Ignition Hazards and Safe Work Practices for Abrasive Blasting of Atmospheric Storage Tanks in Hydrocarbon Service

API RECOMMENDED PRACTICE 2027 FOURTH EDITION, NOVEMBER 2018

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Contents

Page

1. Scope 1

   1. General 1

   2. Applicability 1

   3. Ignition Sources 1

   4. Non-applicability 1

   5. Other Hazards and Applications Not Covered 2

2. Normative References 2

3. Terms and Definitions 3

4. General Requirements and Procedures 6

   1. General Requirements 6

   2. Potential Ignition Hazards 6

5. Potential Ignition Sources and Controls 7

   1. Potential Ignition Sources 7

   2. Static Electric Discharge 7

   3. Internal Combustion Engines and Electric Motors 7

   4. Why Friction Sparks Are Not an Ignition Source 8

   5. Why Heated Metal Surfaces from Abrasive Blasting Are Not an Ignition Source 8

   6. Potential External Ignition Sources 8

6. Operational Considerations 8

   1. Product Level and Movement 8

   2. Isolation 9

   3. Tank Condition 9

   4. Abrasive (Grit) Selection 9

7. Abrasive Blasting Precautions 9

   1. General Precautions 9

   2. Permits and Other Requirements 10

   3. Control of Vapor Releases 10

   4. Testing and Monitoring Requirements 10

   5. Use of Audible Alarms 10

8. Specific Requirements Based on Tank Components 10

   1. Open Top Floating Roof Tanks 11

   2. Floating Roof Tank with Self-Supporting Cover 14

   3. Cone Roof Tank (With and Without Internal Floating Roof) 15

   4. Exterior Shell, Roof, and Appurtenances Storing Class III Fuels 17

9. Class I and II Fuels at Elevated Temperatures 18

Bibliography 19

Tables

1. Summary of Procedures for Abrasive Blasting Tanks in Service by Component 11

2. Flammability of the Vapor Space in Cone Roof Tanks Containing Various Flammable

Liquids with Vapor-Air Mixture in Equilibrium 16

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Ignition Hazards and Safe Work Practices for Abrasive Blasting of Atmospheric Storage Tanks in Hydrocarbon Service

1. Scope

   1. General

      
      

      This recommended practice (RP) provides safe work practices for the prevention and control of vapor, ignition, and other potential hazards during abrasive blasting of aboveground storage tanks in liquid hydrocarbon service at atmospheric pressure. It is generally recognized in the petroleum industry that the preferable method is to empty, vapor-free, and clean aboveground petroleum storage tanks before starting abrasive blasting work. However, this may not be practical or even possible, and may actually increase the risk of an undesirable hazard or incident in some situations. It is, therefore, necessary to understand the potential ignition and safety hazards when planning abrasive blasting and to implement the appropriate safeguards before starting this work.

      
      

      This RP provides assistance to employers in developing operating procedures that provide for hazard recognition to significantly reduce ignition risks during abrasive blasting of hydrocarbon storage tanks in service that may contain or have the potential to develop a flammable atmosphere in the vapor space.

      
      

      This RP does not cover all of the precautions that may be required to safely perform abrasive blasting. Owner/ operators and contractors shall conduct a thorough hazard analysis and prejob start-up safety and health review for each specific abrasive blasting job in order to ensure that all necessary precautions and safeguards have been identified and implemented prior to beginning work.

      
      

   2. Applicability

      
      

      This RP applies to safe work practices required for abrasive blasting of exterior shells and exterior roofs of all aboveground atmospheric storage tanks in liquid hydrocarbon service. It also applies to safe work practices for abrasive blasting conducted on the roofs and inner portions of the exposed surfaces of shells (that portion of the shell above the roof level) on open-top (external) floating roof tanks.

      
      

   3. Ignition Sources

      
      

      This RP also covers recognition and control of ignition hazards that are specific to and may be present during abrasive blasting of aboveground storage tanks in liquid hydrocarbon service at atmospheric pressure. The ignition sources covered in this RP include static electricity, internal combustion engines, electric motors, friction sparks, hot metal surfaces, and external-to-the-work ignition sources.

      
      

   4. Non-applicability

This RP does not apply to the abrasive blasting of the following types of tanks or vessels:

• pressure vessels and low-pressure tanks;

  
  

• cryogenic or refrigerated vessels or tanks;

  
  

• vacuum vessels;

  
  

• process vessels;

1