Connecticut Administrative Code › Title 29 - Public Safety and State Police › 232 - Boiler Design, Construction, Installation, Repair, Use and Operation › Existing Installations - Power Boilers › Section 29-232-55 - Maximum allowable working pressure of nonstandard boilers

Current through July 10, 2024
The maximum allowable working pressure of the shell or drum
				  of a non standard boiler shall be determined by the strength of the weakest
				  section of the structure, computed from the tensile strength of the plate, the
				  thickness of the plate, the efficiency of the longitudinal joint or tube
				  ligament, the inside diameter of the outside course and the factor of safety
				  required by these regulations.
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where:
TS = ultimate tensile strength of shell plates,
				  lb/in2.
t = minimum thickness of shell plate, in weakest course, in
				  inches.
E = efficiency of longitudinal joint or tube ligament.
For riveted construction, E shall be determined by rules
				  given in section I, part PR of the "Rules of Construction of Power Boilers,"
				  1971 edition. For tube ligaments, E shall be determined by rules in paragraph
				  PG52 and PG53, section I, of the "Rules of Construction of Power Boilers"
				  latest edition. For seamless construction, E shall be considered one hundred
				  per cent.
R = one half of the inside diameter of the weakest course of
				  shell or drum in inches.
FS = factor of safety permitted.
(a)
Tensile strength.
When the
				tensile strength of steel or wrought iron shell plates is not known it shall be
				taken as 55,000 lbs. per sq. in. for steel and 45,000 lbs. per sq. in. for
				wrought iron.
(b)
Crushing
				strength of mild steel.
The resistance of crushing of mild steel shall
				be taken at 95,000 lbs. per sq. in. of cross sectional area.
(c)
Strength of rivets in shear.
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:
Iron rivets in single shear
38,000
Iron rivets in double shear
76,000
Steel rivets in single shear
44,000
Steel rivets in double shear
88,000
When the diameter of the rivet holes in the longitudinal
				  joints of a boiler is not known, the diameter and cross sectional area of the
				  rivets after driving may be selected from the following table or ascertained by
				  cutting out one rivet in the body of the joint.
Table I
Sizes of Rivets Based on Plate Thickness
Thickness of plate:
1/4"
9/32"
5/16"
11/32"
3/8"
13/32"
Diameter of rivet after driving:
11/16"
11/16"
3/4"
3/4"
13/16"
13/16"
Thickness of plate:
7/16"
15/32"
1/2"
9/16"
5/8"
Diameter of rivet after driving:
15/16"
15/16"
15/16"
17/16"
17/16"
(d)
				The lowest factor of safety permissible on existing installations shall be
				five. For horizontal return tubular boilers having continuous lap seams more
				than twelve feet in length, the factor of safety shall be eight. When this
				latter type of boiler is removed from its existing setting, it shall not be
				reinstalled for pressures in excess of fifteen psig. Reinstalled or second hand
				boilers shall have a minimum factor of safety of six when the longitudinal
				seams are of lap riveted construction, and a minimum factor of safety of five
				when the longitudinal seams are of butt and double strap
				construction.