ANSI NB 23 (NBIC) PART 4-2017 National Board Inspection Code - Part 4 Pressure Relief Devices.pdf

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10、NB-23NATIONAL BOARD INSPECTION CODE 2017 EDITION DATE OF ISSUE JULY 1, 2017This code was developed under procedures accredited as meeting the criteria for American National Stan-dards. The Consensus Committee that approved the code was balanced to ensure that individuals from com-petent and concerne

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15、hat preclude the issuance of interpretations by individual committee members. The footnotes in this document are part of this American National Standard.RRNRRR The above National Board symbols are registered with the US Patent Office. “National Board” is the abbreviation for The National Board of Bo

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17、 Vessel Code, Sections I, IV, VIII, and X are used with the permission of the American Society of Mechanical Engineers. All Rights Reserved.Library of Congress Catalog Card No. 52-44738 Printed in the United States of America All Rights Reservedwww.nationalboard.orgCopyright 2017 byTHE NATIONAL BOAR

18、D OF BOILER Part 2, Inspection; and Part 3, Repairs and Alterations.The NBIC Committees function is to establish rules of safety governing post-construction activities for the installation, inspection, and repair and alteration of pressure-retaining items, and to interpret these rules when questions

19、 arise regarding their intent. In formulating the rules, the NBIC Committee considers the needs and concerns of individuals and organizations involved in the safety of pressure-retaining items. The objective of the rules is to afford reasonably certain protection of life and property, so as to give

20、a reasonably long, safe period of usefulness. Advancements in design and material and the evidence of experience are recognized.The rules established by the NBIC Committee are not to be interpreted as approving, recommending, or en-dorsing any proprietary or specific design, or as limiting in any wa

21、y an organizations freedom to choose any method that conforms to the NBIC rules.The NBIC Committee meets regularly to consider revisions of existing rules, formulation of new rules, and respond to requests for interpretations. Requests for interpretation must be addressed to the NBIC Secretary in wr

22、iting and must give full particulars in order to receive Committee consideration and a written reply. Pro-posed revisions to the code resulting from inquiries will be presented to the NBIC Committee for appropriate action.Proposed revisions to the code approved by the NBIC Committee are submitted to

23、 the American National Standards Institute and published on the National Board web-site to invite comments from all interested per-sons. After the allotted time for public review and final approval, the new edition is published. The Foreword, Introduction, Personnel and Index Sections of the NBIC ar

24、e provided for guidance and informational purposes only and shall not be considered a part of the Code. Theses sections are not approved by the NBIC Commit-tee or submitted to the American National Standards Institute.Organizations or users of pressure-retaining items are cautioned against making us

25、e of revisions that are less restrictive than former requirements without having assurance that they have been accepted by the Jurisdic-tion where the pressure-retaining item is installed.The general philosophy underlying the NBIC is to parallel those provisions of the original code of construc-tion

26、, as they can be applied to post-construction activities. The NBIC does not contain rules to cover all details of post-construction activities. Where complete details are not given, it is intended that individuals or organizations, subject to the acceptance of the Inspector and Jurisdiction when app

27、licable, provide details XINB-23 2017FOREWARDfor post-construction activities that will be as safe as otherwise provided by the rules in the original code of construction.Activities not conforming to the rules of the original code of construction or the NBIC must receive specific approval from the J

28、urisdiction, who may establish requirements for design, construction, inspection, testing, and documentation.There are instances where the NBIC serves to warn against pitfalls; but the code is not a handbook, and can-not substitute for education, experience, and sound engineering judgment. It is int

29、ended that this edition of the NBIC not be retroactive. Unless the Jurisdiction imposes the use of an earlier edition, the latest effective edition is the governing document.XIINATIONAL BOARD INSPECTION CODE2017PERSONNELPERSONNEL The National Board of Boiler and Pressure Vessel Inspectors Board of T

30、rusteesJ. Burpee ChairmanJ. Amato First Vice ChairmanD. Cook Second Vice ChairmanC. Cantrell Member at LargeE. Creaser Member at LargeA. Oda Member at LargeM. Washington Member at LargeD. Douin Secretary/TreasurerAdvisory CommitteeJ. Pillow Representing welding industriesC. Hopkins Representing Nati

31、onal Board stamp holders H. Richards Representing boiler and pressure vessel usersB. Berquist Representing pressure vessel manufacturersR. Wielgoszinski Representing authorized inspection agencies (insurance companies)P. Molvie Representing boiler manufacturersXIII2017PERSONNELNB-23National Board Me

32、mbersAlabama Marvin ByrumAlaska Kenneth LaneArizona Randall AustinArkansasDennis HannonCalifornia .Donald CookColorado . Steve NelsonDelaware .John EschFlorida . Andrew FrazierGeorgia Benjamin CrawfordHawaii Julius Dacanay Illinois. Michael VogelIndiana . Larry ParkeyKansas.Robert StimsonKentucky .M

33、ark JordanLouisiana .Joseph LeSageMaine . John BurpeeMaryland Karl KraftMassachusetts. Edward KawaMichigan David StenroseMinnesota .Joel AmatoMississippi William AndersonMissouri .Ronald Brockman Nebraska . Christopher B. CantrellNevada . David SandfossNew Hampshire Darrell MalloryNew Jersey . Milto

34、n WashingtonNew York .Matthew SansoneNorth Carolina Clifford DautrichNorth Dakota Trevor SeimeOhio . John SharierOklahoma Thomas GrannemanOregon Mark PerduePennsylvania Nathaniel SmithSouth Carolina Ronald W. SpikerSouth Dakota .Aaron LorimorTennessee Sam ChapmanTexas .Rob TrouttUtah Rick SturmVirgi

35、nia . Edward HiltonWashington . Tony OdaWest Virginia John PorcellaWisconsin Terrence WaldbilligChicago, IL .Michael RyanDetroit, MI Cortney JacksonLos Angeles, CA . Cirilo ReyesMilwaukee, WI Jillian KlugNew York, NY William McGivneySeattle, WA Larry LeetAlberta Michael PoehlmannBritish Columbia .An

36、thony SchollManitoba Ryan DeLuryNew Brunswick Eben CreaserNewfoundland and if found insufficient, additional relieving capacity shall be provided:1) By performing an accumulation test, that is, by shutting off all other steam discharge outlets from the boiler and forcing the fires to the maximum. Th

37、is method should not be used on a boiler with a superheater or reheater or on a high-temperature water boiler.2) By measuring the maximum amount of fuel that can be burned and computing the corresponding evaporative capacity upon the basis of the heating value of the fuel.3) By determining the maxim

38、um evaporative capacity by measuring the feedwater. The sum of the pressure relief valve capacities marked on the valves shall be equal to or greater than the maxi-mum evaporative capacity of the boiler. This method should not be used on high-temperature water boilers.5NATIONAL BOARD INSPECTION CODE

39、2017SECTION 2SECTION 2TABLE 2.2.4.1 MINIMUM POUNDS OF STEAM PER HOUR PER SQUARE FOOT OF HEATING SURFACE LB STEAM/HR FT2(KG STEAM/HR M2)Firetube Boiler Watertube BoilerBoiler Heating Surface Hand-fired 5 (24) 6 (29)Stoker-fired 7 (34) 8 (39)Oil, gas, or pulverized fuel-fired 8 (39) 10 (49)Waterwall H

40、eating Surface Hand-fired 8 (39) 8 (39)Stoker-fired 10 (49) 12 (59)Oil, gas, or pulverized coal 14 (68) 16 (78)Copper-finned WatertubesHand-fired 4 (20)Stoker-fired 5 (24)Oil, gas, or pulverized fuel-fired 6 (29)Notes: When a boiler is fired only by a gas having a heat value not in excess of 200 Btu

41、/ft3(7.5MJ/m3), the minimum relieving capacity should be based on the values given for hand-fired boilers above. The heating surface shall be computed for that side of the boiler surface exposed to the products of combustion, exclusive of the superheating surface. In computing the heating surface fo

42、r 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 gage cock is to be computed. For firetube boiler units exceeding 8000 Btu/ft2(

43、9085 J/cm2) (total fuel Btu (J) Input divided by total heating surface), the factor from the table will be increased by 1 (4.88) for every 1000 Btu/ft.2(1136 J/cm2) above 8000 Btu/ft.2(9085 J/cm2) For units less than 7000 Btu/ft2(7950 J/cm2), the factor from the table will be decreased by 1 (4.88).

44、For watertube boiler units exceeding 16000 Btu/ft2(18170 J/cm2)(total fuel Btu input divided by the total heating surface) the factor from the table will be increased by 1 (4.88) for every 1000 Btu/ft.2(1136 J/cm2) above 16000 Btu/ft.2(18170 J/cm2). For units with less than 15000 Btu/ft.2(17034 J/cm

45、2), the factor in the table will be decreased by 1 (4.88) for every 1000 Btu/ft.2 (1136 J/cm2) below 15000 Btu/ft.2 (17034 J/cm2).2.2.5 SET PRESSUREOne or more pressure relief valves on the boiler proper shall be set at or below the maximum allowable working pressure. If additional valves are used,

46、the highest pressure setting shall not exceed the maximum allowable working pressure by more than 3%. The complete range of pressure settings of all the pressure relief valves on a boiler shall not exceed 10% of the highest pressure to which any valve is set. Pressure setting of pressure relief valv

47、es on high temperature water boilers may exceed this 10% range.62017SECTION 2SECTION 2NB-232.2.6 FORCED-FLOW STEAM GENERATORSFor a forced-flow steam generator with no fixed steamline and waterline, equipped with automatic controls and protective interlocks responsive to steam pressure, pressure reli

48、ef valves may be provided in accordance with the above paragraphs identified in 2.2.5 or the following protection against overpressure shall be provided:a) One or more power-actuated pressure relief valves shall be provided in direct communication with the boiler when the boiler is under pressure an

49、d shall receive a control impulse to open when the maximum allowable working pressure at the superheater outlet is exceeded. The total combined relieving capacity of the power actuated pressure relief valves shall be not less than 10% of the maximum design steam-ing capacity of the boiler under any operating condition as determined by the manufacturer. The valves shall be located in the pressure part system where they will relieve the overpressure. An isolating stop valve of the outside-screw-and-yoke type should be installed between the power actuated