Regulation .22 Power Boiler — Existing Installation: Maximum Allowable Working Pressure.
Regulation .22 Power Boiler — Existing Installation: Maximum Allowable Working Pressure.LinkCopy Citation
A.
The maximum allowable working pressure on a standard boiler shall be determined in accordance with the ASME Code under which it was constructed and stamped.
B.
The maximum allowable working pressure on the shell of a nonstandard boiler shall be determined by the strength of the weakest section of the structure computed by multiplying TS by t and E and dividing the product by R multiplied by FS:
(1)
TS = ultimate tensile strength of the shell plate, PSI, which, if unknown, shall be:
(a)
55,000 PSI for steel; and
(b)
45,000 PSI for wrought iron;
(2)
t = minimum thickness of the shell plate of the weakest course, in inches;
(3)
E = efficiency of the longitudinal joint, which is, for:
(a)
Tube ligaments and riveted construction, established by Section I of the ASME Code for power boilers; and
(b)
Seamless construction, 100 percent;
(4)
R = inside radius of the weakest course of the shell, in inches;
(5)
FS = factor of safety required by this regulation;
(6)
The resistance to crushing of mild steel is assumed to be 95,000 PSI of cross-sectional area;
(7)
When computing the ultimate strength of rivets in shear, the following values, in pounds per square inch, of the cross-sectional area of the rivet shank shall be used:
(a)
Iron rivets in single shear 38,000 PSI;
(b)
Iron rivets in double shear 76,000 PSI;
(c)
Steel rivets in single shear 44,000 PSI; and
(d)
Steel rivets in double shear 88,000 PSI;
(8)
When the diameter of a rivet hole in a longitudinal joint of a boiler is not known, the diameter and cross-sectional area of the rivet, after driving, shall be:
(a)
Ascertained by cutting out one rivet in the body of the joint; or
(b)
As indicated in the following table:
C.
The maximum allowable working pressure on a:
(1)
Water-tube boiler having tubes secured to cast iron or malleable-iron headers, or having cast-iron mud drums, shall be 160 PSIG;
(2)
Cast-iron boiler, except a hot-water boiler, shall be 15 PSIG;
(3)
Boiler having lap-riveted longitudinal joints, operated at a pressure greater than 50 PSI, when removed from an existing setting and reinstalled, shall be 15 PSIG; and
(4)
Reinstalled horizontal-return tubular boiler having a continuous longitudinal lap seam more than 12 feet long, shall be 15 PSIG.
D.
Except as otherwise provided by this regulation, the lowest factor of safety shall be, for:
(1)
An existing installation: 4.5;
(2)
A horizontal-return tubular boiler having continuous longitudinal lap seams more than 12 feet long: 8;
(3)
A reinstalled or secondhand boiler having longitudinal seams of lap-riveted construction: 6; and
(4)
A reinstalled or secondhand boiler with longitudinal seams of butt and double-strap construction: 5.