This document provides basic requirements for hydraulic part-turn valve actuators, both double acting and single acting, used for on-off and modulating control duties. It includes guidelines, recommendations and methods for enclosure and corrosion protection, control and testing. It does not apply, to hydraulic actuators that are integral parts of control valves or to electro-hydraulic actuators. Other requirements or conditions of use different from those indicated in this document shall be subject to negotiations between the purchaser and the manufacturer/supplier prior to order. The terms and definitions applicable to this European Standard are given in FprEN 15714-1.