Aboveground Storage Tank Caulking or Sealing the Bottom Edge Projection to the Foundation

API TECHNICAL REPORT 654 FIRST EDITION, MAY 2019

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Contents

Page

1. Scope 1

   1. Scope 1

   2. Applicability 1

   3. Non-applicability 1

2. Informative Reference Publications 1

3. Terms and Definitions 1

4. Foundation Design and Inspection 2

   1. General 2

   2. Foundation Designs 3

   3. Tank Bottom Design 3

   4. Expectations of Foundation 4

   5. Evaluation of Condition of Foundation for Support or Caulking 4

   6. Evaluation of Foundation Settlement 4

   7. Foundation Repairs 4

   8. Foundation Surface Repairs Prior to Caulking or Sealing 5

   9. Dike Drainage 5

5. Corrosion Considerations 5

   1. Evaluation of Bottom Edge Projection and Lower Shell for Corrosion 5

   2. Effective Length of Bottom Edge Projection due to Corrosion 6

6. Cathodic Protection 6

   1. Evaluating Cathodic Protection Based on Water Table 6

   2. Concerns with Trapped Water 7

   3. Soil-side Corrosion Mitigation Considerations 7

7. Using Caulk or Sealants at the Bottom Edge Projection 7

   1. General 7

   2. Substrate Movement and Joint Design 8

   3. Proper Dimensions for Successful Joint 8

8. Potential Issues When Using Caulk or Sealants 9

   1. General 9

   2. Sealing Foundation to Bottom Edge Projection Leaving Corner Weld Exposed 9

   3. Sealing Foundation to Bottom Edge Projection and Lower Shell 10

   4. Secondary Containment Connecting Directly to Foundation 10

   5. Secondary Containment that Connects to the Bottom Edge Projection or Lower Shell 10

   6. Trapping Water Beneath the Tank Bottom 10

   7. Trapping Product from a Breach in the Bottom 10

9. Decision to Remove Existing Caulking and Sealing 10

10. Maintenance and Inspection of Installed Caulk or Sealant Materials 11

    1. Frequency of Inspection 11

    2. Inspection of Tank Components and Foundation 11

    3. Inspection of Caulk or Sealant 11

       Contents

       Page

    4. Repair of Caulk or Sealant System 11

11. Figures Illustrating Typical Caulking Sealing Details 12

Figures

1. Details of Foundation with Caulk and Backer Rod with Corner Weld Exposed 12

2. Details of Foundation and Sealant Systems with Corner Weld Covered 12

3. Details of Foundation and Sealant System with Corner Weld Exposed 13

4. Details of Foundation and Sealant with Corner Weld Covered 14

Aboveground Storage Tank Caulking or Sealing the Bottom Edge Projection to the Foundation

1. Scope

   
   

   1. Scope

      
      

      The purpose of this technical report is to provide guidance to owner/operators who have tanks that are set on a foundation system with the goal to protect the asset from deterioration by minimizing corrosion and foundation deterioration and allowing for proper support of the tank shell. The asset includes the tank itself, as well as the foundation system.

      
      

   2. Applicability

      
      

      1. This technical report does not require that caulking or sealants be installed at the bottom edge projection and the foundation of aboveground storage tanks. It provides guidance in situations in which caulking or sealants may be advantageous and should be considered.

         
         

      2. This technical report applies to situations where an owner/operator is considering caulk or sealant in this area, or if any regulatory agency requires or recommends that an owner/operator installs some type of caulk or sealant. This document will also consider how to inspect existing caulk and sealant, including maintenance procedures, and includes a suggested inspection schedule.

         
         

   3. Non-applicability

      
      

      This technical report does not offer guidance on tanks resting entirely on the ground or earth with no rigid foun- dation or foundation ring wall.

      
      

2. Informative Reference Publications

   
   

   The following documents offer guidance and supplement this technical report.

   
   

   API Recommended Practice 575, Inspection Practices for Atmospheric and Low-Pressure Storage Tanks

   
   

   API Standard 650, Welded Tanks for Oil Storage

   
   

   API Recommended Practice 651, Cathodic Protection of Aboveground Petroleum Storage Tanks

   
   

   API Recommended Practice 652, Lining of Aboveground Petroleum Storage Tank Bottoms

   
   

   API Standard 653, Tank Inspection, Repair, Alteration, and Reconstruction

   
   

   API Standard 2610, Design, Construction, Operation, Maintenance, and Inspection of Terminal and Tank Facilities

   
   

3. Terms and Definitions

For the purposes of this document, the following definitions apply.

3.1

bottom edge projection

The projection of the tank bottom beyond the shell.