Abstract:
A melt cooler and valving system for an underwater pelletizer has a diverter valve that facilitates multiple modes of melt processing. The cooler has a cooler inlet line that conveys the melt to the cooler, and a cooler outlet line that conveys the cooled melt from the cooler. The diverter valve is configured to convey the melt to and from the cooler during a cooling mode of operation, to convey the melt around the cooler during a bypass mode of operation, and to drain the melt from the cooler and the diverter valve during a drain mode of operation. The diverter valve is compact and therefore contains a minimum of product inventory. The valve is streamlined and direct in its bypass mode, and includes a drain capability to allow for faster, easier cleaning of the process line, which in turn provides a fast changeover time with less lost product.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims the benefit of priority to U.S. Provisional Application for Patent No. 60/793,222 filed Apr. 20, 2006. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention generally relates to underwater pelletizing equipment and a method of processing and pelletizing polymeric resins and similar materials. More specifically, the present invention relates to underwater pelletizing equipment and a method of processing and pelletizing polymeric resins and other extrudable materials in which the melt cooler and associated valving can be utilized to maximum efficiency for the different polymeric resins being processed and pelletized. 
   2. Description of the Prior Art 
   One known production process has been commonly used for many years for a broad array of hot melt and pressure sensitive adhesive products made from such polymer resins as ethylene vinyl acetates (“EVA”), polyethylenes (“PE”), polypropylenes (“PP”), thermoplastic elastomers (“TPE”), thermoplastic urethanes (“TPU”), polyesters and polyamides as their base ingredients, and as combined with many other materials, such as waxes, tackifiers, pigments, mineral fillers, antioxidants, etc. This known process has also been successfully applied to other non-adhesive products such as gum bases, varieties of chewing gum, and asphalts. 
   The aforementioned process can be applied to nearly any polymer application in which the product is made, blended, mixed, or compounded, usually at a relatively high temperature, and then which must be cooled considerably in order to have a more suitable condition just prior to passing through a die plate and then being cut into pellets. Pellets are the most common and desired form for the packaging, transporting, and subsequent handling, blending, melting, molding, and overall use of such aforementioned polymeric materials. 
   The aforementioned known production process generally consists of the following processing components, as shown in  FIG. 1  of the accompanying drawings: reactor, mixing vessel or extruder  1 ; melt pump  2 ; filter  3 ; melt cooler with dedicated heat transfer fluid system  4 ; polymer diverter valve  5 ; die and pelletizer  6  (with optional bypass piping); tempered water system  7  (with optional water filtration equipment); water separator/dryer  8  (with optional pellet screening equipment); and conveying and/or packaging equipment  9 . 
   The melt cooler  4  is basically a heat exchanger, of which there are many types, such as, for example, plate and frame, shell and tube, scraped wall, etc. The melt cooler  4  lowers the melt temperature of the polymer or extrusion product passing through the cooler. However, some types of melt coolers are more efficient than other types, with the primary focus being to most efficiently remove heat energy. But many other functional considerations are important to this component of the overall apparatus and method. For example, some of the considerations associated with the melt cooler include: minimizing pressure drop of the melt; process considerations associated with the elevated process temperatures and pressures; materials of construction considerations associated with the elevated process temperatures and pressures; ease of cleaning; minimizing floor space occupied by the cooler and piping; and providing the flexibility to either cool or heat a product, depending upon the specific processing service. 
   The aforementioned prior art process that is most commonly utilized has a melt cooler of a single pass shell and tube design combined with static mixer elements, as shown in  FIG. 2 . The melt cooler  10  shown in  FIG. 2  achieves good results when working with either a specific product or with a wide variety of products. However, many polymer producers have a broad array of polymer products, including some products that need not be cooled prior to pelletizing. Thus, the step of pumping those particular products through the melt cooler not only may be unnecessary, but could also be undesirable or even problematic. So with this in mind, it has become desirable to have the flexibility to bypass the melt cooler when running certain grades of polymeric materials, and use the melt cooler for other types of materials. 
   One possible method of accomplishing the aforementioned bypass mode of operation is to remove the melt cooler from the process line. Removal of the melt cooler, however, requires both substantial labor and time to change out and/or to re-install. Removal of the melt cooler also requires special adapter plates for connecting the piping, along with short versions (i.e., for normal mode of operation) and long versions (i.e., for bypass mode of operation) of interconnecting wires and pipes. Removal of the melt cooler can also require special track or rail systems on the floor to guide the equipment out of and back into place. Optionally, a “spool” can be inserted in place of the melt cooler, i.e., to connect the piping upstream of the cooler with the piping downstream of the cooler. A spool is a straight large bore pipe with or without any coolant connection, so that adapters, wiring, or piping need not be changed so often. 
   Another prior art method of cooling is shown in  FIG. 3 . A diverter valve  20  is included in the process line upstream of the melt cooler  22  and routes the melt into a bypass line  24  running parallel to the melt cooler  22 . Another valve  26  is installed downstream of the melt cooler  22  in order to return the product to the process line. One disadvantage of this option is that it requires a longer overall process line. Two additional high pressure valves  20  and  26  are also required, and a long hollow tube pipe is needed for the bypass line  24 . The bypass line  24  also must be rated for high pressure and must be heated to maintain the temperature of the melt. The interior of bypass line  24  may also require static mixers, and line  24  will contain product inventory, which is a consideration for cleaning and changeover of the mode of operation. 
   SUMMARY OF THE INVENTION 
   In order to overcome the above-described drawbacks of the prior art melt coolers and related methods of operation, the present invention provides a melt cooler design that conserves space and minimizes product inventory, thus making it easier to clean and/or change over. The melt cooler and associated valving components are easily and quickly reconfigured to accommodate operation with products that require cooling and those that do not. In effect, a far more versatile, yet efficient melt cooler is provided for the known prior art production process described above, and for any of the many other materials or products being processed with this type of equipment. 
   The present invention also includes a diverter valve for use in conjunction with the melt cooler of this invention. The diverter valve is compact in its installation footprint and, therefore, contains a minimum of product inventory. The diverter valve is streamlined and direct in its bypass mode, thereby providing fast throughput of the melt. Additionally, the diverter valve has a drain capability that enables faster, easier cleaning of the process line, which in turn allows for faster changeover time with less lost product. 
   Another novel feature of the present invention is the utilization of a two-pass (or double-pass) type heat exchanger, preferably of the static mixer, shell and tube, design. In combination with the compact diverter valve, the two-pass heat exchanger provides for overall compactness of the linear process. The two-pass heat exchanger, having both its inlet and outlet on the same end or side, can be closely coupled to the diverter valve, thereby permitting its footprint relative to the floor space to be as small as possible. Drainage of the heat exchanger process line, when necessary, can be effected with the aforementioned diverter valve drains. 
   In a preferred embodiment of the invention, the two-pass melt cooler is mounted in a vertical orientation on the top of the diverter valve, with the cooler&#39;s inlet and outlet located on the bottom of the cooler. However, the melt cooler can be mounted in various orientations or angles relative to the center flow axis of the process line without departing from the invention. For example, according to another embodiment of the invention, the melt cooler is installed with its inlet and outlet at the top of the cooler, i.e., so that the cooler is mounted in a vertical orientation beneath the diverter valve. In this bottom-mount configuration, the diverter valve ports are reoriented and the drain mode of operation is not employed. However, the primary functions of melt cooling and process bypass are accomplished. Draining/cleaning of the melt cooler is accomplished by having one or more drain ports located on the bottom end of the melt cooler. 
   According to still another embodiment of the invention, the melt cooler is oriented horizontally, i.e., parallel to the orientation of the melt inlet and outlet piping. Thus, those skilled in the art will appreciate that the orientation of the melt cooler can be in various vertical or horizontal positions. Due to height limitations or due to interferences from neighboring equipment or from existing structural placements, the melt cooler can be mounted/installed on any of various angles between the vertical and horizontal positions. 
   An object of the present invention, therefore, is to provide a melt cooler and valving system that conserves space and minimizes product inventory, thus making it easier to clean and/or change over. 
   Furthermore, since the processing of polymeric materials entails operations with polymers having various process requirements, another object of the present invention is to provide a melt cooler valving system having components that are easily and quickly reconfigured to accommodate operation with those products that require cooling prior to pelletizing and those products that do not. 
   A further object of the present invention is to provide a compact diverter valve that is configured to convey the melt to and from the cooler during a cooling mode of operation, to convey the melt around the cooler during a bypass mode of operation, and to drain the melt from the cooler and from the diverter valve during a drain mode of operation. 
   Additionally, since certain polymeric materials may require heating prior to further processing, yet another object of the present invention is to provide a heat exchanger valving system having components that are easily and quickly reconfigured to accommodate both cooling and heating operations. 
   Still another object of this invention to be specifically enumerated herein is to provide a melt cooler and valving system of an underwater pelletizer in accordance with the preceding objects that will conform to conventional forms of manufacture, be of relatively simple construction and easy to use so as to provide a device that will be economically feasible, long lasting, durable in service, relatively trouble free in operation, and a general improvement in the art. 
   These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like reference numbers refer to like parts throughout. The accompanying drawings are intended to illustrate the invention, but are not necessarily to scale. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic drawing illustrating a known prior art production process utilizing a conventional melt cooler and polymer diverter valve. 
       FIG. 2  is a schematic drawing illustrating a conventional melt cooler of a single pass shell and tube design as used in the prior art apparatus and process of  FIG. 1 . 
       FIG. 3  is a schematic drawing illustrating a conventional melt cooler and bypass line used in the known prior art apparatus and process of  FIG. 1 . 
       FIG. 4  is a schematic drawing illustrating a vertically mounted double pass type melt cooler mounted above a diverter valve in accordance with one embodiment of the present invention. 
       FIG. 5  is a schematic drawing illustrating the operational modes for the diverter valve in combination with the melt cooler as shown in  FIG. 4  in accordance with the present invention. 
       FIG. 6  is a schematic drawing illustrating a vertical positioning of the melt cooler beneath the diverter valve in accordance with another embodiment of the present invention. 
       FIG. 7  is a schematic drawing illustrating the melt cooler mounted horizontally with respect to the diverter valve in accordance with another embodiment of the present invention in which the melt cooler inlet line enters a top portion of the cooler. 
       FIG. 8  is a schematic drawing illustrating the melt cooler mounted horizontally with respect to the diverter valve in accordance with another embodiment of the present invention in which the melt cooler inlet line enters a bottom portion of the cooler. 
       FIG. 9  is a schematic drawing illustrating the melt cooler mounted horizontally with respect to the diverter valve in accordance with another embodiment of the present invention in which the melt cooler inlet line and the melt cooler outlet line are oriented in a side-by-side configuration. 
       FIG. 10  is a schematic drawing illustrating the melt cooler shown in  FIG. 4  with a top-mounted vent. 
       FIG. 11  is a schematic drawing illustrating the melt cooler shown in  FIG. 6  with a bottom-mounted vent and drain. 
       FIG. 12  is schematic drawing illustrating the melt cooler shown in  FIG. 4  with a top head heated/cooled by a thermal transfer fluid. 
       FIG. 13  is schematic drawing illustrating a portion of the melt cooler shown in  FIG. 4  with a top head temperature controlled electrically. 
       FIG. 14  is a perspective view drawing illustrating the diverter valve in accordance with the present invention in a cooling mode of operation. 
       FIG. 15  is perspective view drawing illustrating the diverter valve shown in  FIG. 14  in a bypass mode of operation. 
       FIG. 16  is perspective view drawing illustrating the diverter valve shown in  FIG. 14  in a drain mode of operation. 
       FIGS. 17A ,  17 B, and  17 C are schematic drawings illustrating a melt cooler and diverter valve in accordance with another embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Although preferred embodiments of the invention are explained in detail, it is to be understood that other embodiments are possible. Accordingly, it is not intended that the invention is to be limited in its scope to the details of constructions, and arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways. Also, in describing the preferred embodiments, specific terminology will be resorted to for the sake of clarity. It is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. Where possible, components of the drawings that are alike are identified by the same reference numbers. 
   Referring now specifically to  FIG. 4  of the drawings, there is illustrated a double pass type heat exchanger as the melt cooler, generally designated by reference numeral  30 , for a pelletizing production line such as is shown in  FIG. 1 . The melt cooler  30  includes an inlet  32  and an outlet  34  adjacent to each other at the bottom  36  of the melt cooler. Hence, the polymer entering inlet  32  travels up the left-hand side of the cooler  30 , transfers at the top  38  of the cooler to the right-hand side, where it passes downwardly and exits through outlet  34 . 
   The diverter valve in accordance with the present invention is generally designated by reference numeral  40  in  FIG. 4 . As shown therein, the hot melt entering the diverter valve  40  is directed toward melt cooler inlet  32  by valve component  42  from the pump, such as pump  2  and filter  3  for the process line shown in  FIG. 1 . Similarly, cooled polymer exiting the melt cooler through outlet  34  communicates with valve component  44  of diverter valve  40 , where it is directed out toward the pelletizer, such as the die and pelletizer  6  shown in  FIG. 1 . 
   Turning now to  FIG. 5 , four modes of operation of the diverter valve  40  in conjunction with the melt cooler  30 , as shown in  FIG. 4 , are illustrated. An “x” in a valve line of the diverter valve  40  indicates that the valve line is closed. Starting from the left-hand side, the first illustration in  FIG. 5 , identified as “MC PROCESS MODE A,” shows the diverter valve  40  operating as described in connection with  FIG. 4 . More specifically, diverter valve bypass line  46  between valve components  42  and  44  is closed, as well as valve drain (i.e., melt drain) lines  48  and  50 . As such, polymer or extrudate entering valve  40  through valve entry (i.e., hot melt inlet) line  45  is directed by valve component  42  to melt cooler  30 . Cooled material exiting cooler  30  is directed by valve component  44  out of diverter valve  40  through valve outlet (i.e., cooled melt) line  47  toward the pelletizer.  FIG. 14  provides a detailed view of the diverter valve  40  positioned in the cooling mode of operation. 
   In the second mode, entitled “MC PROCESS MODE B,” the diverter valve  40  is in the bypass mode. As such, diverter valve bypass line  46  is open, valve drain lines  48  and  50  remain closed, and valve cooler entry (i.e., hot melt outlet) line  52 , connecting to inlet  32  of the melt cooler  30 , and valve cooler exit (i.e., cooled melt inlet) line  54 , connecting to outlet  34  of the melt cooler  30 , are also both closed. As such, polymer or other extrudate flows directly from valve entry line  45  to valve outlet line  47  through the diverter valve  40 , thus bypassing the melt cooler  30 .  FIG. 15  provides a detailed view of the diverter valve  40  positioned in the bypass mode of operation. 
   Referring now to the third mode illustrated in  FIG. 5 , entitled “DRAIN MODE C 1 ,” there is illustrated a first drain mode. In this drain mode, the diverter valve bypass line  46  is closed, valve drain lines  48  and  50  are open, along with valve cooler entry line  52  and valve cooler exit line  54 , so that polymer in the melt cooler can drain away. Similarly, valve entry line  45  and valve outlet line  47  are open so that polymer or other extrudate upstream or downstream, respectively, from the diverter valve can also drain out through valve drains  48  and  50 , respectively. 
   In an alternate drain mode shown in the fourth (i.e., most right-hand) illustration in  FIG. 5 , entitled “DRAIN MODE C 2 ,” the diverter valve bypass line  46  is closed. Polymer from the left-hand side (i.e., upstream side) of melt cooler  30  drains out through diverter valve  40  in the same manner as described above in conjunction with DRAIN MODE C 1 , along with polymer upstream of the diverter valve  40  through valve entry line  45 . Polymer on the right-hand side (i.e., downstream side) of melt cooler  30  exits through valve cooler exit line  54  past valve component  44 , out valve outlet line  47 , and then drains out through a separate external polymer diverter valve  56  (which may also serve as a “startup” valve), such as polymer diverter valve  5  shown in  FIG. 1 .  FIG. 16  provides a detailed view of the diverter valve positioned in the Drain Mode C 2  mode of operation. 
     FIG. 6  illustrates an alternate arrangement of the melt cooler and diverter valve in accordance with the present invention. In this embodiment, a melt cooler  60  is vertically positioned below the diverter valve, generally designated by reference numeral  62 , and the inlet  64  to the melt cooler and the exit  66  from the melt cooler are both mounted at the top of the melt cooler, as shown. In the left-hand view of  FIG. 6 , hot melt polymer enters the valve  62  through valve inlet line  68 . With diverter valve bypass line  70  closed and valve cooler inlet line  72  open, valve component  74  directs the hot melt into the cooler  60 . During steady state process conditions, cooled polymer exiting the melt cooler at  66  enters the diverter valve  62  through valve cooler exit line  76 , and by valve component  78  is directed out through valve outlet line  80 . 
   In the bypass mode, as shown in the right-hand illustration of  FIG. 6 , the valve cooler inlet line  72  and valve cooler exit line  76  are both closed, while the diverter valve bypass line  70  is open. Thus, hot melt polymer entering valve  62  through valve inlet line  68  bypasses the cooler  60  by flowing through diverter valve bypass line  70  directly to valve exit line  80 . 
     FIG. 7  illustrates a third possible orientation of the melt cooler with respect to the diverter valve in accordance with the present invention. More specifically, melt cooler  90  is shown positioned horizontally with respect to the diverter valve generally designated by reference numeral  92 . As shown, both the inlet  94  and outlet  96  are positioned at the end of the melt cooler  90  adjacent the diverter valve  92 . The inlet  94  is positioned in a top portion  91  of melt cooler  90  and the outlet  96  is positioned in a bottom portion  93  of melt cooler  90 . The normal operating mode by which the hot melt polymer is directed by the diverter valve  92  through the melt cooler  90  is shown in the left-hand illustration of  FIG. 7 , marked “A.” The bypass mode is shown in the center illustration of  FIG. 7 , marked “B,” and the drain mode is shown in the right-hand illustration, marked “C.” In each mode of operation, the diverter valve  92  operates in the same manner as described above for diverter valves  40  and  62  and, therefore, the description of the operation is not repeated here. 
     FIG. 8  illustrates another embodiment of the invention in which the orientation of the melt cooler with respect to the diverter valve is the same as is shown in  FIG. 7 . More specifically, melt cooler  90  is shown positioned horizontally with respect to the diverter valve generally designated by reference numeral  92 . As shown, both the inlet  94  and outlet  96  are positioned at the end of the melt cooler  90  adjacent the diverter valve  92 . In this embodiment, the inlet  94  is positioned in the bottom portion  93  of melt cooler  90  and the outlet  96  is positioned in the top portion  91  of melt cooler  90 . The normal operating mode by which the hot melt polymer is directed by the diverter valve  92  through the melt cooler  90  is shown in the left-hand illustration of  FIG. 8 , marked “A.” The bypass mode is shown in the center illustration of  FIG. 8 , marked “B,” and the drain mode is shown in the right-hand illustration, marked “C.” In each mode of operation, the diverter valve  92  operates in the same manner as described above for diverter valves  40  and  62  and, therefore, the description of the operation is not repeated here. 
     FIG. 9  illustrates another embodiment of the invention in which the orientation of the melt cooler with respect to the diverter valve is the same as is shown in  FIG. 7 . More specifically, melt cooler  90  is shown positioned horizontally with respect to the diverter valve generally designated by reference numeral  92 . As shown, both the inlet  94  and outlet  96  are positioned at the end of the melt cooler  90  adjacent the diverter valve  92 . In this embodiment, the inlet  94  and the outlet  96  are located in opposing portions  97  and  98  of the melt cooler in a side-by-side configuration. The normal operating mode by which the hot melt polymer is directed by the diverter valve  92  through the melt cooler  90  is shown in the left-hand illustration of  FIG. 9 , marked “A.” The bypass mode is shown in the center illustration of  FIG. 9 , marked “B,” and the drain mode is shown in the right-hand illustration, marked “C.” In each mode of operation, the diverter valve  92  operates in the same manner as described above for diverter valves  40  and  62  and, therefore, the description of the operation is not repeated here. 
   As shown in  FIGS. 10 and 11 , respectively, melt cooler  30  and melt cooler  60  can be configured to vent compressible fluids and to drain the polymeric melt and other fluids.  FIG. 10  illustrates a vent  95  located on the top  38  of melt cooler  30 .  FIG. 11  illustrates a vent and drain  101  located on the bottom  100  of melt cooler  60 . 
   To provide for the desired melt flow regimes in the top  38  of melt cooler  30 , the top  38  can be heated. For example, as illustrated in  FIG. 12 , the top  38  can be heated or cooled by a thermal transfer fluid that passes through flow channel  39 . In another possible heating configuration as illustrated in  FIG. 13 , the top  38  can be heated electrically, such as for example, by an electric heater  41 . Controlling the temperature of the top  38  ensures that the melt does not cool below a predetermined temperature as it turns through top  38  from a first process side of the melt cooler to a second process side of the melt cooler. 
   As indicated above,  FIGS. 14 ,  15 , and  16  provide detailed views of the diverter valve  40  in, respectively, the cooling mode, the bypass mode, and the drain mode of operation. The diverter valve  40  has a body housing capable of being heated by jacket using steam or other thermal transfer fluid or by electric heater cartridges. In a preferred embodiment, the first movable valve component  42  is a hydraulically actuatable bolt having three sets of flow channels therein, and the second movable valve component  44  is a hydraulically actuatable bolt having two sets of flow channels therein. In other possible embodiments of the diverter valve  40 , the bolts can include two or three sets of flow channels, either as a straight-through flow channel or as a 90° turn flow channel or as a tee-flow channel, specifically placed along the bolt length. Each of these flow channels is moved into the required position by a fluid controlled cylinder, and aligns with the corresponding required inlets and/or outlets of the diverter valve, based on the desired position required by the operator running the process, as will be understood by those skilled in the valve art. The positioning of the fluid powered cylinders, and thus the bolt position, can be controlled by manually operating a fluid flow valve or by automatic control such by a PLC, or by both. 
   According to another embodiment of the invention, the melt cooler  30  is oriented perpendicular to the melt flow path through a diverter valve  140 . As illustrated in  FIGS. 17A ,  17 B, and  17 C, the diverter valve  140  has a single movable valve component  145 . Movable valve component  145  is a hydraulically actuatable bolt having three sets of flow channels therein, including a cooling flow channel  141 , a bypass flow channel  142 , and a drain flow channel  143 . The single bolt embodiment of the diverter valve provides a relatively short melt flow path and an economical valve construction. 
   Another embodiment of the invention is directed to a method of cooling a polymeric melt for an underwater pelletizer. See, e.g.,  FIG. 5  for an illustration of the various configurations of the diverter valve that are associated with the method. The method is employed with a diverter valve  40  that has two melt drain lines. The method includes conveying the melt to a diverter valve  40  that conveys the melt to and from a melt cooler  30  during a cooling mode of operation, conveys the melt around the cooler  30  during a bypass mode of operation, and drains the melt from the cooler  30  and from the diverter valve  40  during a drain mode of operation. The diverter valve  40  has a hot melt inlet line  45 , a first movable valve component  42 , a hot melt outlet line  52  to the melt cooler  30 , a hot melt bypass line  46 , a cooled melt inlet line  54  from the melt cooler  30 , a second movable valve component  44 , a cooled melt outlet line  47 , and first  48  and second  50  melt drain lines. 
   The diverter valve  40  is configured for the cooling mode (see  FIG. 5 , MC PROCESS MODE A) by positioning the first movable valve component  42  so as to close the hot melt bypass line  46  and close the first melt drain line  48 , and positioning the second movable valve component  44  so as to open the cooled melt inlet line  54  from the melt cooler  30  and close the second melt drain line  50 , thereby conveying the melt through the melt cooler  30  and out of the diverter valve  40  through the cooled melt outlet line  47 . 
   The diverter valve  40  is configured for the bypass mode (see  FIG. 5 , MC PROCESS MODE B) by positioning the first movable valve component  42  so as to close the hot melt outlet line  52  to the melt cooler  30  and close the first melt drain line  48 , and positioning the second movable valve component  44  so as to close the cooled melt inlet line  54  from the melt cooler  30  and close the second melt drain line  50 , thereby conveying the melt around the melt cooler  30  and out of the diverter valve  40  through the cooled melt outlet line  47 . 
   The diverter valve  40  is configured for the drain mode (see  FIG. 5 , MC DRAIN MODE C 1 ) by positioning the first movable valve component  42  so as to open the hot melt outlet line  52  to the melt cooler  30 , close the hot melt bypass line  46 , and open the first melt drain line  48 , and positioning the second movable valve component  44  so as to open the cooled melt inlet line  54  from the melt cooler  30  and open the second melt drain line  50 . This conveys the melt from the hot melt inlet line  45  and from a first process side of the melt cooler  30  out of the diverter valve  40  through the first melt drain line  48 , and conveys the melt from a second process side of the melt cooler  30  and from the cooled melt outlet line  47  out of the diverter valve  40  through the second melt drain line  50 . 
   Still another embodiment of the invention is directed to a method of cooling a polymeric melt for an underwater pelletizer in which the diverter valve  40  has a single melt drain line  48  (see  FIG. 5 , MC DRAIN MODE C 2 ). The method includes conveying the melt to a diverter valve  40  that conveys the melt to and from a melt cooler  30  during a cooling mode of operation, conveys the melt around the cooler  30  during a bypass mode of operation, and drains the melt from the cooler  30  and from the diverter valve  40  during a drain mode of operation. The diverter valve  40  has a hot melt inlet line  45 , a first movable valve component  42 , a hot melt outlet line  52  to the melt cooler  30 , a hot melt bypass line  46 , a cooled melt inlet line  54  from the melt cooler  30 , a second movable valve component  44 , a cooled melt outlet line  47 , and a melt drain line  48 . 
   The diverter valve  40  is configured for the cooling mode by positioning the first movable valve component  42  so as to close the hot melt bypass line  46  and close the melt drain line  48 , and positioning the second movable valve component  44  so as to open the cooled melt inlet line  54  from the melt cooler  30 , thereby conveying the melt through the melt cooler  30  and out of the diverter valve  40  through the cooled melt outlet line  47 . 
   The diverter valve  40  is configured for the bypass mode by positioning the first movable valve component  42  so as to close the hot melt outlet line  52  to the melt cooler  30  and the melt drain line  48 , and positioning the second movable valve component  44  so as to close the cooled melt inlet line  54  from the melt cooler  30 , thereby conveying the melt around the melt cooler  30  and out of the diverter valve  40  through the cooled melt outlet line  47 . 
   The diverter valve  40  is configured for the drain mode (see  FIG. 5 , MC DRAIN MODE C 2 ) by positioning the first movable valve component  42  so as to open the hot melt outlet line  52  to the melt cooler  30  and close the hot melt bypass line  46 , and positioning the second movable valve component  44  so as to open the cooled melt inlet line  54  from the melt cooler  30 . This conveys the melt from the hot melt inlet line  45  and from a first process side of the melt cooler  30  out of the diverter valve  40  through the melt drain line  48 , and conveys the melt from a second process side of the melt cooler  30  out of the diverter valve  40  through the cooled melt outlet line  47 . 
   It is not intended that the present invention be limited to the specific apparatus and methods described herein. The foregoing is considered as illustrative only of the principles of the invention. For example, the concepts disclosed herein are applicable to a system and method for controlled pelletization processing as described in PCT/US2006/045375, an application owned by the assignee of the present invention, the disclosure of which is expressly incorporated by reference in this application as if fully set forth herein. 
   Additionally, while the various embodiments of the invention have been described primarily in the context of cooling a polymer melt, in another possible embodiment the system described herein can be employed to heat a fluid. Furthermore, while the system has been described in the context of an underwater pelletizing process, the system is equally applicable to other processes in which various heat exchange configurations of a process fluid are required. 
   Further, numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and, accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.