EP1762728B1

EP1762728B1 - Device for the performance adaptation of a liquid ring pump

Info

Publication number: EP1762728B1
Application number: EP06019078A
Authority: EP
Inventors: Fausto Olivares; Christoph Weber; Peter Dr. Trimborn
Original assignee: Gardner Denver Deutschland GmbH
Current assignee: Gardner Denver Deutschland GmbH
Priority date: 2005-09-13
Filing date: 2006-09-12
Publication date: 2012-11-07
Anticipated expiration: 2026-09-12
Also published as: ES2396482T3; DE102005043434A1; CN1932292A; EP1762728A1; US20070059185A1

Description

The invention relates to a pump arrangement as defined in the preamble of claim 1. Such an arrangement is known from JP-A-05118285 . The invention relates further to a method for the performance adaptation of a liquid ring pump.
A liquid ring pump is suitable for conveying dry or liquid-containing gases and is commonly used both as a vacuum pump and also as a compressor. A liquid ring pump of this type has an impeller eccentrically arranged inside a casing that contains an operating fluid. Water is often used as the operating fluid. During operation of the pump, the rotation of the impeller causes the operating fluid in the pump casing to form a liquid ring that lifts off on the suction side from an impeller hub of the impeller and revolves with the same. The liquid ring cooperates with the impeller to draw in fluid at the inlet, compress the fluid, and discharge it at the outlet. Due to the pump principle, the conveyed fluid when discharged via the pressure socket (outlet) is mixed with the operating fluid. The operating fluid is subsequently separated from the conveyed gas in a separator and fed back to the pump. The operating liquid in some pump arrangements can also serve to seal spaces between the shaft impeller and plate port of the pump. A liquid ring pump is revealed, for example, in the printed publication US 4,392,783 . Further examples of liquid ring pumps are revealed, for example, in US 2,230,405 , SU 779 643 B , US 6,558,131 , DE 298 03 322 U1 , US 5,588,806 , DE 662 514 , JP 05 118 285 and US 6,551,071 B1 .
Industrial processes in vacuum and pressure applications, within the framework of which liquid ring pumps are employed, are often subject to periodical and also non-periodical changes. As a result, the performance requirement placed on the given liquid ring pump generally changes as well. Liquid ring pumps, however, for the benefit of a simple design, often are not controllable or adjustable with respect to their driving power. Liquid ring pumps of this type are often sized for maximum load or maximum process requirements, and they therefore typically draw, too much driving power during normal operation. In the vast majority of existing installations, the excess power of the liquid ring pumps is reduced by means of a throttle regulation, false air, or bypass regulation. The excess driving power is simply disposed of in these cases.
Some modem systems employ liquid ring pumps that regulate the power requirement during changing process conditions via a speed adaptation by means of a converter. However, converters consume a certain amount of the conserved energy through electrical losses. Additionally, the use of a converter disadvantageously entails a comparatively high investment expenditure, additional space requirement, and increased susceptibility to failure.
The invention is therefore based on the object of providing a pump arrangement with a device for the performance adaptation of a liquid ring pump, as well as a method carried out especially by said device for the performance adaptation of the liquid ring pump.
With respect to said pump arrangement, the object is met according to the invention with the characteristics of claim 1.
To regulate and change the volume of liquid during operation of the pump, the invention uses a control line fluidly connected to the total drain connection or outlet(s). Standard pumps generally have a total drain connection allowing for the drainage of the operating fluid from the pump when the pump is not in operation i.e., shut down. The control line cooperates with a control element (valve) which is interfaced with a control unit. The control unit actuates the valve of the control line based on input from one or more sensors or other actuators which monitor process parameters. The sensors could be process pressure, temperature, flow volume, or humidity sensors disposed at, in or upstream of the fluid inlet intake socket. Moreover, the volume of process liquid and/or dry content of the product can also be used as a process parameter. The actuator, in addition to sensors, could include a push button on the control unit. The push button activates the valve to release a predetermined amount of operating liquid during operation.
The control unit compares the actual value or values to a pre-set value or values for the process parameters and feeds or discharges a volume of operating fluid during operation to bring the actual values in line with the pre-set values. Therefore, the use of a control unit is advantageous in that it allows for the regulation of the pump by taking into account process parameters such as the physical characteristics of the conveyed fluids, one such characteristic being process pressure. It also, of course, allows one to take into account other process variables such as temperature.
In addition to using the total drain connections (total outflow disposed at the bottom of the workspace), a further control line is interfaced with one or more of the internal shaft sealing supply connections present in known pumps. In this case, fluid is removed during operation through these sealing supply connections.
The object is additionally met according to the invention with a method. The above explanations regarding advantages and embodiments of the inventive device shall be logically translated to a method for controlling the performance of a liquid ring pump as claimed in claim 7.
To explain the device and method in more detail, example embodiments of the invention are described below and in the drawings:

Fig. 1: is a cross sectional view of a liquid ring pump having suitable standard connections for interfacing with a device for performance adaptation of a liquid ring pump; the shown pump includes an impeller bounded on each axial side by a port plate, each port plate being coupled to an end shield.
Fig. 2 and 3: are front plan views of the liquid ring pump shown in Fig. 1.
Fig. 4: is a stripped down schematic diagram showing a device interfaced with a liquid ring pump not covered by the present invention but being presented for illustrative purposes.
Fig. 5: is a stripped down schematic diagram showing a further device interfaced with a liquid ring pump not covered by the present invention but being presented for illustrative purposes.
Fig. 6: is a stripped down schematic illustration of a pump arrangement comprising a liquid ring pump and a further device not covered by the present invention but being presented for illustrative purposes, the device being for the performance adaptation of the liquid ring pump, said device comprising a control line discharging into the total outflow connection of the pump.
Fig. 7: is a stripped down schematic illustration according to Fig. 6 of a variant of the device in accordance with an embodiment of the present invention wherein the device for the performance adaptation additionally incorporates a control line interfaced with the peak of the workspace of the pump.
Fig. 8: is a schematic depiction according to Fig. 6 of an additional variant of the pump device not covered by the present invention but being presented for illustrative purposes.

Fig. 1 to 3 show a liquid ring pump 1 which has an approximately cylindrical workspace 6, total drain connections or outlets 2 and inner shaft seal supply connections or apertures 3. The workspace has a central axis 40 and is radially surrounded by a housing 41. The connections or apertures 2 and 3 are suitable for interfacing with a device or assembly 4 for controlling the volume of an operating fluid 5 in the workspace 6 of the liquid ring pump 1. Operating/sealing supply liquid inlets 7 are also shown. The pump 1 also includes an impeller 11 supported eccentrically relative to the work-space 6 with impeller blades 11a equidistantly arranged around its circumference, a hub 11b and a shaft 12. In axial direction the workspace 6 is confined by port plates 21a, 21b, which are coupled to end shields 18a, 18b. The end shields 18a, 18b are symmetrical with each other. The end shields 18a, 18b each have inlets 13 to the internal shaft seal connections 3. The workspace 6 is partly filled with the operating fluid 5. The operating fluid 5 is usually water. The operating fluid 5 can serve to seal the interstices 43 between the impeller 11, shaft 12 and port plates 21a, 21b.
In operation, the impeller rotates in a direction of rotation 14. An amount of a conveyed fluid 15 is drawn into inlets 16a,16b of the end shields or heads 18a,18b. The conveyed fluid 15 exits the workspace 6 at outlets 20a, 20b.
In more detail, during operation of the pump, the impeller blades or vanes 11a force the operating fluid 5 into a fast rotating movement so that the operating fluid 5, under action of the centrifugal force, forms a fluid ring 5a that is concentric relative to the workspace 6. As a result of the eccentric mounting of the impeller 11, a sickle-shaped space 6b (shown in Fig. 6 to 8) is created between the fluid ring 5a and the impeller 11 within which an amount of the conveyed fluid 15 is transported in the direction of rotation 14 of the impeller 11. The conveyed fluid 15 is a dry or wet gas.
Now referring to Fig. 4, the interface of the device 4 with the total drain or shutdown drain connection 2 can be seen. The device 4 includes a control line, pipe or conduit 22. The control line 22 is interfaced with a total drain line 2a by way of a two way valve 24. The total drain line 2a is at a drive end of the pump 1. For reference the end shield 18a is located at the drive end. The control line 22 is also interfaced with a control element 26 downstream of the valve 24. The control element 26 can be an electronically or mechanically actuated valve.
The control element 26 is interfaced with a control unit 28. Interfaced with the control unit 28 is at least one sensor 30. The at least one sensor 30 can be for sensing process pressure, temperature, humidity or flow volume. The at least one sensor 30 can be located upstream, at, or in the fluid inlets 16a, 16b. Arranging the sensor(s) 30 at the fluid inlets 16a, 16b, i.e., on the suction side, is particularly advantageous, as the values for pressure, volume flow, temperature and humidity of the conveyed fluid 15 are not yet influenced and distorted through pressure loss, leakage, or diffusion of the operating fluid 5 into the conveyed fluid 15. In this embodiment, it is also shown that the control unit 28 receives signals from the temperature sensor 30 located along the pump discharge pathway 71. The reference 4 in the drawings is not intended to refer to the whole pump assembly but rather only to the device which comprises the control unit 28, the at least on sensor 30, and the control line 22.
Line 70 generally shows a flow path of the conveyed fluid 15 which enters the pump 1 via the inlets 16a, 16b. Line 71 generally shows the path of the conveyed fluid 15 exiting the outlets 20a, 20b. Additionally, line 72 generally depicts the pathway of supply liquid which enters the inlets 7. The supply liquid can serve as operating liquid 5 for the liquid ring 5a. It can also serve to seal the interstices 43.
Prior to operation, the control unit 28 is programmed so as to have a specified or desired process parameter Ps. During operation, the control unit 28 compares actual process parameter values Pi to the specified parameters. The actual parameters are collected and transmitted to the control unit 28 via the at least one sensor 30. The control unit 28, in dependence on a comparison result transmits signals to actuate the control element 26 to discharge an amount of the operating fluid 5 from the workspace 6 to vary the actual value Pi to meet the desired value Ps. The control element 26 of course can be a valve directly actuated by the control unit 28 or indirectly actuated by the control unit 28 by way of a motor. In the case of direct activation, one could use a solenoid valve. A motor actuated valve however has the advantage that the size of the valve aperture can be varied by the motor to more precisely control the discharge. In general, to increase the flow of the conveyed fluid 15, an amount of the operating fluid 5 is discharged from the workspace 6, during operation of the pump 1. The amount of discharged fluid is in addition to any fluid being discharged through outlets 20, 20b. The discharged fluid is not immediately recirculated back into the workspace 6. The valve can be actuated in other ways including manually, hydraulically, or pneumatically.
It should be noted that although the device 4 uses the control line 22 which branches off from the total drain line 2a at the drive end, it is contemplated that by using appropriate valves and actuators one could use a single line for both the total drain line 2a and the control line 22 (See discussion of Fig. 6). Further, although the device 4 is shown as regulating discharge out of the total drain outlet 2 in connection with the total drain line 2a, the device 4 could regulate the discharge at the total drain connection 2 on the non-drive end, i.e. at the shield 18b. As a further alternative, the control line 22 could include a conduit which interfaces the total drain connections 2 at both the drive end and non drive end of the pump 1 with the control element 26.
Fig. 5 shows an alternative way of interfacing a control line 32 of the device 4 for controlling the level of the operating fluid 5 with existing pump connections during operation of the pump 1. In this example, the control line 32 is interfaced with the inner shaft seal connections 3 on both the drive and non-drive end. The internal shaft seal supply to which the control line 32 is interfaced is generally shown at 3a. The interface with the connections 3 could be through the inlets 13. The liquid supply line or pathway which feeds the supply liquid into the pump 1 is generally shown by line 73. The supply liquid could serve as operating liquid 5 or to seal the interstices 43.
Interfaced with the control line or conduit 32 is the control element 26. The control element 26 is actuated in the same manner as the control element 26 in the device according to Fig. 4. In this device, it is also shown that the control unit 28 receives signals from the temperature sensor 30 located along the pump discharge pathway 71.
In accordance with Fig. 6, the device 4 comprises a control line 100 for discharging and feeding an amount of the operating fluid 5 into the workspace 6. The control line 100 opens into the total outflow or shutdown drain connection 2 of the workspace 6. The control line 100 has a control element 102, which is designed especially in the style of a bi-directionally operable operating-fluid pump. Depending on the activation of the control element 102, an amount of the operating fluid 5 can thus be either fed to or removed from the workspace 6. The control line 100 can serve as the total drain line after shut down. The device 4 additionally comprises the control unit 28, which enables actuation of the control element 102 via the at least one sensor 30.
Fig. 7 shows an embodiment of the present invention. In contrast to the embodiment according to Fig. 6, the device 4, in this case incorporates two separate control lines namely one feed control line 200a and one discharge control line 200b. The workspace 6 has a peak 202 into which the discharge control line 200b opens. The feed control line 200a opens into the workspace at the total outflow 2. The discharge control line 200b is interfaced with the inner shaft seal connection 3. The interface could be through the inlets 13 (not shown in Fig 7).
The feed control line 200a and the discharge control line 200b each have a control element 206a and 206b in the form of a control valve or pump for regulating the flow of the operating fluid 5 through the control lines 200a, 200b. The control unit 28 enables activation of the control elements 206a, 206b depending on the input from the at least one sensor 30.
In accordance with the example of Fig. 8, the device 4, in contrast to the embodiment according to Fig 7, comprises only a single control line 300 for feeding or discharging an amount of the operating fluid 5 into the workspace 6. The control element 26 is interfaced with the control line 300. The control line 300 could have its own unique connection or interface with the inner shaft seal connections 3.

Claims

A pump arrangement comprising
a. a liquid ring pump (1),

b. a device (4) for performance adaptation of the liquid ring pump (1),

c. said pump (1) comprising
i. a cylindrical workspace (6) for conveying a conveyed fluid (15) with

ii. an inlet (16a, 16b),

iii. an outlet (20a, 20b),

iv. an impeller supported eccentrically relative to the workspace (6),

v. which is in axial direction confined by port plates (21a, 21b)

vi. coupled to end shields (18a, 18b), each having inlets (13) to internal shaft seal connections (3) and

vii. at least one total drain connection (2) disposed at the bottom of the workspace of the pump (1),

viii. wherein an operating fluid (5) is contained in the workspace (6) and generates a liquid ring (5a) during operation of the liquid ring pump (1), characterized by

d. said device (4) comprising
i. at least one control line (200a) interfaced with a total drain line (2a) and fluidly connected to the at least one total drain connection (2),

ii. at least one discharge control line (200b) opening into the peak of the workspace (6) of the pump (1), interfaced with the internal shaft seal connections (3), and

iii. at least one control element (206a, 206b) interfaced with

iv. a control unit (28) interfaced with

v. at least one sensor (30).
Pump arrangement according to claim 1 characterised in that the at least one sensor (30) is a process pressure, temperature, flow volume or humidity sensor.
Pump arrangement according to any of the preceding claims characterised in that at least one sensor (30) is disposed at, in or upstream of the fluid inlet (16a, 16b).
Pump arrangement according to any of the preceding claims characterised in that the at least one control line (200a) is interfaced with the total drain line (2a) by way of a two way valve (24).
Pump arrangement according to claim 4 characterised in that the total drain line (2a) is at a drive end of the pump (1).
Pump arrangement according to any of the preceding claims characterised in that the interface between the at least one control line (200b) and the internal shaft seal connection (3) is through the inlets (13) in the end shields (18a, 18b).
A method for the performance adaptation of a liquid ring pump comprising the following steps:
a. providing a liquid ring pump (1) and a device (4) with
i. at least one discharge control line (200b) opening into the peak of a workspace (6) of the liquid ring pump (1) and interfaced with inner shaft seal connections (3),

ii. a control unit (28) interfaced with the control line (200b) via a control element (206b) and

iii. at least one sensor (30) interfaced with the control unit (28),

b. programming the control unit (28) so as to have at least one specified process parameter Ps,

c. monitoring at least one process parameter value Pi by the at least one sensor (30),

d. transmitting input from the at least one sensor (30) to the control unit (28),

e. comparing actual process parameter values Pi to the at least one specified parameter Ps,

f. transmitting signals from the control unit (28) to actuate the control element (206b) and

g. discharging a volume of operating fluid from the workspace (6) of the pump (1) through the shaft seal connections (3) to vary the actual value Pi to meet the desired value Ps.
Method according to claim 7 characterised in that the control element (206b) is activated pneumatically, hydraulically, electrically or mechanically.
Method according to claim 7 characterised in that the control element (206b) is a valve directly actuated by the control unit (28) or indirectly actuated by the control unit (28) by way of a motor.
Method according to claim 7 characterised in that the control element (206b) is a solenoid valve directly activated by the control unit (28).