SECTION .0500 ‑ NON‑STANDARD BOILERS AND PRESSURE

VESSELS

 

13 NCAC 13 .0501             GENERAL REQUIREMENTS

(a)  All aspects of a nonstandard boiler or pressure vessel

including, but not limited to, its installation, repair, alteration,

inspection, appurtenances, and operation shall conform to the ASME Code and the

National Board Inspection Code and the Rules in this Chapter, except for the

design criteria for the boiler or pressure vessel proper and pressure piping.

(b)  Replacement parts for the boiler or pressure vessel

shall conform to the ASME Code and the Rules in this Chapter.

(c)  An inspector shall determine the maximum allowable

working pressure for a nonstandard boiler or pressure vessel in accordance with

the Rules in this Chapter.

(d)  The maximum allowable working pressure on the shell of

a nonstandard boiler or pressure vessel shall be determined by the strength of

the weakest course computed from the thickness of the plate, the tensile

strength of the material, the efficiency of the longitudinal joint, inside

diameter of the weakest course and the factor of safety set by the Rules in

this Chapter.

(e)  For cylindrical pressure parts subject to internal

pressure:

(TStE)/(RFS) = maximum allowable working pressure, psig.

(f)  Design variables:

(1)           TS =        ultimate tensile strength of

shell plate; if unknown, it shall be taken as 45,000 psi;

(2)           t =           minimum thickness of shell

plate of weakest course, in inches;

(3)           E =          efficiency of longitudinal

joint depending upon construction;

(A)          values for riveted joints are determined by

calculated riveted efficiency; and

(B)          values for fusion welded joints and riveted joints are

determined pursuant to the following table:

 

WELD JOINT DESIGN                                                       EFFICIENCY

Single lap weld                                                                           

0.40

Double lap weld                                                                         

0.50

Single butt weld                                                                         

0.60

Double butt weld                                                                        

0.75

 

RIVETED JOINT DESIGN                                 EFFICIENCY

Single lap                                                                                     

0.58

Double lap                                                                                   

0.74

Double butt and strap                                                                

0.82

Triple butt and strap                                                                  

0.84

Quadruple butt and strap                                                          

0.94

 

(4)           R

= inside radius of weakest course of shell, in inches, provided the thickness

does not exceed 10 percent of the radius; if the thickness is over 10 percent

of the radius, the outer radius shall be used;

(5)           FS = factor of safety allowed by the Rules

in this Chapter.

(g)  The maximum allowable working pressure for cylindrical

nonstandard boilers and pressure vessels subject to external pressure, flat or

formed heads, and non-circular boilers and pressure vessels shall be determined

by the most applicable rules for new construction in the ASME Code.

(h)  The maximum allowable working pressure for cast iron

boilers, including boilers having cast iron shells or heads and steel or

wrought iron tubes, shall be not greater than 30 psig for water service and 15

psig for steam service.

(i)  Replacement parts, repair, and alteration of

nonstandard boilers and pressure vessels shall be as required for ASME stamped

boilers and pressure vessels of similar design.

 

History Note:        Authority G.S. 95‑69.11; 95‑69.14;

Eff. May 29, 1981;

Amended Eff. July 1, 2006; January 1, 1995.