Seat Tightness of Pressure Relief Valves

API STANDARD 527

FOURTH EDITION, NOVEMBER 2014

Special Notes

API publications necessarily address problems of a general nature. With respect to particular circumstances, local, state, and federal laws and regulations should be reviewed.

Neither API nor any of API's employees, subcontractors, consultants, committees, or other assignees make any 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 API nor any of API's employees, subcontractors, consultants, or other assignees represent that use of this publication would not infringe upon privately owned rights.

API publications may be used by anyone desiring to do so. Every effort has been made by the Institute to assure the accuracy and reliability of the data contained in them; however, the Institute makes no representation, warranty, or guarantee in connection with this publication and hereby expressly disclaims any liability or responsibility for loss or damage resulting from its use or for the violation of any authorities having jurisdiction with which this publication may conflict.

API publications are published to facilitate the broad availability of proven, sound engineering and operating practices. These publications are not intended to obviate the need for applying sound engineering judgment regarding when and where these publications should be utilized. The formulation and publication of API 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 API standard is solely responsible for complying with all the applicable requirements of that standard. API does not represent, warrant, or guarantee that such products do in fact conform to the applicable API standard.

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.

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, API Publishing Services, 1220 L Street, NW, Washington, DC 20005.

Copyright © 2014 American Petroleum Institute

Foreword

Nothing contained in any API publication is to be construed as granting any right, by implication or otherwise, for the manufacture, sale, or use of any method, apparatus, or product covered by letters patent. Neither should anything contained in the publication be construed as insuring anyone against liability for infringement of letters patent.

Shall: As used in a standard, “shall” denotes a minimum requirement in order to conform to the specification.

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 API standardization procedures that ensure appropriate notification and participation in the developmental process and is designated as an API standard. Questions concerning the interpretation of the content of this publication or comments and questions concerning the procedures under which this publication was developed should be directed in writing to the Director of Standards, American Petroleum Institute, 1220 L Street, NW, Washington, DC 20005. Requests for permission to reproduce or translate all or any part of the material published herein should also be addressed to the director.

Generally, API standards are reviewed and revised, reaffirmed, or withdrawn at least every five years. A one-time extension of up to two years may be added to this review cycle. Status of the publication can be ascertained from the API Standards Department, telephone (202) 682-8000. A catalog of API publications and materials is published annually by API, 1220 L Street, NW, Washington, DC 20005.

Suggested revisions are invited and should be submitted to the Standards Department, API, 1220 L Street, NW, Washington, DC 20005, standards@api.org.

Contents

Page

1. Scope 1

2. Testing with Air 1

   1. Test Apparatus 1

   2. Procedure 2

   3. Acceptance Criteria 3

3. Testing with Steam 3

   1. Procedure 3

   2. Acceptance Criteria 4

4. Testing with Water 4

   1. Procedure 4

   2. Acceptance Criteria 4

5. Testing with Air—Another Method 4

   1. Type of Valve to be Tested 4

   2. Procedure 5

   3. Acceptance Criteria 5

Figures

1. Apparatus to Test Seat Tightness with Air 1

2. Device to Relieve Body Pressure Caused by Accidental Popping of the Valve 2

Table

1 Maximum Seat Leakage Rates for Metal-Seated Pressure Relief Valves 3

Seat Tightness of Pressure Relief Valves

1. Scope

   This standard describes methods of determining the seat tightness of metal- and soft-seated pressure relief valves, including those of conventional, bellows, and pilot-operated designs.

   
   

   The maximum acceptable leakage rates are defined for pressure relief valves with set pressures from 103 kPa gauge (15 psig) to 41,379 kPa gauge (6000 psig). If greater seat tightness is required, the purchaser shall specify it in the purchase order.

   
   

   The test medium for determining the seat tightness—air, steam, or water—shall be the same as that used for determining the set pressure of the valve.

   
   

   For dual-service valves, the test medium—air, steam, or water—shall be the same as the primary relieving medium.

   
   

   To ensure safety, the procedures outlined in this standard shall be performed by persons experienced in the use and functions of pressure relief valves.

   
   

   Caution—When looking for leakage, the observer shall use a mirror or some other indirect means of observation so that the observer’s face is not in line with the outlet of the valve, in case the valve accidentally pops.

   
   

2. Testing with Air

2.1 Test Apparatus

A test arrangement for determining seat tightness with air is shown in Figure 1. Leakage shall be measured using a tube with an outside diameter of 7.9 mm (5/16 in.) and a wall thickness of 0.89 mm (0.035 in.). The tube end shall be cut square and smooth. The tube opening shall be 12.7 mm (1/2 in.) below the surface of the water. The tube shall be perpendicular to the surface of the water.

Arrangement shall be made to safely relieve or contain body pressure in case the valve accidentally pops (see Figure 2).

Ranged or threaded outlet adapter for pressure relief valve

Tube with outside diameter of

7.9 mm (5/16 in.) and wall thickness of 0.89 mm (0.035 in.)

12.7 mm (1/2 in.)

NOTE See Figure 2 for an example of a device to relieve body pressure in case the valve accidentally pops.

Water

Figure 1—Apparatus to Test Seat Tightness with Air

1