This document specifies 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 which are integral parts of control valves and to hydraulic actuators designed for permanent immersion in fresh or sea water as well as electro-hydraulic actuators. Other requirements, or conditions of use, different from those indicated in this document can vary upon request.