Abstract:
The invention relates to a plate heat exchanger ( 100 ) comprising a package of heat exchanger plates ( 1 ), two end plates ( 2, 3 ) between which the package of heat exchanger plates ( 1 ) is kept together, a plurality of threaded bolts ( 9 ), where the bolts ( 9 ) extends between the end plate ( 2 ) and a drive unit ( 10 ) and through the end plate ( 3 ), the drive unit being arranged for synchronously rotating the bolts ( 9 ) and having bolt heads ( 11 ) arranged to bear directly or indirectly against one ( 2 ) of the end plates, a plurality of nuts ( 12 ), each in threaded engagement with one of the bolts ( 9 ) and arranged to bear directly or indirectly against the other end plate ( 3 ), the bolts ( 9 ) and nuts ( 12 ) being arranged for movement of one of the two end plates ( 3 ) toward or away from the other, the drive unit ( 10 ) further comprising a rotating arrangement each of the bolts ( 9 ), and a motor ( 14 ) in driving engagement with rotating arrangement each of the bolts ( 9 ) for simultaneous rotation of all the bolts ( 9 ), where the bolt heads ( 11 ) and the nuts ( 12 ) being coupled to their respective end plates ( 2, 3 ) in a manner such that they are prevented from moving axially away from their respective end plates ( 2, 3 ) upon operation of the drive unit ( 10 ), where at least one of threaded bolt ( 9 ) is arranged to be partly removable.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a plate heat exchanger of the kind comprising a package of heat transferring plates, two end plates between which the package of heat transferring plates are kept together, and more specifically to a plate heat exchanger having an arrangement for automatically opening the plate heat exchanger for permitting inspection, cleaning, repair, replacement and/or removal of heat transferring plates and the like. 
       BACKGROUND OF THE INVENTION 
       [0002]    When used for certain applications or in certain industries a plate heat exchanger of this kind may need to be opened relatively often, e.g. once every day, for inspection and/or cleaning of the heat transferring plates. This process may require the removal of one or more plates for closer inspection or cleaning. Traditionally, one of the end plates is fixed and the other end plate is moveable towards the fixed end plate to close the plate heat exchanger and is movable away from the fixed end plate to open the plate heat exchanger. Tightening bolts are used to keep the end plates together and the tightening bolts are secured by nuts. To open the plate heat exchanger by moving the end plate either the bolts or the nuts have to be rotated, so that the end plates and thus the heat transferring plates may be moved away from each other. 
         [0003]    Such rotation of the bolts or the nuts, in connection with opening of the plate heat exchanger as well as in connection with restoring of it for operation, means a heavy, time consuming and not quite simple work. Sometimes, particularly in connection with large plate heat exchangers, electrically or pneumatically operated tools are used for the rotation, but a tool of this kind has to be moved often between the different bolts or nuts, particularly at the beginning of an opening operation and at the end of a restoring operation, in order that the bolts and end plates will not be subjected to all too uneven loads or stresses. With respect to the compression of the package of heat transferring plates it is also important that each one of the bolts or nuts is rotated exactly so much that the end plates in their operating positions will be situated in parallel with each other. If not so, leakage may come up between the heat transferring plates. 
         [0004]    In U.S. Pat. No. 5,462,112 is disclosed a plate heat exchanger, a package of heat transferring plates is kept together between two end plates by means of two or more threaded bolts and nuts in threading engagement therewith. A motor is arranged through an endless drive member, such as a tooth belt or the like, simultaneously to rotate all the bolts or all the nuts. The plate heat exchanger thereby may be rapidly, simply and safely opened and restored for operation in connection with inspection and/or cleaning of the heat transferring plates. 
         [0005]    In EP-A2-1 462 752 is disclosed a plate heat exchanger including two end plates, a package of heat transfer plates arranged between the end plates, and a closure system. The closure system includes a plurality of tie bar assemblies. Each tie bar assembly includes a tie bar extending between the first and second plates, and a threaded member engaging the tie bar. The closure system and the end plates are relatively arranged and configured such that relative rotation between the tie bar and the threaded member of each tie bar assembly is operative to move the movable end plate towards and away from the fixed end plate to close and open, respectively, the plate heat exchanger. The plate heat exchanger is arranged and configured such that the heat transfer plates can be removed from the plate heat exchanger without relocating any of the tie bars. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention has for its object to provide an plate heat exchanger having means for automatically and simultaneously opening the opening of a plate heat exchanger and restoring of it for operation, and that further is provided with means for easy removal, cleaning, service and insertion of heat exchanger plate into the plate heat exchanger, without deteriorating the plate heat exchanger capability to withstand high pressures during its operation. 
         [0007]    This object has been solved by providing a plate heat exchanger having automatic opening means and having at least one partly removable tightening bolt. By means of such a device the plate heat exchanger may be rapidly and simply opened to a desired degree and, with the same rapidity and simplicity, restored for operation after removal, inspection, cleaning and service or insertion of heat exchanging plates. Through the simultaneous rotation of all the bolts or nuts much time can be saved in connection with opening and restoring of the plate heat exchanger. Further, it is made sure thereby that the bolts and the end plates are subjected to a uniform load or stress during the whole compression of the package of heat exchanging plates. 
         [0008]    According to a first aspect of the invention the at least one of threaded bolts that are arranged to be partly removable includes two portions, a first removable portion extending from the fixed end plate, through the other movable end plate to a position close to the drive unit and a second portion extending from a position close to the drive unit to a position inside the drive unit. The two portions of the at least two of threaded bolts are connected by a shaft connection, where the shaft connection is designed so that the first removable portion of the partly removable threaded bolts can be separated from the second portion of the partly removable threaded bolts without moving the partly removable threaded bolts axially. 
         [0009]    According to a further aspect of the invention a friction reducing bearing is arranged between each bolt head and the end plate. At least one bolt head is removably attached to the end plate. 
         [0010]    According to another aspect of the invention each nut is connected to a nut fixation device that prevents rotation of the nut in relation to the movable end plate and that prevents axial movement of the nut in relation to the movable end plate. At least one nut fixation device is removably attached to the movable end plate. 
         [0011]    According to yet another aspect of the invention each of the end plates is provided with at least one cut-out or recess on each long side of the end plate for receiving the partly removable threaded bolts. The at least one cut-out or recess on each long side of the end plate for receiving the partly removable threaded bolts enables the partly removable threaded bolts to be removed radially. 
         [0012]    According to yet another aspect of the invention the drive unit comprises a motor that is arranged to simultaneously, rotationally drive all the threaded bolts via a force translating system, and thereby moving the end plate between two positions. The drive unit may be electrically operated, and where each threaded bolt is associated to a separate gear box, where the gear boxes being connected to the motor via a shaft- and belt arrangement. 
         [0013]    According to yet another aspect of the invention the at least one of threaded bolt on the side of the plate package is arranged to be partly removable, thereby giving the user the possibility of to remove heat exchanger plate from any side of the plate heat exchanger. 
         [0014]    According to yet another aspect of the invention the plate heat exchanger is provided with a security system for enabling the interruption the movement of the movable end plate from any places around the plate heat exchanger. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    In the following, the invention will be explained more with reference to the accompanying drawings, where: 
           [0016]      FIG. 1  is a perspective view of a plate heat exchanger according to the invention; 
           [0017]      FIG. 2  is a side view of a plate heat exchanger according to the invention; 
           [0018]      FIG. 3  is a perspective view of a plate heat exchanger according to the invention, seen from a different angle than the plate heat exchanger of  FIG. 1 ; 
           [0019]      FIG. 4  is a side view of a plate heat exchanger according to the invention, where the plate heat exchanger is open; 
           [0020]      FIG. 5  is a perspective view of a plate heat exchanger according to the invention, where the plate heat exchanger is open; 
           [0021]      FIG. 6  is partial detailed view of a bolt or shaft connection; 
           [0022]      FIG. 7  is a partial detailed view of a first bearing unit according to the invention; 
           [0023]      FIG. 8  is partial detailed view of a second bearing unit according to the invention; 
           [0024]      FIG. 9  is another partial detailed view of the second bearing unit according to the invention; 
           [0025]      FIG. 10  is partial detailed view of a first nut arranged on one end plate according to the invention; 
           [0026]      FIG. 11  is partial detailed view of a second nut arranged on one end plate according to the invention; 
           [0027]      FIG. 12  is perspective view of a drive unit according to the invention; 
           [0028]      FIG. 13  is a cross sectional view of a shaft connection according to the invention; 
           [0029]      FIGS. 14   a - 14   c  are different detailed views of a nut fixation device; and 
           [0030]      FIGS. 15   a - 15   b  are different detailed views of the bearing unit according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0031]    Heat exchangers are used for transferring heat between two fluids separated by a solid body. Heat exchangers can be of several types, the most common are spiral heat exchangers, tubular heat exchangers and plate heat exchangers. Plate heat exchangers are used for transferring heat between a hot and a cold fluid that are flowing in alternate flow passages formed between a set of heat exchanger plates. The arrangement of heat exchanger plates defined above is enclosed between end plates that are relatively thicker than the heat exchanger plates. The inner surface of each end plate faces the heat transfer plates. 
         [0032]      FIG. 1  shows a plate heat exchanger  100  comprising a package of heat transferring plates  1 , which are kept together between two end plates  2  and  3 . The heat exchanger or transferring plates  1  are arranged hanging on a carrying bar  4  that substantially extends between the two end plates  2 ,  3 . The carrying bar  4  is in one end fixedly attached to an upper end of the end plate  2  and in the opposite end fixedly attached to an upper end of a support column  5 . The end plate  3 , which is movable along the carrying bar  4 , is used to press the heat exchanger plates  1  together to form a plate package. A guide bar  6 , that guides the heat exchanger plates  1  in their lower end, connects a lower end of the support column  5  with a lower end of the end plate  2 . In  FIGS. 1-3  the plate package is shown as schematic box. The plate package may be housed by a cover to protect for dirt and the like. 
         [0033]    The heat exchanger plate  1  discussed above includes in a manner known per se a corrugation or pattern for increasing the heat transfer and a number of port holes, typically four, for forming a corresponding number of port channels extending through the plate package and being in connection with the flow channels formed between the heat exchanger plates  1 . 
         [0034]    The end plate  2  is suitably provided with a number of port or connections corresponding to ports of the heat exchanger plate  1 . The end plate  3  may also be provided with ports, as well as the port of the end plate  2  may be provided with a blind cover. 
         [0035]    The heat exchanger plates  1 , which between themselves usually have flexible gaskets  8  (best shown in  FIG. 5 ) for defining flow spaces between the heat exchanger plates  1  for two heat exchange fluids. The gasket  8 , which is preferably made of an elastic material, e.g. rubber material, is disposed in a groove which extends along the periphery of the constituent heat exchanger plates  1  and around ports. The gasket  8  may possibly comprise a metal or be surrounded by a second material, e.g. metal, PTFE, etc. 
         [0036]    As mentioned above the movable end plate  3  are pressed towards the fixed end plate  2  to form a plate package of the heat exchanger plates  1 . To keep the heat exchanger plates  1  together threaded tightening bolts  9  are used. The tightening bolts  9  extend between the fixed end plate  2  and a drive unit  10  arranged on the support column  5 , and passing through holes or recesses in the edge portions of the two end plates  2 ,  3 . Each bolt  9  has a bolt head means  11  at one of its ends, possibly situated at the outside (or integrated in) of the end plate  2  (see  FIGS. 7-9 ), and carries nuts  12  on its threaded part, possibly situated at the outside (or integrated in) of the end plate  3  (see  FIGS. 8 and 11 ). 
         [0037]    The drive unit  10  (see  FIG. 12 ) may be based on a solution with one electrical motor  14 , which is driving all the tightening bolts  9  in a synchronized manner. By having a gear box  15  arranged on each bolt  9  the required torque of the motor  14  is reduced. The motor speed is controlled by a motor drive  16 . A programmable logic controller unit (PLC)  17  can be used to program different ramping of speed and acceleration of the electrical motor  14  and to monitor the drive unit system and alarms thereto related. The gear boxes  15  are connected to the motor  14  by a shaft- and belt arrangement  70 - 74 , where three gear boxes  15  are connected to each other by shafts  71  and where another three gear boxes  15  are connected to each other by shafts  72 . The shafts  71  and  72  are connected to the shaft  70  of the motor  14  by belts  73  and  74 . When the motor  14  rotates, the shaft  70 , the belts  73  and  74  transfer the rotational movement from the shaft  70  and the motor  14  to the shaft  71  and  72  and further to the gear boxes  15  to drive all the tightening bolts  9  in a synchronized manner. A non-electrical motor or driving means is also possible. 
         [0038]    As seen in  FIGS. 1-5  and  12  the plate heat exchanger is provided with three tightening bolts  9   a,    9   b,    9   c  on each side of the plate package. To be able to remove, replace or insert heat exchanger plates  1  of the plate heat exchanger at least one tightening bolt  9  on one side of the plate package is removable, preferably the intermediate tightening bolts  9   b  located between the other two tightening bolts  9   a  and  9   c.  The removable tightening bolt  9   b  could be located on any side of the plate package. If only one removable tightening bolt  9   b  is provided it can be located according to the preference of the user. The plate heat exchanger may include two or more removable tightening bolts  9   b.    
         [0039]    The removable bolt  9   b  is equipped with one shaft connection  18  (see  FIGS. 6 and 13 ) between the drive unit  10  and the movable end plate  3 , which is designed in a manner so that it can easily be separated from a shaft  19  of the drive unit  10  without moving the bolt  9   b  axially. In  FIG. 6  one possible shaft connection design is shown, but other shaft connections are also possible.  FIG. 13  shows that the shaft connection  18  comprises two parts  18   a  and  18   b  that put together by a screw joint  30 . The parts  18   a  and  18   b  are typically clamped onto the bolt  9   b  and the shaft  19 , respectively. 
         [0040]    As discussed above the tightening bolt  9  is provided with bolt head means  11  situated at the end plate  2  (see  FIGS. 1-5  and  7 - 9 ). The bolt head means  11  comprises a bearing unit  20 ,  20   a,    20   b,    20   c  on the end plate that supports the bolt  9 ,  9   a,    9   b,    9   c,  and taking up the axial forces. 
         [0041]    The end plate  2  has a cut-out  21  (see FIGS.  1  and  8 - 9 ) located on each long side of the end plate  2  allowing the removable bolt  9   b  to be removed radially. The bearing unit  20  is fixed to the end plate  2  by screws, locking pins or other attaching means  60  to support the bearing unit  20  axially when the movable end plate  3  is moved in direction from the end plate  2 . The center located bearing unit  20   b  comes off together with the bolt  9   b.  By help from the cut-outs  21  in the end plate  2  and cut-outs  40  in a bearing housing plate  22  of the bearing unit  20   b  it is possible to slide out the entire bolt  9   b  and bearing unit  20   b  radially from the end plate  2 . 
         [0042]    The end plate  2  have holes located in each corner of the end plate  2  (see  FIGS. 3 ,  5  and  12 ) to receive the tightening bolts  9   a,    9   c.  Bearing units  20   a  and  20   c  supporting the tightening bolts  9   a,    9   c  are fixed to the end plate  2  by screws, locking pins or other attaching means to support the bearing units  20   a  and  20   c  axially when the movable end plate  3  is moved in direction from the end plate  2 . 
         [0043]    The nuts  12  (see  FIGS. 10 and 11 ) on the threaded part of the tightening bolts  9  that are situated at the outside of the end plate  3  rests towards a flat surface of the end plate  3  which takes up the axial forces of the plate package, resulting from gasket forces and the pressure of the process media. The end plate  3  has a cut-out  23  (see  FIGS. 1 and 11 ) located on each long side of the end plate  3  allowing the removable tightening bolt  9   b  to be removed radially. 
         [0044]    The nut  12 ,  12   a,    12   b,    12   c  is attached to the end plate  3  by a nut fixing device  24 ,  24   a,    24   b,    24   c  (see  FIGS. 10-11  and  14   b - 14   c ). The nut fixing device  24   b  is easily unscrewed from the end plate  3  to allow the nut  12   b  to be removed together with the bolt  9   b.  The function of the nut fixation device  24  is to lock the rotation of the nut  12  and to fix the nut  12  axially to the end plate  3  when moving backwards (away from the end plate  2 ) in an unloaded mode and to keep the nuts  12  synchronized axially. 
         [0045]      FIG. 14   a  shows the nut fixing device  24   b  from the behind.  FIGS. 14   b  and  14   c  show cross sectional views of the nut fixing device  24   b  seen along the lines E and F, respectively, of  FIG. 14   a.    
         [0046]    The nut fixation device  24  only allows the nut  12  to be mounted in two positions, separated rotationally 180°. The tolerances of the fixation mounting screws are smaller that half the thread elevation of the bolt  9   b.  This combined guarantees that the nut  12   b  is correctly refitted and synchronized. As seen from  FIGS. 10 and 11 , the nut fixing devices  24   a - 24   c  may be slightly differently designed, but they all fulfill the same purpose. 
         [0047]    The nut  12  provided at the end plate  3  is designed to take up deviations both radially and in alignment. The nut  12  is resting on spherical washers  25  (see  FIGS. 14   b  and  14   c ), which allow it to incline and follow the angle of the bolt  9 . This reduces unnecessary forces on the treads when the frame is flexing due to the weight of the different components. This feature is especially important when using bolts  9  with threads of low elevation, “M”-thread or similar. Low elevation of the treads help to keep the bolt torque low when closing the plate heat exchanger  100 . 
         [0048]    The nut  12  is allowed to move radially as a hole through the end plate  3  is made with a clearance to the bolt  9 . The nut  12  has groove for rotational fixation which fits to the fixation device  24 . The groove is mounted vertically to allow the nut  12  to slide and incline mainly in vertical direction, the direction which is most likely to deviate. The flexible design is made to allow the nut  12  mainly (only) to take up the axial forces created by the gaskets  8  and media pressure and not be stressed by any forces created by tolerances in the frame. 
         [0049]    The open design of the nut assembly ( 12 ,  24 ,  25 ) provides for easy inspection and cleaning and the clearance between all components allow cleaning water to flush out of the design. This makes seals unnecessary. The nut  12  is equipped with a grease nipple  41  to allow the threads inside the nut  12  to be properly lubricated. 
         [0050]    Now the operation of the plate heat exchanger  100  will briefly be described. By means of the electrical motor  14 , the shafts  70 - 72 , belts  73 - 74  and via the gear boxes  15  connected to each bolt  9  a simultaneous and uniform rotation of all the bolts  9 , and by the fact that the nuts  12  are connected to the end plate  3  and the bolt head means  11  are connected with the end plate  2  in the above described manner the end plate  3  during all of its movement will be maintained in a position in which it is situated in parallel with the end plate  2 . The package of heat exchanger plates  1  will thus be compressed and opened to the same degree along its entire circumference. 
         [0051]    As the plate heat exchanger  100  has been opened the tightening bolt/bolts  9   b  can be removed to enabling full access to the heat exchanger plates  1 . Thus, make it possible to remove heat exchanger plates  1  from the plate heat exchanger  100  for cleaning, inspection or the like of the heat exchanger plates  1 . It also enables the insertion of more heat exchanger plates  1  or the insertion of the cleaned, inspected or exchanged heat exchanger plates  1 . 
         [0052]    The bolt  9   b  is removed from the plate heat exchanger  100  by disconnecting the shaft connection  18  between the drive unit  10  and the movable end plate  3 ; unfasten the bearing unit  20   b  from the end plate  2  and the nut fixation device  24   b  from the end plate  3  and removing the bolt  9   b  radially with its connected parts. After the heat exchanger plates  1  are maintained as desired the process is reversed and the tightening bolt or bolts  9   b  are re-installed and the parts are fastened. The drive unit  10  ensures that the end plate  3  again is moved towards the end plate  2 , pressing the heat exchanger plates  1  together to again form the plate package and making the plate heat exchanger  100  ready for operation. 
         [0053]      FIGS. 4-5  show schematically a plate heat exchanger  100  according to the invention opened for inspection or cleaning of the heat exchanger plates  1 . 
         [0054]    Along the frame of the plate heat exchanger  100  a safety switch is mounted in form of a line breaker  50  or a light barrier following the sides of the plate heat exchanger  100 . This makes it possible for an operator to stop the movement of the end plate  3  from any position around the plate heat exchanger  100 . 
         [0055]    In the described embodiments the plate heat exchanger  100  is provided with three tightening bolts on each side of the plate package having one removable tightening bolt. The number and positions of the tightening bolts is decided based upon most cost effective design of drive unit and heat exchanger plates, and therefore may there be further tightening bolts if that is needed in view of the construction of the plate heat exchanger and the work is aimed to perform. 
         [0056]    Therefore more than one tightening bolt may be needed to be removed to allow the heat exchanger plates to be taken out or inserted in the plate heat exchanger. When a tightening bolt with nut is removed it is very important that it is refitted in a manner that guarantees that the synchronized position between the different nuts of the movable end plate is unchanged. Otherwise the result may be that the plate package is unaligned with leaking gaskets or seized/worn threads as result. 
         [0057]    One advantage with an electrical solution and closed gear boxes as suggested above is that no hydraulic oils or lubricants are necessary, something which is a problem on most known solutions. 
         [0058]    The above described connection of the bolt heads and the nuts with the respective end plates may be accomplished in many different ways within the scope of the present invention. 
         [0059]    By having a partially removable tightening bolt a simple construction can be achieved since the association to the gear boxes of the drive unit or similar driving arrangement will not be affected by the removal of the removable part of the tightening bolt as the shaft (the second part of the tightening bolt) associated to the gear box remains connected to the drive unit after the removal of the removable part of the tightening bolt (the first part of the tightening bolt). 
         [0060]    The drive unit is located as far away as possible from the plate package to avoid that the drive unit is exposed to heat from the process. 
         [0061]    The invention is not limited to the embodiments described above and shown on the drawings, but can be supplemented and modified in any manner within the scope of the invention as defined by the enclosed claims.