Abstract:
A volumetric sample adjustment assembly located outside of a process line to facilitate rapid changes in the sample volume without having to remove the sampler from the process line, from process pressure or without having to manually disassemble the collection head assembly, like some prior art devices. The volumetric sample adjustment assembly has a “gross adjustment” assembly to vary the gross sample volume within the predetermined range. This gross adjustment assembly uses a removable pin to vary the sample size. This removable adjustment pin may be removed and replaced in different positions to change the gross volume of the sample on short notice and without having to remove the sampler from the process line, from process pressure or without having to manually disassemble the collection head assembly.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to and incorporates herein by reference U.S. Provisional Patent Application Ser. No. 61/839,993 filed on Jun. 27, 2013. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Samplers are used to take periodic samples from liquids flowing through a process line, e.g. a pipeline. Such liquids include water, crude oil, refined products including: gasoline, diesel, jet fuel, kerosene, etc., natural gas liquids including: liquid ethane, liquid propane, liquid butane, liquid iso-butane, etc. These samplers typically move a shaft up and down to take a sample which is then accumulated with prior samples in a sample collection container or vessel. This movement is sometimes referred to as a “stroke” in the industry. Further, some samplers are inserted and withdrawn from a process line through an isolation valve while the process line remains under pressure and in operation. In some of these samplers, the sample collection head assembly could be adjusted to vary the volume of sample, but this required removal of the sampler from the process line, removal from process pressure and manual disassembly of the sample head assembly which was time consuming, expensive and disruptive to the sample collection process. There is a need to be able to adjust the volume of a sample while the sampler is under process line pressure and while the process line is in operation. 
         [0003]    Some liquid pipelines sequentially transport product from different customers and/or from different storage tanks. In one example, switching from different sources of product may occur as frequently as every 105 seconds to intervals as long as three days. Obviously, the switching interval varies and can vary widely beyond the intervals mentioned above. 
         [0004]    Some sampling operations take seven liters of sample from each aliquot of product flowing through the line. If the switching interval is long, the volume of sample taken during each stroke of the sampler will be comparatively small. If the switching interval is short, the volume of sample taken during each stroke of the sampler with be comparatively large, in order to accumulate seven liters of sample. There is a need to be able to quickly and easily adjust the volume of sample taken during each stroke of the sampler, without delay or down time and without having to manually disassemble the sample head assembly. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention is a volumetric sample adjustment assembly located outside of a process line to facilitate rapid changes in the sample volume without having to remove the sampler from the process line, from process pressure or without having to manually disassemble the collection head assembly, like some prior art devices. The present invention is sometimes referred to as an “external” sampler because the sample adjustment assembly is located external of the process line. The external sample volume adjustment assembly can be designed to operate within a predetermined range which is usually set by the customer and/or the specific application. For example, one predetermined range could be from near zero to 11 cc. As another example, the predetermined range could be from near zero to 24 cc. Other ranges may be suitable for different applications. 
         [0006]    The volumetric sample adjustment assembly has a “gross adjustment” assembly to vary the gross sample volume within the predetermined range. This gross adjustment assembly uses a removable pin to vary the sample size. This removable adjustment pin is external to the process line and the sampler; further, the adjustment pin may be removed and replaced in different positions to change the gross volume of the sample on short notice and without having to remove the sampler from the process line, from process pressure or without having to manually disassemble the collection head assembly. For example, if the predetermined sample range is from near zero to 11 cc, the gross sample size may be easily changed from 2 cc, to 5 cc, to 8 cc to 11 cc by removal and placement of the adjustment pin in different positions in the gross adjustment assembly. The removable adjustment pin and the gross adjustment assembly are fast and easy to use and are economical to produce. 
         [0007]    The present invention may, as an option, also include a “fine adjustment” assembly to make fine adjustments in the sample volume. This fine adjustment assembly is external to the process line; further, it may be adjusted without having to remove the sampler from the process line, from process pressure or without having to manually disassemble the collection head assembly. For example, if the predetermined sample volume is 11 cc, the sample volume could be adjusted to range from 2.5 cc, to 5.5 cc, to 8.5 cc to 11 cc. Other sample volumes may be set using the fine adjustment assembly, e.g. 0.5 cc, to 3.5 cc, to 6.5 cc to 9.5 cc. The fine adjustment assembly includes an O-ring which is positioned between a pair of opposing locking rings all of which surround a barrel connected to a middle shaft. Rotation of the opposing locking rings up or down the barrel “fine adjusts” to the volume of the sample. The gross adjustment assembly and the fine adjustment assembly cannot increase the predetermined range. But the predetermined range can be changed to, for example, near zero to 24 cc by removal of the sampler from the pipeline and disassembly of the sample head assembly. If required, both the gross adjustment assembly and the fine adjustment assembly may be combined in the volumetric sample adjustment assembly. Or the volumetric sample adjustment assembly may only include the gross adjustment assembly, depending on the application or the customer&#39;s wishes. 
         [0008]    In this application, the term “down” will refer to movement towards the pipeline or devices/components proximate the pipeline. The term “up” will refer to movement away from the pipeline and devices/components opposite the pipeline. The sampler of this invention strokes “down” to take a sample and strokes “up” to replenish fluid in a variable volume sample chamber. A complete cycle is one stroke down and one stroke up. The distance of the up stroke of the sample head may be adjusted by the gross adjustment assembly and/or the fine adjustment assembly to vary the volume of the fresh sample taken into the sample chamber during each up stroke. The volume of the sample taken on the down stroke is determined by the volume of fresh sample taken into the volume chamber during the previous up stroke. 
         [0009]    The sample chamber is sometimes referred to herein as a “variable volume sample chamber” because the distance of the up stroke of the sample head may be adjusted by the gross adjustment assembly and the fine adjustment assembly. The distance of the up stroke, which is adjustable, will control the volume of sample taken into the variable volume sample chamber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a section view of a liquid sample apparatus mounted on a liquid pipeline with the sample head assembly withdrawn from the liquid pipeline. 
           [0011]      FIG. 2  is a section view of the liquid sample apparatus of  FIG. 1  with the sample head assembly inserted in the liquid pipeline. 
           [0012]      FIG. 3  is an enlarged section view of a portion of the insertion assembly showing the insertion piston and a portion of the insertion shaft of  FIG. 1  in the withdrawn position of  FIG. 1 . 
           [0013]      FIG. 4  is an enlarged section view of the sample head assembly of  FIG. 1 . This sample head assembly is designed to sample in a predetermined range of from less than 1 cc to 11 cc. 
           [0014]      FIG. 5  is an enlarged section view of the first check valve assembly of  FIG. 4 . The first check valve assembly is shown in the closed position. 
           [0015]      FIG. 6  is an enlarged section view of the second check valve assembly of  FIG. 4 . The second check valve assembly is shown in the closed position. 
           [0016]      FIG. 7  is an enlarged section view of the first check valve assembly of  FIG. 5 . In  FIG. 7 , the first check valve assembly is in the open position with flow arrows indicating the direction of liquid flow. The first check valve assembly is only in the open position when the middle shaft  26  strokes up to allow fresh liquid to flow into the variable volume sample chamber  80  from the pipeline. When the first check valve assembly is open, the second check valve assembly is closed and vice a versa. 
           [0017]      FIG. 8  is an enlarged section view of the second check valve assembly of  FIG. 6 . In this view, the second check valve assembly is in the open position with flow arrows indicating the direction of liquid flow up the annulus. The second check valve assembly is only in the open position when the middle shaft strokes down to take a sample. 
           [0018]      FIG. 9  is an enlarged section view of the sample head assembly of  FIG. 4 , except the sample head  134  is in the lower position. In this figure, the bottom surface  138  of the sample head  134  touches the bottom surface  104  of the variable volume sample chamber  80 . When the middle shaft is traveling down towards the pipeline, to take a sample, the second check valve assembly is open as shown in this figure and the first check valve assembly is closed. 
           [0019]      FIG. 10  is a section view of an alternative embodiment of the sample head assembly. This sample head is designed to sample in a predetermined range of from less than 1 cc to 24 cc. 
           [0020]      FIG. 11  is an enlarged section view of the first check valve assembly of  FIG. 10 . In this view, the first check valve assembly is in the closed position. 
           [0021]      FIG. 12  is an enlarged section view of the second check valve assembly of  FIG. 12 . In this view, the second check valve assembly is in the closed position. 
           [0022]      FIG. 13  is an enlarged section view of the sample actuation assembly and the sample adjustment assembly of  FIG. 1 . 
           [0023]      FIG. 14  is a section view along the line  14 - 14  of  FIG. 13  showing the removable adjustment pin and the sample size adjustment assembly. 
           [0024]      FIG. 15  is an enlarged section view of the fine adjustment assembly and a portion of the middle shaft. In this view, the upper locking ring is separated from the lower locking ring, solely for illustrative purposes to better show the structure. Unless being adjusted, the opposing locking rings are typically closer together as shown in  FIG. 13 . 
           [0025]      FIG. 16  is a plan view of the removable adjustment pin. 
           [0026]      FIG. 17  is a section view of the removable adjustment pin along the line  17 - 17  of  FIG. 16 . 
           [0027]      FIG. 18  is a plan view of the tools that may be used to make adjustments to the fine adjustment wheels of  FIG. 15 . 
           [0028]      FIG. 19  is an end view of one of the adjustment tools along line  19 - 19  of  FIG. 18 . These tools are circular in cross section. 
           [0029]      FIG. 20  is an enlarged section view of the sample adjustment assembly with the adjustment pin in the first set of adjustment apertures. In this view, the middle shaft travels through a maximum stroke as indicated by the arrows. In this position, the sampler can take the maximum volume of sample in the predetermined range. 
           [0030]      FIG. 21  is an enlarged section view of the sample size adjustment assembly with the removable pin in the fourth set of adjustment apertures. In this view, the middle shaft travels through a minimum stroke. 
           [0031]      FIG. 22  is an enlargement of the gap between the removable adjustment pin and the fine adjustment assembly of  FIG. 21  showing the small amount of travel of the middle shaft during a minimum stroke of the sampler as indicated by the arrows. In this position, the sampler will take the minimum volume of sample in a predetermined range. 
           [0032]      FIG. 23  is an enlarged section view of the flushing fluid flowing through a portion of the sampler  20 . 
           [0033]      FIG. 24  is an enlarged section view of the sample head similar to  FIG. 4 , except the various positions of the sample head during the up stroke are shown in phantom. These various positions are selected by adjustment of the gross adjustment assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0034]    Referring now to  FIGS. 1 ,  2  and  3 , the liquid sampler is generally identified by the numeral  20  and is shown in section view. The sampler is designed to be installed on a liquid pipeline  22 . Typically, the sampler connects to an isolation valve, not shown, which connects to the pipeline, as is well known to those skilled in the art. The isolation valve has been omitted from these drawings to save space and have more room to show the sampler  20 . When the isolation valve is closed, the sampler may be removed from the isolation valve without having to shut down or otherwise depressurize the pipeline. The sampler  20  may be designed to operate at varying pressures and temperatures depending on the application. As an example, the sampler  20  could be built with a maximum allowable operating pressure of 285 PSIG and an allowable operating temperature range from −20° F. to +100° F. The sampler may also be designed for different operating pressures and temperatures for different applications. 
         [0035]    The sampler includes three concentric tubes, better seen in  FIG. 3 : the insertion shaft  24 , the middle shaft  26  and the flush tube  28 , which run for a portion of the length of the liquid sampler. The sampler also includes an insertion assembly  30  identified by the dashed lines in  FIG. 1 . An enlarged portion of the insertion assembly is shown in section view in  FIG. 3 . The purpose of the insertion assembly  30  is to insert at least a portion of the sample head assembly  70 , better seen in  FIG. 4 , into the pipeline as shown in  FIG. 2  or to withdraw the entirety of the sample head assembly  70  from the pipeline as shown in  FIG. 1 . During normal operation, a portion of the sample head assembly  70  is inserted into the pipeline as shown in  FIG. 2  in order to take samples of the product flowing through the pipeline. 
         [0036]    Referring to  FIG. 1 , the insertion assembly  30  includes a first shut off valve  32 , a second shut off valve  34 , and tubing  36 ; in addition, an insertion piston  38  slides back and forth in an insertion cylinder  40 . The insertion shaft  24  is attached to or is an integral part of the insertion piston  40 . The insertion piston divides the insertion cylinder  38  into an upper fluid chamber  42  and a lower fluid chamber  44 . 
         [0037]    Referring now to  FIGS. 1 and 3 , in order to insert at least a part of the sampler into the pipeline, the second shut off valve  34  is closed and the first shut off valve  32  is opened. This allows the pressurized fluid from the pipeline to flow through the tubing  36  into the upper fluid chamber  42  which forces the insertion piston  38  towards the pipeline to insert at least a portion of the sample head assembly  70  in the pipeline as shown in  FIG. 2 . 
         [0038]    In order to remove the entirety of the sampler from the pipeline, the first shut off valve  32  is closed, and the second shut off valve  34  is opened to bleed off the fluid pressure from the upper fluid chamber  42 . The pipeline pressure will push the entire sampler out of the pipeline and back into the withdrawn position of  FIG. 1 . 
         [0039]    An insertion shaft locking assembly  50  is shown by the dotted line in  FIG. 2 . In  FIG. 1 , the insertion shaft locking assembly  50  is in the disconnected position because the sampler is out of the pipeline. But in  FIG. 2 , the insertion shaft locking assembly  50  is in the locked position. A plurality of bolts  52 , best seen in  FIG. 1 , fit through a plurality of openings in a lock collar  58 . The lock collar  58  is permanently connected to the insertion shaft  24  and travels up and down with the movement of the insertion shaft. The bolts  52  are threaded into a plurality of lower bolt receptacles  54 , thus securing the lock collar  58  to the lower bolt receptacles which secures the sampler in the pipeline against pipeline pressure. If the bolts are removed from the lower bolt receptacles  54 , the sampler will be pushed from the pipeline by pipeline pressure as shown in  FIG. 1 . A direction indicator  56  shows the direction of the sample head assembly  70  to make sure the sampler is properly oriented to pipeline flow. Those skilled in the art will recognize that it is desirable for the pipeline owner/operator to be able to insert and withdraw the sampler from the pipeline without having to shut down or reduce pressure in the pipeline. In  FIG. 3 , a plurality of slotted bearings  142  surround the insertion shaft  24  to facilitate alignment and movement of a portion of the insertion shaft  24  in and out of the pipeline. 
         [0040]    A sample head assembly is shown by the dotted line  70  in  FIG. 2  and in enlarged section view in  FIG. 4 . A variable volume sample chamber  80  is positioned between the first check valve assembly  76  and the second check valve assembly  78 . The size of the sample chamber may vary depending on the application. As an example, the variable volume sample chamber  80  in  FIG. 4  was designed to hold about 11 cc; but other sizes can be manufactured using this invention. As another example, the variable volume sample chamber  86  in  FIG. 10  holds about 24 cc. Other sizes are within the scope of this invention. In  FIG. 4 , slotted bearings  142  surround the middle shaft  26  to facilitate alignment and movement of the middle shaft  26  when the sampler is stroked up and down. 
         [0041]    In  FIG. 5 , the first check valve assembly  76  is shown in an enlarged section view, and is shown in the closed, no-flow position. In  FIG. 6 , the second check valve assembly  78  is shown in an enlarged section view, and is also shown in the closed, no-flow position. 
         [0042]    In  FIG. 7 , the first check valve assembly  76  is shown in the open position; liquid flow is represented by the flow arrows. The first check valve assembly  76  opens when the sampler strokes up. The fluid moves from the pipeline  22 , through the inlet  88 , past the first check valve assembly  76 , into the variable volume sample chamber  80 . 
         [0043]    During sampling, the shut off valve  46 , better seen in  FIG. 1 , is in the closed position. In order to take a sample, the middle shaft  26  is stroked down causing the second check valve assembly  78  to open as shown in  FIG. 8 . Liquid sample is pumped from the variable volume sample chamber  80  up past the second check valve assembly  78  and up the annulus  90  as indicated by the flow arrows in  FIGS. 8 and 9 . As better seen in  FIG. 2 , the sample flows through an elbow  92 , then through the third shut off valve  94 , past a check valve  96 , and through flexible tubing  98  and to the outlet  100 . The sample is typically collected in a sample collection vessel/container  106 . Once a sufficient volume of fluid is in the sample collection vessel/container, it may be taken to a laboratory for analysis or it may simply be held for archival purposes. 
         [0044]    Referring now to  FIG. 9 , the sample head  134  is indirectly connected to the middle shaft  26  so the sample head travels up and down as the middle shaft is stroked up and down. During the down stroke, the second check valve assembly  78  opens and liquid flows from the variable volume sample chamber  80  up past the second check valve assembly  78  into the annulus  90  as shown by the flow arrows. At the conclusion of a down stroke of the sampler, the bottom surface  138  of the sample head  134  contacts the bottom surface  104  of the variable volume sample chamber  80  which limits the downward travel of the middle shaft  26  and the sample head assembly  134  as shown in this figure. It is desirable to fully pump all of the fluid out of the variable volume sample chamber  80  during each down stroke of the middle shaft  26  because there is no dead space or stale sample left in the variable volume sample chamber  80 . 
         [0045]    Referring now to  FIG. 10 , a section view of an alternative embodiment of the sample head assembly  74  is shown in section view. A first check valve assembly  82  is shown in section view in  FIG. 11 ; in this view the first check valve assembly  82  is shown in the closed, no-flow position. 
         [0046]    In  FIG. 12 , a second check valve assembly  84  is shown in section view, and in the closed no-flow position. A variable volume sample chamber  86  is positioned between the first check valve assembly  82  and the second check valve assembly  84 . The size of the variable volume sample chamber  86  may vary according to the application. This particular chamber was sized to hold about 24 cc of liquid. 
         [0047]    Referring now to  FIG. 13 , the sample actuation assembly  120  is generally identified by the dashed line. The sample actuation assembly  120  includes an actuation piston  122  which slides up and down in an actuation cylinder  124  in response to opposing fluid forces acting on the actuation piston  122 , which will be described below. In  FIG. 13 , the actuation piston  122  is shown in the upper position. The lower position  136  is shown in phantom. The actuation piston  122  divides the actuation cylinder  124  into an upper actuation fluid chamber  126  and a lower actuation fluid chamber  132 . The upper actuation fluid chamber  126  is in fluid communication with an upper inlet/outlet port  128 ; the lower actuation fluid chamber  132  is in fluid communication with a lower inlet/outlet port  130 . The upper inlet/outlet port  128  is connected to a hydraulic fluid pump not shown. The middle shaft  26  threadably connects to the actuation piston  122  at the upper end and indirectly connects to the sample head  134  at the lower end. When pressurized fluid passes through the upper inlet/outlet port  128 , it fills the upper actuation fluid chamber  126  which forces the actuation piston  122  into the lower position  136  shown in phantom. 
         [0048]    When the middle shaft  26  travels down in response to forces acting on the actuation piston  122 , as best seen in  FIG. 9 , the sample head  134  travels down into the variable volume sample chamber  80 . When the sample head  134  travels down into the variable volume sample chamber  80 , the second check valve assembly  78  opens allowing a sample of liquid to flow up the annulus  90 ; the act of taking a sample as just described is sometimes called a “grab” in the industry. When the middle shaft  26  moves down, this is also referred to in the industry as a “down stroke”. When fluid is bled from the upper actuation fluid chamber  126 , the middle shaft  26  will travel up and out of the variable volume sample chamber  80 . Further, as the sample head  134  travels up and out of the variable volume sample chamber  80 , the first check valve assembly  76  will open allowing fresh liquid from the pipeline to flow past the first check valve assembly  76  and into the variable volume sample chamber  80 . 
         [0049]    The volume of sample may be adjusted by a sample adjustment assembly  150  indicated by the dashed line in  FIG. 1 . The sample adjustment assembly  150  includes a “gross adjustment” assembly  152 . As an option, a “fine adjustment” assembly  180 , as shown in  FIG. 15 , may also be added to the sample adjustment assembly  150 . Both the gross adjustment assembly  152  and the fine adjustment assembly  180  are shown in section view in  FIG. 13 . The gross adjustment assembly  152  includes a cylindrical transparent Plexiglas® plastic housing  154 . 
         [0050]    Referring now to  FIGS. 13 and 14 , a removable adjustment pin  164  is shown in section view outside the cylindrical transparent Plexiglas® plastic housing  154 . The removable adjustment pin  164  has two elongate prongs, as shown in  FIG. 14 . The removable adjustment pin  164  may be placed in different positions in the cylindrical transparent Plexiglas® plastic housing  154  to vary the stroke distance during the up stroke of the middle shaft, thus limiting the size of the variable volume sample chamber  80  and the amount of fresh liquid taken into the variable volume sample chamber  80  from the pipeline. The variable volume of the variable volume sample chamber  80  is best seen in  FIG. 24 . 
         [0051]    The number of adjustment pin positions is determined by the application and/or the customer. In this example in  FIG. 13 , the pin may be set in any of four different positions. But in another application, five or more pin positions may be necessary. Or in the alternative, only three or fewer pin positions may be necessary in some other application. 
         [0052]    The position of the removable adjustment pin  164  is determined by a set of adjustment apertures formed in the cylindrical transparent Plexiglas® plastic housing  154 . In this example, the four sets of adjustment apertures are shown. The first set of adjustment apertures  156  are arranged in the upper most position in the cylindrical transparent Plexiglas® plastic housing  154 . This first set of adjustment apertures  156  are sized and arranged to receive the elongate prongs of the removable adjustment pin  164 , as are all the other adjustment apertures described hereinafter. Each set of adjustment apertures includes four openings aligned on a parallel axis to receive the elongate prongs of the removable adjustment pin  164 . 
         [0053]    Below the first set of adjustment apertures  156  are a second set of adjustment apertures  158 . Below the second set of adjustment apertures  158  are a third set of adjustment apertures  160 . Below the third set of adjustment apertures  160  are a fourth set of adjustment apertures  162 . As can be seen from  FIG. 13 , the removable adjustment pin  164  can only be inserted into one set of adjustment apertures at a time. 
         [0054]    When the removable adjustment pin  164  is inserted in the first set of adjustment apertures  156 , the middle shaft  26  has maximum up travel and the sampler will take in approximately 11 cc of sample into the variable volume sample chamber  80 , in this embodiment. The embodiments can be varied to adjust the amount of total sample taken during a maximum stroke. When the removable adjustment pin  164  is inserted in the second set of adjustment apertures  158 , the middle shaft  26  has a shorter distance of up travel and the sampler will take approximately 8 cc of fresh sample into the variable volume sample chamber  80  during each up stroke. When the removable adjustment pin  164  is inserted in the third set of adjustment apertures  160 , the middle shaft  26  has even less travel and the sampler will take approximately 5 cc of fresh sample each time the sampler strokes up. When the removable adjustment pin  164  is in the fourth set of adjustment apertures  162 , the middle shaft  26  has the minimum amount of travel and will take approximately 2 cc of fresh sample into the variable volume sample chamber  80  every time the sampler strokes up. 
         [0055]    Hydraulic fluid introduced into the sample actuation assembly  120  causes the actuation piston  122  to travel up and down in the actuation cylinder  124 . But the distance of travel of the middle shaft  26  is not limited by the travel of the actuation piston  122 . Rather, the distance of up travel of the middle shaft  26  is determined by the gross adjustment assembly  152  and optionally by the fine adjustment assembly  180 . The sampler shown in these drawings has both the gross adjustment assembly  152  and the fine adjustment assembly  180 , but not all embodiments of the invention have the fine adjustment assembly  180 . 
         [0056]    Referring now to  FIGS. 13 and 9 , the upper limitation of the gross travel distance of the middle shaft  26  is determined by the location of the removable adjustment pin  164  in the cylindrical transparent Plexiglas® housing  154 . When the actuation piston  122  is in the upper position as shown in  FIG. 13 , the upper surface  210  of the upper lock ring  188  is stopped by the bottom surface  172  of the removable adjustment pin  164 . When the actuation piston  122  is stroked down, the actuation piston  122  moves to the lower position  136  as shown in phantom in  FIG. 13 . In this position, the travel of the middle shaft  26  is stopped when the bottom surface  138  of the sample head  134  contacts the bottom surface  104  of the variable volume sample chamber  80  as better seen in  FIG. 9 . A plurality of Poly Pak™ seals  140  surround the middle shaft  26  above and below the sample actuation assembly  120 . These Poly Pak™ seals  140  also surround the middle shaft  26  below the sample adjustment assembly  150 . Poly Pak™ seals are available from Parker Hannifin Corp. of Haverhill, Mass. (www.parker.com). 
         [0057]    Referring now to  FIGS. 14 and 15 , the fine adjustment assembly is generally identified by the numeral  180 . This fine adjustment assembly  180  is used to make fine adjustments in the volume of sample; these adjustments are more precise than those that can be made by the removable adjustment pin  164 . Access to the fine adjustment assembly  180  is through an access window  194  in the cylindrical transparent Plexiglas® housing  154 . The fine adjustment assembly  180  includes a barrel  182 , which is not threaded on the inside diameter but is threaded on the outside diameter. The barrel  182  may be locked in place on the middle shaft  26  by an upper locking lug  184  and a lower locking lug  186 ; the exterior of the barrel  182  is threaded, as shown in  FIG. 15 . An upper locking ring  188  and a lower locking ring  190  are threaded on the inside diameter and are sized and arranged to threadably engage the threaded exterior of the barrel  182 . A plurality of adjustment openings  200  are radially arranged along the outside circumference of the upper locking ring  188 . The diameter of each adjustment opening is the same. The size of each adjustment opening  200  is sized and arranged to receive and engage with either of the tools shown in  FIG. 18 . A plurality of adjustment openings  202  are radially arranged along the outside circumference of the lower locking ring  190 . The diameter of the adjustment openings  200  and  202  are the same. Each of the adjustment openings  202  are sized and arranged to receive and engage with either of the tools shown in  FIG. 18 . 
         [0058]    In order to adjust the fine adjustment assembly  180 , both tools are inserted through the access window  194 . Tool  196  may be inserted in one of the plurality of adjustment openings  202  in the lower locking ring  190 . Tool  198  may be inserted in one of the plurality of adjustment openings  200  in the upper locking ring  188 . Clockwise movement of the tool  196  moves the lower locking ring  190  down; counter-clockwise movement of the tool  196  moves the lower locking ring  190  upward, away from the pipeline. Clockwise movement of the tool  198  moves the upper locking ring  188  down; counter-clockwise movement of the tool  198  moves the upper locking ring  188  upward, away from the pipeline. In this fashion, the upper and lower locking rings,  188  and  190  respectively, may be moved up or down relative to the barrel  182 . After adjustment, the locking rings  188  and  190  are tightened against each other to releasably lock the rings at a desirable location on the barrel  182 . 
         [0059]    In  FIG. 15 , when the locking rings,  188  and  190 , are rotated up, which is away from the pipeline, the volume of the sample is slightly decreased. When the locking rings,  188  and  190 , are rotated down as shown in  FIG. 13 , the volume of the sample is slightly increased. (Down is towards the pipeline). 
         [0060]    An O-ring  192  is positioned between the upper locking ring  188  and the lower locking ring  190 ; the purpose of the O-ring  192  is not to provide a seal. Rather, the O-ring  192  is used in this application as a resilient spring which will exert force on both locking rings  188  and  190  to releasably lock the two locking rings,  188  and  190 , together when tightened by the tools,  196  and  198 , shown in  FIGS. 18 and 19 . Applicant has determined than a Buna-N O-ring with a Shore D 90 Durometer hardness is suitable for this application. Other O-rings may function in this application, such as a Viton® O-ring, provided that the O-ring is stiff enough to act as a spring and not be permanently deformed when the locking rings  188  and  190  are tightened against each other. 
         [0061]      FIG. 20  is an enlarged section view of the sample adjustment assembly  150  with the removable adjustment pin  164  in the first set of adjustment apertures  156 . In this view, the middle shaft  26  travels through a maximum stroke up and down as indicated by the arrows  208 . In this position, the sampler can take the maximum volume of sample in the predetermined range. The length of the stroke of the middle shaft  26  in  FIG. 20  is from the bottom surface  172  of the removable adjustment pin  164  to when the sample head  134  touches the bottom surface  104  of the variable volume sample chamber  80  as better seen in  FIG. 9 . 
         [0062]      FIG. 21  is an enlarged section view of the sample adjustment assembly  150  with the removable adjustment pin  164  in the fourth set of adjustment apertures  162  and  FIG. 22  is an enlargement of the gap between the bottom surface  172  of the removable adjustment pin  164  and the top surface  210  of the upper lock ring  188 . In these views, the middle shaft  26  travels through a minimum stroke up and down as indicated by the arrows  206 . In this position the sampler will take the minimum volume of sample in the predetermined range. The length of the down stroke of the middle shaft  26  in  FIGS. 21 and 22  is from the bottom surface  172  of the removable adjustment pin  164  to when the sample head  134  touches the bottom surface  104  of the variable volume sample chamber  80  as better seen in  FIG. 9 . 
         [0063]      FIG. 22  is an enlargement of the gap between the bottom surface of the  172  of the removable adjustment pin  164  and the top surface  210  of the upper lock ring  188 . The bottom surface  168  of the lower lock ring  190  does not contact the housing shoulder  166 . Rather, the travel of the middle shaft  26  is limited on the down stroke when the sample head  134  touches the bottom surface  104  of the variable volume sample chamber  80  as better seen in  FIG. 9 . 
         [0064]      FIG. 23  is a section view of the shut off valve  46  where it contacts the first elbow  92  and related equipment on the upper end of the sampler  20 . Flushing may not be done while sampling; but flushing may be done while the sample head assembly  70  is withdrawn from the pipeline as shown in  FIG. 1  or when a portion of the sample head assembly  70  is inserted in the pipeline as shown in  FIG. 2 . A flushing fluid may be a liquid such as the product flowing through the pipeline or a gas such as nitrogen. Nitrogen is preferred. In order to flush the sampler, the shut off valve  46  is opened and the flushing fluid is pumped from a source of flushing fluid  212  through the shut off valve  46  down through the flush tube  28  (towards the pipeline). At the end of the flush tube  28 , the flushing fluid changes directions and flows up the annulus  90  through the first elbow  92 , the third shut off valve  94 , past the check valve  96 , through the elbow  216 , through the flexible tubing  98 , through the elbow  218 , and exits the outlet  100  into a removable flushing fluid sample collection vessel/container  106 . 
         [0065]    Flushing of the liquid sampler may be done as often as the operator requires. Typically, flushing occurs when the product in the pipeline changes from one product to another. As an example, flushing may occur when the fluid pipeline is being switched from gasoline to diesel. Flushing may also be done when product from one customer is switched to product from another. 
         [0066]      FIG. 24  is a section view of the sample head assembly  70  similar to  FIG. 4 , except the various positions of the sample head  134  are shown in phantom. The volume of the variable volume sample chamber  80  is about 11 cc maximum, but the volume of the sample size can vary depending on the position of the gross adjustment assembly  152  and optionally by the fine adjustment assembly  180 . When the sample head  134  is stroked up, the first check valve assembly  76  opens and fresh sample is drawn into the variable volume sample chamber  80 ; during the up stroke, the second check valve assembly  78  is closed. The volume of the fresh sample is determined by the position where the sample head  134  comes to rest in the variable volume sample chamber  80  during the up stroke, which can vary as shown in this figure. The variable position of the sample head assembly  70  is determined by the distance of travel of the middle shaft  26  during the up stroke which is limited by the position of the removable adjustment pin  164  in the gross adjustment assembly  152  and as may be further varied by the optional fine adjustment assembly  180 . On the down stroke, the first check valve assembly  76  closes and the second check valve assembly  78  opens allowing the sample in the variable volume sample chamber  80  to be pumped up the annulus  90  as shown elsewhere. The distance of the down stroke stops when the sample head  134  bottoms in the variable volume sample chamber  80  better seen in  FIG. 9 . 
         [0067]    When the removable adjustment pin  164  is in the first adjustment apertures  156 , as better seen in  FIG. 20 , the middle shaft  26  travels its maximum distance during an up stroke, and the sample head  134  comes to rest at position  230 . At position  230 , the sampler will take about 11 cc of fresh sample into the variable volume sample chamber  80 . On the down stroke, the 11 cc of fresh sample will be pumped past the second check valve assembly  78  and up the annulus  90 . 
         [0068]    When the removable adjustment pin  164  is in the second adjustment apertures  158  as better seen in  FIG. 13 , the middle shaft  26  travels less during the up stroke and the sample head  134  comes to rest at position  232 . At position  232 , the sampler will take about 8 cc of fresh sample into the sample collection chamber  80 . On the down stroke, the 8 cc of fresh sample will be pumped past the second check valve assembly  78  and up the annulus  90 . 
         [0069]    When the removable adjustment pin  164  is in the third adjustment apertures  160 , as better seen in  FIG. 13 , the middle shaft  26  travels even less during the up stroke and the sample head  134  comes to rest at position  234 . At position  234 , the sampler will take about 5 cc of fresh sample into the variable volume sample chamber  80 . On the down stroke, the 5 cc of fresh sample will be pumped past the second check valve assembly  78  and up the annulus  90 . 
         [0070]    When the removable adjustment pin  164  is in the fourth adjustment apertures  162 , as better seen in  FIG. 21 , the middle shaft  26  travels a minimum distance during the up stroke and the sample head  134  comes to rest at position  236 . At position  236 , the sampler will take about 2 cc of fresh sample into the variable volume sample chamber  80 . On the down stroke, the 2 cc of fresh sample will be pumped past the second check valve assembly  78  and up the annulus  90 . The distance the sample head moves during the up stroke defines the volume of the collection chamber and the volume of the fresh sample taken into the sample variable volume chamber  80 . The positions  232 ,  234  and  236  are for illustrative purposes only and not meant to be the same scale or size of the arrows  206  and  208  in prior figures.