Unfired steam boilers shall be constructed under the provisions of Section I or Section VIII.
Expansion tanks connected to high-temperature water boilers without intervening valves shall be constructed to the requirements of Section I or Section VIII.
A pressure vessel in which an organic fluid is vaporized by the application of heat resulting from the combustion of fuel (solid, liquid, or gaseous) shall be constructed under the provisions of Section I. Vessels in which vapor is generated incidental to the operation of a processing system, containing a number of pressure vessels such as used in chemical and petroleum manufacture, are not covered by the rules of Section I.
GENERAL REQUIREMENTS FOR ALL
METHODS OF CONSTRUCTION
The requirements of Part PG apply to power boilers and high pressure, high-temperature water boilers and to parts and appurtenances thereto and shall be used in conjunction with the specific requirements in the applicable Parts of this Section that pertain to the methods of construction used.
PG-2 SERVICE LIMITATIONS
PG-2.1 The rules of this Section are applicable to the following services:
(a) boilers in which steam or other vapor is generated at a pressure of more than 15 psig (100kPa)
(b) high-temperature water boilers intended for operation at pressures exceeding 160 psig (1.1 MPa) and/or temperatures exceeding 250°F (120°C)
PG-2.2 For services below those specified in PG-2.1 it is intended that rules of Section IV apply; however, boilers for such services may be constructed and stamped in accordance with this Section provided all applicable requirements are met.
PG-2.3 Coil-type hot water boilers where the water can flash into steam when released directly to the atmosphere through a manually operated nozzle may be exempted from the rules of this Section provided the following conditions are met:
(a) There is no drum, header, or other steam space.
(b) No steam is generated within the coil.
(c) Tubing outside diameter does not exceed 1 in. (25 mm).
(d) Pipe size does not exceed NPS ¾ (DN 20).
(e) Nominal water capacity does not exceed 6 gal (23 L).
(f) Water temperature does not exceed 350°F (175°C).
(g) Adequate safety relief valves and controls are provided.
PG-3 REFERENCED STANDARDS
Specific editions of standards referenced in this Section are shown in A-360.
Either U.S. Customary units or SI units may be used for compliance with all requirements of this edition, but one system shall be used consistently throughout for all phases of construction.
Either the U.S. Customary units or SI units that are listed in Mandatory Appendix II are identified in the text, or are identified in the nomenclature for equations, shall be used consistently for all phases of construction (e.g., materials, design, fabrication, and reports). Since values in the two systems are not exact equivalents, each system shall be used independently of the other without mixing U.S. Customary units and SI units.
When SI units are selected, U.S. Customary values in referenced specifications that do not contain SI units shall be converted to SI values to at least three significant figures for use in calculations and other aspects of construction.
PG-5.1 Except as otherwise permitted in PG-8.2, PG-8.3, PG-10, and PG-11, material subject to stress due to pressure shall conform to one of the specifications given in Section II and shall be limited to those that are listed in the Tables of Section II, Part D. The manufacturer shall ensure that the correct material has been received and is properly identified before proceeding with construction (see A-302.4). Materials shall not be used at temperatures above those for which stress values are limited, for Section I construction, in the Tables of Section II, Part D. Specific additional requirements described in PG-5 through PG-13 shall be met as applicable.
PG-5.2 Material covered by specifications in Section II is not restricted as to the method of production unless so stated in the specification, and as long as the product complies with the requirements of the specification.
PG-5.3 If, in the development of the art of boiler construction, it is desired to use materials other than those herein described, data should be submitted to the Boiler and Pressure Vessel Committee in accordance with the requirements of Appendix 5 of Section II, Part D. Material not completely identified with any approved Code specifications may be used in the construction of boilers under the conditions outlined in PG-10.
PG-5.4 Size Limits and Tolerances
PG-5.4.1 Materials outside the limits of size or thickness given in the title or scope clause of any specification in Section II may be used if the material is in compliance with the other requirements of the specification, and no similar limitation is given in the rules for construction.
PG-5.4.2 Pipe having a tolerance of ±1% on either the O.D. or the I.D. rather than the tolerance specified in the material specification, may be used, provided the material complies with all other requirements of the specifications. When used under external pressure, such pipe shall be limited to a maximum of 24 in. (600 mm) in diameter. The pipe shall include the designation 1% O.D. or 1% I.D., as appropriate, in any required documentation and marking of the material.
The use of austenitic alloy steel is permitted for boiler pressure parts that are steam touched in normal operation. Except as specifically provided in PG-9.1.1, PG-12, and PEB-5.3, the use of such austenitic alloys for boiler pressure parts that are water wetted in normal service is prohibited.7
- See PDF for table
7 Austenitic alloys are susceptible to intergranular corrosion and stress corrosion cracking when used in boiler applications in water wetted service. Factors that affect the sensitivity to these metallurgical phenomena are applied or residual stress and water chemistry. Susceptibility to attack is usually enhanced by using the material in a stressed condition with a concentration of corrosive agents (e.g., chlorides, caustic, or reduced sulfur species). For successful operation in water environments, residual and applied stresses must be minimized and careful attention must be paid to continuous control of water chemistry.
PG-5.6 P-No. 15E, Group 1 Materials
PG-5.6.1 If during any phase of manufacturing or erection any portion of the component that does not contain a weld is heated to a temperature greater than 1,470°F (800
°C), one of the following actions shall be performed:
(a) The component shall be reaustenitized and retempered in its entirety in accordance with the specification requirements.
(b) That portion of the component heated above 1,470°F (800°C), including the heat-affected zone created by the local heating, must be replaced or must be removed, reaustenitized, and retempered in accordance with the specification requirements and then replaced in the component.
(c) If the allowable stress values to be used are less than or equal to those provided in Table 1A of Section II, Part D for Grade 9 (e.g., SA-213 T9, SA-335 P9, or equivalent product specifications) at the design temperature, then the requirements stated above may be waived, provided that the portion of the component heated above 1,470°F (800°C) is retempered in accordance with the specification requirements. The use of this provision shall be noted on the Manufacturer's Data Report.
PG-5.6.2 If during any phase of manufacturing or erection of the component, any portion that does contain a weld is heated above 1,425°F (775°C), then the requirements of Notes (3) and (4) of Table PW-39 for P-No. 15E, Group 1 Materials, shall apply for reheat treatment.
PG-6.1 Steel plates for any part of a boiler subject to pressure, whether or not exposed to the fire or products of combustion shall be of pressure vessel quality in accordance with one of the following specifications:
SA-202 Pressure Vessel Plates, Alloy Steel, Chromium-Manganese-Silicon
SA-204 Pressure Vessel Plates, Alloy Steel, Molybdenum
SA-240 (Type 405 only) Pressure Vessel Plates, Alloy Steel (Ferritic Stainless), Chromium
SA-285 Pressure Vessel Plates, Carbon Steel, Low-and Intermediate-Tensile Strength
SA-299 Pressure Vessel Plates, Carbon Steel, Manganese-Silicon
SA-302 Pressure Vessel Plates, Alloy Steel, Manganese-Molybdenum and Manganese-Molybdenum-Nickel
SA-387 Pressure Vessel Plates, Alloy Steel, Chromium-Molybdenum
SA-515 Pressure Vessel Plates, Carbon Steel, for Intermediate- and Higher-Temperature Service
SA-516 Pressure Vessel Plates, Carbon Steel, for Moderate- and Lower-Temperature Service
SA/AS 1548 Steel Plates for Pressure Equipment
SA/EN-10028-2 Flat Products Made of Steels for Pressure Purposes
SA/JIS G3118 Carbon Steel Plates for Pressure Vessels for Intermediate and Moderate Temperature Service
PG-55 SUPPORTS AND ATTACHMENT LUGS
PG-55.1 Lugs or hangers when used to support a boiler of any type shall be properly fitted to the surfaces to which they are attached.
PG-55.2 Lugs, hangers, or brackets may be attached by fusion welding provided the welding meets the requirements of Part PW, including stress relieving but omitting volumetric examination and provided they are attached by full penetration welds, combination groove and fillet welds, or by fillet welds along the entire periphery or contact edges. Some acceptable forms of welds for lugs, hangers, or brackets are shown in Fig. PW-16.2. The materials for lugs, hangers, or brackets are not limited to those listed in Tables 1A and 1B of Section II, Part D, but shall be of weldable quality. The allowable load on the fillet welds shall equal the product of the weld area based on minimum leg dimension, the allowable stress value in tension of the material being welded, and the factor 0.55. When using welded pipe, the stress values given in Table 1A of Section II, Part D, may be increased to that of the basic material by eliminating the stated weld efficiencies.