The minimum size of an access or fire door opening, in which the minimum furnace dimension is 24 in. (600 mm), shall be not less than 12 in. x 16 in. (300 mm x 400 mm) or equivalent area, 11 in. (280 mm) to be the least dimension in any case. A circular opening shall be not less than 15 in. (380 mm) in diameter.
For furnace dimensions less than 24 in. (600 mm), the opening should be 2 ¾ in. x 3 ½ in. (70 mm x 89 mm) or larger where possible. In cases where the size or shape of the boiler prohibits an opening of that size, two openings with a minimum size of 1 in. (25 mm) may be used, preferably opposite each other, to permit inspection and cleaning of the furnace. If the burner is removable so as to permit inspection and cleaning through the burner opening, a separate access opening need not be provided.
The bonnet or smoke hood of a vertical flue or tubular boiler shall be provided with an access opening at least 6 in. x 8 in. (150 mm x 200 mm) for the purpose of inspection and cleaning the top head of the boiler.
PFT-43 REQUIREMENTS FOR INSPECTION
OPENINGS
All firetube boilers shall have sufficient inspection openings, handholes, or washout plugs with a minimum of four openings to permit inspection of the waterside of the tubesheets, furnaces, and tubes and to permit flushing of loose scale and sediment from the boiler. Except where space restrictions would prohibit entry to the boiler, a manhole shall be provided in the upper portion of the shell. All openings shall meet the requirements of PG-32 through PG-44. Where washout plugs are used, the minimum size shall be NPS 1½ (DN 40), except for boilers 16 in. (400 mm) or less in inside diameter, the minimum size shall be NPS 1 (DN 25).
PFT-44 OPENING BETWEEN BOILER AND SAFETY VALVE
The opening or connection between the boiler and the safety valve shall have at least the area of the valve inlet.
After the boiler Manufacturer provides for the opening required by the Code, a bushing may be inserted in the opening in the shell to suit a pressure relief valve that will have the capacity to relieve all the steam that can be generated in the boiler and which will meet the Code requirements. The minimum size of the connection and opening for the pressure relief valve shall be not less than NPS ½ (DN 15).
No valve of any description shall be placed between the required pressure relief valve or valves and the boiler, or on the discharge pipe between the pressure relief valve and the atmosphere. When a discharge pipe is used, the cross-sectional area shall be not less than the full area of the valve outlet or of the total of the areas of the valve outlets discharging thereinto and shall be as short and straight as possible and so arranged as to avoid undue stresses on the valve or valves.
DOMES
PFT-45 REQUIREMENTS FOR DOMES
PFT-45.1 The longitudinal joint of a dome may be butt welded or the dome may be made without a seam of one piece of steel pressed into shape. The dome flange may be double full fillet lap-welded to the shell if all welding complies fully with the requirements for welding in Part PW. Volumetric examination of the fillet welds may be omitted. The opening shall be reinforced in accordance with PG-32 through PG-44.
PFT-45.3 When a dome is located on the barrel of a locomotive-type boiler or on the shell of a horizontal-return tubular boiler, the outside diameter of the dome shall not exceed six-tenths the inside diameter of the shell or barrel of the boiler unless the portion of the barrel or shell under the dome (the neutral sheet) is stayed to the head or shell of the dome by stays which conform in spacing and size to the requirements given in PG-46 and Table 1A of Section II, Part D. With such stayed construction the outside diameter of a dome located on the barrel or shell of a boiler is limited to eight-tenths of the barrel or shell inside diameter.
PFT-45.4 All domes shall be so arranged that any water can drain back into the boiler.
PFT-45.5 Flanges of domes shall be formed with a corner radius, measured on the inside, of at least twice the thickness of the plate for plates 1 in. (25 mm) in thickness or less, and at least three times the thickness of the plate for plates over 1 in. (25 mm) in thickness.
PFT-45.6 Domes and manhole frames attached to shells or heads of boilers shall be designed in accordance with PG-32 through PG-44.
PART PEB
REQUIREMENTS FOR ELECTRIC BOILERS
GENERAL
PEB-1 GENERAL
The rules in Part PEB are applicable to electric boilers and parts thereof and shall be used in conjunction with the general requirements in Part PG as well as with the special requirements in the applicable Parts of this Section that apply to the method of fabrication used.
PEB-2 SCOPE
PEB-2.1 This part contains special rules for construction of electric boilers, both of the electrode and immersion resistance element type. This Part does not include electric boilers where the heat is applied externally to the boiler pressure vessel by electric resistance heating elements, induction coils, or other electrical means. These types of electric boilers shall be constructed in accordance with other applicable Parts of this Section.
PEB-2.2 Electric boilers and parts thereof that do not exceed the diameter, volume, or pressure limits of PMB-2 may be constructed using the applicable paragraphs of Part PMB in conjunction with this Part.
PEB-2.3 An electrode type boiler is defined as an electric boiler in which heat is generated by the passage of an electric current using water as the conductor.
PEB-2.4 An immersion resistance element type boiler is defined as 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.
PEB-2.5 Electric boilers may be field assembled provided the boiler is manufactured and assembled in compliance with the provisions and requirements of Part PEB and other applicable Parts of this Section.
PEB-3 OPTIONAL REQUIREMENTS FOR THE BOILER PRESSURE VESSEL
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.
PEB-3.1 The Manufacturer who certifies and stamps the completed boiler shall specify to the “U" stamp holder all additional requirements of Part PEB, which are not requirements of Section VIII, Division 1, and shall ensure that these requirements are satisfied.
PEB-3.2 These additional requirements are:
PEB-3.2.1 The materials of construction shall comply with the requirements of PEB-5.1 and PEB-5.3.
PEB-3.2.2 Inspection openings shall comply with the requirements of PEB-10.
PEB-3.3 The boiler pressure vessel shall be stamped with the ASME Code “U" symbol and the letters “UB," and be documented with the ASME U-1 or U-1A Data Report.
PEB-3.4 The master Data Report P-2A for the Electric Boiler shall indicate “Boiler pressure vessel constructed to Section VIII, Division 1 as permitted by Part PEB."
MATERIALS
PEB-5 GENERAL
PEB-5.1 Unless specifically permitted elsewhere in this section, materials used in the construction of pressure parts for electric boilers shall conform to one of the specifications in Section II and shall be limited to those permitted by PG-6, PG-7, PG-8, and PG-9 for which allowable stress values are given in Tables 1A and 1B of Section II, Part D. Miscellaneous pressure parts shall conform to the requirements of PG-11.
PEB-5.2 Seamless or welded shells, plates, or heads of electric boilers shall not be less than 3/16 in. (5 mm) in thickness.
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 mS/cm) [minimum specific resistivity of 1 megohm per cm (1 M¿/cm)], is clearly marked on the boiler in a visible location.
DESIGN
PEB-8 GENERAL
PEB-8.1 The rules in the following paragraphs apply specifically to the design of electric boilers and parts thereof. They shall be used in conjunction with the general requirements for design in Part PG, any applicable requirements in Part PMB for miniature boilers, and with the specific requirements for design in applicable Parts of this Section that apply to the method of fabrication used.
PEB-8.2 Responsibility of design of electric boilers to be marked with the “E" symbol shall be that of the holder of the “E" stamp.
PEB-9 WELDING
Electric boilers may be constructed by fusion welding in accordance with all the requirements of this Section except that postweld heat treatment, volumetric examination of the welded joints, and the nondestructive examinations described in PG-93.1 are not required when the limitations in PMB-2.1 are not exceeded.
PEB-10 INSPECTION OPENINGS
PEB-10.1 Electric boilers of a design employing a removable cover, or removable internal electric heating elements that will permit access for inspection, and cleaning and having an internal volume (exclusive of casing and insulation) of not more than 5 ft3 (0.14 m3) need not be fitted with washout or inspection openings.
PEB-10.2 Electric boilers of more than 5 ft3 (0.14 m3) not provided with a manhole, shall have an inspection opening or handhole located in the lower portion of the shell or head. The inspection opening shall not be smaller than NPS 3 (DN 80). In addition, electric boilers of the resistance heating element type designed for steam service shall have an inspection opening or handhole at or near the normal waterline.
PEB-11 FEEDWATER SUPPLY
PEB-11.1 The feedwater source to electric boilers shall be capable of meeting the applicable requirements of PG-61. Feedwater connections to an electric boiler shall not be smaller than NPS ½ (DN 15), except as permitted by PMB-11.
PEB-11.2 Electric boilers that do not exceed the diameter, volume, or pressure limits of PMB-2, may have the feedwater delivered through the blowoff opening if desired.
PEB-12 BLOWOFF
PEB-12.1 The blowoff piping for each electric boiler pressure vessel having a normal water content not exceeding 100 gal (380 L) is required to extend through only one valve.
PEB-12.2 The minimum size of blowoff pipes and fittings shall be NPS 1 (DN 25), except that for boilers of 200 kW input or less the minimum size of pipe and fittings may be NPS ¾
(DN 20). Electric boilers that do not exceed the diameter, volume, or pressure limits of PMB-2 may have blowoff connections in accordance with PMB-12.
PEB-13 WATER LEVEL INDICATORS
PEB-13.1 Electric boilers of the electrode type shall have at least one gage glass. The gage glass shall be located as to indicate the water levels both at startup and under maximum steam load conditions as established by the Manufacturer.
PEB-13.2 Electric boilers of the resistance element type shall have at least one gage glass. The lowest visible water level in the gage glass shall be at least 1 in. (25 mm) above the lowest permissible water level as determined by the Manufacturer. Each electric boiler of this type shall also be equipped with an automatic low-water cutoff on each boiler pressure vessel so located as to automatically cut off the power supply to the heating elements before the surface of the water falls below the visible level in the gage glass.
PEB-13.3 Tubular gage glasses on electric boilers shall be equipped with protective rods or shields.
PEB-14 PRESSURE GAGES
Pressure gages shall meet the requirements of PG-60.6.
PEB-15 PRESSURE RELIEF VALVES
PEB-15.1 Each electric boiler shall have at least one pressure relief valve. Electric boilers with a power input more than 1,100 kW shall have two or more pressure relief valves.
PEB-15.2 The minimum pressure relief valve relieving capacity for electric boilers shall be 3 ½ lb/hr/kW (1.6 kg/hr/kW) input. The pressure setting shall not be higher than the MAWP stamped on the completed boiler (see PEB-18.3.2).
PEB-15.3 Pressure relief valves shall be mounted in accordance with PG-71.2 with the spindle vertical. Electric boilers that do not exceed the diameter, volume, or pressure limits of PMB-2, may have a pressure relief valve(s) installed in other than the vertical position, provided that
(a) the valve design is satisfactory for such position
(b) the valve is not larger than NPS ¾ (DN 20)
(c) the maximum angle of deviation from vertical does not exceed 30 deg
(d) the nozzle location is such that no material that could interfere with the operation of the valve can accumulate at the valve inlet
(e) the discharge opening of the valve body and discharge piping is oriented so that drainage is adequate
PEB-16 AUTOMATIC DEVICES
Electric boilers shall be provided with pressure and/or temperature controls and an automatic low-water fuel cutoff. No low-water cutoff is required for electrode type boilers.
PEB-17 HYDROSTATIC TEST
PEB-17.1 Each electric boiler pressure vessel shall be hydrostatically tested at completion of fabrication in accordance with PG-99 or PMB-21, as applicable.
PEB-17.2 In addition to the above, after assembly of the boiler pressure vessel and the mechanically assembled boiler external piping and trim, the completed electric boiler shall be given a final hydrostatic test at a pressure not less than 1 ½
times the MAWP of the pressure vessel. Miniature electric boilers that are trimmed to operate at less than the MAWP of the pressure vessel shall be given a hydrostatic test at a pressure not less than the safety valve setting.
PEB-17.3 When the electric boiler is to be marked with the “E" symbol, the symbol shall be applied after completion of the hydrostatic test of PEB-17.2.
PEB-18 INSPECTION AND STAMPING OF
BOILERS
PEB-18.1 Inspection of electric boilers shall be as required by PG-90.1 and PG-90.3. Witness by the Authorized Inspector of the hydrotest required in PEB-17.2 for the completed boiler may be omitted for electric boilers that meet all the following limitations:
(a) 800 kW maximum per vessel
(b) 600 V maximum
(c) mechanically assembled boiler external piping (BEP) only
When the Authorized Inspector does not perform a final inspection of the completed boiler, the Manufacturer or Assembler shall make an equivalent examination. The equivalent examination shall be in accordance with a quality control procedure meeting the requirements of PEB-18.2 and PEB-18.5.
PEB-18.1.1 Electric boilers exceeding the size limitations specified in PEB-18.1, and having only mechanically assembled external piping (BEP) and trim, shall have a final inspection by the Authorized Inspector, who shall also witness the hydrostatic test called for in PEB-17.2.
PEB-18.1.2 For electric boilers having welded or brazed boiler external piping (BEP) or trim, the inspection requirements of PG-90.1 and the hydrostatic test requirements of PG-99 apply.
PEB-18.2 Each electric boiler Manufacturer shall comply with the applicable requirements of PG-104 and PG-105.
PEB-18.2.1 An electric boiler Manufacturer or Assembler applying for or renewing the “E" stamp shall have its facilities and organizations subject to a joint review by its Authorized Inspection Agency and the legal jurisdiction involved (see last paragraph of PG-105.4).
PEB-18.2.2 A Manufacturer or Assembler holding an “E" stamp and assembling units where the final shop inspection is not mandatory (see PEB-18.1), shall be subject to periodic review by its Authorized Inspection Agency. The review shall be conducted on a quarterly basis or more frequently if deemed necessary by the Authorized Inspection Agency. The frequency of this review may be reduced subject to written agreement between the Manufacturer or Assembler and its inspection agency and the written approval of the appropriate legal jurisdiction. However, in no case shall the review be less than once every 6 months.
PEB-18.3 The stamping of electric boilers shall conform to the requirements of PG-106. Completed electric boilers shall be marked with the “S" or “M" symbol by the Manufacturer of the boiler pressure vessel except when the boiler pressure vessel is constructed under the provisions of PEB-3 (see PEB-18.4). When the trim, fixtures and fittings (such as valves), threaded boiler external piping, and appurtenances are connected to an electric boiler by a Manufacturer or Assembler not authorized to apply the “S" or “M" stamp, the boiler assembler shall apply an “E" stamp to the completed assembly. “E" stamp holders are limited to the use of assembly methods that do not require welding or brazing.
PEB-18.3.1 The stamping of the boiler pressure vessel shall be located as called for in PG-111.8 and need not indicate the kW input or the maximum designed steaming capacity.
