Abstract:
For regulating engine exhaust and for environmental reasons, aircraft users are restricted from expelling engine fluids from engines onto airport ramps. All such fluid must be collected and subsequently burned or properly disposed of. The present invention installs witness drain valves in the drain lines between seal cavities and environmental collector tank. The witness drain valves have a small reservoir that will retain a known volume of fluid. As fluid passes from a leaking seal to the collector tank, a small sample is captured in the witness drain valve. Once the witness drain valve reservoir is full, the leaking fluid then flows on to a collector tank, which is also provided. During regular engine maintenance, technicians push on a spring loaded drain valve located on the witness drain valve reservoir. If fluid is detected, the seal is beginning to leak, and corrective maintenance may be scheduled while the leak rate is still within operational limits.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to a fluid leakage detection system in a drain line. More particularly, the present invention integrates a commercially available finger push valve into a seal cavity leakage detection system placed inside an enclosed compartment, such as an aircraft engine or industrial machinery, providing a low-cost, non-intrusive means of early leak detection in a new or retrofit design. The method and apparatus disclosed in the present application provides an environmentally friendly alternative to other leak detection methods and improves reliability and maintainability.  
           [0002]    Multi-joint hydraulic systems may have many fittings, which are not readily visible and thus are difficult to inspect on a routine basis. Sometimes minor leakage at such joints are not a problem for operations, therefore routine inspection is not necessary. In other applications, however, such as aerospace, high speed machinery, and transportation equipment, early leakage detection can be critical for operational and personnel safety. Quantifying leakage and leakage rate is necessary in order to distinguish between conditions which are allowable and those which are indicative of accelerated deterioration of a mechanical system. Therefore, a reliable, accurate, and fast determination of hydraulic system leakage can identify the need for maintenance and greatly improve prevention of catastrophic failures during operations.  
           [0003]    Hidden-joints, while not visually accessible, are conventionally inspected by use of such devices as inspection mirrors. However, such efforts are subjective and non-quantitative. Often, visual inspection is not possible due to the compactness of the enclosed compartment and/or lighting conditions in the area of interest. Moreover, when portions of such hydraulic systems are thermally insulated, indirect observation is not possible and leak detection becomes a difficult, time-consuming, and critical task.  
           [0004]    For environmental reasons, there is now a requirement that no engine fluids be expelled onto airport ramps. All such fluids, regardless of leakage source, must be collected, disposed of, or burned in the engine exhaust. Many gas turbine engines include an extensive drain system for transfer of fluid leakage to an interim storage area or reservoir outside the engine compartment. The storage area or reservoir provides a means for leakage detection. For example, one of the fluids that is expelled from an engine is leakage from an accessory drive seal. Before collector tanks were installed, fluid from a leaking seal cavity was routed to an overboard drain and could be observed dripping from the aircraft. That is the source of the term “witness drain”. In such situations, technicians would note existence of the leak and would schedule corrective action to replace the leaking accessory seal. When collector tanks are used to capture the leaking fluid, there is no observable evidence to indicate that a seal is leaking, and the seal may continue to deteriorate until excessive oil loss is noted or other more serious operational symptoms develop. The problem is further complicated, for example, when collector tank drain lines are connected to a plurality of possible sources of joint and seal leakage. Typically, such drain lines are installed near oil, hydraulic or fuel seal points adjacent to moving elements, such as near gearboxes where other components are coupled to the engine via shafts passing through the gearbox housing. Other sources of leakage can be hydraulic actuators and fuel driven valves.  
           [0005]    Traditionally, drain mast assemblies are installed in engines to satisfy the operational needs described above. Such drain systems provide an indication of leakage from a source to which the drain is connected but no indication as to the quantity or leakage rate of that source. In most commercial engine applications, operational drains drain away liquids that might accumulate during operation, and service drains collect liquids for removal during maintenance. Leakage associated with such service drains can be determined during maintenance by measuring the quantity of liquid collected. Typically, there are many drain lines feeding into the drain mast assembly, and for that reason, it is difficult to determine which particular drain line is leaking since the fluids tend to run onto adjacent drain lines. This disadvantage creates a problem for troubleshooting a leaking drain, and requires a time consuming investigation inside the nacelle and cowl assembly.  
           [0006]    Prior art, U.S. Pat. No. 5,285,636, discloses an improved drain mast assembly having a plurality of collection chambers with each of the chambers coupled in liquid receiving relationship with a respective liquid drain line. The assembly allows identifications of individual drain lines having relatively high drain-rates. Each chamber in the improved assembly may include a transparent view window for visually determining the volume of liquid collected by the chamber. The valve in each chamber also includes a standpipe extending a pre-selected distance into the chamber for overflow draining of the chamber when the collected liquid exceeds a predetermined volume.  
           [0007]    This patent essentially discloses a drain mast using a traditional overboard method to dispose of the leakage waste fluids. Once the drain mast fluid leak detection collection chamber is filled, the fluid is expelled from the aircraft. The system requires that the valve and standpipe be integrated within a compact space. This is to avoid creating an excessively large drain mast causing aerodynamic drag for the aircraft. The standpipe height determines the volume of the fluid retained in the detection chamber before being drained overboard, thus significantly complicating the design. Since the system focuses on use of the drain mast concept and is located outside the engine cowling, there is a resulting requirement to incorporate special design features, such as mountings, that must take aerodynamic effects into consideration. This makes the system expensive, heavy, difficult to maintain, and not retrofitable.  
           [0008]    Therefore, there is a need for a cost-effective, accurate, safe, reliable, and efficient witness drain system, using commercially available components, to meet regulatory and environmental considerations and to allow for inspection and quantification of drain line leakage.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention provides an apparatus and method to conveniently and accurately checks drain line leakage. The apparatus and method disclosed is lightweight, usable for both new and retrofit designs, inexpensive, and does not affect aerodynamic drag.  
           [0010]    In one aspect of the present invention, a commercially available finger push valve is integrated into a witness drain valve system allowing excessive fluid in a drain line to continue along its original route. Disclosed is an apparatus comprised of a witness drain valve having a small built in reservoir that retains a small, predetermined portion of leaking fluid along the drain line. The apparatus can be installed in the drain line between the seal cavity and the environmental collector tank. As the fluid passes the leaking seal to the collector tank, a small sample is captured in the apparatus. Once the reservoir of the apparatus is full, the leaking fluid flows on to the collector tank as intended. The apparatus is non-intrusive and provides critical leakage information to engine maintenance crews. No standpipe is required nor is there a need for an overboard drain to dispose of waste fluid.  
           [0011]    In another aspect of the present invention, a method of improving engine reliability and maintainability is disclosed. The method comprises the steps of: installing an improved witness drain valve having variable diameters along the fluid flow path to create a small reservoir of pre-designed volume appending the drain line; disposing the drain witness valve between the leaking seal and environmental collector tank; flowing fluid along the drain line; collecting a leakage fluid sample; inspecting leakage fluid amount through a commercially available finger push valve connected to the witness drain valve perpendicular to the flow direction; determining the need for maintenance of the seal; and scheduling maintenance as required before further seal deterioration occurs. The pre-designed volume may be determined during the design phase by calculating allowable leakages in seal cavity drains based on the maintenance needs of individual engines or operations. This approach is distinguishably different from the prior art which is generally based on the volume of the reservoir being primarily determined by the size of the stand pipe and geometric considerations for reducing aerodynamic drag. By individualizing the drain line cavity volume based on criticality of leakage of each individual seal, the various reservoir volumes can be maximized to realize a system reliability improvement by tailoring the maintenance need of each drain line in the system.  
           [0012]    In yet another aspect of the present invention, there is disclosed a decentralized witness drain valve system comprised of a series of witness drain valves installed along drain lines to accurately determine the leakage amount and leakage rate at each specific drain line. Each witness drain valve incorporates a predetermined reservoir volume and a commercially available finger push valve. The system provides information on leakage amount and rate by determining, by means of the finger push valves, which reservoir has filled between consecutive inspections. The quantitative leakage assessment provides information on seal deterioration rate, and thus improves engine operational safety.  
           [0013]    These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, descriptions and claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 is a perspective view of an engine drain line and collector tank system with witness drain valve applications as conceived by the present invention;  
         [0015]    [0015]FIG. 1 a  is another perspective view of an engine drain line and collector tank system as in FIG. 1 showing flow interface details;  
         [0016]    [0016]FIG. 2 is a representative view of the general assembly of a witness drain valve construction according to one of the embodiments of the present invention;  
         [0017]    [0017]FIG. 3 is an elevational view of a witness drain valve in the flow direction according to one of the embodiments of the present invention; and  
         [0018]    [0018]FIG. 4 is a cross sectional view taken along lines A-A of FIG. 3 depicting one embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]    Referring to FIGS. 1 and 1 a,  there are shown perspective views of a drain system  10  in an engine compartment as conceived by the present invention. The system includes multiple drain lines comprising upstream drain lines  20  and downstream drain lines  26 . Witness drain valves  15  are interposed between the upstream drain lines  20  downstream drain lines  26 . The upstream drain line  20  is connected to the inlet end of the witness drain valve by means of conventional hydraulic interface connections, such as threaded, swaged, or brazed. Similarly, the outlet end of the witness drain valve is connected to the downstream drain line  26 . The third leg of the witness drain valve  15  may be connected to a finger push valve  67 . At the interface of the witness drain valve  15  and finger push valve  67 , a hydraulic connection, such as a threaded or snap connector may be used to form a sealed junction between the drain valve  15  and finger push valve  67 . The third leg of the witness drain valve  15  is typically located in the vertical direction perpendicularly to the flow line formed by the connections between upstream drain lines  20 , witness drain valve  15 , and downstream lines  26 , and generally points in the direction of gravity downward for proper function of the finger push valve  67 .  
         [0020]    The witness drain valves  15  are shown in a functional configuration in FIGS. 1 and 1 a.  The functional aspects of the drain system in an engine compartment are shown during operation, and illustrate how the upstream drain line  20  is connected to a seal cavity (not shown) further upstream. As fluid starts leaking from the seal cavity, it flows down the upstream drain lines  20  toward the witness drain valve  15  forming the in-flow leakage stream  31 . Upon entering the inlet end  37  of the witness drain valve  15 , the fluid starts accumulating in the pre-designed cavity volume formed inside the witness drain valve  15 , generally defined by the interfaces between the upstream drain line  20 , downstream drain line  26  and finger push valve  67 . During normal operations as generally perceived by the present invention, the in-flow leakage stream  31  will begin filling the pre-designed cavity volume inside the witness drain valve  15  before there is flow to the downstream drain line  26 . During normal operation, before the pre-designed cavity inside the witness drain valve fills, the downstream drain line  26  remains practically dry. The accumulation of in-flow leakage stream  31  in the pre-designed cavity volume may be generally located on the upstream side of the connector of the finger push valve  67 . Since the in-flow leakage stream  31  is first captured in the pre-designed cavity volume inside the witness drain valve  15  before it flows further downstream, the engine maintenance crew, during routine maintenance, may identify the first sign of leakage from a particular seal cavity by using the finger push valve  67  to check if there is any accumulation in the pre-design cavity inside the witness valve  15 . When there is no accumulation inside the cavity of the witness drain valve  15  when the finger push valve is operated, it indicates a good sealing condition in the drain line and seal cavity. For minor leakage constituting insufficient fluid to fill the entire inside cavity during periods between two consecutive engine inspections, the total volume of the accumulated fluid inside the pre-design cavity volume inside the witness drain valve  15  can be drained out from the finger push valve  67 . The drained out volume can then be measured to be less than the pre-designed cavity volume. By quantifying the leakage volume during a known period, maintenance crews are provided with the necessary information to determine the seriousness of the leakage and aid in determining if maintenance is needed on a particular seal cavity.  
         [0021]    When the in-flow leakage stream  31  is at a high enough rate to fill the pre-designed cavity inside the witness drain valve  15  during two consecutive inspection periods, the in-flow leakage stream overflows the inside cavity completely and continues toward the connection of the downstream drain line  26 . The over-flow forms a downstream leakage stream  32  in the direction of the downstream drain line  26 . The downstream leakage stream  32  flows generally in the direction of the in-flow leakage stream  31 , thus, the witness drain valve  15  does not interfere or change the course of the leakage flow when interposed between the upstream drain line  20  and the downstream drain line  26 . This over-flow feature as conceived by the present invention overcomes some of the design and operational difficulties of prior art involving over board drain methods. This feature also eliminates the need for a standpipe or mast for centralized fluid leakage accumulation.  
         [0022]    It should be obvious to those skilled in the art that the pre-designed cavity inside the witness drain valve  15  can be tailored for individual seal cavities. For example, a critical seal may be designed with a small inside cavity volume within a witness drain valve so that the cavity will be filled quickly upon the reception of a small in-flow leakage stream  31  in a short period of time. The overflow in the inside cavity may indicate to the engine inspection crew that there is a need for maintenance. A different size cavity inside the witness drain valve can be used for a second drain line and seal corresponding to its leakage criticality. A complete drain system  10  as shown in FIGS. 1 and 1 a  may have several different drain lines with several different sizes of witness drain valves. In one of the embodiment of the present invention, the witness drain valves in a single drain system may have completely different inside cavity volumes depending on the different leakage rates of different seal cavities which are inspected on a routine basis. The drain system  10 , as conceived in the present invention, permits individual tailoring of different drain lines based on the respective criticality of seal cavities, thus, significantly increasing maintainability and reliability characteristics of engine operations. Additionally, this feature of the present invention surpasses prior art designs from the standpoint of safety and operational costs.  
         [0023]    In yet another embodiment of the present invention, witness drain valves  15  are connected upstream of drain lines  20  which are downstream from leaking seals cavities (not shown) within an engine compartment (not shown). The witness drain valves  15  are connected downstream of drain lines  26  which are up stream of a collector tank  30 . The connection between the downstream drain line  26  and the collector tank  30  may be by means of typical hydraulic interface connections such as threaded, swaged, or brazed. The drain line connector  39  connects the downstream drain line  26  to a drain line coupler  41  that is in communication with a drain line coupler panel  35 . The drain line coupler panel  35  hosts a series of drain line couplers  41  providing connections to all the drain lines that maintain flow communication with the collector tank  30 . On the back side of the drain line coupler panel  35 , a series of tank interface lines  43  may be provided to flow the leakage streams into the collector tank  30 .  
         [0024]    The collector tank  30  may be connected to an exhaust ejector line  40  for burning the waste fluid in the engine exhaust, a ground serviceable waste tank connection  24  and an overboard drain mast (not shown) to flow waste fluid to an external environment. The collector tank  30  may be mounted inside an engine compartment (not shown) within cowling (not shown) through a typical mounting bracket  22  with fasteners to an interface wall of an engine. As conceived in the present invention, the drain system  10  as shown in FIGS. 1 and 1 a  fits inside an engine cowling, thus avoiding the external exposure of a traditional drain leakage device. This characteristic of the present invention results in an aerodynamic drag reduction of as much as eight times or more in comparison to traditional systems. Because the drain system  10  may be completely inside the engine, one optional configuration is to install the witness drain valves  15  in close proximity to a maintenance door. This allows technicians to check for cavity drain leaks during engine service when the cowl is opened for other engine related tasks.  
         [0025]    Again referring to FIG. 1, each drain line  20  may be in flow communication with one of the witness drain valves  15 . In accordance with the present invention, the drain lines  20  may be connected to various locations within the engine where different kind of liquids, for example, hydraulic, oil and fuel, may accumulate. These liquids are drained away from accumulation areas, and either collected to determine the volume of leakage, or piped to collector tank  30  and then to exhaust ejector line  40 , or to an external environment through an overboard drain mast (not shown). This alternative option of flowing out the waste fluids to and through exhaust ejector line  40 , ground serviceable waste tank connection  24 , or overboard drain mast (not shown) is critical in the present invention because leakage of fluids has become an important issue in the design and certification of aircraft, both commercial and military. Regulators and operators are requiring that engine installations contend with the waste fluids without polluting the environment. These requirements are fully satisfied by the design features as conceived by the present invention.  
         [0026]    Referring now to FIG. 2, there is shown an enlarged view of the witness drain valves  15  of FIG. 1. In one embodiment, the witness drain valve construction may be comprised of a larger diameter reservoir  61  with drain connections  63  and  65  on both ends. A commercially available finger push valve  67  may be attached to the bottom of the reservoir  61 . As leakage liquids flow in from the first drain line connection  63  to the reservoir inlet end  69 , the leakage liquid start accumulating in the predetermined internal volume within reservoir  61 . Once the internal volume of reservoir  61  is full, the fluid continues along its original route by exiting from the outlet end of the reservoir  71  onto the second drain line connection  65 , and then toward the downstream collector tank  30  shown in FIG. 1. The addition of a witness drain valve to a drain line between a leaking seal and the collector tank does not alter the flow of waste fluid, nor does it create a need for other modifications in the existing engine drain system. The use of the present invention is thus non-intrusive and non-interrupting to a new or existing drain system design, making it fully adaptable to being retrofitted on an existing system with the objective of improving system reliability. In one of the embodiment of the present invention, the witness drain assembly can be a simple, retrofittable, improvement to an existing engine drain system. This will become more apparent as details of the witness drain assembly are further described below.  
         [0027]    As shown in FIG. 2, the witness drain valve  15  has no need for a stand pipe since it overflows at the top of the internal volume of the reservoir  61  instead of the bottom as required with a drain mast. This feature allows use of a commercially available valve instead of a customized standpipe valve. Elimination of the standpipe requirement is also beneficial in that there is no need to design a unique compact space to avoid excessively large aerodynamic drag. Also, since the witness drain valve  15  is situated inside the engine cowling, physical size and shape requirements may be much less restrictive.  
         [0028]    Referring further to FIG. 2, the finger push valve  67  can be used to drain the accumulated fluids when necessary by pushing the spring loaded end  67 A at the bottom end of the finger push valve. Finger push valves  67  are commercially available standard parts, most commonly used for aircraft fuel system sump drains. Flight crews normally open those valves and use a transparent recipient to inspect for water condensation in the fuel tank. The same process may be followed in the present invention to determine the amount of accumulated fluids, types of fluids, and in some instances the rate of waste fluid accumulation. Integration of commercially available finger push valves  67  into the witness drain valve  15  system provides a low cost engine diagnostics approach, improves maintainability of the witness drain valve system by the use of readily available commercial replacement parts, and enhances engine operational safety by detecting abnormally excessive leakage of draining fluid.  
         [0029]    [0029]FIG. 3 is an elevational side view of one embodiment of the present invention. FIG. 4 is a cross-sectional view, taken along section lines A-A of FIG. 3, to further depict details of the present invention. The witness drain valve  70  may be comprised of a flow channel with variable diameters along the flow direction. The first diameter at the upstream end  71 A of the flow channel provides the interface to the upstream drain pipe (not shown) connected to a plurality of leaking seals/fittings (not shown). The drain fluids enter the witness drain valve  70  through the upstream end  71 A. A first circumferential shoulder  72  may be provided for the flow transition into a second diameter  73  of the witness drain valve  70  in the downstream direction. The first circumferential shoulder  72  reduces the flow channel cross section to allow a seal (not shown) to be positioned against the first circumferential shoulder  72  when connecting the witness drain valve  70  to the upstream drain pipe (not shown). The diameter of the flow channel further changes as it proceeds to the downstream end. The transition to larger diameter may be accompanied by a second circumferential shoulder  74  then a third diameter  79 , generally larger than the second diameter  73 . The larger third diameter  79  creates a chamber or cavity  76  toward the longitudinal center  77  of the witness drain valve  70 . The cavity  76  may be primarily located below the axial flow centerline  75  of the drain leakage flow. A third diametric transition occurs along the flow direction toward the downstream end. This third transition may be accompanied by a third circumferential shoulder  78  which effectively reduces the flow channel toward the downstream direction producing a fourth diameter  80  along the flow channel. A fourth diametric transition at the downstream end of the witness drain valve  70  may be accomplished by a fourth shoulder  81  at the downstream end  82 . Fourth shoulder  81  provisionally provides a seat for connecting the witness drain valve  70  and downstream drain valve (not shown) which may be connected to a collector tank  30 , shown in FIG. 1.  
         [0030]    Still referring to FIG. 4, at the bottom of cavity  76 , a commercially available finger push valve  67  may be attached along the longitudinal direction. A hollow bolt  84  and a housing  85  are inserted through the top of opening  83  of cavity  76 . The hollow bolt  84  may be pre-loaded by means of a spring  86 . The housing  85  may be secured to the interior circumferential wall of opening  83 . As the fluids flow through cavity  76 , it begins to accumulate at the bottom portion of said cavity  76 . The bottom portion of cavity  76  also corresponds to the top of the opening  83  and the upper end of hollow bolt  84 . When the spring loaded hollow bolt  84  is pushed, the accumulated fluids are drained out of the cavity providing a quick and accurate way to determine the amount of leakage, types of leakage and rate of leakage. FIG. 4 further illustrates how the finger push valve  67  interfaces with the witness drain valve  70 . The finger push valve can be secured via thread engagement to top of opening  83  at the bottom portion of cavity  76  according to one embodiment of the present invention. The witness drain valve  70  variable diameter flow channel as shown in FIG. 4 may be a single component manufacture using a process such as metal forging or injection molding to produce a low-cost product.  
         [0031]    Although the present invention has been described in considerable detail with reference to certain versions thereof, other versions are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the versions contained therein.