US-12618413-B2 - Method for controlling of a pump unit and a pump unit for pumping liquid or suspension

US12618413B2US 12618413 B2US12618413 B2US 12618413B2US-12618413-B2

Abstract

A method for controlling a pump unit includes controlling the pump unit based on a determination of a combination of an inducer and a centrifugal pump at least on parameters of total volumetric flow rate and pressure difference over the pump unit, and controlling the pump unit based on a surface level on a suction side of the pump unit, and an NPSHaA at an inlet before the pump unit is measured, calculated or otherwise determined, and, the output power of the inducer is increased or decreased to affect a NPSHaB at the flow channel before the impeller, so that during operation of the pump unit the NPSHaB is greater than a NPSHr of the centrifugal pump.

Inventors

Janne Ripattila
Kalle TIITINEN

Assignees

SULZER MANAGEMENT AG

Dates

Publication Date: 20260505
Application Date: 20230615
Priority Date: 20220623

Claims (15)

1 . A method for controlling a pump unit for pumping liquid or a suspension, the pump unit comprising a centrifugal pump, and an inducer in a proximity upstream of an inlet of the centrifugal pump, the centrifugal pump comprising a pump housing forming a flow channel inside the pump housing and an impeller configured to be rotated in the flow channel about a central axis by a shaft, the inducer comprising an inducer rotor having a sleeve-shaped rotor body, the inducer rotor configured to be rotated about the central axis in the flow channel, the rotor body including a number of blades extending inwards from the rotor body, the inducer rotor being separate to the impeller and a rotation speed of the inducer rotor independently controlled in relation to a rotation speed of the impeller, the inducer comprising an electric motor that is an annular motor encircling and connected to the inducer rotor, the method comprising controlling the pump unit based on a determination of a combination of the inducer and the centrifugal pump at least on parameters of total volumetric flow rate and pressure difference over the pump unit, and controlling the pump unit based on a surface level on a suction side of the pump unit, and a first net positive suction head available at an inlet before the pump unit is measured, calculated or otherwise determined, and when necessary, the output power of the inducer is increased or decreased to affect a second net positive suction head available at the flow channel before the impeller, so that during operation of the pump unit the second net positive suction head available is greater than a net positive suction head required of the centrifugal pump.
2 . The method according to claim 1 , wherein the pump unit is controlled so that an output power of the inducer is less than an output power of the centrifugal pump.
3 . The method according to claim 1 , wherein the rotation speed of the inducer rotor is controlled based on detected cavitation at the centrifugal pump, a head generated by the inducer is increased or decreased to maintain a margin to an outbreak of cavitation of the impeller.
4 . The method according to claim 1 , wherein the second net positive suction head available is measured, calculated or otherwise determined, and the rotation speed of the inducer rotor or a head generated by the inducer is driven along a predetermined net positive suction head required curve for a given operation condition.
5 . The method according to claim 1 , wherein the rotation speed of the inducer rotor or the output power of the inducer is controlled based on required gas separation for a fluid to be pumped, the required gas separation capable of being determined based on gas detection or predetermination to determine a gas content in the fluid.
6 . A pump unit for pumping liquid or a suspension, wherein the pump unit is connected to a controller configured to execute the method of claim 1 , the pump unit comprising: the centrifugal pump; the inducer in the proximity upstream of the inlet of the centrifugal pump, the centrifugal pump comprising the pump housing forming the flow channel inside the pump housing and the impeller configured to be rotated in the flow channel about\the central axis by the shaft, the inducer comprising the inducer rotor having the sleeve-shaped rotor body, the inducer rotor configured to be rotated about the central axis in the flow channel, the rotor body including the number of blades extending inwards from the rotor body, the inducer rotor being separate to the impeller and the rotation speed of the inducer rotor being independently controllable in relation to the rotation speed of the impeller, the inducer comprising the electric motor that is the annular motor encircling and being connected to the inducer rotor; and a sensor configured to detect cavitation disposed in the flow channel between the inducer rotor and impeller.
7 . The pump unit according to claim 6 , wherein the inducer rotor and impeller are drivable by separate electric motors electrically connected to the controller.
8 . The pump unit according to claim 6 , wherein the inducer rotor is rotatable in an opposite or a same direction as the impeller.
9 . The pump unit according to claim 6 , wherein the inducer comprises the inlet, an inducer housing to enclose a stator, an annular motor and the inducer rotor, the inducer housing being connected to the pump housing via a flange attachment at a distance from 0.01 up to 10 times a diameter of the flow channel.
10 . The pump unit according to claim 6 , wherein guide vanes are disposed between the inducer and the impeller, the guide vanes having fixed or adjustable pitch.
11 . The pump unit according to claim 10 , wherein the guide vanes comprise conduits for gas removal from the liquid.
12 . The pump unit according to claim 6 , wherein the rotation speed of the inducer rotor is variably or independently controllable in relation to the rotation speed of the impeller.
13 . The pump unit of claim 6 , the sensor is one of the following sensors to monitor the centrifugal pump or to determine the first net positive suction head available or the second net positive suction head available values: a pressure sensor, an acoustic sensor for cavitation monitoring, a vibration monitoring sensor, an on-line consistency sensor, an on-line gas content meter, or a thermometer.
14 . The pump unit of claim 6 , further comprising a sensor configured to monitor the centrifugal pump by application of calculations using software of variable speed drive.
15 . A controller for controlling the pump unit for pumping liquid or the suspension according to the method of claim 1 , comprising executable instructions to control the rotation speed of the the inducer rotor or the output power of the inducer based on a sensor signal of at least one sensor, and the at least one sensor configured to detect cavitation disposed in the flow channel between the inducer rotor and the impeller.

Description

PRIORITY This application is a U.S. National Stage application of PCT/EP2023/066115, filed Jun. 15, 2023, which claims priority to European Application No. 22180825.6, filed Jun. 23, 2022, the contents of each of which are hereby incorporated by reference. BACKGROUND Technical Field The present disclosure relates to a method for controlling a pump unit. Especially the disclosure relates to a method for controlling a pump unit for pumping liquid or suspension, the pump unit comprises a centrifugal pump and an inducer in a proximity upstream of an inlet of the centrifugal pump: the centrifugal pump comprises a pump housing forming a flow channel inside the pump housing and an impeller configured to be rotated in the flow channel around a central axis by a shaft,the inducer comprises an inducer rotor having sleeve-shaped rotor body, the inducer rotor is configured to be rotated around the central axis in the flow channel, the rotor body is provided with a number of blades extending inwards from the rotor body. The present disclosure relates also to a pump unit. Background Information Centrifugal pumps with conventional inducers can be used in pumping applications where there are challenging pumping conditions for example due to multiphase suspension consisting of fluid in gas, liquid and solid phases. These conventional inducers are mounted on a same axel as there is an impeller, thus rotating the same speed as the impeller. A prior art publication CN111828391A provides a blade-adjustable shaftless inducer for a pump. The inducer comprises a pump shell and an impeller, wherein the impeller is arranged in the pump shell, a plurality of inducer blades are evenly distributed on the extending section of an impeller cover plate of the impeller, a positioning device is arranged at the joint between each inducer blade and the impeller cover plate, external force enables the inducer blades to overcome positioning of the positioning devices and drives the inducer blades to rotate so as to adjust the angle of the inducer blades, and a thrust rotating device is arranged outside the pump shell and used for providing the external force. According to the inducer, by adjusting the placement angle of the blades, the pump can operate at the optimal working condition point under different working conditions; the inducer is suitable for the condition that inlet incoming flow is low-pressure; and the inducer adopts a hub-free form, and the blades are arranged at the lengthened part of the cover plate of the impeller, so that the weight of the inducer is reduced, more inlet area is provided, and then the efficiency of the pump is improved. In this disclosure there will be used the following determinations of expressing a Net Positive Suction Head (NPSH) relative to a centrifugal pumping system. It equals to total pressure that is expressed as height of liquid column of pumped medium (Head in meters): NPSHa: The Net Positive Suction Head Available at the pump impeller inlet. NPSHa is a value that expresses the total pressure of a liquid as it enters the pump. It is a measure of the pressure that stands between the liquid in its current state and the formation of vapor bubbles (boiling).NPSHr: The Net Positive Suction Head Required by the pump to operate without experiencing damaging cavitation and a dramatic reduction in pumping production. NPSHr is a value that expresses the minimum total head that must be acting on a liquid as it enters the pump impeller to avoid excessive cavitation and degradation of pump performance. An object of the disclosure is to provide an inducer/centrifugal pump combination in which the performance is considerably improved compared to the prior art solutions. One object is to improve the versatility of the inducer/centrifugal pump combination so that it would be suitable for pumping in various operating conditions, for example, due to variations in inlet pressure due to varying surface level in a tank or due to changes in prevailing consistency of the fluid to be pumped. As the inducer/centrifugal pump combination is intended for constant use of 24/7 in a process industry for years, the pumping efficiency is among top priorities with the inducer/centrifugal pump combination. SUMMARY Objects of the disclosure can be met substantially as is disclosed in the present disclosure, which describes more details of different embodiments of the disclosure. According to an embodiment of the disclosure a pump unit for pumping liquid or suspension is provided, the pump unit comprises a centrifugal pump and an inducer in a proximity upstream of an inlet of the centrifugal pump: the centrifugal pump comprises a pump housing forming a flow channel inside the pump housing and an impeller configured to be rotated in the flow channel around a central axis by a shaft,the inducer comprises an inducer rotor having sleeve-shaped rotor body, the inducer rotor is configured to be rotated around the central axis in the flow chan