Venting Atmospheric and Low-pressure Storage Tanks

ANSI/API STANDARD 2000

SIXTH EDITION, NOVEMBER 2009

ISO 28300:2008 (Identical), Petroleum, petrochemical and natural gas industries—Venting of atmospheric and low-pressure storage tanks

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Contents Page

API Foreword ii

Foreword iv

Introduction v

1. Scope 1

2. Normative references 1

3. Terms, definitions and abbreviated terms 1

4. Non-refrigerated aboveground tanks 4

   1. General 4

   2. Causes of overpressure or vacuum 4

   3. Determination of venting requirements 7

   4. Means of venting 18

   5. Considerations for tanks with potentially flammable atmospheres 19

   6. Relief-device specification 20

   7. Installation of venting devices 22

5. Refrigerated aboveground and belowground tanks 23

   1. General 23

   2. Causes of overpressure or vacuum 23

   3. Relief-device specification 26

   4. Installation of venting devices 26

6. Testing of venting devices 27

   1. General 27

   2. Flow-test apparatus 28

   3. Method for determining capacities 29

   4. Production testing 33

7. Manufacturer's documentation and marking of venting devices 34

   1. Documentation 34

   2. Marking 34

Annex A (informative) Alternative calculation of normal venting requirements 36

Annex B (informative) Basis of emergency venting for Tables 7 and 8 45

Annex C (informative) Types and operating characteristics of venting devices 49

Annex D (informative) Basis of sizing equations 58

Annex E (informative) Basis for normal out-breathing and normal inbreathing 70

Annex F (informative) Guidance for inert-gas blanketing of tanks for flashback protection 72

Bibliography 75

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Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights.

ISO 28300 was prepared by Technical Committee ISO/TC 67, Materials, equipment and offshore structures for petroleum, petrochemical and natural gas industries, Subcommittee SC 6, Processing equipment and systems.

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Introduction

This International Standard was developed from the 5th edition of API Std 2000 and EN 14015:2005, with the intent that the 6th edition of API Std 2000 be identical to this International Standard.

This International Standard has been developed from the accumulated knowledge and experience of qualified engineers of the oil, petroleum, petrochemical, chemical and general bulk liquid storage industry.

Engineering studies of a particular tank can indicate that the appropriate venting capacity for the tank is not the venting capacity estimated in accordance with this International Standard. The many variables associated with tank-venting requirements make it impractical to set forth definite, simple rules that are applicable to all locations and conditions.

In this International Standard, where practical, US Customary (USC) units are included in parentheses or in separate tables, for information.

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API Standard 2000/ISO 28300

Petroleum, petrochemical and natural gas industries — Venting of atmospheric and low-pressure storage tanks

1. Scope

   
   

   This International Standard covers the normal and emergency vapour venting requirements for aboveground liquid petroleum or petroleum products storage tanks and aboveground and underground refrigerated storage tanks, designed for operation at pressures from full vacuum through 103,4 kPa (ga) [15 psig]. Discussed in this International Standard are the causes of overpressure and vacuum; determination of venting requirements; means of venting; selection, and installation of venting devices; and testing and marking of relief devices.

   
   

   This International Standard is intended for tanks containing petroleum and petroleum products but it can also be applied to tanks containing other liquids; however, it is necessary to use sound engineering analysis and judgment whenever this International Standard is applied to other liquids.

   
   

   This International Standard does not apply to external floating-roof tanks.

   
   

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.

   
   

   ISO 4126-4, Safety devices for protection against excessive pressure — Part 4: Pilot operated safety valves

   
   

   ISO 16852, Flame arresters — Performance requirements, test methods and limits for use

   
   

   ISO 23251, Petroleum, petrochemical and natural gas industries — Pressure-relieving and depressuring systems IEC 60079-10, Electrical apparatus for explosive gas atmospheres — Part 10: Classification of hazardous areas DIN 41191) (all parts), Above-ground cylindrical flat-bottom tank structures of metallic materials

   
   

3. Terms, definitions and abbreviated terms

For the purposes of this document, the following terms, definitions and abbreviated terms apply.

3.1

accumulation

pressure increase over the maximum allowable working pressure or design pressure of the vessel allowed during discharge through the pressure-relief device

NOTE Accumulation is expressed in units of pressure or as a percentage of MAWP or design pressure. Maximum allowable accumulations are established by pressure-design codes for emergency operating and fire contingencies.

1. Deutsches Institut für Normung (DIN), Burggrafenstrasse 6, Berlin, Germany D-10787.

2. American Petroleum Institute, 1220 L Street, N.W., Washington, D.C., 20005-4070, USA.

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