Abstract:
A sampling apparatus is described which contains a cylindrical member containing first and second annular recesses on opposing sides thereof and an opening therethrough. At least one resilient sealing member is disposed in each of the recesses. At least one foraminous support disposed in the cylindrical member over the opening adjacent the first recess. A porous medium is adjacent the foraminous support between the foraminous support and the sealing member. A compression housing is provided which contains first and second housing members for compressing the cylindrical member, sealing members, foraminous support and porous medium between the first and second housing members and a clamping means for compressing the sealing members to form a fluid tight seal. A fluid sample is fed by means of a fluid inlet in the first housing member which inlet is in flow communication with the opening, porous medium and foraminous support. The fluid sample is also in flow communication with a fluid outlet in the second housing member. The clamping means is specially adapted to provide rapid insertion and removal of porous media from the sampling apparatus.

Description:
FIELD OF THE INVENTION 
     The invention relates to an apparatus and method for making filter patch samples and for determining properties of particulates in a fluid. 
     BACKGROUND OF THE INVENTION 
     Rotating and reciprocating equipment is subject to failure before the economic life of the equipment has been reached due to a variety of reasons. One reason for premature failure is misalignment of the equipment causing excessive wear to moving parts. Another cause of failure is an increase in particulate material in fluids used to lubricate the moving parts of the equipment. Still another cause of failure is due to chemical changes in tile lubricating fluid compositions caused by moisture, excessive heat or other liquid contaminants. 
     Despite the advances made in tile field of lubricant analysis, there continues to be a need for the ability to precisely quantify the level and size distribution of particulate contaminants in lubricating fluids as well as identifying the particulates which may cause premature failure of the equipment so that corrective action can be taken at the earliest possible date. There is also a need for a relatively simple analytical device which can be used in a field setting to determine the quantity of contaminants and the size distribution thereof in an oleaginous fluid with a relatively high level of confidence. 
     SUMMARY OF THE INVENTION 
     The present invention provides an analytical device for determining various quantitative and qualitative properties of particulate contaminants in a fluid which is relatively simple and which can be used on a variety of fluids for particulate analysis thereof. In one aspect the invention provides a sampling apparatus which includes a compression housing containing first and second housing members. A filter media holder having opposed surfaces and having an opening therethrough is disposed between the first and second housing members. At least one resilient sealing member is disposed adjacent each of the surfaces of the holder for scaling between the holder and the first and second housing members. At least one foraminous support is adjacent at least one surface of the holder. A porous medium is disposed adjacent the foraminous support and a medium sealing member is adjacent the porous medium and the first housing member. A clamping means is attached to the first and second housing members for clamping the holder and sealing members between the first and second housing members for forming a fluid tight seal thereby defining a closed volume through which fluids may flow. The first housing member includes a fluid inlet which is in flow communication with the opening, porous medium and foraminous support. The second housing member includes a fluid outlet which is in flow Communication with the opening, porous medium and foraminous support, whereby a fluid flow path is formed from the inlet, through the porous medium and out the outlet for depositing particulates on the porous medium to thereby produce a sample of the particulates in the fluid. 
     In another aspect, the invention provides an optical sample preparation device which includes a fluid inlet reservoir connected in flow communication with an inlet port attached to a filter patch device. The filter patch device includes a cylindrical member containing first and second annular recesses on opposing sides thereof and an opening therethrough in flow communication with the inlet port. At least one resilient sealing member is disposed in each of the recesses. At least one foraminous support is disposed in the cylindrical member over the opening adjacent the first recess. At least one porous medium is disposed adjacent the foraminous support between the foraminous support and the sealing member. A compression housing containing first and second housing members maintains the cylindrical member, sealing member, foraminous support and porous medium in compression between the first and second housing members by use of a clamping means for compressing the sealing members to form a fluid tight seal. A fluid inlet in the first housing member is in flow communication with the inlet port, the opening, the porous medium and the foraminous support. A fluid outlet in the second housing member in flow communication with the opening, porous medium and foraminous support. A vacuum source is connected in flow communication with the field outlet for drawing a sample through the sample preparation device. 
     Another aspect of the invention provides a method for preparing a filter patch sample for optical analysis which includes providing an optical sample preparation device containing a fluid inlet reservoir connected in flow communication with an inlet port attached to a sampling apparatus according to the first aspect of the invention. According to the method, a fluid sample to be analyzed is fed to the fluid inlet reservoir of the sampling apparatus. A pressure is applied to the sample with the vacuum source to draw the fluid through the porous medium of the sampling apparatus. Upon drawing all of the fluid in the inlet reservoir through the sampling apparatus, a solvent or gas is flowed through the porous medium so as to remove residual fluid therefrom. Upon removal of residual fluid from the medium, the clamping means is unclamped in order to remove the porous medium from the medium holder. 
     Still another aspect of the invention provides a method for determining quantitative or qualitative properties of particulate solids in an oleaginous. material. The method includes providing an oleaginous fluid sample, feeding the fluid sample to a fluid sample holder having a defined volume in flow communication with a dual filter patch device containing first and second porous media, applying a reduced pressure to the filter patch device to draw tile fluid sample sequentially through the porous media, removing residual fluid sample from the porous media using a solvent for the fluid, and optically observing particulate material on the porous media. 
     The invention provides a compact, highly effective apparatus for obtaining filter patch samples for quantitative and/or qualitative analysis. The apparatus provides a liquid tight sealing means and may be used to provide multiple filter patch samples essentially simultaneously for determination of properties of contaminants having different particle sizes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features and advantages of the invention will become apparent by reference to the detailed description when considered in conjunction with the figures, which are not to scale, wherein like reference numbers indicate like elements through the several views, and wherein: 
     FIG. 1 is a perspective view, not to scale, of a sampling apparatus according to the invention; 
     FIG. 2 is a cross-sectional view, not to scale, of an inlet housing for a sampling apparatus according to the invention; 
     FIG. 3 is a cross-sectional view, not to scale, of an outlet housing for a sampling apparatus according to the invention; 
     FIG. 4 is a cross-sectional view, not to scale, of a filter media holder for a sampling apparatus according to the invention; 
     FIG. 5 is a cross-section view not to scale of an inlet sample reservoir for a sampling apparatus according to the invention; 
     FIG. 6 is an exploded side view of sealing members, support members and filter media for a sampling apparatus according to the invention; 
     FIG. 7 is a simplified schematic flow diagram of a process for making filter patch samples according to the invention; 
     FIG. 8 is a side elevational view of a support frame and base for a sampling apparatus according to the invention; and 
     FIG. 9 is a rear elevational view of a support frame and base for a sampling apparatus according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In order to prepare one or more filter patches for determining quantitative and/or qualitative particulate contaminant in a liquid sample, a device  10  as shown in FIG. 1 is preferably used. The device  10  includes a support base  12  to which is attached a support frame  14  having two L-shaped sections  16  and  18 . Section  16  is attached to the base  12  by means of attachment devices  20  such as bolts, screws, adhesives, welding and the like. The frame  14  and base  12  may be made of the same materials or different materials which may include wood, steel, aluminum, fiberglass, glass, rigid plastics and the like. 
     A sampling apparatus  22  is attached to a vertical member  24  of the frame  14 . The sampling apparatus  22  includes an inlet housing  26  fixedly attached to memliber  24 , a moveable outlet housing  28  aid a filter media holder  30  disposed between the inlet housing  26  and the outlet housing  28 . A clamping device  32 , such as an over-center clamp provides a positive locking and compression arrangement for making a fluid-tight seal during a filtering operation. The clamping device  32  includes a first arm  34  rotatably attached at a first end  36  to the outlet housing  28  and a second arm  38  having a first end  40  attached to a handle  42 . The distal end  44  of handle  42  is pivotally attached to the inlet housing  26  by means of an axle  46  that is linked by a spindle  48  to a distal end  50  of the first arm  34 . Rotation of the handle  42  and second arm  38  about axle  46  causes the first arm to move outlet housing  28  vertically toward or away from tile inlet housing  26  thereby clamping or releasing media holder  30 . As shown in FIG. 1, the clamping device  32  has two sets of first arms  34  and second arms  38 , joined by handle  42  and pivotally attached to opposite sides of the inlet and outlet housings  26  and  28 . 
     In order to more precisely align the inlet and outlet housings  26  and  28  for a fluid-tight seal, it is preferred to guide the outlet housing  28  during the clamping step along tracks, slide bars or guide rods  52  and  54 . Housing movement stop lugs, such as lug  56  attached to rod  52 , effectively limit the distance the second housing  28  can travel along rod  52 . The rods  52  and  54  should be long enough, however, to allow sufficient spacing between housings  26  and  28  when inserting and removing the filter media holder  30 . 
     Construction details of a preferred inlet housing are shown in cross-section in FIG.  2 . The inlet housing  26  consists of a substantially rectangular cast or machined block  27  containing an inlet port  58  connected in flow communication with an inlet fluid cavity  60  which has a generally frustum conical shape. The side members of tile fluid cavity  60  preferably make an angle  62  of about 60° with a vertical axis  64  vertically through the fluid cavity  60 . The cavity  60  preferably has a volume ranging from about 0.5 to about 5 milliliters. 
     A preferred outlet housing  28  is shown in cross-sectional in FIG.  3 . The outlet housing  28 , like the inlet housing  26 , consists of a substantially rectangular cast or machined block  66  containing an outlet port  68  which is in fluid flow communication with a fluid collection cavity  70  which has a generally frustum conical shape. The side members of collection cavity  70  preferably make an angle  72  of about 60° with a vertical axis  74  through the collection cavity  70 . Raised ledge  76  assists in locating and holding a sealing member for forming a fluid tight seal between the upper surface  77  of outlet housing  28  and the filter media holder  30 . 
     A preferred filter media holder  30  is shown in a cross-sectional view in FIG.  4 . The Filter media holder  30  is a substantially cylindrical holder which nay be machined or cast from a solid material such as aluminum, steel, plastic and the like. The holder  30  preferably has a thickness ranging from about 0.2 to about 0.5 inches and an outside diameter ranging from about 1 to about 2.0 inches. The holder has first and second annular recesses  78  and  80  respectively therein for support of filter media, filter media support screens and filter media sealing members. Details of the media, screen and sealing members are described in detail with reference to FIG. 6 below. Tile first annular recess  78  preferably has a diameter ranging from about 0.875 to about 1.125 inches and the second annular recess  80  preferably has a diameter ranging from about 0.95 to about 1.05 inches. The difference in diameter of the annular recesses assists in placing the holder  30  in the correct orientation between the inlet and outlet housing members  26  and  28 . The depth D 1  of annular recess  78  preferably ranges from about 3.5 to about 5.5 millimeters and the depth D 2  of annular recess  80  preferably ranges from about 1 to about 3 millimeters. It is preferred that the depths D 1  and D 2  be sligthly less than the combined thicknesses of the sealing members, filter media and support screens so that there is sufficient compression of the sealing members between the inlet and outlet housings to form a fluid tight seal. 
     Referring again to FIG. 1, filter patch samples are obtained for a fluid sample by introducing a fluid into fluid reservoir  82  which is attached to the upper L-shaped section  18  of frame  14 . A cross-sectional view of fluid reservoir  82  is shown in FIG.  5  and includes a substantially cylindrical shell  84  defining a fluid cavity  86  which preferably has a fluid volume ranging from about 10 to about 100 milliliters in order to flow a fixed amount of fluid through the filter media when making the filter patches so that the concentration of particulate in the fluid may be determined. The fluid flows from the reservoir  82  through an outlet port  85  and through an inlet conduit  86  (FIG. 1) to the inlet port  58  of inlet housing  26  (FIG.  2 ). 
     Details of the filter media, media support and sealing members are shown in FIG.  6 . Preferred filter media  90  and  92  include, glass fiber, polymeric, paper or cellulosic filter paper having a wide range of pore size openings or particle size retention. in this regard it is particularly preferred to use filter media  90  having a pore size ranging from about 5 to about 30 microns, preferably from about 6 to 10 microns and filter media  92  having a pore size ranging from about 0.5 to about 20 microns, preferably from about 1 to about 5 microns. 
     Because the Filter media is typically relatively thin and flexible it is preferred to support the filter media with support screens  94  and  96 . The support screens may be made of a variety of thin relatively rigid materials having a mesh size ranging from about 50 microns to about 50 millimeters. Materials for the support screens  94  and  96  include metals, plastics, fiberglass and the like. Particularly preferred support screens  94  and  96  are stainless steel screens having a thickness ranging from about 5 to about 15 mils and having openings therethrough ranging from about 50 to about 60 mils in diameter. 
     In order to form a fluid tight seal between the filter media  90  and  92  and the media holder  30 , and between the holder  30  and the inlet housing  26 , sealing members  98  and  100  are used. The sealing members  98  and  100  are preferably elastomeric materials selected from fluoropolymer or synthetic rubber. Each of the sealing members  98  and  100  have a thickness ranging from about 2 to about 3 millimeters and a diameter ranging from about 20 to about 60 millimeters such that the sealing members  98  and  100  sealingly engage the media and support screen within annular recess  78  in media holder  30  (FIG.  4 ). Sealing member such as  98  also seals against tile surface  81  of inlet housing  26  (FIG.  2 ). 
     An elastomeric o-ring or gasket  102  is preferably inserted in annular recess  80  to seal between the media holder  30  and surface  77  of outlet housing  28 . In this regard, it is particularly preferred that the side walls of annular recess  80  circumscribe raised ledge  76  of outlet housing  28  and so that gasket  102  is retained within the inner circumference of raised ledge  76 . The thickness of sealing member  102  preferably ranges from about to about 2 to about 3 millimeters and the diameter thereof preferably ranges from about 20 to about 60 millimeters. While it is preferable to position the sealing  21  members  98 ,  100  and  102  within the recesses  78  and  80 , they may be placed elsewhere according to the defined function thereof, namely, forming seals between the media holder  30  and the housings  26  and  28 . 
     After passing through the filter media, the fluid exits the outlet housing  28  through outlet port  68  (FIG. 3) and outlet conduit  88  (FIG.  1 ). Inlet and outlet conduits  86  and  88  may be any suitable material including rigid tubes or flexible hoses. The fluid may be caused to flow from the reservoir  82  through the inlet and outlet housings  26  and  28  and filter media  90  and  92  by gravity or preferably by applying a reduced or subatmospheric pressure to the fluid flow path by connecting a vacuum pump to outlet conduit  88 . If a vacuum pump is used, it is preferred to use a pulp which has a flow volume of at least about 10 scfm in order to draw the sample through the apparatus in a relatively short period of time. Typically, the entire fluid sample is preferably drawn through the filter media in no more than about 120 seconds. 
     A simplified schematic flow diagram of a dual filter patch apparatus including dual filter media is shown in FIG.  7 . Fluid  104  is introduced into fluid reservoir  82  and is caused to flow through filter media  90  and  92  through conduits  106 ,  108  and  110  by applying a reduced pressure to the conduits  106 ,  108  and  110 , filter media  90  and  92  and fluid reservoir  82  by action of a vacuum pump  112 . In order to prevent liquid from flowing into the vacuum pump  112 , a liquid entrainment vessel or knock-out pot  114  is used to capture liquid  1   16  which may be drained therefrom through drain conduit  118 . 
     Once a predetermined amount of fluid has been drawn through the filter media, the filter media  90  and  92  may be rinsed with water or a solvent to remove traces of the fluid from the media. The media holder  30  containing the filter patch samples is then removed from between the inlet and outlet housings  26  and  28  by rotating handle  42  so that outlet housing  28  moves vertically away from inlet housing  26  along slide rods  52  and  54  (FIG. 1) as shown in FIG.  8 . The Filter media  90  and  92  containing captured particulate from the fluid may be separated from the sealing members  98  and  100  and support screens  94  and  96  (FIG. 6) and dried. The amount and size distribution of particles captured by the filter media  90  and  92  may be determined for a fixed volume of fluid by any conventional optical or visual techniques. 
     As shown in FIG. 8, as the handle  42  is rotated in a clockwise direction, the outlet hosing  28  moves vertically downward along slide rod  52 . As the housing  28  moves downward, the conduit  88  connected to the outlet port  68  of the housing  28  also moves downward. In order to permit the conduit  88  to moved, it is preferred that the vertical flame member  24  contain a slotted opening  120  (FIG. 9) for movement therein of conduit  88  during rotation of handle  42 . Circular slot  122  in frame member  24  provides an opening for conduit  86  attached to outlet port  85  of reservoir  82 . 
     The device as described above may be used to make a single filter patch sample or to make two filter patch samples essentially simultaneously thereby reducing the time required to prepare multiple samples having a different range of particulate retention. In this regard it is preferred to use a larger pore filter paper  90  in the upper position of the filter media stack (FIG. 6) and a smaller pore filter paper  92  in the lower position of the filter media stack. This arrangement provides a means for more effective flow through the filter media so that the time required to prepare the filter patch samples is minimized. 
     In yet another aspect of the invention, various techniques may be used in combination with the above described device for identifying the type of particles in a fluid sample and determining their size distribution and concentration. A method for identifying the type of particles deposited on a substrate using optical colored filters is described, for example, in U.S. Pat. No. 4,047,814 to Westcott, incorporated herein by reference as if fully set forth. 
     Other methods for determining the identity, concentration and particle size distribution of particulate or contaminants in a fluid include preparing standard filter patch samples containing known particulates of known size distribution and/or concentration and comparing the standards to filter patch samples made from a fluid to be analyzed. lie comparison of the filter patch samples and standard filter patch samples may be made with the unaided eye, by use of a microscope, microscopic comparison with standard photographs or by using electronic image analysis techniques. Filter patch samples made according to the invention may also be compared by use of a weighing balance, an x-ray fluorescence spectroscopy device, magnetometer device, Hall effect flux analyzer, atomic emission spectrometer, or other devices suitable for analysis of different types of particulate material. In addition, the particulates on the filter patch samples may be re-suspended in a solution and the solution passed through an in-line optical contamination meter or the re-suspended particles may be chemically treated or reacted with solvents or other chemical reagents. 
     A particularly preferred use of the device according to the invention is to determine the quantity and/or size distribution of ferrous particles in a fluid sample. One method for determining such particle size and concentration is to first isolate the ferrous particles from the fluid sample such as by stirring the sample in the fluid reservoir  82  with a magnetic rod to remove the ferrous particles from the fluid before filtering the fluid sample through the filter media in media holder  30 . The remaining fluid and particles are then filtered through the media as described above and the particles concentration, size distribution and identity may determined as by a variety of techniques including the methods set forth in U.S. Pat. No. 4,047,814 to Westcott. 
     The ferrous particles attached to the magnetic rod are then reslurried in an appropriate fluid and placed in the fluid reservoir  82  for filtering through fresh filter media in media holder  30 . Tile resulting filter patches may be analyzed by well known techniques to determine the size distribution and concentration of ferrous particles which were in the original fluid sample. 
     While the invention has been described in detail, it is to be expressly understood that various changes of form, design or arrangement may be made to the invention by those skilled in the relevant art without departing from the spirit and scope of the invention. Therefore, the above mentioned description is to be considered exemplary, rather than limiting, and the scope of the invention is defined by the following claims.