FABRICATION
PG-75 GENERAL
The fabrication of boilers and parts thereof shall conform to the general fabrication requirements in the following paragraphs and in addition to the specific requirements for fabrication in the Parts of this Section that pertain to the methods of construction used.
PG-76 CUTTING PLATES AND OTHER STOCK
PG-76.1 Plates may be cut by machining, punching, shearing, or cutting by the electric arc or gas process, providing enough metal is left at any unfinished edges to meet the requirements of PG-79.
PG-76.2 When end faces of nozzle or manhole necks are to remain unwelded in the completed vessel, these end faces shall not be cut by shearing unless at least 1/8 in. (3 mm) of additional metal is removed by any method that will produce a smooth finish.
PG-91 QUALIFICATION OF INSPECTORS
The inspection required by this Section shall be by an Inspector employed by an ASME accredited Authorized Inspection Agency,
12 that is, the inspection organization of a state or municipality of the United States, a Canadian province, or of an insurance company authorized to write boiler and pressure vessel insurance. These Inspectors shall have been qualified by written examination under the rules of any state of the United States or province of Canada which has adopted the Code.
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PG-93 INSPECTION AND REPAIR OF FLAT PLATE IN CORNER JOINTS
PG-93.1 When flat plate greater than ½
in. (13 mm) thickness is welded to other pressure parts to form a corner joint, such as in flat heads [Fig. PG-31, illustrations (g), (i-1), and (i-2)], waterlegs of firebox boilers or combustion chambers of wetback boilers [Fig. A-8, illustrations (l), (m), (n), and (p)], and the exposed edges of the plate are closer to the edge of the weld than a distance equal to the thickness of the plate, the peripheral plate edges and any remaining edges and any remaining exposed surface of the weld joint preparation shall be examined after welding by either the magnetic particle or liquid penetrant method. When the plate is nonmagnetic, only the liquid penetrant method shall be used. The requirements of this paragraph shall not apply to those joints when 80% or more of the pressure load is carried by tubes, stays, or braces, or when the exposed edges of the plate are farther from the edge of the weld than a distance equal to the thickness of the plate.
PG-93.2 Laminations, cracks, or other imperfections found during the examination required by PG-93.1 that would affect the safety of the vessel shall be repaired in accordance with PG-78. The imperfection(s) may be pursued by any suitable method (grinding, chipping, etc.). The repaired area shall be subjected to the same examination that first revealed the imperfection.
PG-93.3 Methods and acceptance criteria for magnetic particle and liquid penetrant examination shall be in accordance with A-260 or A-270, respectively.
PG-99 HYDROSTATIC TEST
Hydrostatic testing of the completed boiler unit shall be conducted in accordance with the following requirements:
After a boiler has been completed (see PG-104), it shall be subjected to pressure tests using water at not less than ambient temperature, but in no case less than 70°F (20°C). Where required, test pressures are specified in this paragraph; whether minimum or maximum pressures, they apply to the highest point of the boiler system. When the boiler is completed in the Manufacturer's shop without boiler external piping, subsequent hydrostatic testing of the boiler external piping shall be the responsibility of any holder of a valid “S," “A," or “PP" stamp. The safety valves need not be included in the hydrostatic test. The tests shall be made in two stages in the following sequence:
PG-99.1 Hydrostatic pressure tests shall be applied by raising the pressure gradually to not less than 1 ½ times the maximum allowable working pressure as shown on the data report to be stamped on the boiler. No part of the boiler shall be subjected to a general membrane stress greater than 90% of its yield strength (0.2% offset) at test temperature. The primary membrane stress to which boiler components are subjected during hydrostatic test shall be taken into account when designing the components. Close visual inspection for leakage is not required during this stage.
PG-99.2 The hydrostatic test pressure may then be reduced to the maximum allowable working pressure, as shown on the Data Report, to be stamped on the boiler and maintained at this pressure while the boiler is carefully examined. The metal temperature shall not exceed 120°F (50°C) during the close examination.
PG-99.3 A completed forced-flow steam generator with no fixed steam and waterline, having pressure parts designed for different pressure levels along the path of water-steam flow, shall be subjected to a hydrostatic pressure test by the above procedure (PG-99.1 and PG-99.2) based upon:
PG-99.3.1 For the first stage test (PG-99.1) a hydrostatic test pressure of not less than 1 ½ times the maximum allowable working pressure at the superheater outlet as shown in the master stamping (PG-106.3) but no less than 1 ¼ times the maximum allowable working pressure of any part of the boiler, excluding the boiler external piping.
PG-99.3.2 For the second stage test (PG-99.2) the hydrostatic test pressure may be reduced to not less than the maximum allowable working pressure at the superheater outlet.
PG-99.4 Test Gages
PG-99.4.1 An indicating gage, visible to the operator controlling the pressure applied, shall be connected to the pressure parts. Hydrostatic head on the gage shall be considered such that the required test pressure is achieved at the top of the boiler.
PG-99.4.2 Dial pressure gages used in testing shall preferably have dials graduated over their entire range of about double the intended maximum test pressure, but in no case shall the range be less than 1 ½ times that pressure. The spacing between graduations shall be such that the inspector and the operator controlling the test shall be able to determine when the required test pressure has been applied. Digital pressure gages having a wider range of pressure readings may be used provided the readings give the same or greater degree of accuracy as obtained with dial pressure gages.
PG-100 HYDROSTATIC DEFORMATION TEST
Where no rules are given and it is impossible to calculate with a reasonable degree of accuracy the strength of a boiler structure or any part thereof, a full-sized sample shall be built by the Manufacturer and tested in accordance with the Standard Practice for Making a Hydrostatic Test on a Boiler Pressure Part to Determine the Maximum Allowable Working Pressure, given in A-22 or in such other manner as the Committee may prescribe.
CERTIFICATION BY STAMPING AND DATA REPORTS
PG-101 HEATING SURFACE COMPUTATION
PG-101.1 For the stamping required by PG-106, the heating surface shall be computed as specified in PG-101.1.1 through PG-101.1.3.
PG-101.1.1 Heating surface, as part of a circulating system in contact on one side with water or wet steam being heated and on the other side with gas or refractory being cooled, shall be measured on the side receiving heat.
PG-101.1.2 Boiler heating surface and other equivalent surface outside the furnace shall be measured circumferentially plus any extended surface.
PG-101.1.3 Waterwall heating surface and other equivalent surface within the furnace shall be measured as the projected tube area (diameter x length) plus any extended surface on the furnace side. In computing the heating surface for this purpose, only the tubes, fireboxes, shells, tubesheets, and the projected area of headers need to be considered, except that for vertical firetube steam boilers only that portion of the tube surface up to the middle of the gage glass is to be computed.
PG-104 GENERAL
PG-104.1 The completed boiler unit includes all piping and piping components as defined in the Introduction.
The Manufacturer [see Note (1) below] of any complete boiler unit to be stamped with the Code symbol has the responsibility of assuring through proper Code certification that all work performed by him or others responsible to him complies with all requirements of the Code, including design, construction, materials, and workmanship. With the exception of field installed boiler external piping, when some portions of a complete boiler unit are supplied by, or Code work is performed by others not responsible to the Manufacturer, the Manufacturer has the duty of obtaining from these other organizations their proper Code certification, covering such portions of work.
When the Manufacturer furnishes a shop assembled boiler that is complete except for boiler external piping, and the boiler has been hydrostatically tested in the shop and properly stamped with the Manufacturer's “S" symbol, the subsequent installation in the field of the external piping within the scope of Section I is not by itself considered “field assembly of the boiler" [see Note (2) below].
No Manufacturer or assembler may accept Code responsibility for work that falls within the scope of the Code, that is performed by workmen employed by any other organization, except through proper Code certification. The responsibilities set forth herein relate only to Code compliance and are not to be construed as involving contractual relations or legal liabilities.
NOTES: (1) Boiler Manufacturer or Manufacturer as used in PG-104 or other paragraphs referenced to this Note may also be an Engineering Contractor organization with or without fabricating facilities, but having the capability of providing a design specification that establishes the pressure and temperature conditions for each component of a complete boiler unit and of assembling the fabricated parts in the field with authorization from the Society to use the Code symbol stamp “S" in accordance with the Code provisions in PG-105.3.
(2) When boiler external piping within the scope of Section I is furnished by other than the boiler Manufacturer, the boiler Manufacturer is not responsible for the Code certification of such piping. The organizations that furnish and that install such external piping by welding shall furnish proper Code certification (PG-104.2) for such piping including Manufacturers' Data Report Form P-4A as required by PG-112.2.5 and PG-112.3.
PG-104.2 Proper Code certification refers to the furnishing of stamping and Data Reports as evidence to establish the following.
PG-104.2.1 The organization that performed that portion of the work held an appropriate Certificate of Authorization.
PG-104.2.2 By signing and furnishing the appropriate data report, that organization certified compliance with Code rules for that portion of the work.
PG-104.2.3 By proper use of the Code symbol stamp, that organization identified the portions of the work covered by its Data Report Form.
PG-104.2.4 By countersignature on the same Data Report a qualified Inspector confirmed that portion of the work complied with applicable Code rules.
PG-105 CODE SYMBOL STAMPS
PG-105.1 Authorization. Except as permitted in PG-105.5, no organization may assume responsibility for Code construction without having first received from the ASME a Certificate of Authorization to use one of the Code symbol stamps shown in Figs. PG-105.1 through PG-105.4. There are six such stamps, defined as follows:
(a) S - power boiler symbol stamp (see Fig. PG-105.1)
(b) M – miniature boiler symbol stamp (see Fig. PG-105.1)
(c) E – electric boiler symbol stamp (see Fig. PG-105.1)
(d) A – boiler assembly symbol stamp (see Fig. PG-105.2)
(e) PP – pressure piping symbol stamp (see Fig. PG-105.3)
(f) V – safety valve symbol stamp (see Fig. PG-105.4)
Stamps for applying the Code symbol shall be obtained from the Society. Each boiler, superheater, waterwall, economizer, or boiler part to which a Code symbol is to be applied shall be fabricated by a Manufacturer who is in possession of an appropriate Code symbol stamp. A Certificate of Authorization to use the Code symbol “S," “M," “E," “A," “PP," or “V" stamp will be granted by the Society pursuant to the provisions of these paragraphs.
PG-109 STAMPING OF PRESSURE PIPING
PG-109.1 Boiler external piping, as defined in the Introduction, may be fabricated by a manufacturer other than the Manufacturer of the boiler, provided that the manufacturer has been issued a Certificate of Authorization to use the “S" or “PP" symbol stamp. Boiler external piping may be installed by welding by a manufacturer or contractor other than the Manufacturer of the boiler, provided such an organization has been issued a Certificate of Authorization to use the “S," “PP," or “A" symbol stamp. When boiler external piping is installed by welding, the welding, including the qualification of welding procedures, welders, and welding operators, shall be done in accordance with the applicable rules of ASME B31.1. The welding shall be inspected by an Authorized Inspector at such stages of the work as he may elect. The organizations which fabricate or install such piping shall furnish proper code certification (PG-104.2) for it including a Manufacturer's Data Report Form P-4A as required by PG-112.2.5 and PG-112.3.
PG-109.2 Welded boiler external piping included within the scope of this Code, over NPS 2 (DN 50), shall be stamped with a Code symbol, together with the manufacturer's or contractor's name and serial number. Such stamping shall be on the pipe, valve or fitting adjacent to the welded joint farthest from the boiler. For piping operating at temperatures above 800o F (425o C) the symbol may be stamped on a nameplate that is irremovably attached by welding, provided such welding is postweld heat treated, or on a circular metal band at least ¼ in. (6 mm) thick. This band around the pipe shall be secured in such a manner as to prevent it from slipping off during handling and installation.
Welded piping NPS 2 (DN 50) or less included within the scope of this Code shall be marked with an identification acceptable to the Inspector and traceable to the required Data Report. Such marking shall be of a type that will remain visible until the piping has been installed.
PG-109.3 A manufacturer in possession of the pressure piping symbol stamp may
(a) design and fabricate welded piping. Such fabrications shall be stamped and reported on a Form P-4A, Manufacturer's Data Report for Fabricated Piping, as called for in PG-112.2.5.
(b) fabricate other parts of boilers, such as superheater, waterwall, or economizer headers, where complete design requirements are provided by others. Such parts shall be stamped or marked as required by PG-106.8 and reported on a Form P-4, Manufacturer's Partial Data Report, as called for in PG-112.2.4.
PG-109.4 Mechanically assembled boiler external piping which contains no pressure boundary welds does not require stamping, and as such may be assembled by a non-stamp holder. Note that the responsibility for documentation and hydrostatic testing of a mechanically assembled boiler external piping must be assumed by a holder of a valid “S," “A," or “PP" stamp (see PG-112.2.5).
PG-110 STAMPING OF BOILER PRESSURE
RELIEF VALVES
Each pressure relief valve shall be plainly marked with the required data by the Manufacturer or Assembler (see PG-73.4.4) in such a way that the marking will not be obliterated in service. The marking shall be placed on the valve or on a nameplate securely fastened to the valve. The Code "V" symbol shall be stamped on the valve or nameplate by the Manufacturer or Assembler, as applicable. The other required data may be stamped, etched, impressed, or cast on the valve or nameplate. For units other than those included below, see PG-4. The marking shall include the following:
(a) the name (or an acceptable abbreviation) of the Manufacturer and Assembler, as applicable
(b) Manufacturer's design or type number
(c) NPS (DN) (the nominal pipe size of the valve inlet)
(d) set pressure __ psi (MPa)
(e) Capacity
(1) capacity __ lb/hr (kg/hr) (for saturated steam service in accordance with PG-69.2) or
(2) capacity __ lb/hr (kg/hr) at __ °F (°C) (for superheated steam service in accordance with PG-68.7 or supercritical steam service in accordance with PG-69.2.3) or
(3) capacity __ gal/min (l/min) at 70
°F (20
°C) and lb/hr (kg/hr) steam for economizer service in accordance with PG-69.2
(f) year built, or alternatively, a coding may be marked on the valve such that the valve Manufacturer or Assembler can identify the year the valve was assembled and tested
(g) ASME symbol as shown in Fig. PG-105.4
(h) The pilot of a pilot-operated pressure relief valve shall be plainly marked by the Manufacturer or Assembler showing the name of the Manufacturer, the Manufacturer's design or type number, the set pressure in pounds per square inch (MPa), and the year built, or alternatively, a coding that the Manufacturer can use to identify the year built.
PG-111 LOCATION OF STAMPINGS
The location of the required stampings shall be as listed below. These stampings shall be left uncovered or an easily removable marked cover may be provided over the stamping when a boiler is covered with insulation, or jacketed. No piping, boiler appliance, or other obstructions shall interfere with reading of the stamping.
PG-111.1 Horizontal-return tubular boilers – on the front head above the central rows of tubes.
PG-111.2 Horizontal-flue boilers – on the front head above the flues.
PG-111.3 Traction, portable, or stationary boilers of the locomotive type or Star watertube boilers – on the furnace end above the handhole. Or on traction boilers of the locomotive type – on the left wrapper sheet forward of the driving wheel.
PG-111.4 Vertical firetube and vertical submerged tube boilers – on the shell above the firedoor and handhole opening.
PG-111.5 Watertube Boilers
PG-111.5.1 Drum type – on a head of the steam outlet drum near and above the manhole.
PG-111.5.2 Forced-flow steam generator with no fixed steam and waterline – the master stamping (PG-106.3) shall be located on a major pressure part, located near the main operating floor where readily visible. The Data Report Form shall record the location of the master stamping.
PG-111.6 Scotch marine boilers – on either side of the shell near the normal water level line and as near as practical to the front tubesheet.
PG-111.7 Economic boilers – on the front head, above the center row of tubes.
PG-111.8 Miniature and electric boilers – on some conspicuous and accessible place on the boiler proper, or on a stamping plate at least 3/64 in. (1.2 mm) thick, permanently fastened (adhesives prohibited) to the boiler.
PG-111.9 On any of the above types where there is not sufficient space in the place designated, and for other types and new designs – in a conspicuous place on the boiler proper. The Data Report Form shall record the location of the required stamping.
