Description: time period during which all the performance requirements are met; Name: usefull life
Description: Time interval from first use until the instant when a limiting state is reached ; Name: useful life
Description: Speed that characterizes a pump in terms of its speed, flow rate per impeller eye, i.e. total flow for single-flow impeller, half flow for double-flow impeller, at the best efficiency point and head per stage at maximum impeller diameter ; Name: Specific speed