the distance h between a base end face 12 ta of a stator - blade - wheel outer ring part 12 a and the corresponding rotor - blade end face 4 aa , is set at a value larger than the maximum deformation of the running rotor blade wheel 4 a during the pump operation . the larger distance h keeps perfectly stator - rotor separation , while the outer ring part 12 a of a stator blade wheel 12 goes , in assembling , into the rotor area on account of large shift of any half of stator blade wheels owing to the wide cutting width . it makes also easy stator blade wheel assembling of the pump , as it is allowable to arrange half stator blade wheels with some eccentricity .