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    The provisions of sections 183.38 to 183.62, shall not apply to:
    (1) boilers in buildings occupied solely for residence purposes with accommodations for
not more than five families;
    (2) railroad locomotives operated by railroad companies for transportation purposes;
    (3) air tanks installed on the right-of-way of railroads and used directly in the operation
of trains;
    (4) boilers and pressure vessels under the direct jurisdiction of the United States;
    (5) unfired pressure vessels having an internal or external working pressure not exceeding 15
p.s.i.g. with no limit on size;
    (6) pressure vessels used for storage of compressed air not exceeding five cubic feet in
volume and equipped with an ASME code stamped safety valve set at a maximum of 100 p.s.i.g.;
    (7) pressure vessels having an inside diameter not exceeding six inches;
    (8) every vessel that contains water under pressure, including those containing air that
serves only as a cushion, whose design pressure does not exceed 300 p.s.i.g. and whose design
temperature does not exceed 210 degrees Fahrenheit;
    (9) boiler or pressure vessels located on farms used solely for agricultural or horticultural
purposes; for purposes of this section, boilers used for mint oil extraction are considered used
for agricultural or horticultural purposes, provided that the owner or lessee complies with the
inspection requirements contained in section 183.42;
    (10) tanks or cylinders used for storage or transfer of liquefied petroleum gases;
    (11) unfired pressure vessels in petroleum refineries;
    (12) an air tank or pressure vessel which is an integral part of a passenger motor bus, truck,
or trailer;
    (13) hot water heating and other hot liquid boilers not exceeding a heat input of 750,000
BTU per hour;
    (14) hot water supply boilers (water heaters) not exceeding a heat input of 500,000 BTU per
hour, a water temperature of 210 degrees Fahrenheit, a nominal water capacity of 120 gallons, or
a pressure of 160 p.s.i.g.;
    (15) a laundry and dry cleaning press not exceeding five cubic feet of steam volume;
    (16) pressure vessels operated full of water or other liquid not materially more hazardous
than water, if the vessel's contents' temperature does not exceed 140 degrees Fahrenheit or
a pressure of 200 p.s.i.g.;
    (17) steam powered turbines at paper-making facilities which are powered by steam
generated by municipal steam district facilities at a remote location; and
    (18) manually fired boilers for model locomotive, boat, tractor, stationary engine, or antique
motor vehicles constructed or maintained only as a hobby for exhibition, educational or historical
purposes and not for commercial use, if the boilers have an inside diameter of 12 inches or less, or
a grate area of two square feet or less, and are equipped with an ASME stamped safety valve of
adequate size, a water level indicator, and a pressure gauge.
    An engineer's license is not required for hot water supply boilers.
    An engineer's license is not required for boilers, steam cookers, steam kettles, steam
sterilizers or other steam generators not exceeding 100,000 BTU per hour input, 25 kilowatt,
2-1/2 horsepower and a pressure of 15 p.s.i.g.
    Electric boilers not exceeding a maximum working pressure of 50 p.s.i.g., maximum of 30
kilowatt input or three horsepower rating shall be inspected as pressure vessels and shall not
require an engineer license to operate.
History: (5492) RL s 2186; 1919 c 240 s 7; 1955 c 817 s 1; 1957 c 503 s 1; 1Sp1981
c 4 art 1 s 92; 1982 c 379 s 20; 1987 c 70 s 6; 1987 c 382 s 1; 1991 c 331 s 2; 1992 c 436
s 1; 2007 c 140 art 9 s 16

Official Publication of the State of Minnesota
Revisor of Statutes