standards. The ISO Organization made slight editorial changes to 2nd Edition, including correcting typographical errors and unit conversions. Therefore, API had to re-issue a corrected 2nd edition but choose to label it as 3rd edition. API 682 3rd Edition was published in September 2004. API and ISO no longer have the agreement to jointly issue standards. The 2004 issue of ISO 21049 is the only issue and plans to update it are unknown. API 682 4th edition A twenty-five member task force spent six years updating 3rd Edition to 4th Edition. The 4th Edition of API 682 is organized similarly to the 2nd and 3rd Editions: Scope Normative references Terms, Definitions, and Symbols Sealing Systems General Design Requirements Specific Seal Configurations Accessories Instrumentation Inspection, Testing, and Preparation for Shipment Data Transfer Annexes Annex A – Recommended Seal Selection Procedure Annex B – Typical Materials and Material Specifications Annex C – Mechanical Seals Datasheets Annex D – Seal Codes Annex E – Mechanical Seals Data Requirement Forms Annex F – Technical Tutorials and Illustrative Calculations Annex G – Standard Piping Plans and Auxiliary Hardware Annex H – Inspectors’ Checklist for All Seals Annex I – Seal Qualification Testing Configurations Seal Configuration refers to the orientation of the seal components in an assembly. In previous editions, orientations were defined as face-to-back, back-to-back, and face-to-face and these terms are carried over into the 4th Edition. In 4th Edition, any orientation (face to back, back to back, face to face) can be used in a dual seal provided that the design features are appropriate to the functionality of that particular arrangement. Clearances Fourth Edition added additional specifications for clearances, placed these requirements in the form of tables and noted that seal components are not to be considered as “shaft catchers” to restrict shaft movement. The minimum clearances specified apply only to equipment within the scope of the standard. Equipment outside that scope, such as non-cartridge seals, older pumps, non-API 610 pumps and certain severe services, might benefit from larger clearances. Codes Before API 682, API 610 (the pump standard) used a simple seal code to specify seals. API 682 attempted to use a more comprehensive seal code; however, that code changed with every edition of API 682. The 4th Edition code, described in Annex D, is probably the best to date and includes some concepts and codes from the historical API 610 seal code.