Vertical double-suction pump having beneficial axial thrust
Apparatus, including a vertical double-suction pump, is provided featuring a pump casing and a double suction impeller arranged therein on a shaft. The pump casing has a pump casing wall. The double suction impeller has upper and lower shrouds with metal rims configured to form upper and lower isolating annuli between the double suction impeller and the wall of the pump casing in order to impede a recirculation flow from an impeller discharge to be able to act of the upper and lower shrouds and create a controlled axial thrust load from differentiated hydraulic pressure on the upper and lower shrouds. The upper and lower isolating annuli may also be geometrically varied between the upper and lower shrouds of the double suction impeller to create a pressure differential in a direction parallel to an axis of rotation of the double suction impeller.
1. A vertically suspended double-suction pump ( 10 ) comprising:
a discharge pipe assembly ( 100 ) that extends vertically along a vertical axis (A) of rotation;
a motor assembly ( 110 ) arranged on a motor mounting assembly ( 115 );
impeller discharges ( 120 , 122 ) coupled to the discharge pipe assembly( 100 );
a pump casing ( 12 ) having a pump casing wall ( 16 ) and being coupled to the impeller discharges ( 120 , 122 );
a pump shaft ( 15 ) coupled to the motor mounting assembly ( 115 ) to rotate on the vertical axis (A) of rotation and configured in the discharge pipe assembly ( 100 ) to extend into the pump casing ( 12 ) so as to form part of a pump rotor system; and
a double suction impeller ( 14 ) arranged in the pump casing ( 12 ) and coupled to the pump shaft ( 15 ), having upper and lower shrouds ( 18 , 20 ) with metal rims ( 22 , 24 ) configured to form upper and lower isolating annuli ( 22 , 24 ) between the double suction impeller ( 14 ) and the pump casing wall ( 16 ) of the pump casing ( 12 ) in order to impede a recirculation flow (F) from the impeller discharges ( 120 , 122 ) to be able to act upon the upper and lower shrouds ( 18 , 20 ) so as to dampen secondary flows from pump casing recirculation and isolate such flows from buffing the upper and lower shrouds ( 18 , 20 ) of the double suction impeller ( 14 ) which mitigates undesirable axial vibration on the pump rotor system of the vertically suspended double-suction pump ( 10 ), the upper and lower isolating annuli ( 22 , 24 ) being geometrically varied between the upper and lower shrouds ( 18 , 20 ) to create a pressure differential in a downward direction parallel to the vertical axis (A) of rotation of the double suction impeller ( 14 ) caused from differentiated hydraulic forces on the upper and lower shrouds ( 18 , 20 ) so as to apply an axial thrust load (L A ) to the pump shaft ( 15 ) in tension to increase rotor dynamic stiffness in the pump rotor system.
2. The vertically suspended double-suction pump ( 10 ) according to claim 1 , wherein the metal rims ( 22 , 24 ) are configured to extend substantially completely around the upper or lower shrouds( 18 , 20 ).
3. The vertically suspended double-suction pump ( 10 ) according to claim 1 , wherein the double suction impeller ( 14 ) has an outer diameter, and the metal rims ( 22 , 24 ) are configured or located on the upper and lower shrouds ( 18 , 20 ) closer to the outer diameter nearer the impeller discharges ( 120 , 122 ).
4. The vertically suspended double-suction pump ( 10 ) according to claim 1 , wherein the double suction impeller ( 14 ) has an inner periphery, and the metal rims ( 22 , 24 ) are configured or located on the upper and lower shrouds ( 18 , 20 ) closer to the inner periphery nearer the pump shaft ( 15 ).
5. The vertically suspended double-suction pump ( 10 ) according to claim 1 , wherein the metal rims ( 22 , 24 ) are configured at a specific location on the upper and lower shrouds ( 18 , 20 ) and with a sufficient height so as to impede the recirculation flow (F) from the impeller discharges ( 120 , 122 ) to be able to act upon the upper and lower shrouds ( 18 , 20 ), and create the axial thrust load (L A ) from the differentiated hydraulic forces on the upper and lower shrouds( 18 , 20 ).