Mr. Austin has introduced three threads to this forum of the past couple of weeks about lap seam boilers. His approach is much like a terrorist setting off a car bomb and then sitting back and watching the collateral damage occur. This subject crosses several lines in regards to boiler safety and has caused a lot of concerns for everyone involved in safe boiler operation both on the locomotive side as well as with traction boilers. There are a number of ongoing schools of thought about proper inspection of antique boilers both lap and butt strap design. I would again point out that at no time has Mr. Austin done anything to contribute to this thread other than throw a hand grenade with the pin pulled into the crowd. He has been asked in the previous thread for information about the sample and we have gotten nothing out of him except silence. He then posts a series of pictures and information about a boiler failure in 1905 in an industrial power house. Makes a point to reference the lap seam issue. Is he not aware that all boilers built for those applications during that time period were lap seam because of the diameter and length? At no point has he offered any information about how old this boiler was or how was it being operated he just implies that because it was of a lap seam construction it is bad.
It is time to ask Mr. Austin to put up or shut up. There have been solid discussions about this issue both here as well as on the steam traction sites. It is a known problem with boilers that were mfg. prior to around 1910. The issue is not that laps are bad but that proper inspection occur on a regular basis on all boilers regardless of their age or construction method. Boilers fail because of human error, either from improper operation, lack of good inspection procedures or a combination of both. So with this in mind I ask you, Mr. Austin, what is your problem and if you are unwilling to talk about it please stop your terrorists approach to this issue. To all of you who have concerns about this understand I don’t want to sweep anything under the rug concerning boiler safety, I want it to be out in the open so all can benefit and learn.
John Deck

Austin does seem to have included documentation from Hartford Steam Boiler, Machinery's Handbook, and an official Australian source in his posts.

I haven't seen any sources documented in any opposing posts. I agree we need source material to judge credibility, but suggest you might be aiming your cannon in the wrong direction.

dave

I think that what Mr. Austin is intending to is to try and educate people - which is one of the most important reasons for this board.

What he is done is try to 1) educate us to the dangers of lap seam boilers; 2) alert us that there are failure conditions that many of us are not aware of and do not know how to diagnois and 3) provided us with fundamental tools that we can use to make our own determinations of the safety of these boilers. He has done this without a lot of words and that has stimulated a lot of very valuable discussion amongst ourselves, which is a very effective method of learning.

Based on what I know of his experience, he has looked at a lot more boilers than most of us, and is well suited to know if it is a big enough problem for him to spend his time trying to educate us.

Rather than griping - lets listen and learn - there is ALWAYS something more to learn. If you really are so self confident and self assured that you know all the answers - then simply don't read the thread. Just hope that you are never in a position of responsibility where you need to make a call about the safety of such a boiler.

I've been preaching boiler shop practices and stress corrosion cracking as an issue, much more than any design criteria. I'm sure in the modern world of full penetration welded seams, this type of seam failure has virtually gone away.

Think again......
http://www.youtube.com/watch?v=PsSVfAg1kRg

Well folks.....

I see my post above has generated no less than THREE new threads. Therefore, I'm done posting here about this subject. I contend that I have much to discuss about the subject, but don't feel that the continous overwhelming posts by others warrants further discussion, and clogging up this board.

Thanks,
Mark

Personally, I appreciate Mr. Austin's posts for the reason cited above - education. These posts generate a lot of comments, and many are very inciteful. Mr. Jordan's post regarding a modern boiler failure is excellent as well.

The bottom line is this. Regardless of the type of construction, boilers can fail. The failure can be from many causes - poor design, poor construction, poor maintenance, poor operation, and/or poor inspection. If all these items are done poorly, the boiler will probably fail prematurely. If they are all done very well, the boiler may last forever. Typical reality usually lies somewhere in between.

I think the lesson to be learned is how do we error prone humans try to ensure the best outcome? I believe the answer lies in evaluating each scenario for its merits and detriments. For instance, a lap seam does have an eccentric load that can vary depending upon how it was constructed. The shell can (will) be out of round when constructed. Where the seam falls within this geometry will effect the cyclic load. Was a kick built into the joint? Was the joint properly calked? These can mitigate or worsen the situation. As I see it, it would be pretty hard to ascertain the stressed condition of the joint. That takes us to inspection which is just as critical for a lap seam as it is for a butt weld. How easy is it to inspect? Based upon Mr. Jordan's post, the indicated corrosion should have been easily visible long before the welded boiler failed. Lap seams are a different animal to inspect. I have talked with many NDE folks and nobody is willing to say they can detect a crack as described by Mr. Austin with absolute reliability. Net result is you are probably better off with a seam that is easily inspected. Of course, you do have to inspect it.

I don't think any boiler is immune from failure. The best defense against failure is not ignoring what has been learned over the years. I have no doubt that there are still many unknowns out there that are ready to ambush us. Ignoring what we know to be facts only gives the unknown gremlins an advantage.

It seems to me there are many lap-seam boilers, built many decades ago, still in limited operation today. I am sure the owners of these boilers inspect and maintain their boilers with varying degrees of diligence, but failures still seem rare. My statements are based only on my own perception and I may be completely wrong about the regularity of lap-seam failures.

Is anyone aware of a finite element analysis (FEA) conducted on a lap seam design for a pressure vessel typically found at the beginning of the 20th century? I am not capable of this type of analysis, but it would be interesting to compare the results of an FEA to a design-by-rule case (using the ASME Code for example).

S.O.

FEA would require very precise recording of the joint and shell geometry to be of any use in establishing where there might be high concentrations of stress in any given seam. Not knowing what may have occurred during the fabrication process that may have affected the joint is something FEA could not make up for. Lastly, the difficulty of detecting early indications of a problem makes the lap seam a less desirable choice in my opinion.

I know there are issues in the high pressure field with the exotic alloys, but most of the stuff we use is pretty plain vanilla - or is supposed to be. That being said, just about all the structures in a locomotive style boiler can be verified reasonably easily using most NDE procedures. Also, most structures will not cause a catastrophic event if they fail singly and are not ignored. The lap seam is probably the toughest component to verify whose single failure will invariably lead to catastrophe.

Lap seams on small boilers don't seem to be a problem according to most anecdotal evidence, but I believe they are something that needs to be watched, and probably not something that should be made new any more.

If one of the concerns with existing lap seam joints in pressure vessels is the inability to evaluate the condition of the seam over time, shouldn't there be an equal concern over butt-strap joints? From a design stand point butt-straps are more stable and not subject to the stresses of a lap joint, but couldn't there be issues from corrosion, erosion, poor workmanship, poor material and other detrimental conditions that build up over time and go undetected? How do you inspect the condition of the material under the strap? I have seen a demonstration of phased array ultrasound inspection that may be able to detect discontinuities in either joint design, but I am not familiar enough with the technology to speak accurately about it.

The way I see it, there are people that own boilers with lap-seam construction that feel they can continue to operate their boilers safely. Sure, the evidence to support the continued safe use of existing lap-seam boilers is anecdotal (apparent lack of recent failures), but maybe instead of a blanket statement that all lap-seam boilers should be taken out of service, some effort should be made in coming up with a reasonably priced inspection process.

S.O.