Hexagon solution for NPL reference gauge measuring

The National Physical Laboratory (NPL) is the UK's National Measurement Institute responsible for the certification of reference master gauges to American Petroleum Institute (API) specifications, a role they undertake on behalf of the European Association of National Metrology Institutes (EURAMET) for the whole of Europe. API gauges are commonly used in the oil and gas industry. Until recently the process to certify API gauges has been extremely time consuming and labour intensive. In order to reduce the time required for calibration the NPL and Hexagon Metrology undertook a project to look at other methods for measuring the majority of features on these taper thread gauges. Engineers from the NPL and Hexagon Metrology's Leitz factory in Germany worked together to investigate how a co-ordinate measuring machine (CMM) could be utilised. Two key requirements were the need for a highly accurate measurement facility and a software platform competent of coping with the necessary calculations. "The Leitz PMM-C Infinity with a specified maximum permissible error of 0.3 + L/1,000 was chosen as the CMM. It is capable of automatically measuring API gauges to the measurement uncertainties required", explains David Flack from NPL Engineering Measurement. "In addition the software application deemed suitable for the task was QUINDOS, in particular the module for screw thread inspection. The software, Hexagon Metrology's applications team, and trials on NPL's existing Leitz PMM have proven to us that this is the right solution." NPL is now also looking to use the Leitz PMM-C Infinity as a platform for measuring artefacts such as: ring gauges; plug gauges; end standards; and line standards.