US4435193A — Controlling operation of a centrifugal pump

Claim 1

Independent Claim 145 words

A method for controlling the operation of a centrifugal pump pumping a suspension having a consistency of about 8-12 percent and containing gas, the pump having an inlet suspension pressure, a pressure head, and a suspension discharge flow rate, comprising the steps of: (a) effecting rotation of the suspension within the pump so that a gas bubble is created in a central part of the pump; (b) discharging gas from the gas bubble in the pump central part, at a gas discharge pressure; (c) rotating the pump impeller at a speed sufficient to effect fluidization of the suspension, and effecting discharge of the fluidized suspension at a flow rate; (d) determining the differential pressure between the suspension inlet pressure and the gas discharge pressure; and (e) controlling the head and/or discharge flow rate of the pump by controlling the differential pressure determined in step (d).

Claim 2

Independent Claim 145 words

A method for controlling the operation of a centrifugal pump pumping a suspension having a consistency of about 8-12 percent and containing gas, the pump having an inlet suspension pressure, a pressure head, and a suspension discharge flow rate, comprising the steps of: (a) effecting rotation of the suspension within the pump so that a gas bubble is created in a central part of the pump; (b) discharging gas from the gas bubble in the pump central part, at a gas discharge pressure; (c) rotating the pump impeller at a speed sufficient to effect fluidization of the suspension, and effecting discharge of the fluidized suspension at a flow rate; (d) determining the differential pressure between the suspension inlet pressure and the gas discharge pressure; and (e) controlling the head and/or discharge flow rate of the pump by controlling the differential pressure determined in step (d).

Claim 3

Dependent Claim 21 words

A method as recited in claim 1 wherein step (e) is practiced by controlling the discharge rate of gas in (b).

Claim 4

Dependent Claim 39 words

A method as recited in claim 2 wherein the flow rate of discharged gas is controlled by applying a suction force on the gas to effect discharge thereof, and metering the volume of gas passing through said suction source.

Claim 5

Dependent Claim 63 words

A method as recited in claim 1 wherein the discharge rate of the flow of the fluidized suspension is maintained substantially constant by measuring the flow at a particular point in the discharge line from the pump; and controlling a valve in the discharge line upstream of said point, in response to the flow rate measurement to maintain the discharge rate substantially constant.

Claim 6

Dependent Claim 52 words

A method as recited in claim 1 wherein step (b) is practiced by discharging the gas into an air vessel distinct from the pump, the motive force for effecting discharge of the gas to the gas vessel being provided by applying a suction source on the gas downstream of the air vessel.

Claim 7

Dependent Claim 71 words

A method as recited in claim 5 comprising the further step of, at start up of the centrifugal pump, or where a rapid pressure change is desired, automatically feeding air--from a source independent of the pump gas discharge--at a controlled pressure and flow rate to the air vessel; and wherein the gas discharge pressure utilized for determining the differential pressure set forth in step (d) is determined in the air vessel.

Claim 8

Dependent Claim 41 words

A method as recited in claim 1 wherein step (b) is practiced by discharging gas to an air vessel; and wherein the gas discharge pressure set forth in step (d) is determined by measuring the gas pressure in the air vessel.

Claim 9

Dependent Claim 53 words

A method as recited in claim 1 wherein the pump central part from which gas is discharged comprises an gas chamber directly connected to a gas discharge pipe; and comprising the further step of periodically flushing materials that collect in the gas chamber by supplying a liquid under pressure to the gas chamber.

Claim 10

Independent Claim 155 words

A method for controlling the operation of a centrifugal pump pumping a cellulosic fiber suspension having a consistency of about 8-12 percent, and having gas entrained therein, comprising the steps of: (a) effecting rotation of the suspension so that a gas bubble is created in a central part of the pump; (b) effecing discharge of gas from the central part of the pump; (c) rotating the pump impeller at a speed sufficient to effect fluidization of the suspension, and effecting discharge of the fluidized suspension at a flow rate; (d) determining the differential pressure between the suspension just prior to fluidization thereof and the gas being discharged; (e) maintaining the rotational speed of the pump substantially constant and the discharge flow rate of the fluidized suspension substantially constant; and (f) significantly reducing the power consumption of the pump by controlling the pump head, which is accomplished by controlling the differential pressure determined in step (d).

Claim 11

Independent Claim 155 words

A method for controlling the operation of a centrifugal pump pumping a cellulosic fiber suspension having a consistency of about 8-12 percent, and having gas entrained therein, comprising the steps of: (a) effecting rotation of the suspension so that a gas bubble is created in a central part of the pump; (b) effecing discharge of gas from the central part of the pump; (c) rotating the pump impeller at a speed sufficient to effect fluidization of the suspension, and effecting discharge of the fluidized suspension at a flow rate; (d) determining the differential pressure between the suspension just prior to fluidization thereof and the gas being discharged; (e) maintaining the rotational speed of the pump substantially constant and the discharge flow rate of the fluidized suspension substantially constant; and (f) significantly reducing the power consumption of the pump by controlling the pump head, which is accomplished by controlling the differential pressure determined in step (d).

Claim 12

Dependent Claim 63 words

A method as recited in claim 9 wherein the discharge rate of the flow of the fluidized suspension is maintained substantially constant by measuring the flow at a particular point in the discharge line from the pump; and controlling a valve in the discharge line upstream of said point, in response to the flow rate measurement, to maintain the discharge rate substantially constant.

Claim 13

Dependent Claim 75 words

A method as recited in claim 10 wherein step (f) is practiced by measuring the difference in pressure between the suspension just prior to fluidization, and the fluidized suspension when discharged from the pump; determining a set value in response to the measured pressure difference; and controlling the gas discharge rate so that the differential pressure between the suspension just prior to fluidization thereof and the gas being discharged is approximately at said set value.

Claim 14

Dependent Claim 75 words

A method as recited in claim 9 wherein step (f) is practiced by measuring the difference in pressure between the suspension just prior to fluidization, and the fluidized suspension when discharged from the pump; determining a set value in response to the measured pressure difference; and controlling the gas discharge rate so that the differential pressure between the suspension just prior to fluidization thereof and the gas being discharged is approximately at said set value.

Claim 15

Dependent Claim 41 words

A method as recited in claim 9 wherein step (b) is practiced by discharging gas to an air vessel; and wherein the gas discharge pressure set forth in step (d) is determined by measuring the gas pressure in the air vessel.

Claim 16

Independent Claim 173 words

A method for controlling the operation of a centrifugal pump pumping a suspension having a consistency of about 8-12 percent and containing gas, the pump having an inlet suspension pressure, a pressure head, a suspension discharge flow rate, and a suspension discharge pressure, comprising the steps of: (a) effecting rotation of the suspension within the pump so that a gas bubble is created in a central part of the pump; (b) discharging gas from the gas bubble in the pump central part, at a gas discharge pressure; (c) rotating the pump impeller at a speed sufficient to effect fluidization of the suspension, and effecting discharge of the fluidized suspension at a flow rate; (d) determining the differential pressure between the suspension inlet pressure and the suspension discharge pressure; (e) determining a differential pressure set value in response to the differential pressure measured in step (d); and (f) controlling the differential pressure between the suspension inlet pressure and the gas discharge pressure so that said differential pressure is approximately said differential pressure set value.

Claim 17

Independent Claim 173 words

A method for controlling the operation of a centrifugal pump pumping a suspension having a consistency of about 8-12 percent and containing gas, the pump having an inlet suspension pressure, a pressure head, a suspension discharge flow rate, and a suspension discharge pressure, comprising the steps of: (a) effecting rotation of the suspension within the pump so that a gas bubble is created in a central part of the pump; (b) discharging gas from the gas bubble in the pump central part, at a gas discharge pressure; (c) rotating the pump impeller at a speed sufficient to effect fluidization of the suspension, and effecting discharge of the fluidized suspension at a flow rate; (d) determining the differential pressure between the suspension inlet pressure and the suspension discharge pressure; (e) determining a differential pressure set value in response to the differential pressure measured in step (d); and (f) controlling the differential pressure between the suspension inlet pressure and the gas discharge pressure so that said differential pressure is approximately said differential pressure set value.

Claim 18

Dependent Claim 45 words

A method as recited in claim 14 wherein step (f) is practiced by applying a suction force to the gas to effect discharge thereof, and metering the volume of gas passing under the influence of the suction force to thereby control the gas discharge rate.

Claim 19

Dependent Claim 63 words

A method as recited in claim 14 wherein the discharge rate of the flow of the fluidized suspension is maintained substantially constant by measuring the flow at a particular point in the discharge line from the pump; and controlling a valve in the discharge line upstream of said point, in response to the flow rate measurement to maintain the discharge rate substantially constant.

Claim 20

Dependent Claim 41 words

A method as recited in claim 14 wherein step (b) is practiced by discharging gas to an air vessel; and wherein the gas discharge pressure set forth in step (f) is determined by measuring the gas pressure in the air vessel.

Claim 21

Independent Claim 168 words

A method for controlling the operation of a centrifugal pump pumping a liquid or suspension containing gas, the pump having an inlet liquid or suspension pressure, a pressure head, and a liquid or suspension discharge flow rate, comprising the steps of: (a) effecting rotation of the liquid or suspension within the pump so that a gas bubble is created in a central part of the pump; (b) discharging gas from the gas bubble in the pump central part, at a gas discharge pressure, to an air vessel; (c) determining the differential pressure between the liquid or suspension inlet pressure and the gas discharge pressure, the gas discharge pressure measured in the air vessel; (d) controlling the head and/or discharge flow rate of the pump by controlling the differential pressure determined in step (c); and (e) at pump start up, or when a rapid differential pressure change is desired, feeding air at a controlled pressure and flow rate--from a source independent of the pump gas discharge--to the air vessel.

Claim 22

Independent Claim 168 words

A method for controlling the operation of a centrifugal pump pumping a liquid or suspension containing gas, the pump having an inlet liquid or suspension pressure, a pressure head, and a liquid or suspension discharge flow rate, comprising the steps of: (a) effecting rotation of the liquid or suspension within the pump so that a gas bubble is created in a central part of the pump; (b) discharging gas from the gas bubble in the pump central part, at a gas discharge pressure, to an air vessel; (c) determining the differential pressure between the liquid or suspension inlet pressure and the gas discharge pressure, the gas discharge pressure measured in the air vessel; (d) controlling the head and/or discharge flow rate of the pump by controlling the differential pressure determined in step (c); and (e) at pump start up, or when a rapid differential pressure change is desired, feeding air at a controlled pressure and flow rate--from a source independent of the pump gas discharge--to the air vessel.

Claim 23

Dependent Claim 146 words

Apparatus for controlling the operation of a centrifugal pump pumping a suspension having gas entrained therein, comprising: a centrifugal pump having a suspension chamber with an impeller disposed therein, and a gas chamber in fluid communication with said suspension chamber and having rotating blades disposed therein; a suspension inlet to said suspension chamber, and a suspension outlet from said suspension chamber; a gas outlet from said gas chamber; means for measuring the flow in said suspension discharge line at a particular point; a valve in said suspension discharge line upstream of said particular point; means for determining the differential pressure between the suspension in said suspension chamber and the gas discharge in said discharge line; and means for controlling said valve in said suspension discharge line in response to the flow rate measurement by said flow measuring means, to maintain the suspension discharge rate substantially constant.

Claim 24

Dependent Claim 146 words

Apparatus for controlling the operation of a centrifugal pump pumping a suspension having gas entrained therein, comprising: a centrifugal pump having a suspension chamber with an impeller disposed therein, and a gas chamber in fluid communication with said suspension chamber and having rotating blades disposed therein; a suspension inlet to said suspension chamber, and a suspension outlet from said suspension chamber; a gas outlet from said gas chamber; means for measuring the flow in said suspension discharge line at a particular point; a valve in said suspension discharge line upstream of said particular point; means for determining the differential pressure between the suspension in said suspension chamber and the gas discharge in said discharge line; and means for controlling said valve in said suspension discharge line in response to the flow rate measurement by said flow measuring means, to maintain the suspension discharge rate substantially constant.

Claim 25

Dependent Claim 69 words

Apparatus as recited in claim 19 further comprising: an air vessel operatively connected to said gas discharge line; means for measuring the gas discharge pressure for determining the differential pressure between the suspension in said suspension chamber and the gas being discharged; and a suction source downstream of said air vessel and operatively connected thereto for providing the motive force for effecting discharge of gas to the gas vessel.

Claim 26

Dependent Claim 25 words

Apparatus as recited in claim 20 further comprising valve means disposed in said gas discharge conduit between said air vessel and said pump gas chamber.

Claim 27

Dependent Claim 34 words

Apparatus as recited in claim 20 further comprising means for automatically feeding gas from a source independent of said pump gas discharge line at a controlled pressure and flow rate to said air vessel.

Claim 28

Dependent Claim 123 words

Apparatus for controlling the operation of a centrifugal pump pumping a suspension, comprising: said pump having a suspension chamber with an impeller, and a gas chamber in fluid communication with said suspension chamber, and rotatable blades in said gas chamber; an inlet to said suspension chamber, and an outlet from said suspension chamber; a gas discharge outlet from said gas chamber; an air vessel disposed in said gas discharge outlet; means for sensing the suspension inlet pressure; means for sensing the gas discharge pressure in said air vessel; means for determining the differential pressure between said sensed suspension inlet pressure and gas discharge pressure; and means for controlling the head and/or discharge flow rate of the pump by controlling the determined differential pressure.

Claim 29

Dependent Claim 123 words

Apparatus for controlling the operation of a centrifugal pump pumping a suspension, comprising: said pump having a suspension chamber with an impeller, and a gas chamber in fluid communication with said suspension chamber, and rotatable blades in said gas chamber; an inlet to said suspension chamber, and an outlet from said suspension chamber; a gas discharge outlet from said gas chamber; an air vessel disposed in said gas discharge outlet; means for sensing the suspension inlet pressure; means for sensing the gas discharge pressure in said air vessel; means for determining the differential pressure between said sensed suspension inlet pressure and gas discharge pressure; and means for controlling the head and/or discharge flow rate of the pump by controlling the determined differential pressure.

Claim 30

Dependent Claim 41 words

Apparatus as recited in claim 23, further comprising a suction source disposed in operative communication with said air vessel, said suction source providing the motive force for effecting discharge of the gas from the pump gas chamber to said air vessel.

Claim 31

Dependent Claim 34 words

Apparatus as recited in claim 23 further comprising means for automatically feeding gas from a source independent of said pump gas discharge line at a controlled pressure and flow rate to said air vessel.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1987-03-06	1987-09-05	1988-03-06	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1991-03-06	1991-09-05	1992-03-06	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1995-03-06	1995-09-05	1996-03-06	$7700.00	Window Closed / Lapsed

Controlling operation of a centrifugal pump

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