# COMAR Title 09 — Maryland Department of Labor

## Subtitle 12 — Division of Labor and Industry

### Chapter 01 — Board of Boiler Rules

#### Regulation .10 Heating Boiler — Existing Installation: Maximum Allowable Working Pressure

*COMAR 09.12.01.10*

A. The maximum allowable working pressure on a standard boiler may not exceed the pressure stamped or cast by the manufacturer on:

  (1) The boiler; or

  (2) A plate secured to the boiler.

B. The maximum allowable working pressure on:

  (1) The shell of a nonstandard riveted heating boiler shall be determined in accordance with Regulation .22 of this chapter, except that the maximum allowable working pressure on a:

    (a) Steam heating boiler may not exceed 15 PSIG; and

    (b) Hot water boiler may not exceed:

      (i) 160 PSIG, or

      (ii) 250°F.

  (2) A nonstandard steel or wrought iron heating boiler of welded construction:

    (a) May not exceed 15 PSIG for steam; and

    (b) For service other than steam, shall be calculated in accordance with the ASME Code, Section IV.

  (3) A nonstandard boiler composed principally of cast iron, or having a cast iron shell or heads and steel or wrought iron tubes, may not exceed:

    (a) 15 PSIG for steam service; and

    (b) 30 PSIG for hot water service.