Sizing, Selection, and Installation of Pressure-relieving Devices Part Illnstallation API STANDARD 520 SIXTH EDITION, MARCH 2015 API energy AMERICAN PETROLEUM INSTITUTE Special Notes APlpublicationsnecessarilyaddressproblemsofageneralnature.Withrespecttoparticularcircumstances,local state, and federal laws and regulations should be reviewed. NeitherAPnoranyofAPl'semployees,subcontractors,consultants,committees,orotherassigneesmakeany warranty or representation, either express or implied, with respect to the accuracy, completeness, or usefulness of the information contained herein, or assume any liability or responsibility for any use, or the results of such use, of any information or process disclosed in this publication. Neither APl nor any of APl's employees, subcontractors APlpublicationsmaybeusedbyanyonedesiringtodoso.EveryefforthasbeenmadebytheInstitutetoassurethe guarantee in connection with this publication and hereby expressly disclaims any liability or responsibility for loss o damage resulting from its use or for the violation of any authorities having jurisdiction with which this publication may conflict. APl publications are published to facilitate the broad availability of proven, sound engineering and operating regarding when and where these publications should be utilized. The formulation and publication of APl publications is not intended in any way to inhibit anyone from using any other practices. Any manufacturer marking equipment or materials in conformance with the marking requirements of an APl standard is solely responsible for complying with all the applicable requirements of that standard. APl does not represent, Users of this Standard should not rely exclusively on the information contained in this document. Sound business scientific, engineering, and safety judgment should be used in employing the information contained herein. business, scientific, engineering, and judgment safety when using this Standard. All rights reserved. No part of this work may be reproduced, translated, stored in a retrieval system, or transmitted by any means electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher. Contact the Publisher, APIPublishing Services,1220 LStreet, NW, Washington,DC 20005 Copyright @ 2015 American Petroleum Institute Foreword manufacture, sale, or use of any method, apparatus, or product covered by letters patent. Neither should anything containedinthepublicationbeconstruedasinsuringanyoneagainstliabilityforinfringementofletterspatent Shall:Asusedinastandard,"shall"denotesaminimumrequirement inordertoconformtothespecification Should: As used in a standard, “should" denotes a recommendation or that which is advised but not required in order to conform to the specification. This document was produced under APl standardization procedures that ensure appropriate notification and participation in the developmental process and is designated as an APl standard. Questions concerning the interpretationofthecontentofthispublicationorcommentsandquestionsconcerningtheprocedures underwhich ofthematerialpublishedhereinshouldalsobeaddressedtothedirector Generally, APl standards are reviewed and revised, reaffirmed, or withdrawn at least every five years. A one-time API Standards Department, telephone (202) 682-8000. A catalog of API publications and materials is published annually by APl, 1220 L Street, NW, Washington, DC 20005. Suggested revisions are invited and should be submitted to the Standards Department, APl, 1220 L Street, NW, Washington, DC 20005, [email protected] 三 Contents Page 1 Scope 2 Normative References. 3 Terms and Definitions. . . 4 PRDLocation 4.1 4.2 Proximity to Protected Equipment 4.3 Pressure Fluctuations.. . 4.4 Vibration 4.5 Operating Environment. 4.6 Free-draining 4.7 Maintainability 5 Inlet Piping Requirements . 5.1 General. . 5.2 Minimum Diameter ... 5.3 Layout. . 5.4 Isolation Valves in Inlet Piping 5.5 Process Laterals Conne