Reg. 591, Reg. 591 A, Reg. 591
Gusset Link, Brace and Similar Stays
For welded Lancashire, Cornish and cylindrical horizontal
multi-tubular type boilers, all welded gusset stays
shall not be used. To ensure flexibility, link stays,
bar stays, brace stays and other similar stays or suitably
designed gusset stays other than the all-welded type
shall be used. All welded gusset stays, however, may
be used in cylindrical horizontal waste heat and cylindrical
vertical multitubular boilers.
Welded gusset stays and braces may be used for welded
Lancashire, Cornish and Cylindrical Horizontal Multi-tubular
boilers provided their method of attachment is approved
by the Inspecting Authority.
Reg. 591 a
Load on each stay
Each gusset or link stay supporting the flat end plate
of a boiler shall be designed to carry the whole load
due to pressure on the area it supports. The area supported
by any one stay shall be obtained by considering the
total area to be supported which lies within the limits
of the flat plate margins and dividing this area by
boundary lines drawn between the stays. These boundary
lines shall be at all points equidistant from the adjacent
points of support in the area under consideration.
The effective uniformly distributed load on a triangular
gusset plate or on a diagonal link stay shall be assumed
to be equal to the perpendicular load on the portion
of the end plate to be supported (determined as above)
multiplied by L/L1 (see Figs. XII/81,
Reg. 591 b
Gusset plates shall be so proportioned that the angle
V (see Figs. XII/81
less than 60°.
The thickness of the gusset plate shall be such that
the stress in the plate to withstand the effective uniformly
distributed load (as defined above) calculated on the
smallest cross-section on Line XX or YY (Figs. XII/81
and XII/82, shall not exceed one-seventh of the minimum
tensile stress of the plate used but in no case shall
be the thickness be less than seven-eighths of the thickness
of the shell plate with a minimum of 7/16 inch.
Where all-welded gusset stays are used a stiffening
plate shall be welded at the toe of the gusset where
it is secured to the end plate (i.e., where the maximum
stress occurs) (see Fig. XII/81).