DIAMETER OF BRACE.

Tensile
strength per
square inch of
section allowed		1⁄2″5⁄8″3⁄4″7⁄8″1″11⁄8″11⁄4″11⁄2″13⁄4″2″
5000 98115332208300639274970613688351202615708
60001178184026503607471259647363106021443118849
70001374256730924209549769588590123691683721991
75001472275033134509589074559204132531803923562

Shop Names for Boiler Braces.—1. Gusset brace ([fig. 47]). 2. Crowfoot brace. 3. Jaw brace ([fig. 44]). 4. Head to head brace ([fig.50]). These shop terms refer to braces used in the tubular form of boiler.

A Stay and a Brace in a steam boiler fulfil the same office, that of withstanding the pressure exerted outward of the expanded and elastic steam.

Socket Bolts are frequently used instead of the screw stay between the inside and outside plates that form the centre space. Socket bolts are driven hot the same as rivets.

The method of bracing with T bars is considered the best; the bars make the flat surface rigid and unyielding even before the brace is applied. The braces should be spaced about 8 inches apart on the T bar and 7 inches from the edge of the flange T the bar should be 4″ × 41⁄2″ T iron and riveted to the head or flat surface with 11⁄16″ rivets spaced 41⁄2 inches apart.

Hollow Stay Bolts are used in locomotive fire boxes to show when fracture has occurred by permitting an escape of steam or water.

The flange of a boiler head 1⁄2″ thick will amply support 6 inches from the edge of the flange.

A radius of 2 inches is ample for bend of flange on the head. The lower braces should be started 6 inches above the top row of tubes. Braces should be fitted so as to have a straight pull, i.e. parallel with the boiler shell. The heads of the boiler should be perfectly straight before the braces are fitted in place. Gusset brace plates should not be less than 30 inches long and 14 inches wide. Braces are best made of 1 inch O iron of highest efficacy with tensile strength of not less than 58,000 lbs. to the square inch.