Abstract:
A continuous flow slurry cleaning method, apparatus and system including a filter portion and a mud re-circulation manifold for receiving partially filtered slurry, containing the slurry and mixing the slurry with liquid ready for use and thereby enabling a continuous, re-circulating flow through the filter portion. The continuous flow slurry cleaning apparatus and system further include a tank for storing and delivering liquid ready to be used by a drilling machine. The continuous flow slurry cleaning method, apparatus and system further includes a mud circulation/agitation system for keeping solids in suspension and for mixing additives along with the liquid ready for use and thereby modifying the makeup of the liquid ready for use.

Description:
TECHNICAL FIELD 
     A continuous flow liquids/solids slurry cleaning, recycling and mixing method, apparatus and system used with drilling apparatus in drilling operations for cleaning slurries so that solids and liquids are separated from each other in a continuous process. 
     BACKGROUND 
     Conventional liquids/solids (slurry hereinafter), recycling and mixing systems generally include several components such as a pit pump, a shaker screen, a primary tank, one or more secondary tanks, reservoir tanks and mixing systems. The pit pump is generally provided for delivering a slurry from a drilling rig to the slurry cleaning, recycling and mixing system. The shaker screen is generally provided for performing an initial removal and separation of solid constituents of the slurry. The tank, generally known as the sand trap, is provided for containing the liquid constituent of the slurry after it has passed over the shaker screen. 
     The tank allows additional solids to settle out of the slurry before passing over a top weir and to additional secondary tanks. The secondary tanks ranging from a single tank for holding partially cleaned mud to multiple tanks serving as reservoirs can also be provided. The secondary tanks are generally used as reservoirs for desander/desilter systems. The multiple tanks generally serve as reservoirs for a variety of other systems used in drilling operations including degassers, desanders, desilters and centrifuges. 
     Additional tanks can also generally be provided for holding a reservoir of completely cleaned mud slurry that is ready to be reused by a drilling rig and mixed with other materials that are useful in drilling operations. For example, mud slurries used for drilling are generally mixed prior to reuse by adding polymers or Bentonite as may be required by a given drilling operation. Accordingly, the mixing systems are generally provided for initial mixing of the Bentonite and/or the polymers. 
     However, the related art systems described above have several disadvantages. First, the tanks are typically square and thus as slurries flow through them, there is a wide variation in the flow velocity of the slurry within the tanks. For example, in some areas, the flow velocity of the slurry approaches zero and allows the solids to settle out of suspension in a process known as sedimentation. As sedimentation occurs, the tanks eventually fill with the sedimentary solids and require periodic cleaning. Having to conduct periodic cleaning is disadvantageous because it requires additional labor for cleaning the tanks. Moreover, opening the tanks creates a potential for environmental contamination by the inevitable spilling of the tank&#39;s contents in the local environment. Furthermore, the periodic cleaning operation results in additional cost in making the tanks accessible for cleaning. In order to reduce the sedimentation, several conventional systems have added a mechanical agitator to each tank in an effort to keep the solids in suspension. 
     Other disadvantages of conventional systems include having a significant volume of slurry in process and thereby rendering a portion of that slurry unavailable as cleaned slurry ready for use in the end operation, e.g., drilling. Moreover, in conventional systems the slurry passes through each various filtering component one at a time. 
     SUMMARY 
     The present invention is generally directed to a continuous flow slurry cleaning, recycling and mixing system and method used with a drilling apparatus in drilling operations. The invention provides a method, apparatus and system for cleaning slurry so that the solid and liquid constituents of the slurry can be separated in a continuous process. The invention also provides continuous circulation of slurry which keeps solids in suspension and maintains an adequate slurry fluid velocity. 
     One aspect of the invention provides a method of cleaning liquid/solids slurry having first and second filter stages. The method includes filtering the liquid/solids slurry at the first filter stage; mixing the filtered slurry with liquid ready for use; and re-circulating the mixed liquid through the second filter stage. 
     An alternative aspect of the invention provides an apparatus for cleaning liquid/solids slurry. The apparatus includes a tank; first and second filter stages, each filter stage having an input portion and output portion, the input portion of the first filter stage being adapted to receive liquid/solids slurry to be cleaned, the first and second filter stages being adapted to filter the liquid/solids slurry; and a manifold in fluid communication with the output portion of the first filter stage and the tank, the manifold being arranged to receive and mix the filtered liquid with liquid ready for use; wherein, the mixed liquid is transferred from the manifold to the second filter stage. 
     Yet another alternative aspect of the invention provides a system for cleaning liquid/solids slurry. The system includes a drilling apparatus; and an apparatus for cleaning liquid/solids slurry. The apparatus includes a tank; first and second filter stages, each filter stage having an input portion and output portion, the input portion of the first filter stage being adapted to receive liquid/solids slurry to be cleaned, the first and second filter stages being adapted to filter the liquid/solids slurry; and a manifold in fluid communication with the output portion of the first filter stage and the tank, the manifold being arranged to receive and mix the filtered liquid with liquid ready for use; wherein, the mixed liquid is transferred from the manifold to the second filter stage. 
     Still another alternative aspect of the invention provides a method of cleaning liquid/solids slurry. The method includes transferring the liquid/solids slurry to a first filter stage; separating solids from the slurry and discharging a first filter stage underflow liquid from the first filter stage; routing the first filter stage underflow liquid to a continuous suction manifold assembly; mixing the first filter stage underflow liquid with a second filter stage underflow liquid discharged from the second filter stage and liquid ready for use, resulting in a combined liquid mixture; transferring the combined liquid mixture to the second filter stage; routing the second filter stage underflow liquid from the second filter stage to the continuous suction manifold assembly; and discharging liquid ready for use from the second filter stage into a tank. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the drawings in which like reference numbers represent corresponding parts throughout the several views, where: 
     FIGS. 1-1C illustrate flow diagrams of several embodiments of a system of a slurry cleaning, mixing and recycling system in accordance with the present invention; 
     FIG. 2 illustrates a flow diagram of one embodiment of a slurry cleaning, mixing and recycling system including a manifold assembly in accordance with the present invention; 
     FIG. 3 is an isometric view of one embodiment of an enclosure of a slurry cleaning, mixing and recycling system in accordance with the present invention; 
     FIG. 4 is a side view of one embodiment of a slurry mixing and recycling system in accordance with the present invention with the near side tank wall removed; 
     FIG. 5 is an end view of one embodiment of a slurry cleaning, mixing and recycling system in accordance with the near side tank wall removed; 
     FIG. 6 is an isometric view of one embodiment of a manifold assembly with primary and secondary filters removed; 
     FIGS. 7A-7D are flow diagrams of alternative embodiments of manifold assembly arrangements; and 
     FIG. 8 is a flow diagram of one embodiment of a slurry cleaning, mixing and recycling system using two manifold assemblies. 
    
    
     DESCRIPTION 
     In the following description of specific embodiments, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be made and used without departing from the scope of the invention, which is defined by the claims attached hereto. 
     FIG. 1 illustrates a system  3  comprising a drilling apparatus  5  and a slurry cleaning, mixing and recycling system  8  for cleaning slurry laden with solids and other impurities that is pumped from the drilling apparatus  3 . The slurry to be cleaned is continuously drawn from a slurry reservoir  9  by a pit pump  14  via a pit pump suction line  11  and is then routed to a first filter  17  (shaker hereinafter) via a slurry line  15 . The shaker  17  outputs partially cleaned slurry comprising predominantly the liquid portion of the slurry (filtered slurry hereinafter) which then enters a Continuous Suction Multi-Mud Manifold Assembly  98  (manifold assembly hereinafter) through a combined underflow line  90 . The filtered slurry from a second filter  30  (cleaner hereinafter) follows an underflow path  44  and is then combined with filtered slurry from the shaker  17 . The combined filtered slurries enter the combined underflow line  90  and then enter the manifold assembly  98 . 
     Upon entering the combined underflow line  90 , a pump  32  draws the combined filtered slurries from the combined underflow line  90  into a multi-input suction line  92 . Simultaneously, the pump  32  draws liquid ready for use  81  which is contained in a reservoir tank  82 . The pump  32  draws the combined filtered slurries and liquid ready for use through an inlet orifice  86  into the multi-input suction line  92 . The filtered slurries from the combined underflow line  90  and liquid ready for use  81  contained in the reservoir tank  82  merge in the multi-input suction line  92 . The combined filtered slurries and liquid ready for use  81  leave the manifold assembly  98  and are pumped through a feed line  33  to the cleaner  30 . The cleaner  30  is a combination filtration unit comprised of hydrocyclones and a shaker. The hydrocyclones separate the liquid constituent from the combined filtered slurries and liquid ready for use  81  that enter the second filter via the feed line  33  by way of pump  32 . The second filter  30  outputs the underflow liquid into the reservoir tank  82  where it is combined with the liquid ready for use  81 . 
     The liquid ready for use  81  stored in the reservoir tank  82  is drawn into a pump  109 , in this case a rig charge pump, via a rig charge pump suction line  111 . The pump  109  discharges liquid ready for use  81  from the tank  82  through discharge line  113 . The liquid ready for use  81  is thus recycled to the drilling apparatus  5  for continued drilling. 
     FIG. 1A illustrates a system  3 A comprising a slurry cleaning, mixing and recycling system  3 A for cleaning slurry that is pumped from a drilling apparatus  3 A. The slurry cleaning, mixing and recycling system  3 A is in fluid communication with a mixing system  83 . The mixing system  83  is comprised of a reservoir tank  82  and a pump  109 . Liquid ready for use  81  is drawn from the reservoir tank  82  through line  39  and subsequently flows into the manifold assembly  98 . 
     FIG. 1B illustrates a system  3 B comprising a slurry cleaning, mixing and recycling system  8 B for cleaning slurry that is pumped from a drilling apparatus  3 B. The slurry cleaning, mixing and recycling system  8 B is in fluid communication with a mixing system  83 . Liquid ready for use  81  is drawn from line  39  and flows into the manifold assembly  98 . The drilling system  3 B further includes a vacuum inducing nozzle  35  which is coupled to the output of the pump  32  and to the slurry line  15 . The vacuum inducing nozzle  35  transfers the slurry to be cleaned to the shaker  17  via the slurry line  15 . Furthermore, the system  3 B transfers 75% of the liquid ready for use  81  from the mixing system  83  to the cleaner  30  via the feed line  33 . Accordingly, 25% of the liquid ready for use  81  is transferred to the vacuum inducing nozzle  35  via flow line  37 . 
     FIG. 1C illustrates a system  3 C comprising a slurry cleaning, mixing and recycling system  3 C for cleaning slurry that is pumped from a drilling apparatus  3 C. The slurry is transferred by vacuum system  43  through flow line  41  and is then transferred to the shaker  17  through flow line  45 . 
     Those skilled in the art will appreciate that a variety of filters such as shaker separators and hydrocyclones may be used in various series or parallel combinations to provide the necessary filtration function without departing from the scope of the claimed invention. Also, it will be appreciated that the outputs of the various filters may be brought together in various ways in order to combine the filtered slurry and mix it with the liquid ready for use  81  contained in the reservoir tank  82 . 
     FIG. 2 illustrates a flow diagram of one embodiment of a closed loop slurry cleaning, mixing and recycling system  8 . The system  8  can be used, for example, in the horizontal directional drilling industry. The slurry (e.g., drilling fluid, or mud) to be cleaned is pumped from the slurry reservoir  9 . The cleaned slurry, liquid ready for use, is returned through the rig discharge line  113  to the drilling apparatus. One sequence for processing the slurry to be cleaned begins by pulling the slurry, a mixture of treated fluid and drilling solids, from the slurry reservoir  9  by the pit pump  14  via the pit pump suction line  11  and routing the slurry to the shaker  17  via the slurry line  15 . 
     The slurry reservoir  9  includes liquid having a high percentages of drilling solids, e.g., entrained solids, silts and other impurities that normally accrue in the drilling fluid during subterranean boring. The pit pump  14  may be turned “ON” or “OFF” by an operator as needed, in order to regulate the level of slurry in the slurry reservoir  9 . The shaker  17  separates the slurry into spoils comprising coarse drilling solids and partially cleaned liquid referred to herein as filtered slurry. The spoils follow a discharge path  19  and fall into a spoils discharge tank  22 . The filtered slurry emanating from below the shaker  17  follows a shaker flow path  24  into the manifold assembly  98 . 
     The manifold assembly  98  is a device that combines the processed drilling liquids at various stages of processing and controls their flow path. In one embodiment, the manifold assembly  98  includes underflow troughs  46  and  26 , a combined underflow line  90 , a combined underflow liquid merging fin  88 , an inlet orifice  86 , a multi-input suction line  92  and a cleaner pump  32 . 
     Filtered slurry flowing from the shaker  17  via underflow path  24  enters the manifold assembly  98  from the shaker underflow trough  26 . The combined filtered slurry and liquid ready for use from the cleaner flow via the underflow path  44  to the manifold assembly  98  from the cleaner underflow trough  46 . Under the force of gravity, the shaker underflow fluid (e.g., the filtered slurry) and the cleaner underflow fluid (e.g., the filtered combined filtered slurry and liquid ready for use) merge into the combined underflow line  90 . The combined underflow line  90  is sufficiently large to allow entrained air within the liquid from the cleaner underflow trough  46  and liquid from the shaker underflow trough  26  to escape before entering the combined underflow liquid merging fin  88 . 
     The liquids from the shaker and cleaner underflow troughs  26 ,  46  merge into a combined liquid in the combined underflow line  90 . The cleaner pump  32  then draws the combined liquid from the combined underflow line  90  into the multi-input suction line  92 . Simultaneously, the cleaner pump  32  draws liquid ready for use  81  from the tank  82  through the orifice  86  into the multi-input suction line  92 . The combined liquid from the combined underflow line  90  and liquid ready for use  81  subsequently merge in the multi-input suction line  92 . 
     The amount of liquid ready for use  81  that is drawn into the multi-input suction line  92  depends upon the amount of combined liquid present in the combined underflow line  90  and the pre-set pumping rate of the cleaner pump  32 . Under normal operating conditions, the cleaner pump  32  has a pumping rate that is greater than the pit pump  14 . The amount of liquid ready for use  81  drawn into the multi-input suction line  92  is equal to the difference in output between the pit pump  14  and the cleaner pump  32 . Regardless of the pumps&#39;  14 ,  32  transfer rates, the multi-input suction line  92  will always contain some percentage of liquid ready for use  81 . 
     In one embodiment, the manifold assembly  98  allows the liquid ready for use  81  to be mixed with the combined liquid from the combined underflow line  90  in such a manner that a wide variety of flow rates can exist without starving the cleaner pump  32 . For example, if there is no flow from either shaker  17 ,  42 , the cleaner pump  32  will draw 100% of the liquid ready for use  81  from within the tank  82 . 
     When the pit pump  14  is turned off, the combined liquid within the multi-input suction line  92  includes a lower percentage of underflow fluid from the cleaner  30  and a higher percentage of liquid ready for use  81 . When the pit pump  14  is turned “ON,” the combined liquid within the multi-input suction line  92  includes a higher percentage of combined liquid from the combined underflow line  90  and a lower percentage of liquid ready for use  81 . 
     Generally, the density of the liquid in the combined underflow liquid line  90  is higher than the density of the liquid ready for use  81  which is contained within the drilling mixing tank  82 . Therefore, under the influence of gravity, the liquid within the combined underflow liquid line  90  will be drawn into the multi-input suction line  92  before the drilling liquid ready for use  81 . However, if the density of the liquid in the combined underflow liquid line  90  is close to the density of the liquid ready for use  81 , then a means to ensure that the liquid within the combined underflow liquid line  90  enters the multi-input line suction line  92  is required. This is accomplished by creating a low pressure area in the discharge area of the combined underflow liquid merging fin  88 . From elementary fluid dynamics, if the velocity of a fluid passing through a given cross section is increased, then a low pressure condition will result. 
     The combined underflow liquid merging fin  88  provides a means for increasing the velocity of the liquid ready for use  81  as it moves through the manifold assembly  9 . In one embodiment, the combined underflow liquid merging fin  88  has a small cross sectional area relative to the cross sectional area of the multi-input suction line  92 . Through testing, it has been determined that the average velocity of the liquid ready for use  81  passing along the combined underflow liquid merging fin  88  is approximately 1.4 feet per second (fps), while the average velocity preceding the combined underflow liquid merging fin  88  is approximately 1.3 fps. 
     This slight increase in the average velocity of liquid ready for use  81  creates a slight pressure drop at the discharge side of the combined underflow liquid merging fin  88 . This slight difference in pressure creates a slight vacuum acting on the liquid within the combined underflow liquid line  90 , which may help to draw fluid through the combined underflow liquid merging fin  88 . Additionally, the volume of liquid ready for use that is drawn through the inlet orifice  86  varies in response to changes in the volume of fluid being drawn through the combined underflow liquid merging fin  88  varies so that the volume of fluid that is drawn by the cleaner pump  32  is substantially consistent. 
     Accordingly, when the flow rate of fluid through the underflow liquid merging fin  88  is zero, there is minimal, if any, air that is drawn through the underflow liquid merging fin  88 . Minimizing the amount of air that is drawn through the underflow liquid merging fin  88  prevents air pockets from reaching the cleaner pump  32  and thus minimized the chance that the cleaner pump  32  will lose its prime. 
     In contrast, if the design is such that the cross sectional area of the combined underflow liquid merging fin  88  is large relative to the cross sectional area of the multi-input suction line  92 , then excessive vacuum is induced on the liquid within the combined underflow liquid line  90 . In those cases when little or no liquid enters into the combined underflow liquid line  90 , air will be sucked in the multi-input suction line  92 , thereby resulting in loss of prime in the cleaner pump  32 . 
     While the underflow liquid merging fin  88  is narrow in cross section, it has a long overall length. The length is dictated by the volumetric flow rate of the liquid with in the combined underflow liquid line  90  and the width of the combined underflow liquid merging fin  88 . 
     In one embodiment, the design of the combined underflow liquid merging fin  88  has an aerodynamic profile having tapered leading and trailing edges. This aerodynamic profile will reduce unwanted disturbances in the liquid ready for use  81  as it flows past the liquid merging fin  88 . 
     The combined fluid within the manifold assembly  98  is pumped through the cleaner feed line  33  to the cleaner  30  (the secondary cleaning system). The cleaner  30  is a combination filtration unit comprised of one or more hydrocyclones  36  and a secondary shaker  42 . The hydrocyclones  36  separate the combined fluid from the cleaner feed line  33  into underflow liquid and liquid ready for use  81 . The underflow fluid follows the hydrocyclones underflow path  40  and flows into the secondary shaker  42 . 
     The secondary shaker  42  separates the liquid emerging from the hydrocyclone underflow path  40  into spoils and underflow liquid. The spoils follow the cleaner spoils discharge path  47  into the spoils discharge tank  22 , while the secondary shaker underflow liquid follows the cleaner underflow path  44  to the cleaner underflow trough  46 . As discussed above, the liquid flowing from the cleaner underflow trough  46  merges with the liquid from the primary shaker trough  26  and makes up the combined liquid which then flows into the manifold assembly  98 . 
     The liquid discharged from the hydrocyclones  36  overflow, classified as the cleanest filtered liquid within the system  8 , flows to the tank  82  via the cleaner overflow line  38 . The tank  82  is designed with a flat bottomed semi-circular shape in order to reduce the number of “dead areas” where sedimentation may occur. The tank  82  includes an active flow system for keeping all of the liquid contained in the tank  82  in constant agitation. The active flow system comprises a mixing system  51  and a roll gun system  63 . 
     The mixing system  51  is used to mix additives, such as Bentonite and polymers, with the liquid ready for use  81 . In one embodiment, the mixing pump  50  draws liquid ready for use  81  from within the tank  82  via the mixing suction line  52 . The liquid ready for use  81  is then pumped through the mixing/roll gun line  54  and the hopper fluid inlet valve  56 . Additives may be mixed with the liquid ready for use  81  in the mixing hopper  58 . The additives are mixed as they pass through the mixing discharge line  62 . In one embodiment, a roll gun system  63  is used to thoroughly mix the additives combined with the newly treated liquid from the mixing discharge line  62  and the liquid ready for use  81  from within the tank  82 . 
     The roll gun system  63  is to used to evenly mix the liquid from the cleaner overflow line  38 , mixing discharge line  62  and the liquid ready for use  81 , all within the tank  82 . The roll gun system  63  is also used for keeping the additives and any other micro-solids  108  in suspension within the liquid ready for use  81 . In one embodiment, the roll gun system  63  includes a mixing/roll gun line  54 , a roll gun valve  66 , a roll gun line manifold  64  and a plurality of roll gun jets  68 . 
     In one embodiment, the liquid ready for use  81  is drawn from the tank  82  via the mixing suction line  52  by the mixing pump  50  and is delivered under pressure to the mixing/roll gun line  54 . The liquid ready for use  81  passes through the roll gun valve  66 , into the roll gun line manifold  64  and is discharged at a high velocity through the roll gun jets  68 . The roll gun jets  68  are positioned to direct the, liquid flow towards the bottom of the tank  82 , thus providing a rolling effect to the liquid flow. The velocity at which the liquid ready for use  81  passes through the roll gun jets  68  agitates the liquid ready for use within the tank  82 , which keeps all of the unmixed additives and newly treated liquid from the mixing discharge line  62 , micro-solids  108  and liquid ready for use  81 , in suspension within the tank  82 . 
     The micro-solids  108  remain suspended in the liquid ready for use  81  until they are either discharged from the tank  82  through the rig charge pump  109  or drawn into the manifold assembly  98 . The liquid ready for use  81  is drawn into the rig charge pump  109  via the rig charge pump suction line  111  and discharged from the slurry cleaning, mixing and recycling system  8  through the rig charge pump discharge line  113 . 
     The actual construction of one embodiment of a slurry, cleaning, mixing and recycling system  8  is shown in FIGS. 3 through 5. FIG. 3 is one view of a slurry cleaning, mixing and recycling system  8  for processing slurry used in the horizontal directional drilling industry comprising the manifold assembly  98  in accordance with the claimed invention. 
     FIG. 4 is a side view of one embodiment of a slurry cleaning, mixing and recycling tank system  8  with the near side tank wall removed in order to show the placement of the shaker  17 , the cleaner  30  and the components comprising the manifold assembly  98 . FIG. 4 also shows the shaker underflow path  24 , the cleaner underflow path  44  into the combined underflow line  90  and the liquid flow path  84  into the multi-input suction line  92 . 
     FIG. 5 is an end view of one embodiment of a slurry, cleaning, mixing and recycling tank system  8 , as viewed from the cleaner  30  end of the tank  82 , with the near side tank wall removed. This view shows the flat bottomed semi-circular shape of the tank  82 . FIG. 5 also shows the angular position of the roll gun jets  68  relative to the bottom of the tank  82 . The liquid within the roll gun line manifold  64  exits the roll gun jets  68  at a high velocity and is resisted by the liquid ready for use  81  within the tank  82 . Therefore, the liquid within the tank  82  follows a circular/rolling liquid flow path  69 . Accordingly, any micro-solids  108  and un-mixed additives are kept in suspension. Moreover, FIG. 5 shows one embodiment of the manifold assembly combined underflow liquid merging fin  88 . 
     FIG. 6 is an isometric view of one embodiment of the manifold assembly  98 . As shown in FIG. 4, the manifold assembly  98  is an internal component of the slurry, cleaning, mixing and recycling tank system  8 . It may also be placed externally or located as a separate independent element between multiple tanks. 
     In more detail, the manifold assembly  98  includes the multi input suction line  92 , which forms a horizontal fluid line. The horizontal fluid line has a wall  85  that defines a lumen  87  through which a stream of fluid can flow. The inlet orifice  86 , which has an elbow configuration in one possible embodiment, is connected to one end of the multi input suction line  92 . The opposite end of the multi-input suction line is tapered  89  to reduce the diameter of the lumen  87  as it feeds into the cleaner pump  32 . This taper  89  reduces the risk of inducing turbulence in a fluid stream as it flows from the multi input suction line  92 , through a reduced diameter of the lumen  87 , and into the cleaner pump  32 . 
     The underflow line  90  forms a vertical fluid line that has an input portion and an output portion. The input portion has two inputs. The first input is formed by the underflow trough  26  and is in fluid communication with the first filter  17 . The second input is formed by the underflow trough  46  and is in fluid communication with the second filter  30 . 
     The output portion forms the underflow liquid merging fin  88 , which passes through the wall  85  of the multi input suction line  92 . In this configuration, the underflow liquid merging fin  88  is positioned within the lumen  87 . As described above, the underflow liquid merging fin  88  is elongated and is substantially parallel to the lumen  87 . The end portions  91  and  93  of the underflow liquid merging fins  88  are tapered to reduce the coefficient of drag and minimize the turbulence caused by fluid flowing through the lumen  87  of the multi input suction line  92 . Given this configuration, there is a reduced pressure in the stream of liquid as it passes by the underflow liquid merging fin  88 . 
     Furthermore, the underflow liquid merging fin  88  has a bottom edge  95  that is positioned proximal to the wall  85  of the multi input suction line  92 . In this configuration, the underflow liquid fluid line  90  is in fluid communication with the lumen  87 . In one possible embodiment, the bottom edge  95  of the fluid line does not touch the wall  85  of the multi input suction line  92 . In other possible configurations, the bottom edge  95  of the underflow liquid merging fin  88  is in contact with or anchored to the wall  85 , but there are still orifices or fluid passages providing fluid communication between the underflow line  90  and the lumen  87 . FIGS. 7A-7D illustrate four alternative embodiments for combining multiple fluid flows into the multi-input suction line  92 . FIG. 7A shows a primary flow  150  and a secondary flow  152  simultaneously combining with the multi-input suction line  92  via the combined underflow liquid merging fin  88 . FIG. 7B shows a secondary flow  152  combining with a primary flow  150  then into the multi-input suction line  92  via the combined underflow liquid merging fin  88 . FIG. 7C shows the primary flow  150  and secondary flow  152  individually entering into the multi-input suction line  92  via the combined underflow liquid merging fin  88 . FIG. 7D, shows a primary flow  150 , a secondary flow  152  and a tertiary flow  154  individually entering into the multi-input suction line  92  via the combined underflow liquid merging fin  88 . The manifold design allows a variety of suction entries into the manifold assembly  98 . 
     It can be appreciated that additional slurry, cleaning, mixing and recycling processes can be added without departing from the scope of the claimed invention. One embodiment of a cleaning, mixing and recycling system  8  is shown in FIG.  8 . (Note that reference numbering shown in FIG. 8 for components previously described are the same and the additional components have been referenced by the same numbers increased by the value of 800.) 
     FIG. 8 illustrates a flow diagram of one embodiment of a slurry cleaning, mixing and recycling system using two manifold assemblies  98 ,  898 . The dual manifold assembly slurry cleaning, mixing and recycling system  808  can be used, for example, in the horizontal directional drilling industry. 
     The flow diagram in FIG. 8 illustrates one embodiment of a closed loop system. As discussed above, the drilling slurry to be cleaned is pumped from the slurry reservoir  9  and the cleaned liquid is returned through the rig charge pump discharge line  113 . One sequence for processing the slurry begins by pulling the slurry to be cleaned, a mixture of treated drilling liquid and drilling solids, from the slurry reservoir  9  by the pit pump  14  via the pit pump suction line  11  and routing the slurry to the shaker  17  via the slurry line  15 . The shaker  17  separates the slurry into spoils, coarse drilling solids and a partially cleaned liquid referred to as filtered slurry. The spoils from the shaker  17  follow the spoils discharge path  19  and fall into the spoils discharge tank  22 . The filtered slurry follows the shaker flow path  24  into the first manifold assembly  98 . 
     The first manifold assembly  98  is used for combining the various processed drilling liquids and controls their flow path. In one embodiment, the first manifold assembly  98  includes an underflow trough  26 , an underflow line  90 , a combined underflow liquid merging fin  88 , an inlet orifice  86 , a multi-input suction line  92  and a cleaner pump  32 . 
     Filtered slurry follows the shaker underflow path  24  to the shaker underflow trough  26  and is received by the first manifold assembly  98 . Liquid flowing from the shaker  42  follows the underflow path  844  to underflow trough  846  and is eventually received at the second manifold assembly  898 . The spoils from shaker  42  follow the spoils discharge path  47  and fall into the spoils discharge tank  22 . Under the influence of gravity, underflow liquid from the shaker  17  falls into the underflow line  90 . The underflow line  90  is sufficiently large to allow entrained air within the liquid flowing from the underflow trough  26  to escape before entering the combined underflow liquid merging fin  88 . 
     Upon entering the underflow line  90 , the cleaner pump  32  draws the liquid from the combined underflow line  90  into the multi-input suction line  92  via the combined underflow liquid merging fin  88 . Simultaneously, the cleaner pump  32  draws liquid ready for use  81  from the tank  82  through the inlet orifice  86  into the multi-input suction line  92 . The liquid from the underflow line  90  and liquid ready for use  81  are merged in the multi-input suction line  92 . 
     The merged combined liquid the first manifold assembly  98  and is pumped through the cleaner feed line  33  to the cleaner  30  which is a secondary cleaning system. The cleaner  30  is a combination filtration unit comprised of hydrocyclones  36  and a secondary shaker  42 . The hydrocyclones  36  separate the liquid from the cleaner feed line  33  into underflow liquid and slurry  81 . The underflow liquid follows the hydrocyclones underflow path  40  into the second shaker  42 . 
     The second shaker  42  separates the liquid emerging from the hydrocyclone underflow path  40  into spoils and underflow liquid. As discussed above, the spoils follow the cleaner spoils discharge path  47  into the spoils discharge tank  22 , while the second shaker underflow liquid follows the cleaner underflow path  844  to the cleaner underflow trough  846 . 
     The second manifold assembly  898  combines the various processed drilling liquids and controls their flow path. In one embodiment, the first manifold assembly  898  includes underflow troughs  896  and  846 , an underflow line  890 , a combined underflow liquid merging fin  888 , an inlet orifice  886 , a multi-input suction line  892  and a cleaner pump  832 . 
     Partially cleaned liquid emerging from the shaker underflow paths  844  and  894  flow into the shaker underflow troughs  846  and  896 . Under the influence of gravity, the underflow liquid from the second and third shakers  42  and  842  are combined into the underflow line  890 . second manifold assembly  898 . Through the underflow line  890 , the combined liquid from the cleaner underflow paths  844  and  894  enters the second manifold assembly  898 . The underflow line  890  is sufficiently large to allow entrained air within the liquid from the underflow troughs  846  and  896  to escape before entering the combined underflow liquid merging fin  888 . 
     Upon entering the underflow line  890 , the cleaner pump  832  draws the liquid from the combined underflow line  890  into the multi-input suction line  892 . Simultaneously, the cleaner pump  832  draws slurry  81  from the tank  82  through the inlet orifice  886  into the multi-input suction line  892  via the combined underflow liquid merging fin  888 . The liquid from the underflow line  890  and  81  merge in the multi-input suction line  892  in the area near the discharge of the combined liquid merging fin  888 . 
     The liquid leaves the second manifold assembly  898  and is pumped through the cleaner feed line  833  to a second cleaner  830  which is also a secondary cleaning system. The cleaner  830  is a combination filtration unit comprised of hydrocyclones  836  and a third shaker  842 . The hydrocyclones  836  separate the liquid from the cleaner feed line  833  into underflow liquid and slurry  81 . The underflow liquid follows the hydrocyclones underflow path  840  into the third shaker  842 . 
     The third shaker  842  separates the liquid emerging from the hydrocyclone underflow path  840  into spoils and underflow liquid. The spoils follow the cleaner spoils discharge path  847  into the spoils discharge tank  822 , while the third shaker underflow liquid follows the cleaner underflow path  894  to the cleaner underflow trough  896 . It will be appreciated that if optional underflow trough  46  is provided, the underflow exiting the second shaker  42  may partially follow flow path  44  and partially follow flow path  844 . 
     The liquid from the cleaner underflow trough  846  merges with the liquid from the second cleaner underflow trough  896  and the liquid from the hydrocyclone  836  overflow via the cleaner overflow line  838 . The combined liquid flows into the second manifold assembly  898 . The liquid from the hydrocyclone  836  overflow, classified as the cleanest filtered liquid within the system, is transported to the tank  82  via the cleaner overflow line  838 . 
     The foregoing description of the specific embodiments of the invention has been presented for the purpose of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not with this description, but rather by the claims appended hereto.