API SPEC 13A pdf download.Petroleum and natural gas industries一Drilling fluid materials – Specifications and tests 4 Requirements 4.1 Quality control instructions All quality control work shall be controlled by manufacturer’s documented instructions, which include appropriate methodology and quantitative or qualitative acceptance criteria. 4.2 Use of test calibration materials in checking testing procedures 4.2.1 Test Calibration Barite and Test Calibration Bentonite...