Flare Details for Petroleum, Petrochemical, and Natural Gas Industries

ANSI/API STANDARD 537 THIRD EDITION, MARCH 2017

ADDENDUM 1, JUNE 2020

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.

Classified areas may vary depending on the location, conditions, equipment, and substances involved in any given situation. Users of this Standard should consult with the appropriate authorities having jurisdiction.

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.

Where applicable, authorities having jurisdiction should be consulted.

Work sites and equipment operations may differ. Users are solely responsible for assessing their specific equipment and premises in determining the appropriateness of applying the Standard. At all times users should employ sound business, scientific, engineering, and judgment safety when using this Standard.

API is not undertaking to meet the duties of employers, manufacturers, or suppliers to warn and properly train and equip their employees, and others exposed, concerning health and safety risks and precautions, nor undertaking their obligations to comply with authorities having jurisdiction.

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 © 2017 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 standard.

Should: As used in a standard, “should” denotes a recommendation or that which is advised but not required in order to conform to the standard.

May: As used in a standard, “may” denotes a course of action permissible within the limits of a standard. Can: As used in a standard, “can” denotes a statement of possibility or capability.

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.

iii

Contents

Page

1. Scope 1

2. Normative References 1

3. Terms and Definitions 2

4. Design 8

   1. General 8

   2. System Design 9

   3. Process Definition 9

   4. Types of Flares 10

   5. Flare Burners 10

   6. Mechanical Design 11

   7. Pilots 12

   8. Pilot Ignition Systems 13

   9. Pilot Flame Detection 14

   10. Piping 14

   11. Auxiliary Components 14

5. Mechanical Details-Elevated Flares 15

   1. Mechanical Design-Design Loads 15

   2. Design Details 19

   3. Flanges 20

   4. Materials of Construction 21

   5. Welding 22

   6. Inspection 22

   7. Surface Preparation and Protection 23

   8. Attachments 23

   9. Aircraft Warning Lighting 23

   10. Platforms and Ladders 23

6. Mechanical Details-Enclosed-flame Flares 24

   1. Combustion Chamber 24

   2. Burners 25

   3. Burner Piping 25

   4. Pilots 25

   5. Wind Fence 26

   6. Radiation Shielding 26

Annex A (informative) Flare Equipment Overview 27

Annex B (informative) Components of Multi-burner Staged Flare Equipment 87

Annex C (informative) Enclosed-flame Flares 90

Annex D (informative) Offshore Flare Systems 103

Annex E (informative) Instructions for Flare Datasheets 112

Annex F (informative) Flare Datasheets 123

Annex G (normative/informative) Migration of Technical Content from the Sixth Edition

of API Standard 521 159

Bibliography 183

v

Contents

Figures

Page

1. Flare Type Selection 28

2. Self-supported Structure 30

3. Guyed-support Structure 31

4. Typical Fixed Derrick Support Structure 32

5. Demountable Derrick with Multiple-section Riser 33

6. Demountable Derrick with Single-section Riser 35

7. Horizontal Flares 35

8. Enclosed-flame Flare 36

9. Multi-burner Staged Flare 37

10. Multi-burner Flare Staging Curve 38

11. Air-assisted Flare 39

12. Flare Pilot Assembly 54

13. Flame Front Generator Panel Arrangement 59

14. Flare/Pilot/Flame Front Generator Panel Arrangement 60

15. Centrifugal Fan 75

16. Vaneaxial Fan 76

17. Simplified Control Diagram for a Three-stage Flare System 83

B.1 Multi-burner Staged Flares 87

1. Typical Enclosed Flare Staged to Elevated Flare 91

2. Enclosed-flame Flare 92

3. Wind Fence for an Enclosed-flame Flare 96

1. Steam-injected Smokeless Flare Burners 166

2. Typical Forced-air Assisted Smokeless Flare 168

3. Flare Structures 173

4. Purge-recduction Device—Buoyancy Seal 179

Tables

1. Number of Pilots for Single-point Flares 12

2. Allowable Forces and Moments for Flare Nozzles 18

3. Flange-Bolting Dimensions for Flare Burners Larger than DN 600 (NPS 24) 21

1. Combustion Noise Spectrum 47

2. Troubleshooting of Pilots 57

3. Troubleshooting of Ignition Systems 65

4. Troubleshooting of Flame Detection Systems 69

5. Troubleshooting of Purge Gas Conservation Seals—Buoyancy Type 72

6. Troubleshooting of Blower Systems 77

7. Troubleshooting of Blower Staging and Control Systems 81

8. Troubleshooting of Pressure-staging Equipment 85

C.1 Troubleshooting of Enclosed-flame Flare Systems 102

1. API 537 to API 521 Cross-reference 159

2. Suggested Steam Injection Rates 163

vi

Notice

Instructions for Submitting a Proposed Revision to this Standard Under Continuous Maintenance

The American Petroleum Institute maintains this standard under continuous maintenance procedures. These procedures establish a document program for regular publication of addenda or revisions, including timely and documented consensus action on requests for revisions to any part of the standard. Proposed revisions shall be submitted to the Director, Standards Department, American Petroleum Institute, 1220 L Street, NW Washington, D.C. 20005-4070, standards@api.org.

Introduction

A flare is a critical mechanical component of a complete system design intended for the safe, reliable, and efficient discharge and combustion of hydrocarbons from pressure-relieving and vapor-depressurizing systems.

The high-level safety and operating goals of a flare are summarized as follows:

• to provide safe, reliable, and efficient discharge and combustion of hydrocarbons with a high combustion efficiency;

• to ensure that the discharged hydrocarbons burn with stable combustion over the entire defined operating range;

• to ensure a continuity of the flare flame under severe weather conditions;

• to ensure that ground level concentrations of specified compounds do not exceed environmental limits;

• to ensure that the back pressure does not exceed the maximum allowable;

• to ensure that velocity throughout the flare piping and the flare burner does not exceed the maximum specified;

• to ensure that the opacity limit at the smokeless flow rate range does not exceed that defined;

• to ensure that the flare radiation intensity does not exceed the maximum allowable; and

  
  

• to ensure that noise levels do not to exceed the maximum permissible.

For new designs, the development of a design can be advanced using the guidance and examples of good engineering practice that are identified in this standard.

A flare design basis is developed in consideration of the performance expectations, the functional requirements and mechanical details required to fulfill the safety and operating goals established for each application. Section 4 provides the basis for design and functional requirements related to the primary components critical to fulfilling these safety and operating goals. Section 5 and Section 6 provide requirements more specific to the arrangement and mechanical details of design.

The functional requirements in this standard are supported by the technical guidance provided in Annex A, Annex B, Annex C, and Annex D. The technical guidance provided in the informative annexes addresses alternative designs or techniques and provides good practices on the basis of which, through sound engineering judgment, the practitioner can make appropriate design decisions and selections.

Datasheets are provided in Annex F in order to properly communicate and preserve the finalized basis of design and requirements. Annex E provides instructions for completing the flare datasheets in Annex F.

Users of this standard should be aware that further or differing requirements may be needed for individual applications. This standard is not intended to inhibit a vendor from offering, or the purchaser from accepting, alternative equipment or engineering solutions for the individual application. This may be particularly applicable where there is innovative or developing technology. Where an alternative is offered, the vendor should identify any variations from this standard and provide details.

The International System of Units (SI) is used in this standard. Where practical, U.S. customary (USC) units are included in brackets for information.

A bullet ( ● ) at the beginning of a section or subsection indicates that either a decision is required or further information is to be provided by the purchaser. This information should be indicated on datasheets (see examples in Annex F) or stated in the inquiry or purchase order.

Addendum 1 contains a new annex (Annex G) added to the Third Edition of API Standard 537. Annex G contains a combination of normative and informative content migrated from the Sixth Edition of API Standard 521 through joint API Standard 521/API Standard 537 committee review. Both the Seventh Edition of API Standard 521 and Addendum 1 of the Third Edition of API Standard 537 are being issued concurrently to align both standards and ensure preservation of technical requirements and information. The normative content contained, and that which may be derived through further development of this Annex, will be removed and incorporated into the normative sections of the next edition of API Standard 537.

vii

Flare Details for Petroleum, Petrochemical, and Natural Gas Industries

1. Scope

   
   

   This standard specifies requirements and provides guidance for the selection, design, specification, operation, and maintenance of flares and related combustion and mechanical components used in pressure- relieving and vapor-depressurizing systems for petroleum, petrochemical, and natural gas industries. While this standard is primarily intended for onshore facilities, guidance related to offshore applications is included.

   
   

   Annex A, Annex B, Annex C, and Annex D provide further guidance and best practices for the selection, specification, and mechanical details for flares and on the design, operation, and maintenance of flare combustion and related equipment.

   
   

   Annex E explains how to use the datasheets provided in Annex F; it is intended that these datasheets be used to communicate and record design information.

   
   

2. Normative References

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

API Recommended Practice 2A-WSD:2000, Planning, Designing and Constructing Fixed Offshore Platforms—Working Stress Design

API Standard 521, Pressure-Relieving and Depressuring Systems

API Standard 560, Fired Heaters for General Refinery Service

ASME B16.5 1, Pipe Flanges and Flanged Fittings NPS 1/2 Through NPS 24 Metric/Inch Standard

ASME STS-1, Steel Stacks

ASTM A123/A123M 2 , Standard Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products

ASTM A143/A143M, Standard Practice for Safeguarding Against Embrittlement of Hot-Dip Galvanized Structural Steel Products and Procedure for Detecting Embrittlement

ASTM A153/A153M, Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware

ASTM A384/A384M, Standard Practice for Safeguarding Against Warpage and Distortion During Hot-Dip Galvanizing of Steel Assemblies

ASTM A385/385M, Standard Practice for Providing High-Quality Zinc Coatings (Hot-Dip)

ASTM A475-03, Standard Specification for Zinc-Coated Steel Wire Strand

ASTM A586-04a, Standard Specification for Zinc-Coated Parallel and Helical Steel Wire Structural Strand

1 ASME International, 2 Park Avenue, New York, New York 10016-5990, www.asme.org.

2 ASTM International, 100 Barr Harbor Drive, West Conshohocken, Pennsylvania 19428, www.astm.org.