The American Petroleum Institute (API) Manual of Petroleum Measurement Standards (MPMS), Chapter 14.3 is a living document, constantly reviewed and reconsidered for revision as new information and research data become available relative to the design and operation of orifice metering systems. In spite of this scrutiny within the API, the American Gas Association (AGA), and the International Standards organization (ISO), the latest recommendations and revisions are not well known in many areas of our industry. Many companies are still designing to AGA 3 1985 standards