Stays

Hello,
I have a question. I read an article about the Gettysburg Boiler explosion and I wondered about the stays...

We in Germany use straight stays with threads only on copper fireboxes. The stays were screwed in and the end is widened and the edges hammered to seal the thread.
Boilers with iron fireboxes have welded stays, some straight, others were drop forged as given by the Henschel engineer Tross, who invented those double thickness stays. Flexible stays had a knucke head, placed onto a ring and sealed with a welded on cap.

But what are mentioned US straight thread stays and what are button head stays - and how they were mounted? Are all US stay bolts screwed in the material? Don't you used welded stays?

I believe that traditionally the US has used threaded stays and it was not until the "Chinese Steam" arrived in the late 1980's that US regs allowed for welded stays but I could be wrong. I think that the button head stays refer the flexible staybolts used in the crown sheet.

Rigid threaded stays traditionally are installed as you descibe in your copper fireboxes.

Hopefully some else can weigh in on this for more clarification.

In the US, welded stays were introduced when welding qualities improved. World War Two caused so many technological strides and welding was one of them. Later locomotive boilers featured both threaded and welded stays. The threaded stays went in and out easier, the welded stays required more work to install and remove.

Button-head stays are flexible, and have more range of movement due to expansion and contraction, as mentioned above.