Abstract:
For a device ( 4 ) for the performance adaptation of a liquid ring pump, said liquid ring pump ( 1 ) comprising a cylindrical workspace ( 6 ) for conveying a conveyed fluid ( 15 ) between an intake socket ( 16   a ) and a pressure socket ( 18   a ). The device ( 4 ) comprises a control unit ( 28 ), control line ( 22 ) and a control element ( 26 ) connected with the workspace ( 6 ). The device is designed to vary the amount of operating liquid of the liquid ring pump ( 1 ) during operation (running) of said pump. Also, a method for adapting the performance of the liquid ring pump ( 1 ), which is performed in particular via the device ( 4 ) is specified.

Description:
[0001]     We hereby claim foreign priority under section 119 of the US Patent statute, based on German application 102005043434.7, filed Sep. 13, 2005.  
       FIELD  
       [0002]     The invention relates to a device for the performance adaptation of a liquid ring pump, said pump comprising a cylindrical workspace for conveying a conveyed fluid between a fluid inlet (intake socket) and a fluid outlet (pressure socket), wherein an operating fluid is contained in the workspace, said device controls the volume of operating liquid in the pump during operation of the pump.  
       BACKGROUND  
       [0003]     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 a pump. A liquid ring pump is revealed, for example, in the printed publication U.S. Pat. No. 4,392,783.  
         [0004]     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.  
         [0005]     Some modern 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.  
       SUMMARY  
       [0006]     The invention is therefore based on the object of providing 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.  
         [0007]     Accordingly, one embodiment of the device comprises a control line interfaced with a control element. The control line is fluidly connected to the workspace or chamber of the pump. The control line and element are designed to modify, as a correcting variable, a hydraulic characteristic of the liquid pump. The modified characteristic is preferably the volume of operating liquid in the chamber during operation (running) of the pump.  
         [0008]     As an alternative to the variation of the quantity of operating fluid, or in combination therewith, the device could be designed to modify the viscosity of the operating fluid contained in the workspace.  
         [0009]     To regulate and change the volume of liquid during operation of the pump, one embodiment of 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 up stream 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.  
         [0010]     The control unit compares the actual value or values to a pre-set value or values for the process parameters and 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.  
         [0011]     As an alternative to the use of a control unit, the controlling element, such as the valve, may be activated manually. The control element may also be activated, pneumatically or hydraulically by signals from the control unit or from other means.  
         [0012]     As an alternative to using the total drain connections (total outflow disposed at the bottom of the workspace), the 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.  
         [0013]     As a further alternative, the control line is interfaced with the pump by providing a unique connection in the pump for the control line.  
         [0014]     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.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     To explain the device and method in more detail, example embodiments of the invention are described below and in the drawings:  
         [0016]      FIG. 1  is a cross sectional view of a liquid ring pump having suitable standard connections for interfacing with an embodiment of our 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.  
         [0017]      FIGS. 1   a , and  1   b  are front plan views of the end shields shown in  FIG. 1 .  
         [0018]      FIG. 2  is a stripped down schematic diagram showing an embodiment of our device interfaced with a liquid ring pump.  
         [0019]      FIG. 3  is a stripped down schematic diagram showing our device interfaced with a liquid ring pump.  
         [0020]      FIG. 4  is a stripped down schematic illustration of a pump arrangement comprising a liquid ring pump and our device for the performance adaptation of the liquid ring pump, said device comprising a control line discharging into the total outflow connection of the pump.  
         [0021]      FIG. 5  is a stripped down schematic illustration according to  FIG. 4  of a variant of the device wherein the device for the performance adaptation additionally incorporates a control line interfaced with the peak of the workspace of the pump.  
         [0022]      FIG. 6  is a schematic depiction according to  FIG. 5  of an additional variant of the pump device.  
     
    
     DETAILED DESCRIPTION  
       [0023]      FIG. 1  shows 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 housing  41  The connections or apertures  2  and  3  are suitable for interfacing with the device or assembly  4  for controlling the volume of operating fluid  5  in the workspace or operating chamber  6  of liquid ring pump  1 . The operating/sealing supply liquid inlets  7  are also shown. The pump also includes an impeller  11  supported eccentrically relative to the workspace  6  with impeller blades  11   a  and hub  11   b , and a shaft  12 . In the axial direction, the workspace  6  is bounded by port plates  21   a ,  21   b  which are coupled to end shields  18   a ,  18   b . The end shields are symmetrical with each other. The end shields each have inlets  13  to internal shaft seal connections  3 . The work space  6  is filled with operating liquid  5 . The operating liquid or fluid  5  is usually water. See  FIG. 4 . The operating fluid or liquid  5  can serve to seal the interstices  43  between impeller  11 , shaft  12  and port plates  21   a ,  21   b.    
         [0024]     In operation, the impeller rotates in the direction  14 . An amount of conveyed fluid  15  is drawn into inlets  16   a ,  16   b  of end shields or heads  18   a ,  18   b . The conveyed fluid  15  exits outlets  20   a ,  20   b.    
         [0025]     In more detail, during operation of the pump, the impeller blades or vanes  11   a  force the operating fluid  5  into a fast rotating movement so that the operating fluid  5 , under action of the centrifugal force, forms a liquid ring  5   a  that is concentric relative to the workspace  6 . As a result of the eccentric mounting of the impeller  11 , a sickle-shaped space  6   b  is created between the liquid ring  5   a  and impeller  11  within which conveyed fluid  15  is transported in the direction of rotation  14 . The conveyed fluid  15  is a dry or wet gas.  
         [0026]     Now referring to  FIG. 2 , the interface of device  4  with a total drain or shutdown drain connection  2  can be seen. The device  4  includes a control line, pipe or conduit  22 . The line  22  is interfaced with total drain line  2   a  by way of a two way valve  24 . Total drain line  2   a  is at the drive end. For reference end shield  18   a  is located at the drive end. Line  22  is also interfaced with a control element  26  downstream of valve  24 . The control element may be an electronically or mechanically actuated valve.  
         [0027]     Control element  26  is interfaced with control unit  28 . Interfaced with control unit  28  is sensor or sensors  30 . The sensor or sensors  30  can be for sensing process pressure, temperature, humidity or flow volume. Sensors  30  can be located up stream, at, or in fluid inlets  16   a ,  16   b . Arranging the sensor(s) at the intake socket, i.e., on the suction side, is particularly advantageous, as the values for pressure, volume flow, temperature and humidity of the conveyed fluid are not yet influenced and distorted through pressure loss, leakage, or diffusion of the operating fluid into the conveyed fluid. In this embodiment, it is also shown that the control unit  28  receives signals from a 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 the Device which is the control unit, sensors, and control line.  
         [0028]     Line  70  generally shows a flow path of the conveyed fluid  15  which enters the pump via inlets  16   a ,  16   b . Line  71  generally shows the path of conveyed fluid  15  exiting outlets  20   a ,  20   b . Additionally line  72  generally depicts the pathway of supply liquid which enters inlets  7 . The supply liquid can be operating fluid  5  and can serve as sealing fluid to seal the spaces  43 .  
         [0029]     Prior to operation, the control unit is programmed so as to have a specified or desired process parameter Ps. During operation, the control unit compares actual process parameter values Pi to the specified parameters. The actual parameters are collected and transmitted to the control unit  28  via sensors  30 . The control unit, in dependence on a comparison result transmits signals to actuate control element  26  to discharge an amount of operating fluid from chamber  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 control unit  28  or indirectly actuated by the control unit 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 conveyed fluid  15 , an amount of operating fluid  5  is discharged, during operation of the pump. The amount of discharged fluid is in addition to any fluid being discharged through outlets  20 ,  20   b . The discharged fluid is not immediately re-circulated back into the workspace  6 . The valve can be actuated in other ways including manually, hydraulically, or pneumatically.  
         [0030]     It should be noted that although device  4  uses a line  22  which branches off from total drain line  2   a  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  2   a  and control line  22  (See discussion on  FIG. 4 , supra.). Further, although device  4  is shown as regulating discharge out of total drain outlet  2  in connection with total drain line  2   a , device  4  could regulate the discharge at the total drain connection  2  on the non-drive end, i.e. at shield  18   b . 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 with valve  26 .  
         [0031]      FIG. 3  shows an alternative way of interfacing a control line  32  of device  4  for controlling the level of the operating fluid  5 , during operation of the pump, with existing pump connections. In this embodiment, the control line 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 is interfaced is generally shown at  3   a . The interface with connections  3  could be through inlets  13 . A liquid supply line or pathway which feeds the liquid into the pump is generally shown by line  73 . The fluid could be operating fluid  5  for the liquid ring or for the sealing of the spaces  43   
         [0032]     Interfaced with control line or conduit  32  is control element  26 . The control element  26  is actuated in the same manner as control element  26  in  FIG. 2 . In this embodiment, it is also shown that the control unit  28  receives signals from a temperature sensor  30  located along the pump discharge pathway  71 .  
         [0033]     In accordance with  FIG. 4 , the device  4  comprises a control line  100  for discharging and feeding operating fluid  5  into the workspace  6 . The control line  100  opens into total outflow or shutdown drain connection  2  of the workspace  6 . The control line  100  has a controlling element  102 , which is designed especially in the style of a bi-directionally operable operating-fluid pump. Depending on the activation of the controlling element  102 , operating fluid  5  can thus be either fed to or removed from the workspace  4 . The control line  100  can serve as the total drain line after shut down. The device  4   b  additionally comprises control unit  28 , which enables actuation of the controlling element  102  via sensors  30 .  
         [0034]      FIG. 5  shows an additional embodiment. In contrast to the embodiment according to  FIG. 4 , the device, in this case incorporates two separate control lines namely one feed control line  200   a  and one discharge control line  200   b . The discharge control line  200   b  opens into the peak  202  of the workspace  6 . The feed control line  200   a  opens into the workspace at the total outflow  2 . The control line  200   b  is preferably is interfaced with the inner shaft seal connection  3 . The interface could be through inlets  13   
         [0035]     The feed control line  200   a  and the discharge control line  200   b  each have a controlling element  206   a  and  206   b  in the form of a control valve or pump for regulating the flow of the operating fluid through control lines  200   a ,  200   b . Control unit  28  enables activation of controlling elements  206   a ,  206   b  depending on the input from the sensor(s)  30 .  
         [0036]     In accordance with  FIG. 6 , the device, in contrast to the embodiment according to  FIG. 5 , comprises only the single control line  300  for discharging operating fluid  5 . Controlling element  26  is interfaced with control line  300 . The control line  300  could have its own unique connection or interface with the inner shaft seal connections. 3