Technical Information

DEFINITIONS:

• ELECTRIC BOILER (ASME B&PVC SECTION I Preamble): a power boiler or a high-temperature water boiler in which the source of heat is electricity
• FIRED STEAM BOILER (ASME B&PVC Section I Preamble): a pressure vessel in which steam is generated by the application of heat resulting from the combustion of fuel (solid, liquid, or gaseous) or from solar radiation
• IMMERSION RESISTANCE ELEMENT TYPE BOILER (ASME B&PVC Section I PEB-2.4): an electric boiler in which heat is generated by the passage of an electric current through a resistance heating element directly immersed in water, or enclosed in a pipe immersed in water
• POWER BOILER (ASME B&PVC Section I Preamble): a boiler in which steam or other vapor is generated at a pressure of more than 15 psig for use external to itself

REFERENCING THE ASME B&PVC

• POWER BOILERS FALL UNDER THE JURISDICTION OF THE ASME:
  • ASME B&PVC Section I PG-2.1 – The rules of Section I are applicable to boilers in which steam or other vapor is generated at a pressure of more than 15 psig for use external to itself (note that ASME B&PVC Section I does not allow for a “size exemption”).
• DEIONIZED WATER MUST BE USED WITH A STAINLESS STEEL STEAM GENERATING POWER BOILER:
  • ASME B&PVC Section I PEB-5.3 – Electric boilers of the immersion element type may be fabricated of austenitic stainless steel type 304, 304L, 316, 316L, and 347 of any material specification listed in PG-6 and PG-9, provided that a precautionary statement indicating that the boiler shall be operated using only deionized water, having a maximum conductance of 1 microSiemen per cm (1 µS/cm) [minimum specific resistivity of 1 megohm per cm (1 MΩ/cm)], is clearly marked on the boiler in a visible location.
• THE “U” DESIGNATOR IS NOT ACCEPTABLE FOR AN ELECTRIC STEAM GENERATING POWER BOILER
  • As is stated above, these boilers are specifically covered in Section I of the ASME B&PVC.
  • The “U” designator is covered in ASME B&PVC Section VIII
  • ASME B&PVC Section VIII U-1(c)(2)(a) states that vessels within the scope of other Sections are not to be included in the scope of Section VIII.
  • Some manufacturers will try to use ASME B&PVC PEB-3 as justification for use of the “U” designator. ASME B&PVC Section I PEB-3 states the following – The boiler pressure vessel may be constructed in compliance with the ASME Pressure Vessel Code Section VIII, Division 1, rules for unfired steam boilers [UW-2(c)] subject to the conditions specified in PEB-3.1 through PEB-3.4.
    • This assertion fails on at least two accounts:
      • As seen above in ASME B&PVC Section VIII U-1(c)(2)(a), vessels within the scope of other Sections are not to be included in the scope of Section VIII
      • These power boilers are FIRED STEAM BOILERS, and not UNFIRED STEAM BOILERS. As a result, ASME B&PVC Section I PEB-3 is invalid for this application.