Due to the following reason.....
When a load is applied to a lap joint, the resulting force causes a bending stress which is maximum underneath the overlapping edges of the seam. During repeated stress cycles, fatigue cracks occur which are undetectable by visual inspection. MANY devastating explosions occurred around the turn of the last century due to lap joint cracking. These explosions were a significant driving force in the creation of the ASME boiler code in 1914. One of the very first rules was the limiting of lap joint use in new boiler contruction to no more than 36" diameter and 100 psi. Any boiler larger in diameter and/or carrying a higher working pressure required mandatory use of double butt straps in longitudinal joint design.

I really like it when the anti-traction crowd trots out lap seam diagrams, and they are always of a SINGLE rivited seam, unheard of in most traction and other uses by 1890. Most single riveted seam boilers didn't make it to the preservation era. And if you want to discuss a failure of a boiler along a longintudonal seam, you gotta go back a century and ignore double rivited lap seams.

dont' forget that the V&T was using double rivited lap seam boilers for 70years in regular service, and the SP and some others had a few old hogs with lap seam boilers right to the end of steam.

It isn't a rivted shell joint that scares me, its a punky crown sheet run dry.

Is it just me, or does the anti-rivited boiler brigade seem like they just might have something to sell?

Matt,

Thanks for posting exactly the case I was trying to describe verbally in the above post.

The V&T locos with the lap seams spent most of their time in the roundhouse, hauled out to do movies or specials--they were not in daily service, the newer ten wheelers were!

(I could be wrong about the ten wheelers--are you out ther Kyle Wyatt?)

Steve

SZuiderveen@aol.com

> Matt,

> Thanks for posting exactly the case I was
> trying to describe verbally in the above
> post.

> The V&T locos with the lap seams spent
> most of their time in the roundhouse, hauled
> out to do movies or specials--they were not
> in daily service, the newer ten wheelers
> were!

> (I could be wrong about the ten
> wheelers--are you out ther Kyle Wyatt?)

> Steve

The V&T didn't get into the movie biz until the late 30's. The Reno, Inyo and a few others were run fairly regularly up until then, especially during times of light traffic. Their old engines were in service from the 1870's into the depression. The last run to Virginia City was pulled by the Reno, which was the regular hog on that turn.

The Tahoe worked in contractor servcice almost till about 1940, maybe later.

The SP kept 180lbs of steam on some old ten wheelers in firetrain service right through the 50s, although they were triple and quadrupal rivited seams with internal welt plates.

Lap seam joints warrent special attention, but not manditory retirement if in serviceable shape.

Honestly, whether single or double riveted, the unwelted lap seam will react the same way to mechanical stress and invisible undercutting may occur between the outer edge of the rivets and the edges of the plate as shown in the diagram.

Perhaps Matt or Dennis or somebody with experience can comment as to whether radiographic or other NDT techniques can be used to determine the extent of this kind of deterioration in a lap seam?

dave

irondave@bellsouth.net

> Lap seam joints warrent special attention,
> but not manditory retirement if in
> serviceable shape.

Which is what I and NBIC and many others have been saying from the outset, JJ. I don't know of anyone who has advocated the mandatory retirement of lap-seam boilers per se.

As for double riveted lap joints with welt plates, fine and dandy; but most were not built that way, and remember, each rivet hole removes meat from the total joint, and pretty soon, efforts to add strenght to a joint by adding more rivets can result in more hole area than plate area.

And my experieince and credentials are not open to question, sir. My 30+ years in the steam locomotive field and ownership of 3 Case traction engines qualify me, but I do not claim to be an expert. Whomever does is dangerous.

It is hard to ignore, however, that as soon as anyone questions the conventional wisdom of traction engines, the radical fundamentalists of that hobby typically overreact, then claim the questioners don't know what they are talking about.

for having questioned your experience.

That being said, there a great deal of difference in stating that lap seam boilers are inherently unsafe and stating that they warrent special attention.

And it is also somewhat alarmist, when discussing lap seams or butt strap seams, to state "Over the years, it has become obvious that these designs, whether in traction engines or locomotives, are more prone to failure, as the seams are weaker than other designs."

My real question was, during the rivited era, what other designs were there, and do we all need to get new, all welded boilers for whatever we operate due to these"inherent"weaknesses?