API STD 20L-2018 Qualification of Polymeric Seal Manufacturers for Use in the Petroleum and Natural API STD 692-2018 Dry Gas Sealing Systems for Axial, Centrifugal, and Rotary Screw Compressors and Ex API SPEC 17L1-2021 Specification for Ancillary Equipment for Flexible Pipes and Subsea Umbilicals - API STD 2015-2018 Requirements for Safe Entry and Cleaning of Petroleum Storage Tanks (EIGHTH EDITIO API SPEC 6A-2018 Specification for Wellhead and Tree Equipment (TWENTY-FIRST EDITION; API Monogram p API 19C-2018 Measurement of and Specifications for Proppants Used in Hydraulic Fracturing and Gravel Mixing in the Process Industries, Elsevier (1997) API TR 13M-5-2018 Procedure for Testing and Evaluating the Performance of Friction (Drag) Reducers i