current edition is 4th Edition. API 682 1st edition The first edition of API 682 was entirely new although parts of it were extracted from the pump standard API 610 and existing API standard paragraphs. The mission statement for the 1st Edition was: This standard is designed to default to the equipment types most commonly supplied that have a high probability of meeting the objective of at least three years of uninterrupted service while complying with emissions regulations. Although this mission statement no longer appears in the standard, it remains the basic principle driving the work of the API 682 Task Force and its relevance remains the same for the 4th Edition as it did for the 1st. In addition to providing requirements for mechanical seals, the 1st Edition of API 682 also provided a guide on how to select the correct seal for a number of common refinery applications. In order to provide this seal selection guide, it was necessary to categorize applications into a number of services: Non-hydrocarbon water sour water caustics/amines acids Non-flashing hydrocarbon Flashing hydrocarbon. It was also necessary to categorize the many different type seals that were used in these services. Three seal types were designated: Type A – O-ring pusher Type B – O-ring metal bellows Type C – flexible gasket (high temperature) metal bellows. Prior to API 682, 1st Edition, multiple seals were designated as being either “tandem” or “double” seals; however, advances in seal design had rendered these classic terms obsolete. As a result, there was some confusion on how multiple seals were designated. The task force decided to use a more descriptive designation and chose to define dual seal arrangements. A dual seal would be two sets of sealing faces used in the same seal chamber. The fluid between these two sets of sealing faces could be either pressurized or unpressurized. Three standard arrangements were defined: Arrangement 1 is a single seal Arrangement 2 is a dual unpressurized seal Arrangement 3 is a dual pressurized seal. API 682 1st Edition did not include containment seals or dry gas barrier seals. After having defined the services, seal types, and seal arrangements, a series of flowcharts were created to help in selecting a seal type, special materials or design requirements, and supporting piping plans. API 682 seals were to have a high probability of three years of reliable service. In order to prove