DIN EN ISO 20844:2015-12

This document (EN ISO 20844:2015) falls within the scope of responsibility of Technical Committee CEN/TC 19 "Gaseous and liquid fuels, lubricants and related products of petroleum, synthetic and biological origin" (secretariat: NEN, Netherlands). The International Standard ISO 20844:2015 on which it is based has been prepared by Technical Committee ISO/TC 28 "Petroleum products and lubricants" (secretariat: NEN, Netherlands). Working Committee NA 062-06-61 AA "Prüfung von Schmierölen, sonstigen Ölen und Paraffinen" ("Testing of lubricating oils, other oils and Paraffin") of Fachausschuss Mineralöl- und Brennstoffnormung (FAM) "(Technical Committee Petroleum, Fuels, Lubricants and Related Products (FAM)") at DIN Standards Committee Materials Testing (NMP) is responsible for the German collaboration. This International Standard specifies a method to assess the resistance to shear stresses applied to mineral oils, synthetic oils, and other fluids containing polymers, when passed through a specified diesel injector nozzle. The shear stability is measured by the change in viscosity of the fluid under test, brought about by the polymer degradation during stress. Under normal circumstances, this International Standard is applied to hydraulic fluids of categories HR and HV as defined in ISO 6743-4 and specified in ISO 11158, but it may also be applied to fire-resistant hydraulic fluids within categories HFA, HFB, HFC, and HFD, with modified conditions as specified in ISO 12922. No formal correlation has been established between the viscosity loss, or the absence of viscosity loss, obtained using the procedures described in this International Standard and that of oils and fluids in actual service. However, it provides standardized conditions for the evaluation of polymer stability under minimized thermal and oxidative stresses. It is normally used by manufacturers of fluids and additives, and users, as a means of ranking existing and potential formulations.