ISO 5781:2016规定了液压减压阀、顺序阀、卸荷阀、节流阀和止回阀安装表面的尺寸和其他相关数据，以确保互换性。 适用于液压减压阀、顺序阀、卸荷阀、节流阀和止回阀的安装面，代表当前的做法；它们通常适用于工业设备。

ISO 5781:2016 specifies the dimensions and other data relating to surfaces on which hydraulic pressure-reducing valves, sequence valves, unloading valves, throttle valves and check valves are mounted in order to ensure interchangeability. It applies to mounting surfaces for hydraulic pressure-reducing valves, sequence valves, unloading valves, throttle valves and check valves, which represent current practice; they are generally applicable to industrial equipment.