CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation application of U.S. application Ser. No. 13/535,033 filed on Jun. 27, 2012, which is a continuation-in-part application of U.S. application Ser. No. 12/795,576 filed on Jun. 7, 2010, which is a continuation-in-part application of U.S. application Ser. No. 12/754,518 filed on Apr. 5, 2010, which are herein incorporated by reference in their entirety. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       BACKGROUND OF THE INVENTION 
       [0003]    1. Field of the Invention 
         [0004]    This invention relates to the field of pipeline maintenance and more specifically to the field of using pipeline pigs for pipeline maintenance and new construction. 
         [0005]    2. Background of the Invention 
         [0006]    Pipeline pigs are conventionally used in the maintenance of pipelines. Pipeline pigs are typically inserted into a pig launcher. Pressure may then be added that pushes the pipeline pig along the pipeline until it reaches a pig receiver for removal from the pipeline. The pipeline pigs are commonly used to remove foreign material that may be in the line during construction of new pipelines. The pipeline pigs may also be used to make sure the pipeline has not become dented or wrinkled during bending or laying as well as also used to check for the ovalness of the pipeline. Further uses of the pipeline pigs may include removing water from pipelines after hydrostatic tests. 
         [0007]    Drawbacks to conventional pig receivers include harm to the environment. For instance, matter removed from the pipelines may not be properly contained. Additional drawbacks to conventional pig receivers include downtime in launching new pipeline pigs when other pipeline pigs are being removed from the pipeline. 
         [0008]    Consequently, there is a need for an improved pig receiver that allows pipeline pigs to be continually launched and received in pipelines. Further needs include improved pig receivers that facilitate environmental concerns. 
       BRIEF SUMMARY OF SOME OF THE PREFERRED EMBODIMENTS 
       [0009]    These and other needs in the art are addressed in one embodiment by a pig receiver that includes a pig receiver unit. The pig receiver also includes a pig gate valve assembly disposed on the pig receiving unit. The pig gate valve assembly includes a gate valve. The pig gate valve assembly also includes a first actuator and a second actuator. The pig gate valve assembly further includes a cylinder guide. In addition, the pig gate valve assembly includes a tie bar. Actuation of the tie bar actuates the gate valve. An end of the tie bar is attached to the first actuator, and an opposing end of the tie bar is attached to the second actuator. The pig receiver also includes a system for removing contaminants from the pig receiver. 
         [0010]    In addition, these and other needs in the art are addressed in an embodiment by a method for retrieving a pipeline pig. The method includes allowing the pipeline pig to run into a pig receiver. The pig receiver includes a pig receiver unit comprising a retrieval door. The pig receiver also includes a pig gate valve assembly disposed on the pig receiving unit. The pig gate valve assembly includes a gate valve. The gate valve is in an open position. In addition, the pig gate valve assembly includes a first actuator and a second actuator. The pig gate valve assembly also includes a cylinder guide. The pig gate valve assembly further includes a tie bar. Actuation of the tie bar actuates the gate valve. An end of the tie bar is attached to the first actuator, and an opposing end of the tie bar is attached to the second actuator. The pig receiver also includes a contaminant removal system. The contaminant removal system includes removing contaminants from the pig receiver unit with a fluid. The method also includes actuating the pig gate valve assembly to move the gate valve to a closed position. In addition, the method includes opening the retrieval door. The method further includes retrieving the pig. 
         [0011]    The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other embodiments for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent embodiments do not depart from the spirit and scope of the invention as set forth in the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    For a detailed description of the preferred embodiments of the invention, reference will now be made to the accompanying drawings in which: 
           [0013]      FIG. 1  illustrates an embodiment of a pig receiver, pig receiving unit, and pig gate valve assembly; 
           [0014]      FIG. 2  illustrates an embodiment of an actuation system; 
           [0015]      FIG. 3  illustrates an embodiment of a pig receiver having a pressure equalization system; 
           [0016]      FIG. 4  illustrates an embodiment of a pig receiver having a contaminant removal system; 
           [0017]      FIG. 5  illustrates an embodiment of a manifould; 
           [0018]      FIG. 6  illustrates a top cross sectional view of an embodiment of a sump and a pig receiver unit  10 ; 
           [0019]      FIG. 7  illustrates a side perspective view of an embodiment of a pig receiver having a contaminant removal system; 
           [0020]      FIG. 8  illustrates a side perspective view of an embodiment of a pig receiver having a contaminant removal system; and 
           [0021]      FIG. 9  illustrates a side perspective view of a portion of an embodiment of a pig receiver having a contaminant removal system. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0022]      FIG. 1  illustrates pig receiver  5  having pig receiver unit  10 , support  15 , and pig gate valve assembly  20 . Pig gate valve assembly  20  is secured to pig receiver unit  10  and allows pig receiver unit  10  to receive pigs (not illustrated) while additional pig or pigs may continue to progress through a pipeline (not illustrated). In an embodiment, pig receiver  5  is attached to the pipeline at pipeline contact end  165 . The pigs enter pig receiver  5  at pipeline contact end  165 . Pipeline contact end  165  may be attached to the pipeline by any suitable means. 
         [0023]    Pig receiver unit  10  has any configuration suitable for facilitating passage of pigs therethrough. In an embodiment as illustrated in  FIG. 1 , pig receiver unit  10  has the typical configuration of a pipeline (e.g., substantially cylindrically shaped). In some embodiments as illustrated in  FIG. 1 , pig receiver unit  10  has an enlarged diameter on pig retrieval end  170 , which is the end of pig receiver unit  10  longitudinally distal from pipeline contact end  165 . Without being limited by theory, pig retrieval end  170  has an enlarged diameter because the enlarged diameter facilitates removing pigs from pig receiver unit  10 . Pig receiver unit  10  has retrieval door  175 . Retrieval door  175  is an openable and closeable door. In embodiments in which retrieval door  175  is open, pigs may be retrieved from pig receiver unit  10 . 
         [0024]    In some embodiments as illustrated in  FIG. 1 , pig receiver unit  10  also has take-off  90 . In embodiments, take-off  90  allows for product or other material in pig receiver unit  10  to be removed. In an embodiment as illustrated in  FIG. 1 , take-off  90  is disposed on the surface of pig receiver unit  10  at a location between gate valve  25  and pipeline contact end  165 . In some embodiments, pig receiver unit  10  has more than one take-off  90 . In other embodiments as illustrated in  FIG. 1 , pig receiver unit  10  also has fastening means  130 . Fastening means  130  include any means for fastening pig receiver  5  to a transportation means for transporting pig receiver  5  and/or for alignment of pig receiver  5  with a pipeline. In an embodiment as illustrated in  FIG. 1 , fastening means  130  is an eye fastener. 
         [0025]    As shown in  FIG. 1 , pig gate valve assembly  20  includes gate valve  25 , actuators  40  and  45 , and cylinder guide  60 . Gate valve  25  refers to an openable/closeable valve comprising a round, rectangular, or the like gate/wedge. Gate valve  25  includes gate valve seat  35 . When gate valve  25  is in the closed position, gate valve seat  35  provides a seal that facilitates prevention of liquid leaking around gate valve  25 . Gate valve  25  is attached to rod  65 . In an embodiment as illustrated, gate valve  25  is attached to rod  65  on the longitudinal end of gate valve  25  distal to gate valve seat  35 . Rod  65  is attached to tie bar  70 . In an embodiment as illustrated, rod  65  is attached to tie bar  70  on the longitudinal end of rod  65  distal to gate valve  25 . It is to be understood that rod  65  is shown in  FIG. 1  by dashed lines for illustrated purposes only to show its location as rod  65  is not visible as shown from the side view of  FIG. 1  (i.e., it is disposed within gate housing  30 ). Rod  65  and gate valve  25  are longitudinally moveable through the interior of gate housing  30 . In an embodiment, gate housing  30  is secured to pig receiver unit  10 . Gate housing  30  may be secured to pig receiver unit  10  by any suitable means. Cylinder guide  60  is secured to gate housing  30 . Cylinder guide  60  extends longitudinally upward from gate housing  30 . Pig gate valve assembly  20  also includes tie bar  70  and actuator support  75 . Tie bar  70  and actuator support  75  are disposed on opposing ends of actuators  40 ,  45  from each other. Tie bar  70  has tie bar end  180  and tie bar end  185  on opposing longitudinal ends, and actuator support  75  has support end  190  and support end  195  on opposing longitudinal ends. Tie bar  70  is attached to both actuator  40  and actuator  45 . Actuator  40  includes cylinder rod  220 , and actuator  45  includes cylinder rod  150 . In an embodiment, tie bar end  180  is attached to cylinder rod  220  at cylinder longitudinal end  200 , and tie bar end  185  is attached to cylinder rod  150  at cylinder longitudinal end  205 . In embodiments, tie bar ends  180 ,  185  may be attached to cylinder rods  220 ,  150 , respectively, by any suitable means. Support ends  190 ,  195  may be secured to cylinder longitudinal ends  210 ,  215  by any suitable means. In an embodiment, cylinder longitudinal ends  210 ,  215  are disposed upon support ends  190 ,  195 , with actuator support  75  providing physical support to actuators  40 ,  45 . Tie bar  70  has tie bar opening  225  through which cylinder guide  60  may longitudinally pass therethrough. In an embodiment, actuator support  75  has support opening  230  through which a portion of gate housing  30  is disposed. 
         [0026]    Actuators  40 ,  45  may include any suitable type of actuator for actuating opening and closing of gate valve  25 . In embodiments, actuators  40 ,  45  are actuated by air and/or liquid (e.g., water). In embodiments, actuators  40 ,  45  are actuated by air. Actuators  40 ,  45  may have any suitable configuration for actuation of gate valve  25 . In embodiments as illustrated in  FIG. 1 , actuators  40 ,  45  are cylindrical actuators. Actuators  40 ,  45  may be operated by any suitable means.  FIG. 2  illustrates an embodiment of manual operation of actuators  40 ,  45 . In an embodiment as illustrated, actuation lever  140  is operated between open and closed positions. In embodiments, the open position actuates actuators  40 ,  45 , and the closed position stops their action. The actuating air and/or liquid are supplied from inlet  155  to actuators  40 ,  45  via actuation lines  145 . The return actuating air and/or liquid may be exhausted via outlet  160 . Actuation lever  140  may be disposed at any suitable location on pig receiver  5 . In an embodiment, actuation lever  140  is disposed on a side of pig receiver  5 . Without limitation, embodiments with two actuators  40 ,  45  facilitate prevention of bending of rod  65 . In an embodiment, actuation of actuators  40 ,  45  includes actuation of cylinder rods  150 ,  220  either in an upward or downward direction (i.e., in relation to pig receiver unit  10 ). 
         [0027]    In embodiments, gate valve  25  is moveable between open and closed positions. To move gate valve  25  to an open position from the closed position shown in  FIG. 1 , actuation lever  140  is moved to the open position. The actuating air and/or liquid flows through actuation lines  145  to actuators  40 ,  45  thereby actuating actuators  40 ,  45  to move cylinder rods  150 ,  220  upwards. Upward movement of cylinder rods  150 ,  220  causes upward movement of rod  65  (via tie bar  70 ) and thereby rod  65  pulls gate valve  25  upward. Tie bar  70  moves upward along with cylinder rods  150 ,  220 . The vertical movement of cylinder rods  150 ,  220  is guided by tie bar  70  having cylinder guide  60  pass therethrough. Cylinder guide  60  facilitates tie bar  70  moving in a substantially vertical direction. It is to be understood that cylinder guide  60  and gate housing  30  are not moving. Cylinder rods  150 ,  220  move upward until gate valve  25  is in an open position. To close gate valve  25 , actuation lever  140  is moved to the closed position. Actuators  40 ,  45  then move cylinder rods  150 ,  220  downward with rod  65  pushing gate valve  25  downward into pig receiver unit  10  until gate valve  25  is in a closed position (i.e., substantially no fluid flows around gate valve  25 ). In an embodiment, the open position of gate valve  25  is in a fully open position with gate valve  25  not restricting any fluid flow within pig receiver unit  10 . 
         [0028]    In embodiments as shown in  FIG. 1 , pig receiver  5  also includes supports  15 . Supports  15  may include any size and configuration suitable for supporting the weight of pig receiver unit  10 . Pig receiver  5  is not limited to two supports  15  but in alternative embodiments may include one support  15  or more than two supports  15 . In some embodiments, pig receiver unit  10  includes drain  95 . 
         [0029]    As illustrated in  FIGS. 1 and 2 , an embodiment of operation of pig receiver  5  includes pig receiver  5  attached to a pipeline (not illustrated). A pig (not illustrated) is progressing through the pipeline. At this instance, no pig is disposed within pig receiver  5 . With the pig progressing through the pipeline, gate valve  25  is in the open position, and retrieval door  175  is closed. In some embodiments, pig receiver unit  10  has exhaust valves  100 ,  115 . Exhaust valve  100  is disposed on pig receiver unit  10  between pig gate valve assembly  20  and pipeline contact end  165 . In an embodiment, exhaust valve  100  is located proximate to pig gate valve assembly  20 . Exhaust valve  115  is disposed between pig gate valve assembly  20  and pig retrieval end  170 . In an embodiment, exhaust valve  115  is disposed proximate retrieval door  175 . Exhaust valves  100 ,  115  may be any type of pressure relief valves suitable for exhausting pressure from pig receiver unit  10 . In embodiments, exhausts valves  100 ,  115  are used to regulate and maintain a constant pressure in pig receiver unit  10 . In some embodiments as illustrated, exhaust valves  100 ,  115  have exhaust silencers  105 ,  120 , respectively. In embodiments as illustrated, a pressure gauge  80  measures the pressure of pig receiver unit  10  upstream of pig gate valve assembly  20 . In an embodiment, pressure gauge  80  is disposed proximate exhaust valve  100 . Additionally, in embodiments as illustrated, a pressure gauge  85  measures the pressure of pig receiver unit  10  downstream of pig gate valve assembly  20 . In an embodiment, pressure gauge  85  is disposed proximate exhaust valve  115 . When the pig passes pig gate valve assembly  20 , the pig gate valve assembly  20  is actuated with actuators  40 ,  45  moving cylinder rods  150 ,  220  downward and pushing gate valve  25  into the closed position by cylinder rods  150 ,  220  pushing rod  65  downward. With gate valve  25  in the closed position, additional pigs may run in the pipeline. In embodiments, both exhausts valves  100 ,  115  remain open. In an embodiment, pressure gauge  85  is monitored, and if it shows a desired pressure, then retrieval door  175  is opened, and the pig is removed. In an embodiment as illustrated, exhaust valve  115  has lever  125 . In an embodiment, lever  125  is disposed to provide an end of lever  125  sufficiently in front of retrieval door  175  to prevent opening of retrieval door  175  until the pressure in pig retrieval end  170  is at a desired pressure. When at a desired pressure, lever  125  is actuated (and the blocking end of lever  125  is no longer preventing opening of retrieval door  175 ), and retrieval door  175  is opened with the pig then being removed. With the pig removed, retrieval door  175  is closed, and pig gate valve assembly  20  is actuated to move gate valve  25  up to the open position. The next pig is then run through pig receiver  5 , and the process may continue as desired. 
         [0030]      FIG. 3  illustrates an embodiment of pig receiver  5  having a pressure equalization system  250 . Pressure equalization system  250  has pressure equalization valve  235  and pressure line  240 . Pressure equalization system  250  facilitates adjusting the pressure in pig receiver unit  10  downstream of gate valve  25 . Pressure line  240  is connected to pig receiver unit  10  on each side of gate valve  25  at downstream pressure connection  255  and upstream pressure connection  260 , respectively. As illustrated, downstream pressure connection  255  is connected to pig receiver unit  10  downstream of gate valve  25  at a suitable location between gate valve  25  and retrieval door  175 . In an embodiment, downstream pressure connection  255  is disposed at a suitable location between fastening means  130  and gate valve  25 . Upstream pressure connection  260  is connected to pig receiver unit  10  upstream of gate valve  25  at a suitable location between gate valve  25  and pipeline contact end  165 . In an embodiment, upstream pressure connection  260  is disposed at a suitable location between gate valve  25  and fastening means  130 . Pressure line  240  may be any line suitable for use with a pipeline. Pressure equalization valve  235  controls the pressure flow through pressure line  240 . Pressure equalization valve  235  may be any type of valve suitable for use with a pig receiver. For instance, in an embodiment, pressure equalization valve  235  is a ball valve. Pressure equalization valve  235  may be disposed at any suitable location on pressure line  240 . In an embodiment, pressure equalization valve  235  is disposed about equidistant between downstream pressure connection  255  and upstream pressure connection  260 . In embodiments, pressure equalization valve  235  is disposed proximate to gate valve  25 . In some embodiments as illustrated, downstream pressure connection  255  and/or upstream pressure connection  260  have a muffler  245 . 
         [0031]    As illustrated in  FIG. 3 , an embodiment of operation of pressure equalization system  250  includes closing gate valve  25  or in which gate valve  25  is closed. In such an embodiment, pressure equalization valve  235  is in a closed position. In an embodiment, pressure equalization valve  235  is in a closed position when gate valve  25  is closed. In some embodiments, pressure equalization valve  235  is opened when gate valve  25  is in a closed position or when gate valve  25  is being closed. With gate valve  25  in a closed position and pressure equalization valve  235  open, the pressure downstream of gate valve  25  is adjusted via pressure line  240  by the pressure from upstream of gate valve  25 . In an embodiment, the pressure downstream is adjusted to be about equal with the pressure upstream. In some embodiments, the pressure upstream and downstream of gate valve  25  is about equalized via pressure line  240 . 
         [0032]    It is to be understood that pig gate valve assembly  20  is not limited to two actuators (actuators  40 ,  45 ). In alternative embodiments (not illustrated), pig gate valve assembly  20  has one actuator. In other alternative embodiments (not illustrated), pig gate valve assembly  20  has more than two actuators. 
         [0033]    It is to be further understood that tie bar  70  and cylinder guide  60  facilitate cylinder rods  150 ,  220  to move substantially parallel in relation to each other. 
         [0034]    In some embodiments as shown in  FIG. 4 , upstream pressure connection  260  has pressure gauge  265  and/or downstream pressure connection  255  has pressure gauge  270 . 
         [0035]      FIG. 4  illustrates an embodiment of pig receiver  5  in which pig receiver  5  has a contaminant removal system that includes manifould  290 .  FIG. 5  shows an embodiment of manifould  290 .  FIG. 7  shows a side view of pig receiver  5  with manifould  290 , and  FIG. 8  shows a side perspective view of pig receiver  5  with fluid lines  315 .  FIG. 9  shows a side view of a bottom side portion of pig receiver  5  with the contaminant removal system. Manifould  290  has an interior through which fluid flows. In an embodiment as shown, manifould  290  has fluid feed port  300  by which fluid is fed to manifould  290 . Fluid feed port  300  is shown disposed about near the bottom of manifould  290 , but in alternative embodiments (not illustrated) fluid feed port  300  may be disposed at any other suitable location on manifould  290 . The fluid is fed to manifould  290  and flows therethrough, exiting manifould  290  through a fluid outlet port  295 . Manifould  290  may have any desirable number of fluid outlet ports  295 . In embodiments, each fluid line  315  is attached to a fluid outlet port  295 . In an embodiment, the contaminant removal system includes fluid piping  400 . Fluid piping  400  is connected to manifould  290  and gate housing  30 . In some embodiments as shown, each fluid outlet port  295  has an open/close valve  330 , which opens and closes the applicable fluid outlet port  295  to the fluid. In some embodiments as shown in  FIG. 4 , contaminant removal system includes lubricator  305 . Lubricator  305  provides lubrication that may be carried with the fluid (i.e., air) to gate valve  25 . In an embodiment, lubricator  305  is disposed on fluid piping  400 . In embodiments, fluid flows through fluid piping  400  from manifould  290 . Lubricator  305  adds the lubrication to the fluid, which is then carried by the fluid with the lubrication through fluid piping  400  to gate housing  30 . The fluid with lubrication contacts the surfaces in pig gate valve assembly  20  to lubricate such surfaces. Any lubrication may be used that is suitable for lubricating machinery, metal parts, and the like. 
         [0036]    The fluid may be any fluid suitable for removing contaminants from pig receiver  5 . Without limitation, contaminants include solids, obstructions, viscous material, tar-like material, and the like. In embodiments, the fluid is air, gas, water, solvent, or any combinations thereof In an embodiment, the fluid is air. The solvent may be any solvent suitable for removing contaminants such as viscous material and/or tar-like matter. Without limitation, examples of suitable solvents include ethanol, hydrogen peroxide, or any combinations thereof. 
         [0037]    As shown in  FIG. 4 , the fluid exits manifould  290  and is fed to a desired portion of pig receiver  5 , via fluid line  315  and/or fluid piping  400 . Fluid line  315  may be any line suitable for allowing the fluid to flow therethrough. In an embodiment, fluid line  315  comprises rubber. Fluid piping  400  may be any piping suitable for allowing the fluid to flow therethrough, such as, without limitation, metal piping. 
         [0038]    In an embodiment as shown in  FIG. 4 , fluid from manifould  290  is fed through fluid line  315  to the bottom portion of gate housing  30  at gate sealing area  370 . Gate sealing area  370  is the area in which gate valve  25  is sealed against the interior of pig receiver unit  10 . The fluid is fed to the bottom portion of gate housing  30  at gate housing port  350 . In some embodiments, an open/close valve  330  is disposed at gate housing port  350 . Open/close valve  330  is in the open position to allow the fluid into gate housing  30 . The fluid flows through gate sealing area  370  to remove contaminants. In an embodiment, the fluid is fed to gate housing  30  with two fluid lines  315 . In an embodiment, the two fluid lines  315  are on opposing sides of gate housing  30  from each other. In alternative embodiments (not illustrated), more than two fluid lines  315  provide fluid to gate housing  30 . 
         [0039]      FIGS. 4 and 7  show an embodiment of the contaminant removal system in which gate housing  30  has bonnet bleed valve  320 . In embodiments, bonnet bleed valve  320  is attached to gate housing  30  at bonnet bleed port  340 . Bonnet bleed valve  320  is any valve suitable for relieving pressure on gate housing  30 . Bonnet bleed valve  320  relieves pressure in gate housing  30 . In embodiments, bonnet bleed valve  320  relieves pressure in gate housing  30  to facilitate opening of gate valve  25 . 
         [0040]    In other embodiments as shown in  FIGS. 4 and 7 , an embodiment of contaminant removal system includes gate housing  30  having bonnet pressure gauge  325 . Bonnet pressure gauge  325  may be any gauge suitable for measuring pressure in gate housing  30 . In embodiments, bonnet pressure gauge  325  measures pressure in gate housing  30 . In some embodiments, bonnet pressure gauge  325  measures pressure in gate housing  30  when gate valve  25  is operating. In an embodiment, bonnet bleed gauge  325  is attached to gate housing  30  at bonnet bleed port  340 . 
         [0041]    In embodiments as shown in  FIGS. 4, 7, 8, and 9 , contaminant removal system also includes pig receiver  5  having bottom valve  285 . In an embodiment, bottom valve  285  is disposed below pig receiver unit  10 . In embodiments as shown, bottom valve  285  is disposed on support  15 . Bottom valve  285  is attached to the bottom of pig receiver unit  10 . In embodiments, bottom valve  285  is attached to the bottom of a slot (not illustrated) in which gate valve  25  seats. As shown, fluid with contaminants from gate sealing area  370  also flow and remove contaminants from gate valve  25  (i.e., the bottom of gate valve  25 ) as the fluid flows through gate valve  25 . The fluid with contaminants exits gate valve  25  through bottom valve  285 . The fluid with contaminants may be removed from bottom valve  285 . In such embodiments, the fluid with contaminants may be directed from bottom valve  285  to a retrieval device (not illustrated) such as a container or line. In an embodiment, a fluid line  315  may provide fluid to bottom valve  285  to provide further force to the contaminants and facilitate their removal to the retrieval device. 
         [0042]    In embodiments as shown in  FIGS. 4, 6, 7, 8, and 9 , the contaminant removal system also includes pig receiver  5  having sump  275 .  FIG. 6  shows a top cross sectional view of sump  275  and pig receiver unit  10 . Sump  275  is disposed at a bottom portion of pig receiver unit  10 . Sump  275  may be disposed at any suitable longitudinal location of pig receiver unit  10 . In embodiments as shown, sump  275  is disposed between gate valve  25  and upstream pressure connection  260 . Embodiments of sump  275  have sump valve  280  and sump outlet  345 . In an embodiment as shown in  FIG. 6 , sump  275  has a plurality of sump bars  335 . In an embodiment as shown, sump bars  335  extend laterally across sump  275  and in a direction about parallel to the direction in pig receiver unit  10  at which a pig travels. In some embodiments, sump bars  335  extend in a direction about perpendicular to a side of sump  275 . It is to be understood that sump  275  is not limited to sump bars  335  extending in such a direction, but in alternative embodiments (not illustrated) sump bars  335  may extend in other suitable directions. Between each sump bar  335  is a sump gap  355 , which is the open area between each sump bar  335 . Without limitation, sump gap  355  has a sufficient width to allow contaminants to fall from pig receiving unit  10  through sump bars  335  to bottom portion  360  of sump  275  but does not have a width that substantially interferes with the velocity at which the pig travels in pig receiving unit  10 . In an embodiment, fluid (i.e., air) from manifould  290  flows through a fluid line  315  to sump  275 . The fluid flows longitudinally through sump  275  to remove contaminants disposed in bottom portion  360 . For instance, contaminants passing through pig receiver unit  10  pass between sump bars  335  and through sump gaps  355  to bottom portion  360 . The fluid with contaminants exits sump  275  through sump outlet  345 . Sump valve  280  may be regulated to open and close sump outlet  345 . In some embodiments, a container (not illustrated) may be attached to sump outlet  345  to collect contaminants. Without limitation, the air supply in pig receiver  5  that propels the pig and the fluid (i.e., air) both remove contaminants. For instance, the air that propels the pig may force the contaminants into bottom portion  360 . 
         [0043]    Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations may be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
A pig receiver and method to retrieve pigs in pipeline pigging operations. In one embodiment, a pig receiver includes a pressure equalization system including a gate valve, wherein a first side of the gate valve is coupled to a downstream pressure connection, and wherein a second side of the gate valve is coupled to an upstream pressure connection. The pressure equalization system also includes a pressure equalization valve disposed between the downstream pressure connection and the upstream pressure connection. The pressure equalization system also includes a pig receiver unit, wherein a first side of the pig receiver unit is coupled to the downstream pressure connection downstream of the gate valve, and wherein a second side of the pig receiver unit is coupled to the upstream pressure connection upstream of the gate valve.