Overfill Protection for Storage Tanks in Petroleum Facilities

API RECOMMENDED PRACTICE 2350 THIRD EDITION, JANUARY 2005

Overfill Protection for Storage Tanks in Petroleum Facilities

API RECOMMENDED PRACTICE 2350 THIRD EDITION, JANUARY 2005

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Copyright © 2005 American Petroleum Institute

FOREWORD

This publication was prepared under the direction of a Support Group comprised of mem- bers of the API Safety and Fire Protection Subcommittee. The second edition of API RP 2350 Overfill Protection for Storage Tanks in Petroleum Facilities was rewritten and expanded with emergency spill prevention programs in mind and replaced the previous edition in whole and in part. This third edition builds on the second edition with an expansion of the Scope to include both Class I and Class II hydrocarbon liquids as well as tankage in broader usage. Appendixes to the document are intended to provide additional information only.

This document covers overfill protection for all aboveground storage tanks in petroleum facilities, including refineries, terminals, bulk plants, and pipeline terminals that receive Class I (flammable) or Class II (combustible) liquids. It is not intended to include service sta- tion tanks, process tanks or tanks used in initial crude oil production activities.

During the development of the current and prior editions of API RP 2350, careful consid- eration was given to the benefits provided by overfill protection for tanks in petroleum facili- ties relative to:

• Safety and environmental protection

• Optimization of the work place and operating practices

• Inspection, testing, and maintenance

• Equipment and system selection and installation

• Safe work and emergency procedures and training

• Management of change programs relative to tank overfill protection

  All of the sections and appendixes in the document were revised and expanded with the second edition. Illustrations and a tank overfill protection summary chart are provided to help understand the tank capacity and level definitions. API RP 2350 covers overfill protec- tion only. It does not address other issues related to aboveground storage tanks, such as man- agement of large diameter storage tanks, tank fire protection, leak control, drainage, and other subjects that are covered by a number of API standards and other publications listed in the references.

  Starting with the second edition the previous definitions for overfill level, tank fill level, and normal fill level were changed. For example, safe fill level became the normal maximum allowable tank capacity (normal operating level). The definitions used in the second edition continue in this third edition.

  The essential elements of this publication are based on current industry safe operating practices and existing consensus standards. Federal, state, and local regulations or laws may contain additional requirements that must be taken into account when a tank overfill protec- tion program is developed for a specific facility.

  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 federal, state, or municipal regulation with which this publication may conflict.

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

  
  

  iii

  
  

  CONTENTS

  
  

  Page

  1. GENERAL 1

     1. Introduction 1

     2. Scope 1

     3. Definition of Terms 1

     4. General Provisions Applicable to All Facilities 3

     5. Referenced Publications 4

  2. ATTENDED FACILITIES 4

     1. Attended Facilities Where Detectors are Not Installed on Tanks 4

     2. Installation of Detectors at Attended Facilities 5

  3. UNATTENDED FACILITIES 5

     1. Installation of Detectors at Unattended Facilities 5

     2. Installation of Independent Detection and Automatic Shutdown or

        Diversion Systems at Unattended Facilities 6

  4. PROCEDURES 7

     1. General Written Operating Procedures 7

     2. Planning the Product Receipt 7

     3. Electronic System Integrity Tests 8

     4. Monitoring the Receipt 8

     5. Completing the Receipt 8

     6. Emergency Procedures and Planning 8

     7. Personnel Performance and Training 9

     8. Testing, Inspection, and Maintenance 10

     9. Abnormal Conditions 10

APPENDIX A OVERFILL PROTECTION SYSTEM INSTALLATION 11

APPENDIX B DETERMINING TANK CAPACITY AND PRODUCT LEVELS . . . 17 APPENDIX C OVERFILL PROTECTION EQUIPMENT 23

Figures

1. Example External Chamber-type Detector Installation 12

2. Example of a Two-stage Detector Installation for an External

   Floating-roof Tank 13

3. Example of a Two-stage Detector Installation for a Cone-roof Tank 14

4. Example of Tank Level Settings Based on Response Time in a

Two-stage Detector System 15

1. Tank Detector Level and Fill Level Work Sheet 20

2. Tank Overfill Level Work Sheet and Record 21

1. Example of a Two-stage Overfill Protection System 24

2. Example of an External Chamber-type Float Switch 25

3. Example of an Optical High-level Detector 26

4. Example for a Heated Thermocouple Assembly—High-level Probe 27

Tables

1 Tank Overfill Protection Summary Chart 9

v

Overfill Protection for Storage Tanks in Petroleum Facilities

1. General

   1. INTRODUCTION

      Preventing petroleum storage tanks from being overfilled is an important safety and environmental concern. The safe operation of a petroleum storage facility is dependent on the receipt of product into the intended storage tank within its defined capacity. Tank overfills can be effectively reduced by developing and implementing practical and safe operating procedures for storage facilities and by providing for careful selection and application of equipment, scheduled mainte- nance programs, and employee training.

      In providing for overfill protection for storage tanks, the objective is to minimize product overflows that can result in environmental and safety hazards, loss of inventory, and dam- age to tanks and adjacent areas. Because the level of risk and potential loss varies from location to location, a flexible approach should be used in providing alternatives for meeting the objectives of the facility overfill protection program. Pro- cedures should provide for options that include the use of trained personnel, safe operating practices, and technology.

      Recognizing the need for flexibility, this document covers both manual procedures and automatic systems that can be used successfully to protect against overfills.

      
      

   2. SCOPE

      1. Applicability

         The scope of this recommended practice (RP) is specifi- cally limited to tanks associated with marketing, refining, pipeline and similar facilities containing Class I or Class II petroleum liquids. This RP does not apply to:

         • Underground storage tanks

         • Aboveground tanks of 1320 U.S. gallons (5000 liters) or less

         • Tanks that are integral to a process

         • Tanks containing Class III liquids

         • Tanks containing non-combustible liquids

         • Service stations

         • Loading or delivery from wheeled vehicles (such as tank trucks or railroad tank cars)

           
           

      2. Relationship of This Recommended Practice to NFPA 30

This document was prepared to include consistency with NFPA 30-2003 Edition, Chapter 4.6, which includes the fol- lowing requirements:

1. Aboveground tanks at terminals receiving transfer of Class I liquids from mainline pipelines or marine vessels shall follow formal written procedures to

   
   

   prevent overfilling of tanks utilizing one of the following methods of protection:

   1. Tanks gauged at frequent intervals by personnel con- tinuously on the premises during product receipt with frequent acknowledged communication maintained with the supplier so that flow can be promptly shut down or diverted.

   2. Tanks equipped with a high-level detection device that is independent of any tank gauging equipment. Alarms shall be located where personnel who are on duty throughout product transfer can promptly arrange for flow stoppage or diversion.

   3. Tanks equipped with an independent high-level detec- tion system that will automatically shut down or divert flow.

   4. Alternatives to instrumentation described in 4.6.1.1(2) and 4.6.1.1(3), where approved by the author- ity having jurisdiction as affording equivalent protection.

2. Instrumentation systems covered in 4.6.1.1(2) and 4.6.1.1(3) shall be electrically supervised or equiva- lent.

3. Formal written procedures required 4.6.1.1 shall include the following:

1. Instructions covering methods to check for proper line-up and receipt of initial delivery to tank designated to receive shipment.

2. Provisions for training and monitoring the perfor- mance of operating personnel by terminal supervision.

3. Schedules and procedures for inspection and testing of gauging equipment and high-level instrumentation and related systems. Inspection and testing intervals shall be acceptable to the authority having jurisdiction but shall not exceed 1 year.

Note: Reprinted with permission from NFPA 30-2003 Flammable and Combustible Liquids Code, Copyright  2003, National Fire Pro- tection Association, Quincy, MA 02269. This reprinted material is not the complete and official position of the NFPA on the referenced sub- ject, which is represented only by the standard in its entirety.

1.3 DEFINITION OF TERMS

For the purposes of this document, the following defini- tions apply:

1.3.1 attended facility: A facility that has assigned per- sonnel continuously on the premises during receipt of product from a mainline pipeline or marine vessel. An unattended facility does not have assigned personnel on the premises continuously during product receipt from a mainline pipeline or marine vessel.

1