Sec. 14-10.2. Factor of safety: butt- and double-strap construction

(a) The factor of safety for boilers of nonstandard construction installed prior to January 1, 1918, the longitudinal joints of which are of butt-and double-strap construction, shall be not less than 5.5 for boilers over 30 years old.

(1) At the beginning of each five-year period thereafter, the factor of safety shall be increased by not less than five tenths except that after a thorough internal and external inspection and a hydrostatic pressure test of one and one-half times the pressure allowed and held for a period of at least 30 minutes, during which no distress or leakage develops, the pressure may be continued at a factor of 5.5.

(2) In no case shall the maximum allowable pressure on old boilers be increased, unless they are being operated at a lesser pressure than would be allowable for new boilers in which case the changed pressure shall not exceed that allowable for new boilers of the same construction.

(b) The factor of safety for all standard boilers shall not be less than the requirements of section 14-1.4 of this Part.