(1) All boilers and unfired pressure vessels which were in use, or installed ready for use in this state prior to the date upon which the first rules and regulations under this chapter pertaining to existing installations became effective, or during the twelve months period immediately thereafter, shall be made to conform to the rules and regulations of the board governing existing installations, and the formulae prescribed therein shall be used in determining the maximum allowable working pressure for such boilers and unfired pressure vessels.

     (2) This chapter shall not be construed as in any way preventing the use or sale of boilers or unfired vessels as referred to in subsection (1) of this section, provided they have been made to conform to the rules and regulations of the board governing existing installations, and provided, further, they have not been found upon inspection to be in an unsafe condition.

     (3) An inspection certificate may also be granted for miniature hobby boilers that do not comply with the code requirements of the American society of mechanical engineers adopted under this chapter and do not exceed any of the following limits:

     (a) Sixteen inches inside diameter of the shell;

     (b) Twenty square feet of total heating surface;

     (c) Five cubic feet of gross volume of vessel; and

     (d) One hundred fifty p.s.i.g. maximum allowable working pressure, and if the boiler is to be operated exclusively not for commercial or industrial use and the department of labor and industries finds, upon inspection, that operation of the boiler for such purposes is not unsafe.

[2009 c 90 § 2; 1995 c 41 § 1; 1993 c 193 § 1; 1951 c 32 § 7.]