Low specific speed pump casing construction
First Claim
Patent Images
1. A low specific speed centrifugal pump having a desired discharge flow rate, which comprises in combination:
- a casing of cast metal construction defining a pump chamber, an inlet opening, a discharge passage having an inlet end communicating with said chamber and an outlet end, and a constriction extending across said outlet end, said pump chamber having an outer boundary surface extending away from a cut-water and about said pump chamber to a point at which it cooperates with said cut-water to define said inlet end of said discharge passage, said constriction having a restrictor flow opening extending therethrough in flow communication with said discharge passage; and
an impeller supported for rotation about an axis within said chamber for transporting fluid between said inlet opening and said outlet end, said chamber and discharge passage leading to said restriction having a size sufficient to provide an other pump discharge flow rate exceeding said desired flow rate by arranging said outer boundary surface at a radial distance from said axis which is greater than that required to provide said desired flow rate, the radial distance between said cut-water and said axis corresponding to that required to provide said desired discharge flow rate, and said restrictor flow opening throttles said pump to reduce said other flow rate to said desired flow rate.
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Abstract
An improved low specific speed pump is disclosed, which provides for greater consistency of pump operating efficiencies obtainable by pumps of any given group of like size pumps. In the present pump, the internal dimensions of the pump chamber and discharge passage are enlarged to provide for a reduction in flow velocities therewithin compared to a conventional pump of a given design flow capacity and a controlled size restrictor is arranged adjacent the pump discharge in order to reduce the resultant increase in flow capacity to such given design value.
47 Citations
13 Claims
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1. A low specific speed centrifugal pump having a desired discharge flow rate, which comprises in combination:
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a casing of cast metal construction defining a pump chamber, an inlet opening, a discharge passage having an inlet end communicating with said chamber and an outlet end, and a constriction extending across said outlet end, said pump chamber having an outer boundary surface extending away from a cut-water and about said pump chamber to a point at which it cooperates with said cut-water to define said inlet end of said discharge passage, said constriction having a restrictor flow opening extending therethrough in flow communication with said discharge passage; and an impeller supported for rotation about an axis within said chamber for transporting fluid between said inlet opening and said outlet end, said chamber and discharge passage leading to said restriction having a size sufficient to provide an other pump discharge flow rate exceeding said desired flow rate by arranging said outer boundary surface at a radial distance from said axis which is greater than that required to provide said desired flow rate, the radial distance between said cut-water and said axis corresponding to that required to provide said desired discharge flow rate, and said restrictor flow opening throttles said pump to reduce said other flow rate to said desired flow rate.
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2. In a method of manufacturing a group of low specific speed centrifugal pumps, comprising the steps of casting like sized pump casings to define pump chambers, inlet openings communicating with said chambers and discharge passages having throat areas communicating with said chambers and outlet ends, said pump chambers having outer boundary surfaces extending away from cut-waters and about said pump chambers for cooperation with said cut-waters to define said throat areas, and fitting said casings with impellers supported for rotation about an axis within each of said chambers for transporting fluid between said inlet openings and said outlet ends, characterized in that said pumps of said group have a design discharge flow rate for any given size impeller, chamber, discharge passage and radial spacing between said cut-waters and said axis, and in that pumps of said group vary in overall efficiency due to variations in surface finish of said chambers and throat areas as a result of casting of said casings;
- the improvement for reducing variations in overall efficiency between pumps of said group comprising;
increasing the size of each of said chambers and said discharge passages, including said throat areas, by increasing the radial distance between said boundary surfaces and said axis beyond that required to provide said pumps with said design discharge flow rate, while maintaining essentially said given radial spacing between said cut-waters and said axis; and providing restrictions within said discharge passages at said outlet ends, said restrictions having uniformly sized restrictor flow openings therethrough serving to limit the discharge flow rate from said pumps to essentially said design discharge flow rate. - View Dependent Claims (3)
- the improvement for reducing variations in overall efficiency between pumps of said group comprising;
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4. An improvement in the method of manufacturing a low specific speed centrifugal pump including the steps of casting a casing from metal to define a pump chamber, an inlet communicating with the chamber and a discharge passage having a throat end communicating with said chamber and an outlet end, and fitting said casing with an impeller supported for rotation about an axis within the chamber for transporting fluid from said inlet opening to said outlet end, wherein said pump chamber has an outer boundary surface extending away from a cut-water and about said pump chamber for cooperation with said cut-water to define said throat end, and wherein surfaces of said chamber and said discharge passage including said throat have an as-cast surface finish tending to produce frictional losses during operation of said pump, and wherein said pump is characterized as having a design discharge flow rate for any given size impeller, chamber, discharge passage and radial spacing between said cut-water and said axis, said improvement tending to reduce said frictional losses of said pump comprising:
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forming said chamber and said discharge passage including said throat end of a size exceeding that required to provide said design discharge flow rate and to reduce said losses by increasing the radial distance between said boundary surface and said axis while maintaining essentially said given radial distance between said cut-water and said axis; and providing a restriction adjacent said outlet end having a flow opening extending therethrough sized to throttle discharge flow from said pump to said design discharge flow rate. - View Dependent Claims (5)
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6. An improvement in the method of manufacturing a group of low specific speed centrifugal pumps, wherein pumps forming said group have decreasing discharge flow rates relative to a given discharge flow rate, including the steps of forming a group of like sized pump casings to define pump chambers, pump inlets communicating with said pump chambers and pump discharge passages having throat ends communicating with said pump chambers and outlet ends, fitting said casings with impellers rotatably supported within said pump casings for rotation about axes of rotation, and providing restrictor openings in said discharge passages to provide said decreasing discharge flow rates, wherein said pump chambers have outer boundary surfaces disposed radially outwardly of said axis to extend away from cut-waters and about said pump chambers for cooperating with said cut-waters to define said throat ends and wherein surfaces of said pump chambers and passages have as-formed surface finishes tending to produce frictional losses during operation of said pumps, which vary between pumps having any given size restrictor opening;
- said improvement including;
forming said pump chambers and passages, including said throat ends, of a size sufficient to provide another discharge flow rate exceeding said given discharge flow rate and to reduce said losses by uniformly increasing the radial distance between said boundary surfaces and said axes while maintaining a radial distance between said cut-waters and said axes corresponding to that required to provide said given discharge flow rate; and sizing said restrictor openings to reduce said discharge flow rate from said other discharge flow rate to and below said given discharge flow rate. - View Dependent Claims (7)
- said improvement including;
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8. In a method of manufacturing a group of low specific speed centrifugal pumps, comprising the steps of casting like sized pump casings to define pump chambers, inlet openings communicating with said chambers and discharge passages having throat areas communicating with said chambers and outlet ends, said pump chambers having outer boundary surfaces extending away from cut-waters and about said pump chambers for cooperation with said cut-waters to define said throat areas, and fitting said casings with impellers supported for rotation about an axis within each of said chambers for transporting fluid between said inlet openings and said outlet ends, characterized in that said pumps of said group have a design discharge flow rate for any given size impeller, chamber, discharge passage and radial spacing between said cut-waters and said axis, and in that pumps of said group vary in overall efficiency due to variations in surface finish of said chambers and throat areas as a result of casting of said casings;
- the improvement for reducing variations in overall efficiency between pumps of said group comprising;
increasing the size of each of said chambers and said discharge passages, including said throat areas beyond that required to provide said pumps with said design discharge flow rate, while maintaining essentially said given radial spacing between said cut-waters and sid axis; and providing restrictions within said discharge passages having uniformly sized restrictor flow openings therethrough serving to limit the discharge flow rate from said pumps to essentially said design discharge flow rate. - View Dependent Claims (9)
- the improvement for reducing variations in overall efficiency between pumps of said group comprising;
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10. An improvement in the method of manufacturing a low specific speed centrifugal pump including the steps of casting a casing from metal to define a pump chamber, an inlet communicating with the chamber and a discharge passage having a throat end communicating with said chamber and an outlet end, and fitting said casing with an impeller supported for rotation about an axis within the chamber for transporting fluid from said inlet opening to said outlet end, wherein said pump chamber has an outer boundary surface extending away from a cut-water and about said pump chamber for cooperation with said cut-water to define said throat end, wherein surfaces of said chamber and said discharge passage including said throat have an as-cast surface finish tending to produce frictional losses during operation of said pump, and wherein said pump is characterized as having a design discharge flow rate for any given size impeller, chamber, discharge passage and radial spacing between said cut-water and said axis, said improvement tending to reduce said frictional losses of said pump comprising:
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forming said chamber and said discharge passage including said throat end of a size exceeding that required to provide said design discharge flow rate while maintaining essentially said given radial distance between said cut-water and said axis; and providing a restriction in said discharge passage having a flow opening extending therethrough sized to throttle discharge flow from said pump to said design discharge flow rate. - View Dependent Claims (11)
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12. An improvement in the method of manufacturing a group of low specific speed centrifugal pumps, wherein pumps forming said group have decreasing discharge flow rates relative to a given discharge flow rate, including the steps of forming a group of like sized pump casings to define pump chambers, pump inlets communicating with said pump chambers and pump discharge passages having throat ends communicating with said pump chambers and outlet ends, fitting said casings with impellers rotatably supported within said pump casings for rotation about axes of rotation, and providing restrictor openings in said discharge passages to provide said decreasing discharge flow rates, wherein said pump chambers have outer boundary surfaces disposed radially outwardly of said axis to extend away from cut-waters and about said pump chambers for cooperating with said cut-waters to define said throat ends and wherein surfaces of said pump chambers and passages have as-formed surface finishes tending to produce frictional losses during operation of said pumps, which vary between pumps having any given size restrictor opening;
- said improvement including;
forming said pump chambers and passages, including said throat ends, of a size sufficient to provide another discharge flow rate exceeding said given discharge flow rate and to reduce said losses while maintaining a radial distance between said cut-waters and said axes corresponding to that required to provide said given discharge flow rate; and sizing said restrictor openings to reduce said discharge flow ratefrom said other discharge flow rate to and below said given discharge flow rate. - View Dependent Claims (13)
- said improvement including;
Specification