Abstract:
The invention relates to a pump arrangement, in particular a centrifugal pump, in particular a main coolant pump for power stations, comprising a pump housing ( 2 ), which defines an interior ( 3 ) with an inlet opening ( 4 ) for aspirating a conveying medium and with an outlet opening ( 5 ) for expelling the conveying medium and which also defines a chamber ( 7 ) that is connected to the interior ( 3 ), a seal water system ( 22 ), which has a first conduit system ( 29 ) in order to supply seal water into the chamber ( 7 ) defined by the pump housing ( 2 ), a second conduit system ( 32 ) for evacuating a controlled leakage flow from the chamber ( 7 ) defined by the pump housing ( 2 ), and a protective valve ( 35 ), which is arranged in the second conduit system ( 32 ) in order to block the leakage flow that is evacuated from the chamber ( 7 ). The invention further relates to a protective valve ( 35 ) and to the use of a protective valve ( 35 ) in a pump arrangement ( 1 ).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of PCT International Application No. PCT/EP2014/054935, filed Mar. 13, 2014, which claims priority under 35 U.S.C. §119 from German Patent Application No. 10 2013 004 908.3, filed Mar. 22, 2013, the entire disclosures of which are herein expressly incorporated by reference. 
     
    
     BACKGROUND AND SUMMARY OF THE INVENTION 
       [0002]    The invention concerns a pump arrangement, in particular a centrifugal pump, in particular a main coolant pump for power stations, a protective valve and the use of a protective valve in a pump arrangement. 
         [0003]    Such pumps have multi-stage hydrodynamic sealing systems with a so-called controlled leakage. These axial face sealing systems allow a defined pressure division between the stages of the axial face sealing system, and the dissipation of the heat yield from the individual steps which amounts to several kilowatts. In normal operation, the controlled leakage is fed from a sealing water system which thus ensures a seal against the system and prevents the hot delivery medium from entering the seal housing. To protect the sealing part from high temperatures and shocks, it must be ensured that if no sealing water is available, either the inflowing hot water is cooled or the pump is shut down and the leakage valve closed. 
         [0004]    The object of the invention is to create a device which, on failure of the sealing water supply, ensures an independent blocking of the controlled leakage and can maintain this block during further operation. 
         [0005]    The object of the invention is achieved by a pump arrangement with a pump housing which defines an interior with an inlet opening for aspirating a delivery medium and an outlet opening for expelling the delivery medium, and which also defines a chamber connected to the interior, a sealing water system comprising a first conduit system for supplying sealing water to the chamber defined by the pump housing, a second conduit system for evacuating a controlled leakage flow from the chamber defined by the pump housing, and a protective valve arranged in the second conduit system for blocking the leakage flow evacuated from the chamber. 
         [0006]    In a preferred implementation of the pump arrangement, the chamber is a multi-stage hydrodynamic sealing system which securely seals the chamber. 
         [0007]    In a particular embodiment, the sealing system comprises a plurality of spring-mounted axial face seals. 
         [0008]    The security of the sealing system is further increased if the sealing system comprises a pressure-controlled seal which is open in operation, in particular a nitrogen seal, water seal or similar. 
         [0009]    A particularly good operating method is achieved if medium is extracted from the leakage flow via a conduit and supplied to a pressure chamber in the seal arranged inside the chamber. 
         [0010]    Since the leakage protection valve, once closed, is not able to open by itself as long as a positive pressure predominates in front of the protection valve, a shut-off fitting is connected in parallel to the protective valve. 
         [0011]    The object of the invention is furthermore achieved by a protective valve with a valve housing part, a valve chamber formed in the valve housing part, a valve housing cover which is arranged on the valve housing part and comprises a passage bore communicating with the valve chamber, a valve seat provided on the housing cover, a valve tappet provided with a valve cone and a rest device, a spring device supported on the valve housing cover and lying on the rest device, and with thermosensitive actuators which expand on heating arranged on the side of the rest device opposite the spring device. 
         [0012]    According to the invention, the actuators are made from a form-memory alloy or comprise a bimetal arrangement. This offers many design possibilities for the actuators. 
         [0013]    The actuators may be configured as a ring or sleeve, of one or more pieces, and/or as a cup spring, whereby these can be optimally adapted to the conditions in the valve chamber. 
         [0014]    In an advantageous refinement of the invention, the valve housing part has a housing portion with reduced inner diameter which serves as a support shoulder for the actuators. 
         [0015]    According to the invention, an axial groove is formed on the inner periphery of the housing portion facing the valve tappet, and an axial groove oriented parallel to the axial groove is formed on the valve tappet, wherein an adjustment spring is inserted in said grooves. The resulting twist prevention serves to ensure that the valve cone and valve seat always meet at the same point and that the actuators are not distorted. 
         [0016]    The object of the invention is furthermore achieved by the use of such a protective valve in a pump arrangement. 
         [0017]    Exemplary embodiments of the invention are shown in the drawings and described in more detail below. These show: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  a pump arrangement according to an embodiment of the invention, 
           [0019]      FIG. 2  the longitudinal section through a protective valve used in the valve arrangement of  FIG. 1 , 
           [0020]      FIG. 3  a further embodiment of the protective valve in longitudinal section, and 
           [0021]      FIG. 4  a further embodiment of the pump arrangement according to  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0022]      FIG. 1  shows a pump arrangement  1  in the form of a main coolant pump. The pump arrangement  1  has a pump housing  2 . The pump housing  2  defines an interior  3  with an inlet opening  4  for aspirating a delivery medium, and an outlet opening  5  for expelling the delivery medium. The interior  3  is connected via an orifice  6  with a chamber  7  which is also defined by the pump housing  2 . 
         [0023]    An impeller shaft  8  extends from the interior  3  through the orifice  6  into the chamber  7  and ends close to or in an orifice  9  opposite the orifice  6 . The impeller  8  is mounted rotatably about the rotary axis A by means of a bearing arrangement  10  accommodated in the chamber  7 , close to the orifice  6 . An impeller  11  is attached to a shaft end of the impeller shaft  8  lying inside the interior  3 . An auxiliary impeller  12  is attached to the impeller shaft  8  inside the chamber  7 , at a defined distance from the bearing arrangement  10 . The shaft end of the impeller shaft  8  close to the orifice  9  is connected to a drive shaft  13  of a drive motor  14  which is arranged coaxially to the rotary axis A, wherein the housing  15  of the drive motor  14  is connected to the housing  2  by means of a lantern piece  16 . 
         [0024]    In the chamber  7 , a multi-stage hydrodynamic sealing system  17  is provided which comprises a plurality of spring-mounted axial face seals  18 ,  19 ,  20 , and if required a pressure-controlled seal  21 , for example a nitrogen seal, water seal or similar, which is open in operation. The sealing system  17  seals the chamber  7  fluid-tight against the environment at the orifice  9 . 
         [0025]    During operation of the pump arrangement  1 , a sealing water system  22 , forming at least part of a fluid circuit, feeds medium—for example water with added additives in some cases, referred to below as sealing water—which is supplied via a supply conduit  23 , via a first conduit system  29  provided with a plurality of shut-off fittings  24 ,  25 , a plurality of temperature sensors  26 ,  27  and a cooler  28 , into the chamber  7  between the auxiliary impeller  12  and the sealing system  17 . The auxiliary impeller  12  delivers part of the sealing water through the bearing arrangement  10 . The sealing water may be guided through channels  30  formed in the bearing arrangement  10  and/or along the plain bearing surfaces (not shown). The sealing water is evacuated from the chamber  7  again between the bearing arrangement  10  and the orifice  6 , wherein a small part is still delivered into the interior  3 . The sealing water thus prevents the penetration of delivery medium from the interior  3  into the chamber  7 , and serves as a coolant and lubricant for the bearing arrangement  10 . 
         [0026]    The other part of the sealing water, which is not evacuated through the bearing arrangement  10 , forms a controlled leakage flow and is guided via bypass channels  31  into and through the axial face seals  18 ,  19 . Choke sections (not shown) fitted to the bypass channels  31  reduce the pressure in stages, and hence distribute the pressure load over the axial face seals  18 ,  19 ,  20 . The final axial face seal  20  before the seal  21  does not have such a bypass channel. The leakage flow is evacuated from the chamber  7  between the axial face seal  19  and the axial face seal  20 , and guided into a second conduit system  32 . After leaving the chamber  7 , the leakage flow passes a shut-off fitting  33 , a temperature sensor  34  and a protective valve  35 , wherein a further shut-off fitting  36  which is closed in normal operation is connected in parallel to the protective valve  35 . 
         [0027]    The reaching of a leakage flow temperature of usually 100° C. is associated with an automatic shut-down of the pump arrangement  1 . This leads to a reduction in temperature of the sealing water in the chamber  7  and of the leakage flow, since sealing water is pumped into the chamber  7  for cooling. 
         [0028]    On a fault in the sealing water system  22 , for example in the absence of the sealing water supplied via the supply line  23 , the temperature inside the chamber  7  however rises further since the sealing water delivered to the chamber  7  is no longer cooled, or hot delivery medium penetrates from the interior  3  into the chamber  7 . If the sealing water in the chamber  7  and hence the leakage flow reaches a specific temperature, the protective valve  35  closes. Because of the construction of the protective valve  35 , its opening remains excluded even after a subsequent fall in temperature. 
         [0029]    An embodiment of the protective valve  35  shown in detail in  FIG. 2  comprises a valve housing part  37  which is provided with a valve chamber  38  and a plurality of passage openings  39  arranged around the valve chamber  38 , wherein the passage bores  39  extend parallel to a center longitudinal axis B of the valve housing part  37 . The passage bores  39  have threaded regions  40 ,  41  at their ends. A valve housing cover  42  is arranged on the side facing away from the shut-off fitting  33  in  FIG. 1  and has a passage bore  43  communicating with the valve chamber  38 . The valve housing cover  42  has a plurality of passage bores  44  which are oriented lying overlapping the passage bores  39 . On the side facing the valve housing part  37 , the valve housing cover  42  has an annular groove  45  which is formed concentrically to the center longitudinal axis B and in which a sealing device  46  is arranged, for example a spiral graphite seal,  0 -ring or similar, which seals the connecting point of the valve housing part  37  and valve housing cover  42  fluid-tightly. 
         [0030]    The valve housing cover  42  has an annular protrusion  47  extending into the valve chamber  38 , the free end of which is formed as the valve seat  48 ; a valve tappet  49  placed in the valve chamber  38  may rest with its valve cone  49   a  on said valve seat  48 . A spring device  50 , for example a cup spring packet, a spring cage, a wavy annular spring or similar, is supported on the valve housing cover  42  and rests against a rest device  51  formed as a ring on the valve tappet  49 . 
         [0031]    Several thermosensitive actuators  52 ,  53  are arranged on the side of the rest device  51  lying opposite the spring device  50 , and on heating expand in the axial direction i.e. along the center longitudinal axis B. The actuators  52 ,  53  are for example made of a form-memory alloy or comprise a bimetal arrangement. 
         [0032]    In form-memory alloys with two-way effect, the actuators  52 ,  53  contract again on cooling, whereas in form-memory alloys with one-way effect, a force is generated in one direction only, wherein the return force is then applied by the spring device. 
         [0033]    The actuators  52 ,  53  may for example be formed as a ring or sleeve, of one or more pieces, and/or as a cup spring. A plurality of actuators  52 ,  53  here surround the valve tappet  49 . In the exemplary embodiment shown, each set of actuators  52  and  53  is internally connected in parallel, and the two sets are connected together in series by means of a holding device  54 . The series connection is advantageous for creating a greater actuating travel and redundancy of the actuators, the parallel connection for producing higher actuating forces. 
         [0034]    The rest device  51  has a plurality of passage openings  55  which overlap with the passage openings  56  present in the actuators  52 ,  53  and the passage openings  57  formed in the holding device  54 . 
         [0035]    The valve housing part  37  has a housing portion  58  with reduced inner diameter which serves as a support shoulder for the actuators  53 . The inner diameter of the housing portion  58  is slightly larger than the valve tappet  49 , so that this can easily be moved to and fro along the center longitudinal axis B. The housing portion  58  also comprises passage openings  59  which in turn are aligned with the passage openings  55 ,  56 ,  57 , so that during normal operation the controlled leakage flow can flow unhindered through the protective valve. 
         [0036]    To produce a heating of the actuators  52 ,  53  which is as rapid and as even as possible, the passage openings  55 ,  56 ,  57 ,  59  may be arranged such that they do not overlap axially. 
         [0037]    So that the valve tappet  49  cannot rotate inside the valve chamber  38  and the passage openings  55 ,  56 ,  57 ,  59  no longer align, an axial groove  60  is formed on the inner periphery of the housing portion  58  facing the valve tappet  49 , and an axial groove  61  oriented parallel to axial groove  60  is formed on the valve tappet  49 ; an adjustment spring  62  is inserted in said grooves. The twist protection also serves to ensure that the valve cone  49   a  and valve seat  48  always meet at the same point and that the actuators  52 ,  53  are not distorted. 
         [0038]    To connect the protective valve  35  to the second conduit system  32  shown in  FIG. 1 , a so-called collar  63  is arranged on the face of the valve housing part  37  and is clamped to the housing part  37  by means of a release flange  64  arranged on the side opposite the valve housing part  37  and by means of screws or threaded bolts  65  which can be screwed into the threaded region  41  of the valve housing part  37 . On the side facing the valve housing part  37 , the collar  63  has an annular groove  66  in which a sealing device  67  is arranged which seals the connecting point of the valve housing part  37  and collar  63  fluid-tightly. The collar  63  is then welded to a pipe element of the second conduit system  32 . 
         [0039]    In the same way, a collar  68  with a ring groove  69  and a sealing device  70  is clamped to the valve housing cover  42  by means of a release flange  71  and several screws or threaded bolts  72 , and welded to a pipe element of the second conduit system  32 . 
         [0040]    In an alternative embodiment, the collar  63  and the collar  68  are welded to the valve housing part  37  or the valve housing cover  42 . In a further embodiment, the collar  63  and the valve housing part  37 , and the collar  68  and the valve housing cover  42  respectively, are formed of one piece. 
         [0041]    In normal operation, the spring device  50  acts against the leakage flow and prevents the closing of the protective valve  35 , since the spring force of the spring device  50  is selected greater than the force acting through the fluid pressure on the valve tappet  49 . If the temperature of the leakage flow rises because of a fault in the sealing water circuit, the actuators  52 ,  53  expand in the axial direction and move the valve tappet  49  via the rest device  51  towards the valve seat  48 , wherein the protective valve  35  is closed and the leakage flow blocked. As soon as the valve is almost closed, a further hydraulic closing force acts on the tappet  49 , in addition to the closing force of the actuators  52 ,  53 . In this way, opening of the protective valve  35  is excluded even after a subsequent fall in temperature. 
         [0042]    Opening of the protective valve  35  after a fall in temperature is possible only by opening the shut-off fitting  36  shown in  FIG. 1  and by the associated pressure drop in front of the protective valve  35 , or the drop in system pressure. The spring element  50  can return the valve tappet  49  to its starting position and thus restore functionality. 
         [0043]      FIG. 3  shows a further embodiment of the protective valve  35 . The housing portion  58  with passage openings  59  is formed on the face of the valve housing part  37  facing the collar  63 . A guide element  72  with passage openings  73  aligned with the passage openings  59  lies on the housing portion  58  in the valve chamber  38 . The guide element  72  stabilizes a supporting spring  74 , which presses the thermosensitive actuator  52  against the rest device  51  of the valve tappet  49 . This prevents the actuator  52 —or for a multi-piece design, parts thereof—or the valve tappet  49  from moving to and fro uncontrolledly in the valve chamber  38  or twisting. Alternatively, the twist protection as described in detail for  FIG. 2  may be used. By selection of a suitable distance, an idle travel may be created between the actuator  52  and the guide element  72 , which can be used for adjustment of the switching point and force ratio. In the present embodiment, the spring device  50  is formed by a plurality of coil compression springs  75  which are arranged in blind holes  76  formed in the protrusion  47  of the valve housing cover  42 , and act against the leakage flow and spring force of the support spring  74 . 
         [0044]      FIG. 4  shows a depiction of the pump arrangement  1  which substantially corresponds to the depiction shown in  FIG. 1 . Since a temperature increase of the leakage flow, as a serious equipment fault, is the only case in which a pressure build-up occurs before the protective valve  35 , the pressure in the second conduit system  32  can be used to activate automatically any pressure-controlled seal  21  which may be present, and thus seal off the pump arrangement  1  hermetically and ensure its fluid-tightness independently of the axial face seals  18 ,  19 ,  20 . For this, medium can be extracted from the leakage flow between the shut-off fitting  33  and the protective valve  35 , via a conduit  77 , and supplied to a pressure chamber  78  in the seal  21  arranged inside the chamber  7 . 
         [0045]    The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof. 
       LIST OF REFERENCE NUMERALS 
       [0000]    
       
           1  Pump arrangement 
           2  Housing 
           3  Interior 
           4  Inlet opening 
           5  Outlet opening 
           6  Orifice 
           7  Chamber 
           8  Impeller shaft 
           9  Orifice 
           10  Bearing arrangement 
           11  Impeller 
           12  Auxiliary impeller 
           13  Drive shaft 
           14  Drive motor 
           15  Motor housing 
           16  Lantern piece 
           17  Sealing system 
           18  Axial face seal 
           19  Axial face seal 
           20  Axial face seal 
           21  Seal 
           22  Sealing water system 
           23  Supply conduit 
           24  Shut-off fitting 
           25  Shut-off fitting 
           26  Temperature sensor 
           27  Temperature sensor 
           28  Cooler 
           29  First conduit system 
           30  Channel 
           31  Bypass channel 
           32  Second conduit system 
           33  Shut-off fitting 
           34  Temperature sensor 
           35  Protective valve 
           36  Shut-off fitting 
           37  Valve housing part 
           38  Valve chamber 
           39  Passage bore 
           40  Threaded region 
           41  Threaded region 
           42  Valve housing cover 
           43  Passage bore 
           44  Passage bore 
           45  Ring groove 
           46  Sealing device 
           47  Protrusion 
           48  Valve seat 
           49  Valve tappet 
           49   a  Valve cone 
           50  Spring device 
           51  Rest device 
           52  Actuator 
           53  Actuator 
           54  Holding device 
           55  Passage opening 
           56  Passage opening 
           57  Passage opening 
           58  Housing portion 
           59  Passage opening 
           60  Axial groove 
           61  Axial groove 
           62  Adjustment spring 
           63  Collar 
           64  Release flange 
           65  Threaded bolt 
           66  Ring groove 
           67  Sealing device 
           68  Collar 
           69  Ring groove 
           70  Sealing device 
           71  Release flange 
           72  Guide element 
           73  Passage opening 
           74  Support spring 
           75  Coil compression spring 
           76  Blind hole 
           77  Conduit 
           78  Pressure chamber 
         A Rotary axis 
         B Center longitudinal axis