felt fabric a 3600 rpm constant speed exhauster line 2 requires 31 less energy than the liquid ring pump over the life of the same felt fabric however the variable speed drive centrifugal exhauster uses 62 less energy than the liquid ring pump application with a variable speed drive motor below approximately 3600 rpm the horsepower will vary and the torque will be constant above approximately 3600 rpm the horsepower will be constant with the torque variable in the present example with a variable speed ac induction drive motor while the horsepower ranged from 96 hp to 100 hp for the variable speed drive exhauster the torque requirements were decreasing from 147 8 foot lbs down to 105 foot lbs the rpm range started at approximately 3425 and increased to approximately 4850 rpm the following comparison table serves to illustrate the advantageous operation of the centrifugal exhauster provided by the present system __________________________________________________________________________new variable speed centrifugal exhauster liquid ring pump hoffman model 75105a 221 nash model cl4001 400 rpm __________________________________________________________________________perm 40 30 25 20 15 10 8 perm 40 30 25 20 15 10 8m sub b 83 76 74 72 705 685 676 m sub b 83 77 738 705 673 668 676m sub a 70 63 61 59 575 555 546 m sub a 70 64 608 575 543 538 546machine speed 4000 4000 4000 4000 4000 4000 4000 speed 4000 4000 4000 4000.