1991_2018.pdf

REAFFIRMED 2018Intentionally left blank AN AMERICAN NATIONAL STANDARD Hose Coupling Screw Threads(Inch)ASME BI.20.7-1991(REVISION OF ANSVASME B1.20.7-1966)The American Society of Mechanical Engineers _ _ _ 345 East 47th Street,New York,N.Y.1001 7-Date of Issuance:April 16,1992 This Standard will be revised when the Society approves the issuance of a new edition.There will be no addenda or written interpretations of the re-quirements of this Standard issued to this edition.ASME is the registered trademark of The American Society of Mechanical Engineers This code or standard was developed under procedures accredited as meeting the criteria for American National Standards.The Consensus Committee that approved the code or standard was balanced to assure that individuals from competent and concerned interests have had an opportunity to participate.The proposed code or standard was made available for public review and comment which provides an opportunity for additional public input from industry,academia,regulatory agencies,and the public-at-large.ASME does not approve,rate,or endorse any item,construction,proprietary device,or activity.ASME does not take any position with respect to the validity of any patent rights asserted in connection with any items mentioned in this document,and does not undertake to insure anyone utilizing a standard against liability for infringement of any applicable Letters Patent,nor assume any such liability.Users of a code or standard are expressly advised that determination of the validity of any such patent rights,and the risk of infringement of such rights,is entirely their own responsibility.Participation by federal agency representative(s)or person(s)affiliated with industry is not to be interpreted as government or industry endorsement of this code or standard.ASME accepts responsibility for only those interpretations issued in accordance with governing ASME procedures and policies which preclude the issuance of interpretations by individual volunteers.No part of this document may be reproduced in any form,in an electronic retrieval system or otherwise,without the prior written permission of the publisher.Copyright 0 1992 by THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS All Rights Reserved Printed in U.S.A.(This Foreword is not part of ASME B1.20.7-1991.)Local standards for small hose coupling threads in use prior to 1920 were summarized in a table in the Proceedings of the National Fire Protection Association,Vol.24,1920,p.180.Of these,the Standard Iron Pipe Thread had been most widely used,and it had been reliably reported that this thread had been in use for small hose couplings since 1894 or earlier.In the case of the three-fourths-inch size,however,11 and 11%threads per inch,with a diameter of 1%6 in.were already in very extensive use for garden hose.It was reported that the first garden hose spray nozzle had been made prior to 1890 in the shops of the W.D.Allen Mfg.Co.,Chicago.In 1918 the Fire Dept.Supply and Linen Hose Section of the War Industries Board rec-ommended that for the duration of the war“hydrants,hose valves,hose couplings,nipples,and nozzles 1%in.to 2 in.,inclusive,to be iron pipe thread for new work,hose gauge or special threads only to be used for replacement or extension of existing plant equipment.The adoption of such a standard will result in the elimination of the various so-called hose threads which are used locally in the different sections of the country.Such a standard will also permit repairs or connections being made in the field by the use of wrought iron pipe connections or fittings.It will also result in considerable saving in correspondence and detail now necessary in endeavoring to ascertain what particular hose standard thread is desired.”A blueprint of the nominal sizes and pitches of hose thread dimensions,dated March 5,1918,of the National Association of Brass Manufacturers was furnished the National Screw Thread Commission in November,1918.Limits of size for iron pipe thread sizes and pitches were designed as National hose coupling thread dimensions and adopted by the National As-sociation of Brass Manufacturers March 18,1920.These were in agreement with those in the Progress Report of the N.S.T.C.,approved June 19,1920,and published January 4,1921 as NBS Miscellaneous Publication No.42.A survey in 1925 of some of the members of the National Association of Brass Manufacturers showed these standards to be satisfactory.These threads from/2 to 2 in.diameter are now designated“NPSH.”In January 1927,The American Society of Mechanical Engineers requested the American Engineering Standards Committee(later changed to the American Standards Association)to authorize the organization of a Sectional Committee to complete the standardization of firehose couplings and to attempt to unify and complete the existing dimensions of small hose cou-plings.This authority was given and the Sectional Committee B33 was organized in October,1928,under the sponso