is lost.  Thanks!
Reply:Will they let you run stick electrode on it?
Reply:Yes, we've tried 1/8" 316L stick on the verticals, but its pretty difficult to get the rod to lay satisfactory in the overhead position.  It still spiders.
Reply:I don't know what to suggest with the metal so fatigued that it spiders. The vessel sounds like it was severely over heated at one point.
Reply:These vessels are run with 252 degress steam for 1.5hr runs 24/365.    They are constantly in service, only down once a month for PM's.   I'm currently welding a few test sections to see if its just local areas or a homogenous defect.   If this fails, I'm at a loss.
Reply:If these are pressure vessels, as you know those spiders can be big trouble. But if the vessel just needs to be water tight, the spiders wouldn't be such an issue, "if they are only surface spiders"...just thinkinPS. Are these UL rated tanks?Last edited by Cofe; 09-18-2009 at 04:43 PM.
Reply:Yeah, they are running about 35psi of superheated steam, so these sterilizer vessels are certainly cause for concern if the spiders don't stop.   It looks like ill have to patch bigger areas than I had hoped for.  Much of the vessel shell is fine and will take a bead no problems, but these isolated areas are causing me more grief than I'm prepared to work with.
Reply:Yea stainless can be rather difficult especially if it has been subject to a lot of stress/heat....sounds like you're doing the right thing by "cutting out enough" to get to good metal....   These things will pass also, but have to be done....Wishing you luck  BR.
Reply:ASME Section 7 tanks......
Reply:Sounds like the SS is worked hardened.   This occures when to many heat/cool cycles have occured.   I would that you SCRAP the tank, or at the very least have it magnafluxed, don't know how well it workes on SS.keith The older the boys, the more expensive the TOYS!!Previous owned;Linde 300 Amp welderMiller Gas drv welder, Tumbstone,Dayton Miller ac to dc converter,High frequency unitLongevity LS60PCurrrently owned;Longevity WeldAll 200PI
Reply:do you have a preheat/post heat procedure? with the size of the vessel and the thermal conductivity characteristics of s.s do you think maybe your welds are cooling too rapidly thus having a quenching effect. I personally only deal with heavy wall stainless pipe, have never done any cylindrical vessel repairs other than patches. But with all my stainless pressure piping ive done in excess of 3000psi ive always had various pre/post heat procedures.
Reply:$3,000,000 + 2 years lead time!This is an FDA-regulated unit. What I don't need is input on telling me to scrap it. $3million dollars on a new unit and 2 years of FDA testing says nope unless all hope is lost. Well, you've welded on it, experiencing  continued evidence of fatigue cracking.Considering the gravity of this deal, just maybe 'management'would consider getting some outside appraisal, and consultation;and apparently,  there's more than one of these units.      Just maybe, this is a problem inherent to the vessel design,and analysis of that (FEA, Finite Element Analysis-for example),can also point the way to a repair plan---that entails somethingmore than welding the bejezzus out of it, while chasing cracks,ad infinitum.Blackbird
Reply:Heimz,You've stated that the tanks were 84" in dia. with a 1/4" wall.  Subjected to 252 deg steam at 35PSI.  These things we know.How long have the tanks been in service?  What was the design life cycle?  Are you currently making repairs in an area that has been repaired previously?  Lots more questions that need to be addressed before an informed recommendation could be made.Actually, I find it somewhat strange that you would come on an internet board with this type question.  Considering the cost of the tanks and the potential safety issues involved, I'd have the best metalurgist available en route to the location.3 million dollars sounds like a lot of money, however, depending on the application, that may not be a lot of money.  A company I used to do consulting for used to do the maintenance contracts for quite a few large companies (Burlington, Dan River, etc) in the textile industry.  Due to the caustic nature of the products, most of the vats, tanks, augers, etc were stainless.   Was not unusual for a two week shutdown (done about every two years) to cost the company in the range of 22-28 Million dollars.  Much of the work was prefabed off site and installed during the shutdown.  Augers were generally "reconditioned" by building up the threads with ss bead.  Vats/tanks were generally replaced.Personally, I'd say that you/they have been lucky so far that the tanks have been telling you that there is a problem.  Failure under pressure could ruin the whole day as well as possibly taking lives.  Superheated steam is not something to take lightly.Bottom line.  Don't take too much from the comments on this board.  Get professional (read paid and accredited) help and do it now.  This is not a "welder/fabricator" issue.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:252 deg. steam is not a high enough temperature to be called "super heated steam"  More like saturated steam.6"XX P5P8 6G
Reply:Originally Posted by HeimzASME Section 7 tanks......
Reply:Heimz,I think that Sundown makes some good points.  If the cost to replace the vessel is so high, then surely it's worth spending a few thousand dollars on some outside help from an experienced metallurgical lab.  You won't eliminate this problem without finding the root cause and then implementing a fix that addresses the real problem.My advice would be that you contact and expert metallurgist.  You need to work with someone who has their P.E. liscense and is experienced in pressure vessel design.  They'll likely have you take some samples from the tank wall, both damaged and not, and get them analyzed.  Chemistry, microstructure, hardness evaluation, and examination of some of the fractures in a scanning electron microscope will provide all the information an expert needs to identify the root cause of your problem.  With that in hand a qualified professional can recommend a welding procedure for repair; preferably one with a proven track record.  Getting certified to perform that procedure or paying an outside pressure vessel contractor to make the repair is the final step.  Either that, or your consultant is going to tell you it's unsafe to continue repairing this particular pressure vessel.  Either way, you'll know that the repairs will work, or it's a dangerous waste of time to try.Nobody on this, or any other board, should be giving out advice on this specific issue because they don't have enough information about the problem to formulate a correct answer.  if you're repairing a pressure vessel that's ASME certified, you need to have an approved welding procedure and a weldor whose's qualified with that procedure performing the work.  Anything else is risky at best, and negligent at worst.If you need the names of some outside labs who can help, let me know and I'll post some contact info for accredited facilities that I've worked with in the past.You could also post a request for this type of info to www.eng-tips.com.  Go to the ASME code forum, the welding/fastening/bonding forum, or the metallurgy forum and ask for a recommendation.  That forum's members tend more toward the engineering side of welding, and are more likely to give you relevant advice.Good luck.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Cofe,You are precisely correct.  The temps/pressures we're talking about here are not in the range of "superheated".  They are however, high enough to warrant extreme caution.  Steam under pressure would have been a better description.My son, who is a Naval Architect, when he was at Newport News Shipbuilding, used to talk about the "superheated" steam they had to deal with aboard the nuc subs and carriers.  Mentioned that one of the standard "advanced" items found aboard a nuc sub is a length of common #2 pine 2"x4".  Used as a wand waved in front of the crewmember when proceeding down a passageway in the area of a high pressure leak in a steam pipe. The idea being that the wood would be cut in half rather than the crewmember.Thanks for the clarification.  I'll try to be more accurate in the future.The main point I was trying to make is that the OP should consider himself fortunate that the tank/vessel has been telling him that there's a problem rather than just failing catastrophically.Last edited by SundownIII; 09-19-2009 at 02:58 PM.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Hi Sundown Yes you are correct on pointing out the liability issues. What I disagree with you on is this comment. "Bottom line. Don't take too much from the comments on this board. Get professional (read paid and accredited) help and do it now."Is this forum only for Beginners?6"XX P5P8 6G
Reply:Cofe,No, the forum is definitely NOT just for beginners.  However, after you've been here for awhile, you'll learn that there's as much bad information put out as there is good.  If the OP had to ask the question to begin with, who says he can decipher the difference.Professional, accredited translates to someone who is a recognized expert in the field and has the credentials to back it up.  If that should be you, then I'd recommend you contact the OP via PM and offer your professional services.As has been mentioned, this situation warrants expert attention.  No professional engineer (and I do have my PE) is going to give a recommendation/suggestion based on the information available or without considerable additional study.  He also isn't going to provide that type of effort for free.  "Experts" who offer guidance in situations such as these provide advice worth exactly what it cost the OP.  Nothing.Your comment about "cutting out the bad material" was just pure bull.  The question about "can you use a stick electrode?" also made no sense.  If you think you can sit in front of a computer, or even eyeball the subject stainless, and tell what portion needs to be cut out and what doesn't, then you need a big S on the front of ;your sweatshirt and a red cape.There are quite a few professionals on this board who really do know what they're talking about.  Part of being a professional is knowing your limitations and advising the OP about where to go to get the right answers.  Just because you may be certified in the welding of pressure vessels doesn't mean you're qualified to address the original issue (which is not a welding issue, but a metalurgy issue).Now, on the other hand, if your comment was designed to take a poke at me to start a little tiff, then go for it.  If you check my posts over the last couple years you'll see where I'm coming from.Last edited by SundownIII; 09-19-2009 at 07:58 PM.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Asking the question if he tried stick welding the tank  was to find if carbide precipitation was the problem.Cutting back to "good metal" is a common practice on ASTM tanks, but not UL listed tanks.Some older "pressure vessels" do not carry a UL stamp. And that regulates it to be repaired pr. ASTM I am not trying to cause a tif......just trying to be practical with a logical approach.Ps. Thanks for your efforts with this forum.6"XX P5P8 6G
Reply:Hey Cofe,No problem man.Always good to see an experienced guy show up.After you've been here awhile, you'll have a better understanding of where I'm coming from regarding some of the "advice" that's dished out on the board.Again, welcome aboard.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Hey SundownIII  I see what you mean about some advice that is dished out here. And It is good to see that you know what your doing, (even though your an Engineer) LOL   " Just had to do that from a Weldor's stand point ".... Hey Thanks again. BR6"XX P5P8 6G
Reply:Hey Cofe,Yea, I'm an engineer, but I was welding long before I ever took my first engineering class or sat for my EIT (Engineer In Training).  Learned the basics from my uncle who had been a hard hat diver/welder in the Navy in WWII.  Now that dude could weld the crack of dawn and the sun wouldn't shine all day.  Tough taskmaster but I guess he taught me well.  Also had some other excellent mentors along the way.Just trying to "give a little back" by being on the board.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Yea I was taught by some very knowledgeable gents over the years. I miss some of them fellas. Real Old School they were, and could back it up.For example I was never allowed to whip  6010 roots. I practiced and practiced then practiced and practiced, even in my sleep. Now uphill is just a relaxed time. I guess those guys cared enough to make me half way good.PS. Some of my best buds are Engineers.....I have learned a lot from them, and they finally gave up, and listened to me just a little...lol"A good Weldor can make a Engineer a better Engineer."         It's just plain hard breaking in a new Engineer......Last edited by Cofe; 09-20-2009 at 12:58 AM.6"XX P5P8 6G
Reply:At 35psi their is absolutely no way this is superheated, it is saturated.If it is a recovery vesssel perhaps the way it is mounted/hangers may be contributing to the problems.That not being the case then the operators may be exceding its operating limits with a larger component of dry steam/pressure which can go as high as 3500psi.Their isn't any welder that can salvage this vessel.The sooner everyone realizes that the quicker they can get on with the repair.Pistolnoon,Did you even read ALL the responses to this thread?I'm glad there are a few members out there that have the sweatshirt with the big S on the front and sport a red cape.Glad you were able to make such an assessment based on what limited information that has been provided.This posting reminds me of an old proverb, "Tis better to remain silent and be thought the fool, than to open one's mouth and remove all doubt".Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Mark twain, hahaanyways with this project in mind if you can see spider cracks, what about the ones you cant see...hopefully you didnt sign some contract for this project because you may have stepped into the wrong ****e pile
Reply:At 35psi their is absolutely no way this is superheated, it is saturated.
Reply:Gentleman, I did not intend on ruffling feathers or starting any terminology wars, so I'm sorry that happened.   I was only looking for ideas for exploration.  The fact is our company built the vessels, and have performed all repairs on them as they age.   Aside from having several engineers on site, we have a Metallurgist at a moments notice and very skilled welders with 30+ years experience on hand.  All repairs are performed to our approved welding procedures , dye-penetrant applied for visual NDT and the vessel will be hydrotested once more, while at the supervision of a Certified Welding Inspector.  The cracks are forming around a previous older welding repair, so we will be replacing a large section of shell.    I was trying to avoid if at all possible due to amount of work entailed, but it is obvious that this large patch is needed.   Safety is NEVER compromised and always put first.    The info I was looking for would be analagous to drilling a small hole at the end of a crack on a car frame or engine block.   There are a lot of experienced individuals here that are students of many disciplines and areas, I was trying to tap into it.  All your suggestions have been thoroughly appreciated and well-received.    Yes, it was built to Section Eight Div. 1 of the ASME code.  Blackberries are difficult to read sometimes, sorry.   Thanks again for all your input.
Reply:Gentleman, I did not intend on ruffling feathers or starting any terminology wars, so I'm sorry that happened.
Reply:Originally Posted by HeimzI'm working on repairing some cracks in a 316 stainless pressure vessel (84" ID, 1/4" shell thickness).   We have been successful in the past with a simple groove and fill with GTAW and 317" filler, but this particular vessel is fighting us every step of the way.   Some of the cracks have spidered and are bad enough to warrant large patches be cut out and welded in with fresh material.  I have tried low heat with 1/16" rod, runnign thin stringers, stitch welds layered up, even boxing the bad area with good weld, then slowly overlaying rod onto the parent meterial.  It will continuously show small hairline cracks otuside of the HAZ after Dye-penetrant.     I need ideas to help stop the cracks.   I've tried a lot, but interested in what some of you experienced folks have come up with over the years.    I cannot use any other rod, strictly 316/317 alloys.  This is an FDA-regulated unit.  What I don't need is input on telling me to scrap it.   $3million dollars on a new unit and 2 years of FDA testing says nope unless all hope is lost.  Thanks!
Reply:Please don't take offense at the blunt advice offered.  Sounds like your operation is atypical of those we hear from on this board.  Some do not have welding procedures, others don't have access to experienced metallurgists or NDT.  They're looking for a magic bullet; something that works without understanding why.Pictures would be very helpful in giving the kind of advice you're looking for.  Still not sure I can help, even with the pictures, but it's a start.  The other thing that pops to mind is what does your staff metallurgist have to say about the issue?  Has he investigated any and if so, is there any test data you can share? Originally Posted by HeimzGentleman, I did not intend on ruffling feathers or starting any terminology wars, so I'm sorry that happened.   I was only looking for ideas for exploration.  The fact is our company built the vessels, and have performed all repairs on them as they age.   Aside from having several engineers on site, we have a Metallurgist at a moments notice and very skilled welders with 30+ years experience on hand.  All repairs are performed to our approved welding procedures , dye-penetrant applied for visual NDT and the vessel will be hydrotested once more, while at the supervision of a Certified Welding Inspector.  The cracks are forming around a previous older welding repair, so we will be replacing a large section of shell.    I was trying to avoid if at all possible due to amount of work entailed, but it is obvious that this large patch is needed.   Safety is NEVER compromised and always put first.    The info I was looking for would be analagous to drilling a small hole at the end of a crack on a car frame or engine block.   There are a lot of experienced individuals here that are students of many disciplines and areas, I was trying to tap into it.  All your suggestions have been thoroughly appreciated and well-received.    Yes, it was built to Section Eight Div. 1 of the ASME code.  Blackberries are difficult to read sometimes, sorry.   Thanks again for all your input.
Reply:That is why you do not see a lot of stainless steel, air compressor tanks. Or scuba tanks. They would develop stress cracks. As well as weigh a lot more.        Sincerely,             William McCormick
Reply:I had to go back and take a look at the post to figure out  "Sundowns hostilty" Re: Need Ideas- "over a bit of hot air you might say".You attack other welders, twice in one post.
Reply:Originally Posted by SundownIIICofe,No, the forum is definitely NOT just for beginners.  However, after you've been here for awhile, you'll learn that there's as much bad information put out as there is good.  If the OP had to ask the question to begin with, who says he can decipher the difference.