Nom press: nominal pressure for which, continous running, life time and volumetric efficiency are garanted; Max press: maximum pressure at which the pumps can intermittently work (max. 20s); average pressure should be lower than nominal pressure. Pressure peaks, in comutation, can be 20 bar higher as maximum pressure. Volumetric efficiency ηvn is guaranted in nominal conditions and viscosoty 30.....40 cSt. The characteristics mentioned above are valid also for double pumps (for every stage).