Patent Publication Number: US-9846001-B2

Title: Heat exchanger assembly and use of an apparatus in a heat exchanger

Description:
TECHNICAL FIELD 
     The present invention relates to a heat exchanger assembly according to the precharacterizing portion of claim  1 , and to the use of a pressure pulse damping apparatus for damping pressure pulses in a heat exchanger 
     BACKGROUND 
     Heat exchangers for heat exchange between at least a first heat exchange fluid and a second heat exchange fluid are used in many different kinds of applications and processes, such as offshore oil platforms, steam condensate systems and fertilizer plants, to name a few. A heat exchanger may be used for many different purposes such as e.g. cooling and heating fluids, condensing gases, and evaporating liquids. 
     In some applications pressure pulses may occur in a heat exchange fluid. For instance, pressure pulses may occur in applications were one heat exchange fluid is a liquid in which slugs of gas may occur. For instance, on offshore oil platforms wet crude oil which contains oil, water, and fossil gas is extracted from a drill hole. The wet crude oil is heated in a heat exchanger for further processing. The fossil gas forms slugs in a conduit flowed through by the wet crude oil. A gas slug reaching the heat exchanger is followed by liquid (i.e. oil and water) which will enter the heat exchanger at high speed and cause a sharp pressure pulse which may damage the heat exchanger. Heat transfer elements may be damaged, gaskets may be blown. A different example of a heat exchange fluid containing gas is condensate or other liquid at a temperature close to the boiling point of the condensate/liquid. When such a condensate/liquid flows at high speed through a conduit, the pressure in the condensate/liquid may be reduced causing the condensate/liquid to boil and thus forming gas. A heat exchanger at an end of such a conduit will be subjected to pressure pulses for the same reason as explained above in connection with offshore oil drilling but also due to the gas expanding in the conduit pushing condensate/liquid ahead of the gas at high speed into the heat exchanger. Again, the heat exchanger may be damaged from such pressure pulses. 
     JP 55014468 suggests the use of a safety valve or a rupture disc connected to conduit at an inlet side of a condenser. When a pressure pulse occurs, the safety valve or the rupture disc opens a connection between the conduit at the inlet side of a condenser and a conduit at an outlet side of the condenser. 
     JP 52120445 suggests a bypass conduit between an inlet side and an outlet side of a condenser. In the bypass conduit a valve is arranged. 
     Although a condenser may be spared from a pressure pulses in the two above mentioned arrangements, the pressure pulse is not damped and equipment downstream of the condenser may be damaged by a pressure pulse. 
     JP 06-313566 discloses an air separator for water hammer prevention to be arranged in a domestic warm water system. The air separator comprises a main part forming a chamber with a water inlet leading to the chamber and an outlet leading from the chamber. Inside the chamber an air layer is formed and an air vent valve is arranged for venting air from the chamber. The air separator is arranged in an outlet conduit leading from a water heater to a radiator or water tap and thus relies on the water flowing through the chamber in order to absorb water hammering. 
     SUMMARY 
     An object of the present invention is to reduce or eliminate pressure pulses reaching a heat exchanger. 
     According to an aspect of the invention, the object is achieved by a heat exchanger assembly comprising a heat exchanger for heat exchange between at least a first heat exchange fluid and a second heat exchange fluid. The heat exchanger comprises at least one heat transfer element delimiting a first fluid path for the first heat exchange fluid from a second fluid path for the second heat exchange fluid inside the heat exchanger. The heat exchanger further comprises a through connection for the first heat exchange fluid arranged at a first side portion of an outer structure of the heat exchanger. The assembly comprises a pressure pulse damping apparatus, the apparatus comprising an elastic element, and a first conduit leading to the elastic element. The first conduit comprises a first opening connected to the through connection of the heat exchanger such that the first conduit is in fluid connection with the first fluid path. The elastic element is in fluid communication with the first fluid path only via the first opening. 
     Since the pressure pulse damping apparatus is connected to the heat exchanger such that the first conduit forms a dead-end at the elastic element, in use a pressure pulse in the first heat exchange fluid will cause the elastic element to be compressed and thus the pressure pulse to be damped. As a result, the above mentioned object is achieved and accordingly, the life time of the heat exchanger may be increased, and/or downtime and operational costs of the heat exchanger may be reduced. 
     In the heat exchanger the first and second heat exchange fluids are in heat exchanging communication with each other via the at least one heat transfer element. The pressure pulse damping apparatus has no further connection through which the first heat exchange fluid may enter and exit the pressure pulse damping apparatus than the first opening. The pressure pulse damping apparatus need not necessary eliminate a pressure pulse. More importantly, the pressure pulse damping apparatus reduces the amplitude of the pressure pulse such that instead of a short pressure impulse, a pressure pulse of lower amplitude will affect the heat exchanger over longer time. Such a pressure pulse may be more easily withstood by the heat exchanger. The heat exchanger and the pressure pulse damping apparatus may be offered separately. 
     According to embodiments the first conduit of the pressure pulse damping apparatus may be connected to the through connection at the first side portion opposite to a second side portion comprising an inlet for the first heat exchange fluid to the heat exchanger. In this manner the pressure pulse damping apparatus may be arranged in suitable position to damp a pressure pulse entering the heat exchanger, or forming inside the heat exchanger and/or the pressure pulse damping apparatus. The pressure pulse damping apparatus thus, may be arranged in a suitable position on the heat exchanger for damping the pressure pulse since the first point of impact for the pressure pulse may be at a side portion opposite to the inlet for the first heat exchange fluid. 
     According to embodiments the heat exchanger may comprise a straight fluid path from the inlet for the first heat exchange fluid to the through connection. In this manner a pressure pulse in the first heat exchange fluid will substantially unimpededly reach the pressure pulse damping apparatus and the point of impact of the pressure pulse may primarily be in the pressure pulse damping apparatus. 
     According to embodiments the elastic element may comprises a movable partition, the movable partition being adapted in use to be subjected to a pressure pulse in the first heat exchange fluid. In this manner the movable partition may delimit the first heat exchange fluid from other parts of the elastic element. 
     According to embodiments the elastic element may comprise a chamber which is at least partially filled with a gas, the chamber and the first conduit forming a closed compartment. Since the gas is enclosed in a chamber and is a compressible medium, the gas may damp a pressure pulse in the first heat exchange fluid. It is to be understood that the closed compartment is closed in all directions except for at the first opening. 
     According to embodiments the chamber may be elongated and arranged substantially perpendicularly to the first conduit. In this manner the pressure pulse damping apparatus may be formed to extend alongside the first side portion of the heat exchanger. In many applications this may be an advantageous arrangement of the pressure pulse damping apparatus, e.g. due to limited available space around the heat exchanger. 
     According to embodiments the gas inside the chamber may be delimited by the movable partition such that in use the pressure pulse in the first heat exchange fluid is transferred via the movable partition to the gas inside the chamber. 
     According to embodiments the movable partition may comprise a membrane or a piston. A membrane may for instance partially or fully enclose a gas in a chamber of the pressure pulse damping apparatus. A piston may abut an inner wall of the pressure pulse damping apparatus such as inner walls of a chamber. 
     According to embodiments the elastic element may comprise a spring, the spring abutting the movable partition. The spring may thus be affected and compressed by a pressure pulse in the first heat exchange fluid and damp the pressure pulse. 
     According to embodiments the heat exchanger may be a plate heat exchanger and the heat transfer element may be formed by a heat transfer plate. A plate heat exchanger may typically have a number of heat transfer plates arranged in a plate package. The heat transfer plates are each provided with for instance four port holes, forming four channels through the plate package. Inlet and outlet conduits for two heat exchange fluids are arranged in fluid communication with four channels. 
     According to embodiments the first side portion of the heat exchanger may be formed by a pressure plate or a frame plate. The second side portion may accordingly be formed by the other of the pressure plate and the frame plate. A plate package of a plate heat exchanger may typically be clamped between the frame plate, which is fixed to a frame, and the pressure plate, which in some types of plate heat exchangers may be movable. The inlet and outlet conduits may be connected to the frame plate. 
     According to embodiments the pressure pulse damping apparatus may comprise a flange arranged circumferentially around the first conduit at the first opening for connecting the pressure pulse damping apparatus to the heat exchanger. The flange may be provided with through holes such that it may be attached to the heat exchanger by means of screws, or nuts and bolts. 
     A further aspect of the invention relates to use of a pressure pulse damping apparatus comprising an elastic element and a first conduit leading to the elastic element for damping pressure pulses in a heat exchanger. The first conduit comprises a first opening adapted to be connected the heat exchanger such that the first conduit is in fluid connection with a first fluid path of the heat exchanger. The elastic element is in fluid communication with the first fluid path only via the first opening. 
     The use of such a pressure pulse damping apparatus will absorb or at least reduce pressure pulses in a first heat exchange fluid in a relevant heat exchanger. Again, since the pressure pulse damping apparatus forms a dead-end at the elastic element, a pressure pulse in the first heat exchange liquid in the first fluid path will cause the elastic element to be compressed and thus the pressure pulse to be damped. As a result, the above mentioned object is achieved. 
     The pressure pulse damping apparatus has no further connection through which the first heat exchange fluid may enter and exit the pressure pulse damping apparatus than the first opening. Again, the pressure pulse damping apparatus need not necessary eliminate a pressure pulse. More importantly, the pressure pulse damping apparatus reduces the amplitude of the pressure pulse such that instead of a short pressure impulse, a pressure pulse of lower amplitude will affect a relevant heat exchanger over longer time. Such a pressure pulse may be more easily withstood by the heat exchanger. 
     According to embodiments, use of the pressure pulse damping apparatus may comprise the first conduit of the pressure pulse damping apparatus to be connected to the through connection at the first side portion opposite to a second side portion comprising an inlet for the first heat exchange fluid to the heat exchanger. 
     According to embodiments, use of the pressure pulse damping apparatus may comprise the heat exchanger comprising a straight fluid path from the inlet for the first heat exchange fluid to the through connection. 
     According to embodiments, the use of the pressure pulse damping apparatus may comprise the elastic element comprising a movable partition, the movable partition being adapted in use to be subjected to a pressure pulse in the first heat exchange fluid. 
     According to embodiments the use of the pressure pulse damping apparatus may comprise the elastic element comprising a chamber which may be at least partially filled with a gas, the chamber and the first conduit forming a closed compartment. 
     According to embodiments the use of the pressure pulse damping apparatus may comprise the chamber being elongated and arranged substantially perpendicularly to the first conduit. 
     According to embodiments the use of the pressure pulse damping apparatus may comprise the gas inside the chamber being delimited by the movable partition such that in use the pressure pulse in the first heat exchange fluid may be transferred via the movable partition to the gas inside the chamber. 
     According to embodiments the use of the pressure pulse damping apparatus may comprise the movable partition comprising a membrane or a piston. 
     According to embodiments the use of the pressure pulse damping apparatus may comprise the elastic element comprising a spring, the spring abutting the movable partition. 
     According to embodiments the use of the pressure pulse damping apparatus may comprise the heat exchanger being a plate heat exchanger and the heat transfer element being formed by a heat transfer plate. 
     According to embodiments the use of the pressure pulse damping apparatus may comprise the first side portion of the heat exchanger being formed by a pressure plate or a frame plate and the second side portion being formed by the other of the pressure plate and the frame plate. 
     Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following detailed description. Those skilled in the art will realize that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention, as defined by the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The various aspects of the invention, including its particular features and advantages, will be readily understood from the following detailed description and the accompanying drawings, in which: 
         FIGS. 1-5  illustrate heat exchanger assemblies according to embodiments comprising a heat exchanger and a pressure pulse damping apparatus.  FIGS. 1-5  also illustrate embodiments of use of pressure pulse damping apparatuses for damping pressure pulses in heat exchangers. 
         FIG. 6  illustrates a portion of a pressure pulse damping apparatus according to example embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention will now be described more fully with reference to the accompanying drawings, in which example embodiments are shown. However, this invention should not be construed as limited to the embodiments set forth herein. Disclosed features of example embodiments may be combined as readily understood by one of ordinary skill in the art to which this invention belongs. Like numbers refer to like elements throughout. 
     Well-known functions or constructions will not necessarily be described in detail for brevity and/or clarity. 
       FIG. 1  illustrates a heat exchanger assembly  2  according to embodiments comprising a heat exchanger  4  and a pressure pulse damping apparatus  6 .  FIG. 1  also illustrates embodiments of use of a pressure pulse damping apparatus  6  for damping pressure pulses in the heat exchanger  4 . The pressure pulse damping apparatus  6  is shown partially in cross section. As well known in the technical field of heat exchangers, the plate heat exchanger  4  is provided with a plate package  8  of heat exchange plates  10  clamped between a frame plate  9  and a pressure plate  11 . The pressure plate  11  may be seen as a first side portion of the heat exchanger  4  and the frame plate  9  may be seen as a second side portion of the heat exchanger  4 . The heat exchange plates  10  are utilized for exchange of heat between a first and a second heat exchange fluid. The plates  10  form plate interspaces adapted to be flowed through by the heat exchange fluids. The plates  10  are provided with four port holes which form inlet and outlet channels  12 ,  14  (two of which are indicated by broken lines in  FIG. 1 ) extending through the plate package  8  and communicating with the plate interspaces. In use, a first heat exchange fluid flows through an inlet conduit  16  into the inlet channel  12 , through every second plate interspace of the plate package  8  to the outlet channel  14 , and out of the heat exchanger  4  to an outlet conduit  18 . 
     The pressure plate  11  forms the first side portion of the plate heat exchanger  4  and is provided with a through connection  20  forming an extension of the inlet channel  12 . The pressure pulse damping apparatus  6  is connected to the pressure plate  11  such that a first conduit  22  of the pressure pulse damping apparatus  6  is in fluid communication with the inlet channel  12  via the through connection  20 . Accordingly, in use the first conduit  22  is filled with the first heat exchange fluid. The pressure pulse damping apparatus  4  comprises a chamber  24  which is filled with a gas such as air. The chamber  24  is closed and a movable partition in the form of a membrane  26  at least partially encloses the gas, and delimits the gas from the first heat exchange fluid. The membrane  26  and the gas in the chamber  24  form an elastic element. 
     Frame plates  9  and pressure plates  11  are frequently manufactured with through holes in positions where the inlet and outlet channels in the plate package  8  are arranged. Through holes which are not required in use are closed by covers. Thus, the through connection  20  may be readily available for forming a fluid connection between the first conduit  22  and the inlet channel  12 . Inlet and outlet channels  12 ,  14  for the heat exchange fluids communicate with the inlet and outlet conduits  16 ,  18  via to the through holes in the frame plate  9 . 
     When in use of a heat exchanger  4  with a first heat exchange fluid, primarily being in liquid form, a pressure pulse arrives with the first heat exchange fluid to the heat exchanger  4 , the pressure pulse will travel along the inlet channel  12  into the first conduit  22  of the pressure pulse damping apparatus  6 . When the pressure pulse arrives at the membrane  26  the gas on the other side of the membrane  26  is compressed by the pressure pulse. Similarly, when a gas slug enters the inlet channel  12  and is followed by liquid at high speed, a pressure pulse is formed when the liquid impacts against the membrane  26 . 
     The pressure pulse will be transmitted to the gas in the chamber  26  and since the gas is compressible, the pressure pulse will be damped. Furthermore, the speed of the pressure pulse will decrease as it gradually compresses the gas. Accordingly, if the pressure pulse is not absorbed by the gas the pressure pulse transmitted from the gas back to the first heat exchange fluid will have lower amplitude and be distributed over a longer time than the original pressure pulse. The pressure pulse affecting the heat exchanger  4  will thus be of a kind which is more easily withstood by the heat exchanger  4  and its plate package  8 , seen in contrast with a pressure pulse impacting, or forming, on an inside of the pressure plate  11  and being transmitted through the plate package  8  towards the outlet conduit  18 . 
     The first conduit  22  comprises a first opening connected to the through connection  20 . A flange  28  is arranged circumferentially around the first conduit  22  at the first opening for connecting the pressure pulse damping apparatus  6  to the pressure plate  11 . The flange  28  may be provided with through holes such that it may be attached to the heat exchanger  4  by means of screws, or nuts and bolts. Thus, the pressure pulse damping apparatus  6  may easily be attached retroactively in an already present installation if it is revealed that the installation is troubled by pressure pulses. Such retroactive installation may also be performed in a flammable environment since no welding is necessary. The pressure pulse damping apparatus  6  may comprise a lid  30 , through which the first conduit  22  of the pressure pulse damping apparatus  6  and the inlet channel  12  of the plate heat exchanger  4  are accessible. A filter (also called port strainer) may be positioned in the inlet channel  12  via the lid  30 . When the heat exchanger  4  is in use, the lid  30  is maintained closed. 
       FIG. 2  illustrates a heat exchanger assembly  2  according to embodiments comprising a heat exchanger  4  and a pressure pulse damping apparatus  6 .  FIG. 2  also illustrates embodiments of use of a pressure pulse damping apparatus  6  for damping pressure pulses in the heat exchanger  4 . The pressure pulse damping apparatus  6  is shown partially in cross section. The pressure pulse damping apparatus  6  comprises a first conduit  22  connected to a pressure plate  11  of the heat exchanger  4 , and an elastic element comprising a piston  40  and a spring  42 . Again, the first conduit  22  communicates with an inlet channel for a first heat exchange fluid in the heat exchanger  4 . The piston  40  is a movable partition, in use delimiting inter alia a chamber  44  and the spring  42  from the first heat exchange fluid in the first conduit  22 . The piston  40  is movable along inner walls of the chamber  44 , which has a uniform inner diameter. The spring  42  is arranged in the chamber  44  and abuts against the piston  40  and an end wall  46  of the chamber  44 . The end wall  46  is provided with a through hole for a rod  48  attached to the piston  40  to pass through. When a pressure pulse in the first heat exchange fluid via the first conduit  22  impacts against the piston  40 , the spring  42  is compressed and the piston  40  is moved into the chamber  44 . Thus, the pressure pulse is damped and at least partially absorbed. 
     A further damping effect may be achieved by air inside the chamber  44 , which is forced through the through hole in the end wall  46  as the piston is moved into the chamber  44 . As the spring  42  again expands, the movement of the piston  40  is damped by air being admitted into the chamber  44  only at a limited rate through the through hole in the end wall  46 . In this manner the pressure pulse may be further damped since any pressure pulse being reflected back into the first heat exchange fluid by the spring  42  and the piston  40  is restricted. 
       FIG. 3  illustrates the assembly  2  of  FIG. 2  when the piston  40  and the spring  42  has been affected by a pressure pulse in the first heat exchange fluid. The spring  42  has thus, been compressed. The rod  48  extends through the through hole in the end wall  46  of the chamber  44 . 
       FIG. 4  illustrates a heat exchanger assembly  2  according to embodiments comprising a heat exchanger  4  and a pressure pulse damping apparatus  6 .  FIG. 4  also illustrates embodiments of use of a pressure pulse damping apparatus  6  for damping pressure pulses in the heat exchanger  4 . The pressure pulse damping apparatus  6  is shown partially in cross section. The pressure pulse damping apparatus  6  comprises a first conduit  22  connected to a pressure plate  11  of the heat exchanger  4 . Again, the first conduit  22  communicates with an inlet channel for a first heat exchange fluid in the heat exchanger  4 . The pressure pulse damping apparatus  6  further comprises an elastic element comprising a piston  40 , a spring  42 , and a chamber  24 . The piston  40  is a movable partition, in use delimiting inter alia the chamber  24  and the spring  42  from the first heat exchange fluid in the first conduit  22 . The piston  40  is movable along inner walls of the chamber  24 , which has a uniform inner diameter. The spring  42  is arranged in the chamber  24  and abuts against the piston  40  and an end wall  46  of the chamber  24 . The chamber  24  is filled with a gas such as air and closed by means of the piston  40 , which delimits the gas from the first heat exchange fluid. The piston  40 , the spring  42 , and the gas in the chamber  24  form an elastic element. 
     In the embodiments according to  FIG. 4 , the spring  42  and the gas enclosed in the chamber  24  cooperate to damp pressure pulses in the first heat exchange fluid. 
       FIG. 5  illustrates a heat exchanger assembly  2  according to embodiments comprising a heat exchanger  4  and a pressure pulse damping apparatus  6 .  FIG. 5  also illustrates embodiments of use of a pressure pulse damping apparatus  6  for damping pressure pulses in the heat exchanger  4 . The pressure pulse damping apparatus  6  is shown partially in cross section. The pressure pulse damping apparatus  6  comprises a first conduit  22  connected to a pressure plate  11  of the heat exchanger  4 . Again, the first conduit  22  communicates with an inlet channel  12  for a first heat exchange fluid in the heat exchanger  4 . However, in these embodiments the inlet channel  12  is arranged at an upper end of the plate package  8 . Accordingly, the inlet conduit  16  is connected to the frame plate  9  at an upper end thereof, and an outlet channel  14  with a matching outlet conduit  18  are arranged at a lower end of the plate package  8  and the frame plate  9 . 
     The pressure pulse damping apparatus  6  further comprises a chamber  24 , which communicates with the first conduit  22 . In use the chamber  24  is filled with a gas, such as air, and the first heat exchange fluid substantially fills the first conduit  22 . The first heat exchange fluid, primary comprising a liquid, forms a liquid surface  60  in the first conduit  22  or the chamber  24 . Under stable operating conditions the liquid surface  60  will remain at substantially the same level. When a pressure pulse in the first heat exchange fluid enters the inlet channel  12 , the pressure pulse is transferred through the first conduit  22  to the gas filled chamber  24 . The gas inside the chamber  24  forms an elastic element. Since the gas is compressible the gas will be compressed by the pressure pulse and thus damp the pressure pulse as explained above. As the pressure pulse compresses the gas in the chamber  24  the liquid level  60  is temporarily raised. 
       FIG. 6  illustrates a portion of a pressure pulse damping apparatus  6  according to example embodiments. A first conduit  22  leads to a non-shown elastic element. A first opening  62  is adapted to be connected to a through connection of a heat exchanger such that the first conduit  22  is in fluid connection with a first fluid path of a heat exchanger. The elastic element is in fluid communication with the first fluid path only via the first opening  62 . A flange  28  is arranged circumferentially around the first conduit  22  at the first opening  62 . The flange  28  is provided with through holes  64 . 
     Purely as an example it may be mentioned that a pressure pulse damping apparatus according to embodiments for damping pressure pulses in a heat exchanger used in offshore wet crude oil heating may have the following dimensions. The first conduit of the pressure pulse damping apparatus leads to a cylinder filled with gas thus, forming the gas filled chamber  24 . The cylinder has a diameter of 1 meter and an approximate height of 4.6 meters thus, housing a volume of approximately 3600 liters of gas. Inlet and outlet conduits for the wet crude oil of the heat exchanger have typically a diameter in the range of 250-500 mm. A pressure pulse damping apparatus of such dimensions is deemed to cope with pressure pulses commonly occurring in typical offshore wet crude oil handling. 
     A further example relates to steam condensate cooling. For instance, where in a conduit condensate at a temperature close to the boiling point of the condensate is subjected to a slightly varying pressure, so-called flash vapour may form. As the vapour expands. it will form a vapour pocket that accelerates and pushes a column of condensate at a high velocity through the conduit. As the condensate column has high kinetic energy, it may cause a pressure pulse when it is brought to a sudden stop at an end of the conduit, e.g. in a plate heat exchanger connected to the conduit and forming a condensate cooler. Such a pressure pulse may damage the plate heat exchanger. Again, a pressure pulse damping apparatus may be utilized for damping such a pressure pulse. The following dimensions are presented purely as an example: A condensate conduit leading to a plate heat exchanger for cooling condensate at a flow of about 66.000 kg/h may have a diameter of approximately 150-200 mm. The plate heat exchanger may have an internal volume of approximately 100 liters A gas volume of a gas filled chamber  24  of a pressure pulse damping apparatus  6  may be about 100 liters, e.g. in the form of a cylinder having a diameter of 300 mm and an approximate length of 1.5 m. 
     Example embodiments described above may be combined as understood by a person skilled in the art. It is also understood by those skilled in the art that heat exchangers benefiting from a pressure pulse damping apparatus may be of many kinds, for example plate heat exchangers provided with gaskets, welded plate heat exchangers, semi-welded plate heat exchangers, and fusion bonded plate heat exchangers. 
     Although the invention has been described with reference to example embodiments, many different alterations, modifications and the like will become apparent for those skilled in the art. The elastic element may comprise other pressure pulse damping elements than the exemplified gas filled chamber and spring, e.g. may the elastic element comprise an elastomer. The pressure pulse damping apparatus may have other shapes than disclosed. The pressure pulse damping apparatus may be directed in a different direction than disclosed, e.g. horizontally. 
     Therefore, it is to be understood that the foregoing is illustrative of various example embodiments and the invention is not to be limited to the specific embodiments disclosed and that modifications to the disclosed embodiments, combinations of features of disclosed embodiments as well as other embodiments are intended to be included within the scope of the appended claims. 
     As used herein, the term “comprising” or “comprises” is open-ended, and includes one or more stated features, elements, steps, components or functions but does not preclude the presence or addition of one or more other features, elements, steps, components, functions or groups thereof. 
     As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     As used herein, the common abbreviation “e.g.”, which derives from the Latin phrase “exempli gratia,” may be used to introduce or specify a general example or examples of a previously mentioned item, and is not intended to be limiting of such item. If used herein, the common abbreviation “i.e.”, which derives from the Latin phrase “id est,” may be used to specify a particular item from a more general recitation. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     It will be understood that when an element is referred to as being “on”, “coupled” or “connected” to another element, it can be directly on, coupled or connected to the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on”, “directly coupled” or “directly connected” to another element, there are no intervening elements present. 
     It will be understood that although the terms first, second, third etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used top distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed herein could be termed a second element, component, region, layer or section without departing from the teachings of the present invention. 
     Spatially relative terms, such as “beneath”, “below”, “bottom”, “lower”, “above”, “top”, “upper” and the like, may be used herein for ease of description to describe one element&#39;s or feature&#39;s relationship to other element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. Also, as used herein, “lateral” refers to a direction that is substantially orthogonal to a vertical direction. 
     Example embodiments of the present invention have been described herein with reference to cross-section illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the invention. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances are to be expected. Thus, embodiments of the present invention should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shape that result, for example, from manufacturing.