This guideline API RP 12J:2024 outlines the necessary criteria and suggestions for the engineering design of gas-liquid and gas-liquid-liquid separators, which are based on pressure vessels and utilized in both stationary installations and those that are subject to movement, like floating production, storage, and offloading (FPSO) units and tension leg platforms. The separators discussed in this document are either vertical (such as scrubbers and knockout drums) or horizontal (like free water knockouts), and they are confined to those equipped with traditional, established separation internals, including intake devices, mist eliminators, agglomeration units, and distribution baffles. Separation systems involving solid jetting systems are governed by corporate specifications and/or the designs of technology providers.

Given that instrumentation is integral to separator design, the document provides direction on the selection of pressure, temperature, and level sensors essential for process control and fault diagnosis within the separator.

Although there are well-recognized mechanical design codes for pressure vessels, it is important to recognize the interdependence between process and mechanical design. Therefore, these should not be treated as distinct activities. The document also includes a general outline of the steps to consider when determining the parameters for the mechanical design of the separator.