BACKGROUND OF INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    Gases, such a natural gas, are often analyzed by gas chromatographs. Other chromatographs are used to analyze liquids. Some gases may have entrained liquids that cannot be analyzed by gas chromatographs. One use of the present invention is to separate liquids from gases so the gas can be analyzed by a gas chromatograph.  
           [0003]    2. Description of Prior Art  
           [0004]    Spot sampling is a procedure that is well known in the natural gas industry and is commonly used. For example, the Gas Processors Association (“GPA”) has established standard 2166 for proper spot sampling techniques. Spot samples of natural gas are taken in the field from a pipeline and placed in a sample cylinder. The sample cylinder and the gas sample are then transferred from the field to a laboratory for analysis, frequently by a gas chromatograph. Because gas chromatographs cannot analyze liquids, it is desirable to try and keep liquids out of spot samples or in the alternative, alert the laboratory when unavoidable liquids are encountered so appropriate measures can be taken to safeguard the chromatograph.  
           [0005]    Welker Engineering Company of Sugar Land, Tex., the assignee of the present patent application, has previously sold a sight glass without a filter called the model SG3. The SG3 sight glass was primarily used with odorant injection systems to provide visual confirmation that the odorant was being properly injected into the system. The SG3 was also used to provide visual confirmation in other chemical injection systems that used glycol. In some situations, the SG3 has been used at a spot sampling station to visually determine if liquid was being transferred into a sample cylinder. The SG3 did not prevent liquids from entering a sample cylinder.  
           [0006]    Welker Engineering Company has also previously sold a filter without a sight glass called the LE2. The LE2 filter has been used at spot sampling stations to keep liquids out of sample cylinders. However, the LE2 did not provide any visual information to the personnel that were taking the spot sample.  
           [0007]    Other companies, such as A+ Corporation of Prairieville, La. also sell liquid separators and filters to keep liquids out of sample cylinders at spot sampling stations. Some of these products from A+ are described in the company web site (www.apluscorporation.com). Pages from this web site are included in the Information Disclosure Statement filed concurrently herewith. In summary, the prior art filters and liquid separators from both Welker Engineering Company and A+ Corporation do not incorporate a sight glass. There is a need to incorporate a sight glass with a liquid separator so operators may modify their technique while a spot sample is being taken. Some liquids can be eliminated through the modification of spot sampling techniques; other naturally occurring liquids many be unavoidable and will persist even if the spot sampling techniques are modified.  
           [0008]    When a spot sample is being taken, improper technique can lead to the unwanted creation of liquids due to the Joule-Thomson effect. Running natural gas through valves and/or a sample cylinder during a spot sampling operation can create a sharp pressure drop which may chill the gas and lead to condensation of unwanted liquids. If an operator can visually observe that liquids are present, adjustments may be made to the sampling technique that will reduce or eliminate the creation of unwanted liquids. A more representative spot sample will be taken if condensation does not occur during the sampling operation which can lead to creation of unwanted liquids.  
           [0009]    However, even if proper techniques are used, some natural gases have entrained liquids that cannot be eliminated by adjusting spot sampling techniques. In these circumstances, it is necessary to have a liquid separator to keep the sample dry for the gas chromatograph. There is a need for a liquid separator that incorporates a sight glass to enhance spot sampling operations.  
         SUMMARY OF INVENTION  
         [0010]    The present invention is a combination sight glass and liquid separator. The present apparatus may be used at spot sampling stations to adjust technique and eliminate liquids from the sample. The present invention includes a high pressure glass window that allows the apparatus to operate at pressures up to 2,000 psi. An optional protective shield protects the glass window from inadvertent damage. A membrane filter is porous to gas and substantially impermeable to liquids. A polytetrafluoroethylene membrane is positioned on a porous sintered stainless steel support. Other membranes and supports may also be suitable provided they allow the gas to pass and stop the liquids. A drain is positioned in the liquid separator to drain liquids from the apparatus. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0011]    [0011]FIG. 1 is a cross-section view of the liquid separator with integral sight glass.  
         [0012]    [0012]FIG. 2 is a cross-section view of the liquid separator with integral sight glass along the line  2 - 2  of FIG. 1. 
     
    
     DETAILED DESCRIPTION  
       [0013]    [0013]FIG. 1 is a cross-section view of the liquid separator with integral sight glass which is generally identified by the numeral  10 . The inlet cap  12  threadably engages the upper section  14  of the body  15 . The inlet cap  12  defines an inlet  16  and an outlet  18 . An o-ring  20  seals the inlet cap  12  to the body  15 . In the preferred embodiment, the o-ring is formed from Viton® a brand of fluoroelastomers produced by Du Pont de Nemours, E. I. &amp; Company of Wilmington, Del. Other elastomeric seals may also be suitable for use in this invention. A drain cap  22  threadably engages the lower portion  24  of the body  15 . The drain cap  22  defines a drain  26 . A drain valve, not shown, is connected to the drain  26  and is normally in the closed position. When fluid accumulates in the liquid separator  10 , the drain valve, not shown, may be opened to drain the fluid. An o-ring  28  seals the drain cap  22  to the body  15 . In the preferred embodiment, the o-ring  28  is also formed from Viton brand fluoroelastomers; however, other elastomers may also be suitable for use in this invention. A glass cylinder  30  is captured between the inlet cap  12  and the drain cap  22  in the body  15 . In the preferred embodiment, the glass is Gold Dot brand tempered glass from Corning of Corning, N.Y. Other brands of glass may be suitable for use in this invention provided they are capable of withstanding the operating pressure of the fluids that pass through the apparatus  10 .  
         [0014]    A filter assembly  32  threadably engages the inlet cap  12  at filter assembly port  34 . An o-ring  36  seals the filter assembly  32  to the inlet cap  12 . In the preferred embodiment, the o-ring  36  is also formed from Viton brand fluoroelastomers; however, other elastomers may also be suitable for use in this invention.  
         [0015]    The filter assembly includes a membrane  38  positioned on a support  40 . The membrane is permeable to gases and impermeable to liquids. In the preferred embodiment, the membrane is formed from Teflon® brand tetrafluoroethylene fluorocarbon polymer produced by Du Pont de Nemours, E. I. Company. However, other membranes may be suitable in this invention provided that they achieve separation of gas from liquids. For example, Tyvek® brand material from Du Pont de Nemours, E. I. Company may also be suitable as well as Millipore four micron filter paper from Pall Specialty Materials, Charlotte, N.C. Nylon and/or cat gut may also be suitable. The only requirement for the membrane is that it be gas permeable and impermeable to liquids.  
         [0016]    In the preferred embodiment, the porous support  40  is formed from sintered stainless steel. However, other supports are within the scope of this invention provided that they allow gas to pass to the outlet  18  and support the membrane  38 .  
         [0017]    An end cup  42  contains the membrane  38  against the support  40 . A bolt  44  threadably engages the free end  46  of the support  40  and holds the end cup  42  and the membrane  38  against the support  40 . A chamber  48  is defined by the inside surface of the glass cylinder  30 , the inlet cap  12  and the drain cap  22 . The filter assembly  32  is positioned in the chamber  48 . The filter assembly has a hollow bore  50  that allows gas to flow from the chamber  48 , through the filter assembly  32  to the outlet  18 .  
         [0018]    The body  15  defines opposing windows  52  and  53  that allow a technician positioned outside the liquid separator  10  to look into the chamber  48  to determine the presence of liquids, if any. In some situations, the technician can see the formation of liquids on the outside surface  39  of the membrane  38 . In other situations, the liquid will pool in the bottom  49  of the chamber  48  and will rise to a level that can be seen through the windows  52  and  53 . Liquids are undesirable when samples are to be analyzed by gas chromatographs. To protect the glass cylinder  30  from inadvertent damage, a transparent plastic shield  54  is mounted on the exterior of the body  15  and is positioned to cover the windows  52  and  53 . In the preferred embodiment, the plastic shield is formed from Plexiglas® brand thermoplastic poly(methylmethacrylate)-type polymers sold by Rohm and Haas Company of Philadelphia, Pa. However, other polymers that are transparent and shatter resistant may also be suitable in this invention.  
         [0019]    [0019]FIG. 2 is a section view of the liquid separator with integral sight glass  10  taken along the line  2 - 2  of FIG. 1. The protective shield  54  is positioned on the outside of the body  15  to provide protection to the glass cylinder  30 . Windows  52  and  53  are formed in the body  15  to allow a technician positioned outside the liquid separator  10  to look through the transparent shield  54  and the transparent cylinder  30  and see inside the chamber  48 . The primary purpose of being able to look inside the chamber  48  is to detect the presence of liquids so that the sampling technique may be modified to possibly eliminate the creation of liquids. Some naturally occurring liquids may not be eliminated by modification of sampling technique, so the separator is an integral part of this invention to consistently produce dry samples for analysis by a gas chromatograph.  
       Operation of the Preferred Embodiment  
       [0020]    Pipeline gas enters the liquid separator with integral sight glass through the inlet  16  and passes through the inlet cap  12  to the chamber  48 . The drain  26  is connected to a valve that is normally in the closed position. The pipeline gas may have liquids therein. As the gas passes through the filter assembly  32 , any unwanted liquids accumulate on the outside of the filter assembly and eventually fall by gravity to the bottom of the chamber and to the drain  26 . A technician positioned outside the apparatus can look through the window  52  and see the presence of liquids on the outside of the filter assembly. This gives the technician the opportunity to adjust the spot sampling technique to possibly eliminate the liquids. The gas passes through the filter assembly  32  and the bore  50  into the outlet  18  which is connected to a sample container, not shown. From time to time, it may be necessary to open the drain valve, not shown, to discharge accumulated liquids from the apparatus.  
         [0021]    A spot sampling station is positioned proximate a natural gas pipeline, typically in a remote location. The spot sampling station includes a manifold connected to a probe in the pipeline by tubing and valves. These valves are typically in the off position. A pipeline technician will travel to the spot sampling station to take a spot sample. This merely provides a snapshot of the gas traveling through the pipeline on the given day and moment when the sample is taken.  
         [0022]    The technician brings a sample container to the spot sampling station. An empty sample cylinder is commonly used for this purpose. The empty sample cylinder typically has an inlet valve on one end and an outlet valve on the other end. The empty sample cylinder is connected to the manifold and both valves on the cylinder are opened. Valves on the manifold are then opened to blow gas through the empty sample cylinder.  
         [0023]    After the sample cylinder has been purged, the outlet valve on the sample cylinder is closed which raises the pressure in the sample cylinder to pipeline pressure. The inlet valve on the sample cylinder is then closed, isolating the sample cylinder from the pipeline. The outlet valve on the sample cylinder is then opened, thus exhausting the pressurized natural gas in the sample cylinder to atmosphere. This procedure is then repeated several times. During this fill and discharge process, the technician should look into the liquid separator to see if liquids are present in the chamber.  
         [0024]    If liquids are present in the chamber, modifications can be made to the sampling technique, to possibly eliminate creation of the liquids. These modifications are well known to those skilled in the art and involve adjustments to the outlet valve on the sample cylinder and perhaps elsewhere on the spot sampling station. Unfortunately, not all liquids can be eliminated so the liquid separator is an integral part of this invention to assure dry samples. After the sample has been taken, the sample cylinder is taken to a laboratory for analysis by gas chromatographs and perhaps other instruments.
The liquid separator with integral sight glass separates liquids, if present, from gases and allows a technician to visually confirm the presence or absence of liquids in the gas. The present invention is typically used when taking a spot sample from a natural gas pipeline. Spot samples of natural gas are often analyzed by gas chromatographs which do not tolerate the presence of liquids in a sample. If the technician visually confirms the presence of liquids, adjustments to the spot sampling technique can be made to possibly eliminate the creation of such liquids due to poor technique.