Patent Publication Number: US-2011072888-A1

Title: Method for leak detection in dosing system

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of U.S. Non-Provisional patent application Ser. No. 12/428,004 filed Apr. 22, 2009, hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The invention relates generally to a method of detecting internal and external leakage in a dosing manifold system including a dosing manifold assembly. 
     BACKGROUND 
     Exhaust gas after treatment systems are commonly used in conjunction with diesel engines for reducing the amount of nitrous oxides (NOx) in an exhaust gas. A typical configuration of the system has a reservoir filled with the treatment fluid, such as ammonia, fuel or urea, which is transported to a dosing injector, including, but not limited to a pump. The dosing injector sprays the treatment fluid into the exhaust gas prior to transport into a catalytic converter. The nitrous oxides in the exhaust gas are reduced when they react with the treatment fluid and are converted into water and nitrogen. After reacting in the catalytic converter, the exhaust gas is released from the catalytic converter into the atmosphere. 
     The use of diesel engines can range from small vehicles to large tractor-trailer truck applications. Due to the large variety of vehicles, the dosing requirements will vary due to different fuel pressures, flow rates, and required accuracy of the system. It is desirable to have a system for distributing the treatment fluid between the reservoir and injector which can easily accommodate various combinations of pressure relief, regulator, and on/off valves to provide scalability for the different dosing applications. 
     Additionally, any transfer of fluid poses the potential for leakage, both internally and externally. When a pump is used to move the treatment fluid, it can create large amounts of pressure against system components, such as closed valves. As a result, these closed valves may leak, allowing fluid to pass. This internal leakage produces undesirable parasitic losses and can compromise leak detection accuracy. External leakage may pose safety concerns, harm to the environment and can damage the system components. Thus, it is also desirable that the dosing manifold assembly be able to detect both internal and external system leaks. 
     SUMMARY 
     In an embodiment, a leak detection method may comprise the following steps. First, a fluid may be transported through a first valve assembly into a control fluid circuit, wherein the first valve assembly may have a first seal and a second seal and may be connected to a manifold body which may have a supply passage. Second, the fluid may be trapped in a portion of the control fluid circuit created between the second seal of the first valve assembly and a device capable of preventing fluid flow. Third, the fluid in the supply passage of the manifold body may be blocked from entering the control fluid circuit. Fourth, pressure build up in the supply passage of the manifold body blocked by the first valve assembly may be relieved. Fifth, pressure of the fluid in the control fluid circuit after trapping the fluid may be measured. Sixth, the pressure measured may be compared with a select pressure value. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate preferred embodiments of the invention and together with the detail description serve to explain the principles of the invention. In the drawings: 
         FIG. 1  is a schematic view of a fluid circuit of a dosing system that includes a dosing manifold assembly connected to a tank, a pump, and a hydraulic component in accordance with an embodiment of the invention. 
         FIG. 2  is a perspective view of the dosing manifold assembly of  FIG. 1  in accordance with an embodiment of the invention. 
         FIG. 3  is a cross-sectional view of the dosing manifold assembly of  FIG. 2 . 
         FIG. 4  is a cross-sectional view of the dosing manifold assembly of  FIG. 2 . 
         FIG. 5  is a cross-sectional view of the dosing manifold assembly of  FIG. 2  including a manifold body, a first valve assembly, a second valve assembly, a pressure relief valve, a sensor, a service plug, and a filter in accordance with an embodiment of the invention. 
         FIG. 6  is a schematic cross-sectional illustration of the first valve assembly in an opened position and partial view of the surrounding dosing manifold assembly within the fluid circuit of  FIG. 1  in accordance with an embodiment of the invention. 
         FIG. 7  is a schematic cross-sectional illustration of the first valve assembly of  FIG. 6  in a closed position. 
         FIG. 8  is a schematic cross-sectional illustration of a valve body portion of the first valve assembly in an opened position in accordance with an embodiment of the invention. 
         FIG. 9  is a schematic cross-sectional illustration of the valve body portion of the first valve assembly of  FIG. 8  in a closed position. 
         FIG. 10  is a graphical illustration of various pressure decay leakage responses for the dosing system of  FIG. 1 . 
         FIG. 11  is a flow chart generally illustrating the steps in a process of detecting a leak in the dosing system of  FIG. 1  in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a fluid circuit for a dosing system may include a dosing manifold assembly  2  configured with an externally connected low-pressure tank, reservoir, or fluid sump  12 , a pump  14 , and a hydraulic component  32 , such as but not limited to hydraulic machinery, valves, pistons, accumulators, or other fluid circuit devices. In an embodiment of the invention, the hydraulic component  32  may comprise an aftertreatment dosing injection. Although an aftertreatment dosing injector is mentioned in detail, other hydraulic components may be used as known to those of skill in the art. 
     The pump  14  may receive fluid  16  from the tank  12  and may supply a pressurized flow of fluid  16  to the dosing manifold assembly  2 . The pump  14  may be an electric or mechanical pump and may include some form of pressure regulation within itself to divert excess flow back to the tank  12 . Some examples of the pump  14  may include an electric pump with a mechanical pressure relief valve, an electric or mechanical pump with a mechanical pressure control, and a mechanical pump without manifold pressure control. While various examples of pumps  14  have been mentioned in detail, other types of pumps  14  may be used as known by those of skill in the art. The dosing manifold assembly  2  may supply the fluid  16  to the hydraulic component  32 . The fluid  16  may be ejected outside of the fluid circuit by the externally connected hydraulic component  32 . The fluid  16  not ejected outside of the fluid circuit may be returned to dosing manifold assembly  2 . The dosing manifold assembly  2  may return the fluid  16  to the tank  12 . 
     In an embodiment, the dosing manifold assembly  2  may include a manifold body  4  and a first valve assembly  18 . In accordance with embodiments of the invention, the dosing manifold assembly  2  may include any combination of additional components, such as a second valve assembly  10 , a filter  9 , a pressure relief valve  8 , and/or a sensor  11  depending upon the end-user&#39;s system requirements. 
     Referring to  FIGS. 2-7 , the manifold body  4  of the dosing manifold assembly  2  may comprise a plurality of cavities and a plurality of passages. At least some of the plurality of cavities may be formed in an outer surface of the manifold body  4 , for example, employing industry standards known in the art to accommodate various standard port fittings and valves. Each of the plurality of passages may be formed to fluidly connect various components that may be connected to the manifold body  4 . In an embodiment of the invention, the manifold body  4  may include a supply passage  26 , an output passage  34 , and a return passage  39 . In accordance with embodiments of the invention, the manifold body  4  may also include a detection passage  17 . Although the supply passage  26 , the output passage  34 , the return passage  39 , and the detection passage  17  are mentioned, other passages may be used as known to those of skill in the art. 
     The supply passage  26  may have an inlet end  25  and a valve end  27 . The inlet end  25  may be configured for receiving a standard-type hydraulic fitting and may be configured to receive fluid  16  from the externally attached pump  14 . The valve end  27  may be configured for receiving the first valve assembly  18 . Fluid  16  may flow from the inlet end  25  to the valve end  27 . In an embodiment where the dosing manifold assembly  2  includes a pressure relief valve  8 , the supply passage  26  may have two branches for the fluid flow: a first branch to the valve end  27  and a second branch  26 ′ to a pressure relief end  29 . The first branch for the valve end  27  may be configured to connect with/to the first valve assembly  18 . The second branch for the pressure relief end  29  may be configured to connect with/to the pressure relief valve  8 . Fluid  16  may flow from the inlet end  25  to the pressure relief end  29  and the valve end  27 . 
     The output passage  34  may have a valve end  31  and an outlet end  35 . The valve end  31  may be configured for receiving fluid  16  from the first valve assembly  18  when the first valve assembly  18  has been actuated to allow fluid  16  to flow from the supply passage  26  to the output passage  34  as described in more detail below. The outlet end  35  may be configured for receiving a standard-type hydraulic fitting and may be configured to send fluid  16  to an externally attached hydraulic component  32 . The fluid  16  may flow from the valve end  31  to the outlet end  35 . 
     The return passage  39  may have a valve end  37  and a port end  45 . The valve end  37  may be configured for receiving fluid  16  from the first valve assembly  18 . The port end  45  may include a first port opening  5  which may be configured for receiving a standard hydraulic fitting. Fluid  16  may flow from the valve end  37  to the first port opening  5 . In an embodiment where the dosing manifold assembly  2  includes the pressure relief valve  8 , the return passage  26  may have an additional branch  80  to accommodate fluid flow from the pressure relief valve  8 . Additionally, in an embodiment where the dosing manifold assembly  2  includes the second valve assembly  10  (e.g.,  FIG. 3 ), the return passage  26  may have an additional branch  82  to accommodate fluid  16  flow from the second valve assembly  10 . The port end  45  may include a second port opening  6  which may be configured for receiving a standard-type hydraulic fitting. The second port opening  6  may be useful in those embodiments of the invention including the pressure relief valve  8  and/or the second valve assembly  10 . Fluid  16  may thus exit the manifold body  4  from either the first port opening  5  and/or second port opening  6 . Depending on an application&#39;s requirements, such as design package orientation, either the first port opening  5 , second port opening  6 , or both first and second port openings  5 ,  6  may be sealed with a service plug  13 . 
     In an embodiment where the second valve assembly  10  is included as part of the dosing manifold assembly  2 , the manifold body  4  may have a detection passage  17 . The detection passage  17  may have an inlet end  19  and a valve end  21 . The inlet end  19  may be configured for receiving a standard-type hydraulic fitting. The valve end  21  may be configured for receiving the second valve assembly  10 . Fluid  16  may flow from the inlet end  19  to the valve end  21 . When the second valve assembly  10  is in the open position, fluid  16  may flow from the detection passage  17  into the return passage  26 . 
     The manifold body  4  may be comprised of various materials. The material or materials employed may depend on the system requirements, such as but not limited to, the type of fluid  16  distributed in the system, leakage tolerance, and surrounding system environment factors. In an embodiment of the invention, the manifold body  4  may, for example, comprise T6061 anodized aluminum which may provide anti-corrosive properties. Although T6061 anodized aluminum is mentioned specifically, the manifold body  4  may comprise any number of the materials known to those of skill in the art in various embodiments of the invention. 
     The shape of the manifold body  4  and the location of the mounting holes may be dependent upon the application requirements. In an embodiment of the invention, the manifold body  4  may be rectangular in shape and may provide a plurality of mounting holes. The manifold body  4  may, for example, include four mounting holes. Each of the mounting holes may be located near the corners of the manifold body  4 . Although four mounting holes located near the corners of the manifold body  4  are mentioned, the manifold body  4  may comprise any number of mounting holes and these mounting holes may be located in various portions of the manifold body  4 , including those anticipated by those of skill in the art. 
     Referring to  FIGS. 1-3  and  FIGS. 5-7 , the first valve assembly may be connected to the manifold body  4 . In an embodiment of the invention, the first valve assembly  18  may be secured to the manifold body  4  with a plurality of spring pins  7 . The use of spring pins  7  may provide a cost-effective attachment method and may provide positional alignment between the first valve assembly  18  and the manifold body  4  during assembly. Although the use of spring pins  7  to attach the first valve assembly  18  to the manifold body  4  has been specifically mentioned, other attachment methods may be used, including those known to persons of ordinary skill in the art. 
     The first valve assembly  18  may be electrically connected to an energy source  28 , labeled ES in  FIG. 1 . The energy source  28  (or ES) may, for example, comprise a battery, a capacitor, or other suitable electrical or electro-chemical storage device, or an electrical outlet, via a wireless or hard-wired electrical connection  30 . If the second valve assembly  10  comprises an electrohydraulic on/off valve, it may likewise be electrically connected to an energy source  28 . 
     Control logic may be implemented to selectively open and close the first valve assembly  18  as needed or desired to control the flow of the fluid  16 . The fluid  16  from the supply passage  26  may be admitted into the first valve assembly  18  through a supply port  20 . When the first valve assembly  18  is turned on, which in a normally-closed device may occur when the first valve assembly  18  is selectively energized, the fluid  16  from the supply passage  26  admitted into the first valve assembly  18  may ultimately be discharged from the first valve assembly  18  via a control port  22  to the output passage  34  of the manifold body  4 . At least one orifice  23  may be in fluid communication with the tank  12  via the return passage  26  to provide a pressure unloading feature as set forth below with reference to  FIGS. 5 and 7 . While a single orifice  23  is shown in the various figures for simplicity, additional orifices  23  can also be used. The number of orifices  23  used may be determined by the amount of available valve stroke, orifice size, and leakage past a lower valve  24  in the open and closed positions as explained below. 
     Referring to  FIG. 7 , the first valve assembly  18  is shown in a closed position, blocking passage of a pressure (P 1 ) to the control port  22 . The first valve assembly  18  may include a solenoid portion  36  and a valve body  38 . The solenoid portion  36  may be electrically connected to an energy source  28 , such as shown in  FIG. 1 . In this embodiment, when the solenoid portion  36  is de-energized in a normally-closed configuration, fluid  16  may be blocked from reaching the control port  22 . That is, fluid  16  may be prevented from being discharged from the valve body  38  via the control port  22 , which may be disposed in a wall  76  thereof. In this manner, the control pressure (P 2 ) (see e.g.,  FIG. 6 ) at the control port  22  may prevent fluid flow to the output passage  34  and may therefore not be made available for use by the externally connected hydraulic components  32  shown in  FIG. 1 . 
     The first valve assembly  18  may be configured as an electro-hydraulic device, and may include a solenoid housing  40  that includes a solenoid winding or coil  41 . The coil  41  may, for example, be wound on a bobbin  43 , and may be selectively energized to actuate or power the first valve assembly  18 . That is, when the coil  41  is de-energized, the first valve assembly  18  may restrict fluid communication between the supply port  20  and the control port  22 . When the coil  41  is energized, a magnetic field may be induced, thus generating magnetic flux which may ultimately open the first valve assembly  18  to allow flow from the supply passage  26  to the output passage  34 . Fluid  16  may pass through the supply port  20  and exit the first valve assembly  18  through the control port  22  as shown in  FIG. 6  and described below. 
     In addition to the control port  22 , the valve body  38  may include an inner wall  44  defining an upper chamber  42  that may define an upper valve seat  46 . An armature  48  may move axially within the upper chamber  42  in the direction of arrow C absent a magnetic field as described above. A resilient member  50 , such as a spring or other suitable return device, may be positioned between a first end  51  of the armature  48  and an undersurface  54  of a pole portion  55  to react against the undersurface  54 , and to thereby provide a sufficient return force for moving the armature  48  in the direction of arrow C when the solenoid portion  36  is de-energized as shown in  FIGS. 6-7 . 
     The armature  48  may be disposed in a magnetic sleeve  15  to move in conjunction therewith. In one embodiment, the magnetic sleeve  15  may circumscribe the armature  48 . The sleeve  15  may be moveably disposed within the upper chamber  42  of the valve body  38  and may define an air gap  47  with the undersurface  54  of the pole portion  55 . A second end  53  of the armature  48  may be configured to seal against the upper valve seat  46  with a predetermined maximum rate of fluid bypass. The armature  48  may extend axially toward a lower chamber  56  of the valve body  38  and may contact a lower valve  24  through a connecting port  33 , with the connecting port  33  providing fluid communication between the upper and lower chambers  42  and  56 , respectively. 
     Still referring to  FIG. 6 , the volume of the lower chamber  56  may be defined by an inner wall  58 , which may contain or house the lower valve  24 . As shown in the embodiment of  FIGS. 6 and 7 , the lower valve  24  may be configured as a spool valve. However, other embodiments are possible without departing from the intended scope of the invention, including but not limited to the ball poppet of  FIGS. 8 and 9  described below. 
     The valve body  38  may also define the supply force balance port  20 A, within which is disposed a stop device  60 , e.g., an annular snap ring or other suitable spool-retaining device. When the energy source  28  of  FIG. 1  energizes the coil  41 , the sleeve  15  may be magnetically attracted toward the pole portion  55 , and thus the armature  48  may move axially in the direction of arrow O within the upper chamber  42 . As a result, the force of the resilient member  50  may be overcome and the resilient member  50  may compress against the undersurface  54  (see e.g.,  FIG. 6 ). As the armature  48  moves in the direction of arrow O, the lower valve  24  may also be free to move in the direction of arrow O in response to fluid pressure at the supply force balance port  20 A. 
     When the lower valve  24  is configured as a spool valve as shown in the embodiment of  FIGS. 6 and 7 , the lower valve may include a spool  62  defining axial fluid passages  64  therein. The spool  62  may include an extension  57  which may contact the armature  48 , such that motion of the armature  48  may move the spool  62 . When the first valve assembly  18  is in an open position as described below, the fluid  16  providing pressure (P 1 ) at the supply port  20 ,  20 A may flow through the axial fluid passages  64 , through the connecting port  33 , and into the upper chamber  42 , where it may ultimately be discharged through the control port  22  to provide the control pressure P 2 . Thus, fluid flow may be provided with minimal pressure drop across the first valve assembly  18 , which may be less than approximately 0.5 bar(g). 
     At least one orifice  23  may be disposed in the valve body  38  between the lower valve  24  and the armature  48 . As noted above, multiple orifices  23  may be used, or just one as shown, depending on a variety of factors. The factors may include, but are not necessarily limited to, available valve stroke, orifice size, allowable leakage past the lower valve  24 , etc. For example, one embodiment may include multiple orifices  23  that are approximately equally spaced, e.g., four orifices  23  positioned 90 degrees apart from each adjacent orifice  23 . The orifices  23  may be sized as needed for a particular application, e.g., approximately 0.5 mm to approximately 1 mm in diameter according to another embodiment. In some applications, proper venting may not be achievable using a single orifice  23 . Also, leakage past the lower valve  24  may be difficult to predict. Therefore, multiple orifices  23  may be provided, with some of the orifices  23  plugged as needed to tune the first valve assembly  18  for a particular application. 
     More particularly, the orifice  23  may be formed within the wall  76  of the valve body  38 . The rate of fluid flow between the lower chamber  56  and the tank  12  (see  FIG. 1 ) may thus be limited by the orifice  23 . In the open position shown in  FIG. 6 , the orifice  23  may be restricted by spool  62  and may limit a flow of fluid  16 , thereby reducing parasitic fluid loss. The orifice  23  also may reduce any appreciable pressure build up due to any fluid leakage occurring past the lower valve  24  in the closed position of  FIG. 7 . 
     When the first valve assembly  18  is in the closed position shown in  FIG. 7 , the orifice  23  may allow for venting of the first valve assembly  18  by dumping fluid  16  that leaks past the spool  62 . According to one embodiment, the upper valve seat  46  and the armature  48  may be manufactured to have less than approximately 100 mg/min of fluid leakage or bypass when in the closed position. Fluid leakage past the lower valve  24  in the closed position may be several orders of magnitude higher and may still provide an acceptable pressure unloading function. The orifice  23  may be configured with a diameter (d) that provides optimal pressure unloading. In one embodiment, the diameter (d) of the orifice  23  may be approximately 0.5 mm to approximately 1 mm. However, other diameter sizes may also be used without departing from the intended scope of the invention. 
     As noted above, the orifice  23  should be large enough to reduce any appreciable pressure buildup due to fluid leakage past the spool  62  in the closed position. The orifice  23  may also be sized small enough to reduce parasitic fluid loss to the tank  12  when the armature  48  and the lower valve  24  are in the open position shown in  FIG. 6 . The diameter (d) may also be sized to sufficiently minimize any pressure drop across the first valve assembly  18  when in the open position, such as generally shown in  FIG. 6 . 
     Referring to  FIG. 6 , the first valve assembly  18  in the illustrated embodiment may be opened when the solenoid coil  41  is energized, thus allowing the fluid  16  to flow from the supply port  20  to the control port  22 . When a magnetic field is generated, the biasing force of the resilient member  50  may be overcome by fluid pressure which may cause the armature  48  to move in the direction of arrow O. As the armature  48  moves in the direction of arrow O, the second end  53  thereof may move away from the extension  57 . No longer opposed by the armature  48 , the lower valve  24  may be free to move in the direction of arrow O which may permit fluid  16  to flow from the port  20  to the control port  22 , and may substantially block the orifice  23 . For example, in an embodiment, at least approximately 75% of the orifice  23  may be blocked. 
       FIGS. 8 and 9  illustrate another first valve assembly  118  where the lower valve  24  may be configured as a ball poppet. For simplicity, the solenoid portion  36 , and partial view of the manifold body  4  of  FIGS. 6 and 7  are omitted from  FIGS. 8 and 9 , with the electro-mechanical structure and operation of the solenoid portion  36  described above applying equally to the embodiment of  FIGS. 8 and 9 . The ball poppet could be used, for example, as a lower-cost device relative to the spool design of  FIGS. 6 and 7 . However, a ball poppet may be expected to leak at a higher rate relative to the spool design, and therefore a performance vs. efficiency tradeoff may be a consideration in deciding between the particular embodiment to employ in a given fluid circuit. 
     In the embodiment of  FIG. 9 , a sphere or ball  70  may be biased towards a closed position by an armature  48 , for example via an axial arm or armature pin  48 A, which can be coupled to the armature  48  described above. A lower valve seat  71  may be shaped to form a fluid seal with respect to the ball  70  when the armature pin  48 A pushes the ball  70  against or near the lower valve seat  71 , such as generally shown in  FIG. 9 . 
     The lower valve seat  71  may be made of a suitable material to define a plurality of axial grooves  72  and a radial orifice  74 . The ungrooved portions of the lower valve seat  71  may contain the ball  70  within an axial path while the grooves  72  may allow fluid  16  to be directed past the ball  70 . The radial orifice  74  may be in fluid communication with the orifice  23  via an annular channel  75  formed in and/or between the lower valve seat  71  and the wall  76  of the valve body  38 . In this embodiment, fluid pressure (P 1 ) acting on the ball  70  at control port  20 B may exceed or overcome the return force of the resilient member  50  (see  FIGS. 6 and 7 ). However, some amount of fluid leakage may be present with respect to the ball  70 . 
     Fluid  16  that bypasses the ball  70  may therefore be directed through the axial grooves  72 , the radial orifice  74 , and/or the annular channel  75 , where it may ultimately be vented to the tank  12  via the orifice  23  to limit pressure acting on the armature  48 . 
     Referring to  FIG. 8 , when the first valve assembly  118  is energized in a normally-closed configuration, the ball  70  may no longer be biased in the direction of arrow C by the armature pin  48 A. Fluid pressure (P 1 ) may then move the ball  70  within the axial grooves  72 . The ball  70  may move only so far as to substantially block the radial orifice  74 , thus minimizing fluid flow into the orifice  23 . In this manner, parasitic losses may be minimized when the first valve assembly  118  is in an energized or open position, for example, as generally shown in  FIG. 8 . 
     As will be understood by those of ordinary skill in the art, solenoid-actuated valves such as first valve assemblies  18  and  118  described hereinabove may be configured either as normally open or normally closed devices. A normally-open device may remain in an open position, in the event of a power failure, closing only when energized. A normally closed device may do precisely the opposite, i.e., remaining in a closed position, requiring energizing current to actuate the device. While the first valve assembly  18  and  118  are each described hereinabove as being normally-closed devices, either embodiment may be modified as normally open devices without departing from the intended scope of the invention. 
     If a second valve assembly  10  is included as part of the dosing manifold assembly  2  in an embodiment of the invention, the second valve assembly  10  may be attached to the manifold body  4 . The second valve assembly  10  may be in fluid communication with the detection passage  17  and the return passage  39 . Examples of the second valve assembly  10  may include, but are not limited to, a mechanical check valve or an electrohydraulic on/off valve. A mechanical check valve may be cost-effective and not require an energy source to power it because it may be configured to open after a selected pressure has been exceeded. An electrohydraulic on/off valve may be less sensitive to particulates in the fluid  16  and may have the ability to more accurately control pressures of the system. In an embodiment of the invention, the second valve assembly  10  may be used to prevent flow from the detection passage  17  to the return passage  39 . The blockage of fluid flow may cause a pressure build up which may be used with the leak detection method described in further detail below. While various examples of the second valve assembly  10  have been explained in detail, other types of the second valve assembly  10  may be utilized as known by those of ordinary skill in the art. 
     If a filter  9  is included as part of the dosing manifold assembly  2  in an embodiment of the invention, the filter  9  may be disposed between at least a portion of the supply passage  26  and the first valve assembly  18 . As generally illustrated in  FIGS. 2 and 4 , the filter  9  may be mounted externally on the manifold body  4 . The filter  9  may be mounted, for example, by spinning the filter  4  onto the manifold body  4 . A hydraulic fitting, such as a union, may be used for attachment purposes. In another embodiment, as generally illustrated in  FIG. 5 , the filter  9  may be mounted internally in the supply passage  26  of the manifold body  4 . The filter  9  may be an in-passage screen or strainer and may be mounted near the inlet end  25  of the supply passage  26 . Although various filter types and mounting solutions have been described in detail, other filter types and mounting solutions may be used as known by those of ordinary skill in the art. 
     If a pressure relief valve  8  is included as part of the dosing manifold assembly  2  in an embodiment of the invention, the pressure relief valve  8  may be attached to the manifold body  4 . The pressure relief valve  8  may be in fluid communication with the supply passage  26  and return passage  39 . Fluid  16  allowed to pass through the pressure relief valve  8  may flow from the supply passage  26  into the return passage  39 . For example, it may be advantageous to use a pressure relief valve  8  to control excess fluid pressure from the pump  14 , to smooth inconsistent fluid pressure, or to protect the components connected to the dosing manifold assembly  2  from potentially large fluid pressures. Although these advantages are mentioned in detail, there may be additional advantages associated with the use of a pressure relief valve as known to those of ordinary skill in the art. 
     If a sensor  11  is included as part of the dosing manifold assembly  2  in an embodiment of the invention, the sensor  11  may be attached to the manifold body  4 . The sensor  11  may be in fluid communication with the output passage  34 . The sensor  11  may monitor pressure and/or temperature. If the externally connected hydraulic component  32  has a return line, the hydraulic component  32  may be in fluid communication with the detection passage  17  in the manifold body  4 . If a second valve assembly  10  is added in an embodiment of the invention, the second valve assembly  10  may be disposed between the detection passage  17  and the return passage  26 . Fluid  16  allowed to pass through the second valve assembly  10  may flow from the detection passage  17  to the return passage  26 . When the first valve assembly  18  and second valve assembly  10  are in the closed position, the sensor  11  may be used to calculate pressure decay which may determine if any fluid leakage has occurred. 
     Referring to  FIG. 11 , with component reference to  FIG. 1 , a leak detection method  200  for use with a dosing manifold assembly  2  may be utilized by trapping fluid  16  under pressure in a closed circuit. A sensor  11  may detect the pressure decay in the closed fluid circuit by measuring the pressures over a set period of time and comparing the measured pressures to a baseline measurement. Additionally, the sensor  11  may also be used to detect temperature variations in the fluid  16  by measuring temperatures over a set period of time and comparing the measured temperatures to a baseline temperature measurement. Variations between the actual measurements versus the baseline measurements may be suggestive of either internal or external leakage. The size of the variation may also be suggestive of the severity of the leak. 
       FIG. 11  generally illustrates an embodiment of the leak detection method  200 . The leak detection method  200  may be utilized when the dosing manifold assembly  2  comprises at least the manifold body  4 , the first valve assembly  18 , the externally connected hydraulic component  32 , and the sensor  11 . A control fluid circuit may exist between at least a portion of the first valve assembly  18  and at least a portion of the externally connected hydraulic component  32 . The control fluid circuit may include at least a portion of the first valve assembly  18 , the output passage  34  of the manifold body  4 , any hosing, tubing, conduit, fittings, or other hydraulic equipment used to externally connect the hydraulic component  32  to the dosing manifold assembly  2 , and at least a portion of the hydraulic component  32 . 
     Referring to  FIG. 11 , an embodiment of the leak detection method  200  may begin at step  202  where the fluid  16  may be transported from the supply passage  26  of the manifold body  4 , through the first valve assembly  18  connected to the manifold body  4 , and into the control fluid circuit. In step  204 , one end of the control fluid circuit may be closed by de-energizing the hydraulic component  32  which may prohibit or eliminate any intentional external injection of the fluid  16  outside of the control fluid circuit. Fluid pressure may be formed in the control fluid circuit as a result of the flow blockage. The first valve assembly  18  may then be configured into the closed position. When the first valve assembly  18  is in a closed position, it may create two seals: a first seal and a second seal. The first seal may be formed when the lower valve  24  blocks the supply port  20 , which may prevent fluid from entering the first valve assembly. The second seal may be formed by contacting the armature  48  with the upper valve seat  46 , which may trap pressurized fluid  16  in the control fluid circuit as well as prevent any fluid leakage past the first seal from entering the control fluid circuit by directing the fluid leakage through the orifice  23 . 
     In another embodiment, the leak detection method  200  may be utilized when the dosing manifold assembly  2  comprises at least the manifold body  4 , the first valve assembly  18 , the externally connected hydraulic component  32 , the sensor  11 , and the second valve assembly  10 . A control fluid circuit may exist between at least a portion of the first valve assembly  18  and a portion of the second valve assembly  10 . The control fluid circuit may include at least a portion of the first valve assembly  18 , the output passage  34  of the manifold body  4 , any hosing, tubing, conduit, fittings, or other hydraulic equipment used to externally connect the hydraulic component  32  to the dosing manifold assembly  2 , the externally connected hydraulic component  32 , the detection passage  17  of the manifold body  4 , and a portion of the second valve assembly  10 . 
     With regard to an embodiment that includes a second valve assembly  10  as part of the dosing manifold assembly  2 , the leak detection method  200  may begin at step  202  where the fluid  16  may be transported from the supply passage  26  of the manifold body  4 , through the first valve assembly  18  connected to the manifold body  4 , and into the control fluid circuit. In step  204 , one end of the control fluid circuit may be closed by configuring the second valve assembly  10  into the closed position. The hydraulic component  32  may also be configured into a closed position by de-energizing the hydraulic component  32  which may prohibit or eliminate intentional external injection of the fluid  16  outside of the control fluid circuit. Fluid pressure may be formed in the control fluid circuit as a result of the flow blockage. The first valve assembly  18  may then be configured into the closed position as described in the embodiment that does not include the second valve assembly  10  as part of the dosing manifold assembly  2 , which may result in trapping pressured fluid  16  in the control fluid circuit. 
     To further increase the accuracy of the leak detection method  200 , the first valve assembly  18  may include an integrated fluid bypass, such as the fluid venting function of the orifice  23  in an embodiment of the first valve assembly  18 . Without an integrated fluid bypass, when the first valve assembly  18  is in the closed position, fluid pressure in the supply passage  26  may build up and may result in leakage into the closed fluid circuit. This additional leakage may bias the sensor  11  measurements in the closed control fluid circuit, reducing the accuracy of any pressure and temperature sensor measurements. However, in step  206 , integrity of the closed control fluid circuit may be maintained by blocking the fluid  16  outside of the control fluid circuit. In step  208 , any leakage which may result from fluid pressure build up outside of the control fluid circuit may be relieved by venting fluid  16  through the orifice  23  of the first valve assembly  18  when in the closed position. This may result in reduction of fluid pressure against the second seal which may preserve the integrity of the closed control fluid circuit from becoming compromised. 
     The resulting trapped fluid pressure in the closed fluid circuit may attempt to escape through internal or external leakage. Any escaping leakage may create a pressure decay which may be characterized by the amount of leakage over a period of time. When no external leakage exists, it may be desirable to characterize the internal leakage as a baseline for future comparisons. It may also be desirable to utilize valve assemblies with low internal leakage because the pressure decay may be fairly linear in slope over a short time interval. 
     For example,  FIG. 10  generally illustrates testing data to characterize the pressure decay of a control fluid circuit of a dosing manifold assembly with various low leakage situations. For the test data shown in  FIG. 10 , the internal fluid pressure in the circuit was initially set at 40.0 psi. Various internal leakage rates were simulated in the circuit, ranging from 0.00 grams/minute to 1.00 grams/minute. For a ten second period of time, the sensor  11  measured the fluid pressure in the control fluid circuit at one second intervals. As seen in FIG.  10 , the pressure measurements compared to time had a pressure decay slope that was substantially linear during the time interval. The slope&#39;s linear nature over a short period of time may allow the data to be more accurately characterized when creating curve fit equations. In an embodiment where both the first valve assembly  18  and second valve assembly  10  are rated at a leakage flow rate of less than 1.00 grams/minute when in a closed state, a trapped pressure of 40.0 psi may have a pressure decay of 1.15 psi/sec.  FIG. 10  represents one set of data measured at an initial pressure of 40.0 psi. The dosing manifold assembly  2  may handle pressures up to 200 psi and one skilled in the art may obtain and characterize the necessary baseline pressure decay data accordingly for various initial pressures and/or other system parameters. Additional testing may be undertaken to obtain data to characterize the temperature decay of the control fluid circuit of the dosing manifold assembly. One skilled in the art may obtain and characterize the baseline temperature decay data for various system parameters. 
     In step  210 , after the baseline pressure decay due to internal leakage has been quantified, the actual pressure decay of the trapped fluid pressure may be measured by the sensor  11 . Additionally, the actual temperature decay of the trapped fluid may measured by the sensor  11 . In step  212 , the measured actual data may be compared to select characterized data, such as baseline pressure decay data or baseline temperature decay data. For example, the comparison may be performed after measuring one actual data point at a certain period of time. Control logic may be programmed to select the relevant characterized pressure and/or temperature decay curve and then compare the actual data point to the selected characterized data point for the same period of time. The relevant characterized pressure and/or temperature decay curve may be determined based on parameters such as the known system pressure, the known system temperature, the known internal leakage of the system, and time. These known parameters may be initially measured prior to the start of the leak detection method  200  or may be established system characteristics. Additionally, the comparison step  212  may be performed after measuring a plurality of actual data points at known times by repeating step  210  at least once. Measuring and comparing a plurality of actual data points may provide better accuracy for detecting leakage and/or may allow the relevant characterized pressure and/or temperature decay curve to be selected with fewer known system parameters. While various examples have been explained in detail, other ways to measure the actual data and perform the comparison may be utilized as known by those of ordinary skill in the art. 
     In step  214 , the size of the variation between characterized data and the actual data may suggest and may quantify any additional leakage in the circuit. For example, an increase in the variation may suggest an increase in leakage. Depending on the end-user&#39;s requirements, the allowable variation may be selected as a tolerance band defined above and below the characterized data. The smaller the tolerance band, the more sensitive the leak detection method  200  may be to variations between the characterized data and the actual data. Likewise, the larger the tolerance band, the less sensitive the leak detection method  200  may be to variations. A leak may be detected when the actual data is outside of the tolerance band of the characterized data. Additionally, multiple tolerance bands may be utilized with a narrow tolerance band for detecting small leaks and a larger tolerance band for detecting larger leaks. One advantage of multiple tolerance bands is that the variation size may trigger different notification events as detailed below in step  222 . While various ways for determining whether a leak has be detected have been explained in detail, other ways may be utilized as known by those of ordinary skill in the art. 
     In step  216 , depending on the contamination requirements of the end-user and the resultant configuration of the dosing manifold assembly  2 , multiple cycles of the leak detection method  200  may be utilized to confirm variations between characterized data and actual pressure data. In step  218 , the measurement data may be stored for later review. In step  220 , the cycle may be started by releasing at least a portion of the fluid  16  in the control fluid circuit by configuring the first valve assembly  18  and the device capable of preventing flow into an opened position. For example, in an embodiment where the second valve assembly  10  is a check valve, contamination in the fluid  16  may cause the valve to internally leak at a higher rate if a particulate is lodged on the sealing surface which may prevent an adequate seal. By repeating the cycle, the fluid  16  in the circuit may be pulsed, potentially removing the particulate from the seal and providing a more accurate pressure decay measurement. If desired, more than one cycle may be repeated. Such use of cycling the leak detection method may reduce the potential for false alerts to the end-user. 
     In step  222 , an end-user or other person which may require the results of the leak detection method  200  may be notified of the potential of a leak in the control fluid circuit. Examples of notifying the end-user may range from basic notification such as a warning light to displaying detailed information utilizing the stored measurement data in step  218 . Additionally, a controller may be utilized to shut off fluid flow to the control fluid circuit to reduce the impact of the detected leakage. A notification may be sent when a measured pressure value deviates from a select pressure value by a threshold amount. The threshold amount will vary depending on the tolerance band. A notification may also be sent when a measured temperature value deviates from a select temperature value by a threshold amount. The threshold amount will vary depending on the tolerance band. While various notifications and actions have been mentioned in detail, other notifications and actions may be used as known by those of ordinary skill in the art. 
     The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and various modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to explain the principles of the invention and its practical application, to thereby enable others skilled in the art to utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The invention has been described in great detail in the foregoing specification, and it is believed that various alterations and modifications of the invention will become apparent to those skilled in the art from a reading and understanding of the specification. It is intended that all such alterations and modifications are included in the invention, insofar as they come within the scope of the appended claims. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.