Nevada Administrative Code › Chapter 455C - Boilers, Elevators and Pressure Vessels › BOILERS AND PRESSURE VESSELS › Boilers › Section 455C.242 - Working pressure for nonstandard boiler

Current through June 11, 2024
1. Except as
				otherwise provided in this section, the maximum allowable working pressure of a
				nonstandard boiler is determined by the following formula:
TStE
- -
=
maximum allowable working pressure, in PSIG
RFS
where:
TS =
ultimate tensile strength of shell plate, in PSIG. If
							 the tensile strength is not known, it shall be deemed to be 55,000 PSIG for
							 steel and 45,000 PSIG for wrought iron.
t =
minimum thickness of shell plate of weakest course, in
							 inches.
E =
efficiency of longitudinal joint:
For tube ligaments, E is determined by the appropriate
							 provisions of section I of the
ASME Boiler and Pressure Vessel
							 Code
, as adopted by reference in NAC
							 455C.108.
For riveted construction, E is determined by the
							 appropriate provisions of the
National Board Inspection
							 Code
.
For seamless construction, E must be 100 percent.
R =
inside radius of weakest course of shell, in
							 inches.
FS =
factor of safety permitted by this chapter.
2.
				The resistance of mild steel to crushing shall be deemed to be 95,000
				PSIG.
3. If computing the ultimate
				strength of rivets in shear, the following values in pounds per square inch of
				the cross-sectioned area of the shank of the rivet must be used:
PSIG
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
4.
				If the diameter of the rivet holes in the longitudinal joints of a boiler is
				not known, the diameter and cross-sectioned area of rivets, after driving, may
				be selected from the following table or ascertained by cutting out one rivet in
				the body of the joint.
Sizes of Rivets Based on Plate
							 Thickness
Thickness of plate, in inches
1/4
9/32
5/16
11/32
3/8
13/32
Diameter of rivet after driving, in inches
11/16
11/16
3/4
3/4
13/16
13/16
Thickness of plate, in inches
7/16
15/32
1/2
9/16
5/8
Diameter of rivet after driving, in inches
15/16
15/16
15/16
1-1/16
1-1/16
5. A
				nonstandard boiler with welded seams may not be operated at pressures exceeding
				15 PSIG for steam and 30 PSIG for water.
6. The maximum allowable working pressure may
				be decreased by the inspector or special inspector if the condition and safety
				of the boiler warrant it.
7. Except
				as otherwise provided in this subsection, the lowest factor of safety
				permissible on existing installations is 4.5 or as set forth in the edition of
				the code that was applicable at the time of construction. The lowest factor of
				safety permissible on existing installations is 8 for horizontal-return tubular
				boilers having continuous longitudinal lap seams more than 12 feet in length.
				If such a horizontal-return tubular boiler is removed from its existing
				setting, it must not be reinstalled for pressures in excess of 15
				PSIG.
8. Reinstalled or secondhand
				boilers must have a minimum factor of safety of 6 if the longitudinal seams are
				of lap-riveted construction, and a minimum factor of safety of 5 if the
				longitudinal seams are of butt- and double-strap construction.
Added to NAC by Div. of Industrial Relations by R101-02,
					 eff. 12-15-2004
NRS 455C.110