Patent Document

CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a continuation-in-part of application Ser. No. 12/861,595, filed on Aug. 23, 2010, which is a continuation-in-part of application Ser. No. 12/838,104, filed on Jul. 16, 2010, which is incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field 
         [0003]    This invention relates to methods and devices for measuring the thermal characteristics of fluids. Specifically, this invention relates to the priming and flushing of devices used for measuring the thermal oxidation tendencies of fuels used in liquid hydrocarbon-burning engines. 
         [0004]    2. Background Art 
         [0005]    When turbine engines were developed for use in jet aircraft, problems with fouling of engine components arose. The fouling was traced back to fuels having poor thermal stability characteristics. At higher temperatures, the poor quality fuels oxidized and formed carbonaceous deposits, clogging fuel nozzles and fuel filters. These deposits would also collect within the fuel delivery system. 
         [0006]    While various tests were devised and used in the 1950s and 1960s to evaluate the thermal oxidation characteristics of jet fuels prior to being used in jet aircraft, Alf Hundere developed the apparatus and method which became the standard in the industry. In 1970, Alf Hundere filed what became U.S. Pat. No. 3,670,561, titled “Apparatus for Determining the Thermal Stability of Fluids”. This patent was adopted in 1973 as ASTM D3241 Standard, entitled “Standard Test Method for Thermal Oxidation Stability of Aviation Turbine Fuels”, also known as the “JFTOT® Procedure”. This early Hundere patent was designed to test the deposition characteristics of jet fuels by determining (1) deposits on the surface of a heater tube at an elevated temperature and (2) differential pressure across a filter due to collection of particulate matter. To this day, according to ASTM D3241, the two critical measurements are still (1) the deposits collected on a heater tube and (2) differential pressure across the filter due to the collection of particulate matter on the filter. 
         [0007]    According to ASTM D3241, 450 mL of fuel flows across an aluminum heater tube at a specified rate, during a 2.5 hour test period at an elevated temperature. Currently six different models of JFTOT 1  instruments are approved for use in the ASTM D3241-09 Standard. The “09” refers to the current revision of the ASTM D3241 Standard. 
         [0008]    While over the years various improvements have been made in the apparatus to run the tests, the basic test remains the same. Improvements in the apparatus can be seen in U.S. Pat. Nos. 5,337,599 and 5,101,658. The current model being sold is the JFTOT 230 Mark III, which is described in further detail in the “Jet Fuel Thermal Oxidation Tester—User&#39;s Manual”. The determination of the deposits that occur on the heater tube can be made visually by comparing to known color standards or can be made using a “Video Tube Deposit Rater” sold under the Alcor mark. 
         [0009]    The determination of the amount of deposits formed on the heater tube at an elevated temperature is an important part of the test. The current ASTM D3241 test method requires a visual comparison between the heater tube deposits and known color standard. However, this involves a subjective evaluation with the human eye. To take away the subjectivity of a person, an electronic video tube deposit rater was developed. 
         [0010]    Also, there has been considerable discussion as to the polish or finish of the heater tube. (See U.S. Pat. No. 7,093,481 and U.S. Patent Application Publication No. US 2002/083,760.) The finish of the heater tube is very important in determining the amount of fuel deposits that will form thereon. Therefore, it is important that the quality of the finish on heater tubes made today be consistent with the finish of heater tubes made since 1973. 
         [0011]    The same test apparatus and method is used repeatedly to test fuel samples. To insure against cross contamination between test samples and to insure the accuracy of the test, the test apparatus must be properly primed at the beginning of a test and properly flushed at the end of the test. Prior systems were not as effective at priming or flushing the test sample. 
         [0012]    In the past, containers used for (1) the test sample or (2) waste fuel had limitations. The containers were primarily open vessels that did not provide the operator feedback about being securely positioned, did not contain or capture fuel vapors, and were difficult to secure in place. Aeration of the test sample while in the container also requires a coarse glass dispersion tube. Once the thermal oxidation stability test has been performed on a batch of fuel, the recorded information and the heater tube are preserved. This provides sample traceability and in general is considered good laboratory practice. 
       BRIEF SUMMARY OF THE INVENTION 
       [0013]    It is an object of the present invention to provide an apparatus and method for testing thermal oxidation stability of fluids, particularly aviation fuels. 
         [0014]    It is another object of the present invention to provide an apparatus and method to measure the tendency of fuels to form deposits when in contact with heated surfaces. 
         [0015]    It is another objective of the present invention to provide an apparatus and method for testing the thermal oxidation tendency of fuels utilizing a test sample to determine if solid particles will form in the fuel at an elevated temperature and pressure. 
         [0016]    It is another objective of the present invention to provide an apparatus and method for determining thermal oxidation stability of a batch of aviation fuel by testing a sample at an elevated temperature and pressure to determine (1) deposits that form on a metal surface and (2) solid particles that form in the fuel. 
         [0017]    It is another objective of the present invention to provide an apparatus and method for priming the test sample at the beginning of the test and flushing the test sample at the end of the test, which determines thermal oxidation tendency of the test sample. 
         [0018]    It is yet another objective of the present invention to provide a method of priming and flushing a test sample during a thermal oxidation stability test. 
         [0019]    It is another objective of the present invention to have an apparatus for priming before a test and flushing after the test. 
         [0020]    At the beginning of a thermal oxidation stability test, the test sample is aerated with dry air for a period of time. After the aeration stops, the test sample is forced into the test apparatus. Upon purging air from the test apparatus using the test sample, the main part of the thermal oxidation test begins. After the test is complete, all of the test sample remaining in the test apparatus is flushed to a waste container. 
         [0021]    The apparatus automatically primes the test sample without operator intervention and ensures the thermal oxidation stability tester is full of the test sample at the onset of the test. Also, apparatus is provided to flush or remove the test sample from the thermal oxidation stability tester at the end of the test. Thereafter, (a) the heater tube is removed for analysis, (b) components of the thermal oxidation stability tester are cleaned before the next test and (c) a new heater tube and filters are installed prior to the next test. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a general block diagram of a thermal oxidation stability test apparatus illustrating flow and electrical controls. 
           [0023]      FIGS. 2 and 2A  are a more detailed block diagram showing a thermal oxidation test apparatus used to perform ASTM D3241 Standard. 
           [0024]      FIG. 3  is a pictorial diagram of the coolant flow for  FIGS. 2 and 2A . 
           [0025]      FIG. 4  is a pictorial diagram of the airflow in  FIGS. 2 and 2A   
           [0026]      FIG. 5  is a pictorial diagram showing flow of the test sample in  FIGS. 2 and 2A . 
           [0027]      FIG. 6A  is a perspective view of the sample container. 
           [0028]      FIG. 6B  is a perspective view of the internal components of the sample container. 
           [0029]      FIG. 7A  is a perspective view of the waste container. 
           [0030]      FIG. 7B  is a perspective view of the internal components of the waste container. 
           [0031]      FIG. 8A  is an elevated view of the aeration frit. 
           [0032]      FIG. 8B  is a cross sectional view of  FIG. 8A  along section lines  8 B- 8 B. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0033]      FIG. 1  is a schematic block diagram of a thermal oxidation stability tester referred to generally by the reference numeral  20 . The thermal oxidation stability tester  20  has an embedded computer  21  with a touch screen  23  for user interface. While many different types of programs could be run, in the preferred embodiment, applicant is running C++ in the embedded computer  21 . The touch screen  23  displays all of the information from the thermal oxidation stability tester  20  that needs to be conveyed to the user. The user communicates back and forth with the embedded computer  21  through the touch screen  23 . If a batch of fuel is to be tested, a test sample is put in the sample delivery system  25 . 
         [0034]    It is important to the test to make sure the test sample is oxygen saturated through aeration. Therefore, the embedded computer  21  operates a sample aeration control  31  for a period of time to make sure the sample is fully aerated. The aeration of the sample takes place at the beginning of the test. 
         [0035]    The embedded computer  21  turns on a sample flow control  27 , which is a pump used to deliver the sample throughout the thermal oxidation stability tester  20 . Simultaneous with the sample flow control  27  pumping the test sample throughout the system, sample pressure control  29  maintains a fixed pressure throughout the system. It is important to maintain pressure in the system to prevent boiling of the test sample when at elevated temperatures. In the present thermal oxidation stability tester  20 , the sample is maintained at approximately 500 psi when undergoing the thermal oxidation stability test. 
         [0036]    Also, the embedded computer  21  controls parameters affecting the intelligent heater tube  33 . The test data is recorded to the intelligent heater tube  33  via intelligent heater tube writer  35  from the embedded computer  21 . Critical test parameters are recorded on a memory device (as described subsequently) on an end of the intelligent heater tube  33  via the intelligent heater tube writer  35 . The rating of the deposit formed on the intelligent heater tube  33  will be recorded on the memory device at a later time. 
         [0037]    In performing the thermal oxidation stability test on a test sample, the intelligent heater tube  33  is heated by tube heater control  37 . The tube heater control  37  causes current to flow through the intelligent heater tube  33 , which causes it to heat up to the temperature set point. 
         [0038]    To prevent the hot intelligent heater tube  33  from heating other parts of the thermal oxidation stability tester  20 , bus-bar coolant control  39  provides coolant upper and lower bus-bars holding each end of the intelligent heater tube  33 . This results in the center section of the intelligent heater tube  33  reaching the prescribed temperature while the ends of the intelligent heater tube  33  are maintained at a lower temperature. This is accomplished by flowing coolant via the bus-bar coolant control  39  across the ends of the intelligent heater tube  33 . 
         [0039]    The test parameters, such as the dimension of the heater tube, pressure of the test sample or flow rate are fixed by ASTM D3241. 
         [0040]    Referring now to  FIGS. 2 and 2A  in combination, a schematic flow diagram is shown connecting the mechanical and electrical functions. The embedded computer  21  and the touch screen  23  provide electrical signals as indicated by the arrows. A test sample is contained in the sample container  41 . To make sure the sample and the sample container  41  is fully aerated, an aeration pump  43  is turned ON. The aeration pump  43  pumps air through a dryer  45  where the air is dehumidified. From the dryer  45 , a percent relative humidify sensor  47  determines the humidity level of the pumped air and provides that information to the embedded computer  21 . Assuming the percent humidity of the pumped air is sufficiently low, the test procedure will continue pumping air through the flow meter  49  and aeration check valve  50  into the sample container  41 . During aeration, flow meter  49  should record approximately 1.5 liters of air per minute. Since the flow meter  49  runs for approximately six minutes, the aeration pump  43  will sparge approximately nine liters of air into the test sample. This is sufficient time to saturate the test sample with dry air. 
         [0041]    Within the sample container  41 , a sample temperature measurement  51  is taken and provided to the embedded computer  21 . The sample temperature measurement  51  is to ensure that the test sample is between 15° to 32° C. If the test sample is outside of this temperature range, results can be impacted. Also, if the test sample is outside this temperature range, the embedded computer  21  would not let the test start. 
         [0042]    Once the test sample has been aerated and if all the other parameters are within tolerance, then the sample drive pump  53  will turn ON. The sample drive pump  53  is a single piston reciprocating pump, also known as a metering pump. With every stroke of the piston, a fixed volume of the sample is delivered. The speed of the sample drive pump  53  is controlled so that it pumps 3 mL/min of the test sample. The sample drive pump  53  is configured for fast refill. Pulsations, associated with pumps of this design are minimized with the use of a pulse dampener and a coil tubing on the outlet side as will be subsequently described. 
         [0043]    To get air out of the tubing between the sample container  41  and the sample drive pump  53  at the start of the test, an auto pump priming valve  55  is opened, a sample vent valve  54  is closed and the aeration pump  43  is turned ON by the embedded computer  21 . The auto pump priming valve  55  opens and remains open while a combination of sample and air is discharged into waste container  57 . At the same time, the aeration pump  43  provides positive pressure in the sample container  41  to force test sample from the sample container  41  to the sample drive pump  53 . The sample vent valve  54  closes to prevent venting of the air pressure to atmosphere to maintain a pressure of 2 to 3 psi. A sample vent check valve  56  across the sample vent valve  54  opens at 5 psi to prevent the pressure in the sample container  41  from exceeding 5 psi. Once the sample drive pump  53  starts pumping the test sample, auto pump priming valve  55  will close and the sample vent valve  54  will open. Thereafter, the sample drive pump  53  will pump the test sample through check valve  59  to the prefilter  61 . The check valve  59  prevents fluid from flowing backwards through the sample drive pump  53 . The check valve  59  operates at a pressure of approximately 5 psi. The check valve  59  prevents siphoning when the sample drive pump  53  is not pumping. Also, check valve  59  prevents fluid from being pushed backwards into the sample drive pump  53 . 
         [0044]    The prefilter  61  removes solid particles in the test sample that could affect the test. The prefilter  61  is a very fine filter, normally in the order of 0.45 micron in size. The purpose of the prefilter  61  is to make sure particles do not get into the test filter as will be described. The prefilter  61  is replaced before every test. 
         [0045]    From the prefilter  61 , the test sample flows through an inlet  63  into the cylindrical heater tube test section  65 . Outlet  67 , while illustrated as two separate outlets, is actually a single outlet at the upper end of the cylindrical heater tube test section  65 . Extending through the cylindrical heater tube test section  65  is the intelligent heater tube  69 , sealed at each end with ceramic bushings and an o-ring (not shown). While the test sample flows through the cylindrical heater tube test section  65  via inlet  63  and outlet  67  and around the intelligent heater tube  69 , the housing of the cylindrical heater tube test section  65  is electrically isolated from the intelligent heater tube  69 . Only the test sample comes in contact with the center section of the intelligent heater tuber  69 . Inside of the intelligent heater tube  69  is a thermocouple  71  that sends a signal back to the embedded computer  21  as to the temperature of the center section of the intelligent heater tube  69 . 
         [0046]    Test sample flowing from the cylindrical heater tube test section  65  flows through a differential pressure filter  73 , commonly called the “test filter”. In a manner as will be explained in more detail, the intelligent heater tube  69  heats up the test sample inside of the cylindrical heater tube test section  65  to the test parameter set point. Heating of the test sample may result in degradation of the test sample, or cause solid particles to form. The solid particles may deposit on the center section of the intelligent heater tube  69 , and/or may collect on the differential pressure filter  73 . The pressure drop across the differential pressure filter  73  is measured by differential pressure sensor  75 . Pressure across the differential pressure filter  73  is continuously monitored by the embedded computer  21  through the differential pressure sensor  75 . When the pressure across the differential pressure filter  73  exceeds a predefined pressure difference of approximately 250 mm to 280 mm of mercury, the differential pressure bypass valve  77  opens to relieve the pressure. By test definition, exceeding a differential pressure of 25 mm Hg results in failure of the test sample. 
         [0047]    For this test to be performed, the test sample must remain as a liquid. At testing temperatures of 250° C. to 350° C., many hydrocarbon fuels will transition to the vapor phase at ambient pressures. To keep the test sample in the liquid phase, the back pressure regulator  79  maintains approximately 500 psi pressure in the system. This system pressure is monitored by the system pressure sensor  81 , which reports information to the embedded computer  21 . During a test, normal flow of a test sample is through differential pressure filter  73  and through the back pressure regulator  79 . From the back pressure regulator  79 , the test sample flows through sample flow meter  83  to waste container  57 . The sample flow meter  83  accurately measures the flow rate of the test sample during the test. The sample flow meter  83  provides sample flow rate information to the embedded computer  21 . 
         [0048]    A system/safety vent valve  85  is connected into the system and controlled via the embedded computer  21 . The system/safety vent valve  85  acts to relieve excess system pressure in the case of power loss, improperly functioning system components or other system failures. In the event of this occurrence, the system pressure sensor  81  sends a signal to the embedded computer  21 , triggering the system/safety vent valve  85  to open and relieve excess pressure. Also, at the completion of a test, the system/safety vent valve  85  opens to vent pressure from the system. The system/safety vent valve  85  is normally set to the open position requiring a program command to through the embedded computer  21  to close the system/safety vent valve  85 . Therefore, if power is lost, the system/safety vent valve  85  automatically opens. 
         [0049]    At the end of the test, after the system/safety vent valve  85  is opened and system pressure is relieved, the flush air pump  87  turns ON and flushes air through flush check valve  89  to remove the test sample from the system. The flush air pump  87  pushes most of the test sample out of the system via the system/safety vent valve  85  into the waste container  57 . 
         [0050]    The system may not operate properly if there are air pockets or air bubbles in the system. During a test, it is important to maintain an air-free system. Therefore, at the beginning of each test, the solenoid operated differential pressure plus vent valve  91  and the differential pressure minus vent valve  93  are opened, flushed with test sample, and vented to remove any air pockets that may be present. During the beginning of each test, the position of the differential pressure vent valves  91  and  93  ensure there is no air in the differential pressure lines. 
         [0051]    During the running of a test on a test sample, the sequence of priming and flushing the thermal oxidation stability tester  20  is very important. The table given herein below gives the sequence of auto priming and flushing during a test. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                 Table of sequence timing for JFTOT with Auto Prime and flushing 
               
             
          
           
               
                   
                   
                   
                   
                 Flush 
                   
                   
                 Auto 
                 Differential 
                 System 
                   
                   
                 Heater 
               
               
                   
                   
                   
                   
                 air 
                 Sample 
                 Sample 
                 Pump 
                 Pressure 
                 safety 
                 DP+ 
                   
                 Tube 
               
               
                   
                 State 
                 Time 
                 Acration 
                 pump 
                 drive 
                 vent 
                 Prime 
                 Bypass 
                 vent 
                 Vent 
                 DP− Vent 
                 Module 
               
               
                 Step # 
                 Description 
                 Duration 
                 pump 43 
                 87 
                 pump 53 
                 valve 54 
                 Valve 55 
                 valve 77 
                 valve 85 
                 valve 91 
                 valve 93 
                 103 
               
               
                   
               
               
                 — 
                 Idle 
                 — 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
               
               
                   
                   
                   
                   
                   
                   
                 (open) 
                 (closed) 
                 (closed) 
                 (open) 
                 (closed) 
                 (closed) 
               
               
                 1 
                 Auto Prime 
                 30 sec 
                 ON 
                 OFF 
                 ON 
                 ON 
                 ON 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
               
               
                   
                 pump 
                   
                   
                   
                   
                 (closed) 
                 (open) 
                 (closed) 
                 (open) 
                 (closed) 
                 (closed) 
               
               
                 2 
                 Aeration + 
                 30 sec 
                 ON 
                 OFF 
                 ON 
                 OFF 
                 OFF 
                 ON (open) 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
               
               
                   
                 system vent 
                   
                   
                   
                   
                 (open) 
                 (closed) 
                   
                 (open) 
                 (closed) 
                 (closed) 
               
               
                   
                 &amp; bypass 
               
               
                 3 
                 Aeration + 
                 30 sec 
                 ON 
                 OFF 
                 ON 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
               
               
                   
                 system vent 
                   
                   
                   
                   
                 (open) 
                 (closed) 
                 (closed) 
                 (open) 
                 (closed) 
                 (closed) 
               
               
                 4 
                 Aeration + 
                  1 min 
                 ON 
                 OFF 
                 ON 
                 OFF 
                 OFF 
                 OFF 
                 ON 
                 ON 
                 OFF 
                 OFF 
               
               
                   
                 DP+ purge 
                   
                   
                   
                   
                 (open) 
                 (closed) 
                 (closed) 
                 (closed) 
                 (open) 
                 (closed) 
               
               
                 5 
                 Aeration + 
                  1 min 
                 ON 
                 OFF 
                 ON 
                 OFF 
                 OFF 
                 OFF 
                 ON 
                 OFF 
                 ON 
                 OFF 
               
               
                   
                 DP− purge 
                   
                   
                   
                   
                 (open) 
                 (closed) 
                 (closed) 
                 (closed) 
                 (closed) 
                 (open) 
               
               
                 6 
                 Aeration 
                  1 min 
                 ON 
                 OFF 
                 ON 
                 OFF 
                 OFF 
                 OFF 
                 ON 
                 OFF 
                 OFF 
                 OFF 
               
               
                   
                   
                   
                   
                   
                   
                 (open) 
                 (closed) 
                 (closed) 
                 (closed) 
                 (closed) 
                 (closed) 
               
               
                 7 
                 Aeration + 
                 30 sec 
                 ON 
                 OFF 
                 ON 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
               
               
                   
                 system vent 
                   
                   
                   
                   
                 (open) 
                 (closed) 
                 (closed) 
                 (open) 
                 (closed) 
                 (closed) 
               
               
                 8 
                 Aeration (&amp; 
                  1 min 
                 ON 
                 OFF 
                 ON 
                 OFF 
                 OFF 
                 OFF 
                 ON 
                 OFF 
                 OFF 
                 OFF 
               
               
                   
                 pressurize) 
                 30 sec 
                   
                   
                   
                 (open) 
                 (closed) 
                 (closed) 
                 (closed) 
                 (closed) 
                 (closed) 
               
               
                 9 
                 Run test 
                 150 min 
                 OFF 
                 OFF 
                 ON 
                 OFF 
                 OFF 
                 OFF 
                 ON 
                 OFF 
                 OFF 
                 ON 
               
               
                   
                   
                   
                   
                   
                   
                 (open) 
                 (closed) 
                 (closed) 
                 (closed) 
                 (closed) 
                 (closed) 
               
               
                 10 
                 Cool Down 
                 (cool to 
                 OFF 
                 OFF 
                 ON 
                 OFF 
                 OFF 
                 OFF 
                 ON 
                 OFF 
                 OFF 
                 ON 
               
               
                   
                   
                 40 C.) 
                   
                   
                   
                 (open) 
                 (closed) 
                 (closed) 
                 (closed) 
                 (closed) 
                 (closed) 
               
               
                 11 
                 Vent 
                 (pressure 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
               
               
                   
                 pressure 
                 to &lt;xx 
                   
                   
                   
                 (open) 
                 (closed) 
                 (closed) 
                 (open) 
                 (closed) 
                 (closed) 
               
               
                   
                   
                 psi) 
               
               
                 12 
                 Flush 
                 20 sec 
                 OFF 
                 ON 
                 OFF 
                 OFF 
                 OFF 
                 ON (open) 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
               
               
                   
                 System 
                   
                   
                   
                   
                 (open) 
                 (closed) 
                   
                 (open) 
                 (closed) 
                 (closed) 
               
               
                   
                 (1/2) 
               
               
                 13 
                 Flush 
                 20 sec 
                 OFF 
                 ON 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
               
               
                   
                 System 
                   
                   
                   
                   
                 (open) 
                 (closed) 
                 (closed) 
                 (open) 
                 (closed) 
                 (closed) 
               
               
                   
                 (2/2) 
               
               
                 14 
                 Idle 
                 — 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
                 OFF 
               
               
                   
                   
                   
                   
                   
                   
                 (open) 
                 (closed) 
                 (closed) 
                 (open) 
                 (closed) 
                 (closed) 
               
               
                   
               
             
          
         
       
     
         [0052]    During the flushing, the flush air pump  87  created about 15 psi air pressure in the thermal oxidation stability tester  20  to force the test sample there from. The flush air pump  87  generates about 4.2 liters/minute flow during flushing. 
         [0053]    If the waste container  57  is properly installed in position, a signal will be fed back to the embedded computer  21  indicating the waste container  57  is correctly connected. This also applies for the sample container  41  which sends a signal to the embedded computer  21  when it is properly connected. The system will not operate unless both the waste container  57  and the sample container  41  are properly positioned. 
         [0054]    The center portion of the intelligent heater tube  69  is heated to the test parameter set point by flowing current through the intelligent heater tube  69 . Instrument power supplied for current generation and all other instrument controls is provided through local available power  95 . Depending on local power availability, local available power  95  may vary drastically. In some areas it is 50 cycles/sec. and in other areas it is 60 cycles/sec. The voltage range may vary from a high of 240 Volts down to 80 Volts or less. A universal AC/DC converter  97  takes the local available power  95  and converts it to 48 Volts DC. With the universal AC/DC converter  97 , a good, reliable, constant 48 Volts DC is generated. The 48 Volts DC from the universal AC/DC converter  97  is distributed throughout the system to components that need power through the DC power distribution  99 . If some of the components need a voltage level other than 48 Volts DC, the DC power distribution  99  will change the 48 Volts DC to the required voltage level. 
         [0055]    To heat the intelligent heater tube  69 , the 48 Volts from the universal AC/DC converter  97  is converted to 115 Volts AC through 48 Volt DC/115 Volts AC inverter  101 . While taking any local available power  95 , running it through a universal AC/DC converter  97  and then changing the power back to 115 Volts AC through a 48 Volts DC/115 Volts AC inverter  101 , a stable power supply is created. From the 48 Volts DC/115 Volts AC inverter  101 , power is supplied to the heater tube module  103 . The heater tube module  103  then supplies current that flows through the intelligent heater tube  69  via upper clamp  105  and lower clamp  107 . The heater tube module  103  is controlled by the embedded computer  21  so that during a normal test, the thermocouple  71  inside of the intelligent heater tube  69  will indicate when the intelligent heater tube  69  has reached the desired temperature. 
         [0056]    While the center section of the intelligent heater tube  69  heats to desired test set point, the ends of the intelligent heater tube  69  will be maintained near room temperature. To maintain the ends of the intelligent heater tube  69  near room temperature, a coolant flows through an upper bus-bar  109  and lower bus-bar  111 . The coolant inside the upper bus-bar  109  and lower bus-bar  111  cools the upper clamp  105  and lower clamp  107  which are attached to the ends of the intelligent heater tube  69 . The preferred cooling solution is a mixture of approximately 50% water and 50% antifreeze (ethylene glycol). As the coolant flows to the coolant container  115 , the flow is measured by flow meter  113 . To circulate the coolant, a cooling pump  117  pumps the coolant solution into a radiator assembly  119 . Inside of the radiator assembly  119 , the coolant is maintained at room temperature. The radiator fan  121  helps remove heat from the coolant by drawing air through the radiator assembly  119 . From the radiator assembly  119 , the coolant flows into the lower bus-bar  111  then through upper bus-bar  109  prior to returning via the flow meter  113 . 
         [0057]    The flow meter  113  is adjustable so that it can ensure a flow of approximately 10 gal./hr. The check valve  123  helps ensure the cooling system will not be over pressurized. Check valve  123  will open at around 7 psi, but normally 3-4 psi will be developed when running the coolant through the entire system. 
         [0058]    To determine if the intelligent heater tube  69  is shorted out to the housing (not shown in  FIGS. 2 and 2A ), a heater tube short detector  110  monitors a short condition. If a short is detected, the embedded computer  21  is notified and the test is stopped. 
         [0059]    On one end of the intelligent heater tube  69  there is a memory device  125  to which information concerning the test can be recorded by IHT writer  127  as will be discussed in more detail. While a test is being run on a test sample, the IHT writer  127  will record information into the memory device  125 . At the end of the test, all electronic information will be recorded onto the memory device  125  of the intelligent heater tube  69 , except for the manual tube deposit rating. To record this information, the intelligent heater tube  69  will have to be moved to another location to record the deposit rating either (a) visually or (b) through a Video Tube Deposit Rater. At that time, a second IHT writer will write onto the memory device  125 . The Video Tube Deposit Rater may be built into the system or may be a standalone unit. 
         [0060]    The intelligent heater tube  69  is approximately 6¾″ long. The ends are approximately 3/16″ in diameter, but the center portion that is heated is approximately ⅛″ in diameter. Due to very low electrical resistance of aluminum, approximately 200 to 250 amps of current flows through the intelligent heater tube  69 . Both the voltage and the current through the intelligent heater tube  69  is monitored by the embedded computer  21 , but also the temperature of the center section of the intelligent heater tube  69  is monitored by the thermocouple  71  which is also connected to the embedded computer  21 . The objective is to have the center section of the intelligent heater tube  69  at the required temperature. To generate that type of stable temperature, a stable source of power is provided through the universal AC/DC converter  97  and then the 48 VDC/115 VAC inverter  101 . By using such a stable source of power, the temperature on the center section of the heater tube  69  can be controlled within a couple of degrees of the required temperature. 
         [0061]    Referring now to  FIG. 3  of the drawings, a pictorial representation of the coolant flow during a test is illustrated. Like numbers will be used to designate similar components as previously described. A pictorial illustration of the heater tube test section  129  is illustrated on the lower left portion of  FIG. 3 . Coolant from the radiator assembly  119  is provided to the lower bus-bar  111  and upper bus-bar  109  via conduit  131 . From the upper bus-bar  109 , the coolant flows via conduit  133  to flow meter  113 . From flow meter  113 , the coolant flows through conduit  135  to the coolant container  115 . The cooling pump  117  receives the coolant through conduit  137  from the coolant container  115  and pumps the coolant into radiator assembly  119 . If the pressure from the cooling pump  117  is too high, check valve  123  will allow some of the coolant to recirculate around the cooling pump  117 .  FIG. 3  is intended to be a pictorial representation illustrating how the coolant flows during a test. 
         [0062]    Likewise,  FIG. 4  is a pictorial representation of the aeration system for the test sample. Similar numbers will be used to designate like components as previously described. An aeration pump  43  pumps air through conduit  139  to a dryer  45 . The dryer  45  removes moisture from the air to prevent the moisture from contaminating the test sample during aeration. From the dryer  45 , the dried air will flow through conduit  141  to humidity sensor  47 . If the percent relative humidity of the dried air blowing through conduit  141  exceeds a predetermined amount of 20% relative humidity, the system will shut down. While different types of dryers  45  can be used, it was found that Dry-Rite silica gel desiccant is an effective material for producing the desired relative humidity. 
         [0063]    From the percent humidity sensor  47 , the dried air flows through conduit  143  to flow meter  49 , which measures the air flow through conduit  143  and air supply conduit  145 . From air supply conduit  145 , the dried air flows through aeration check valve  50  and conduit  146  sample container arm mounting clamp  147  and sample container arm  149  to aeration conduit  151  located inside of sample container  41 . In the bottom of sample container  141 , a glass frit  153  connects to aeration conduit  151  to cause the dried air to sparge through the test sample in sample container  41 . When the sample container  41  is in place and the sample container arm  149  is connected to the sample container arm mounted clamp  47 , contact  155  sends a signal to the embedded computer  21  (see  FIG. 2 ) indicating the sample container  41  is properly installed. 
         [0064]    Referring now to  FIG. 5 , a pictorial illustration of the flow of the test sample in connection with  FIGS. 2 and 2A  is shown in a schematic flow diagram. The test sample is contained in sample container  41 , which is connected via sample container arm  149  to the sample container arm mounting clamp  147 . Vapors given off by the test sample are discharged through a vent  157 , normally through a vent hood to atmosphere. Simultaneously, the sample drive pump  53  draws some of the test sample out of the sample container  41 . The sample drive pump  53  is a single piston reciprocating pump connected to a pulse dampener. While the pulse dampener  159  may be configured a number of ways, the pulse dampener  159  in the preferred configuration has a diaphragm with a semi-compressible fluid on one side of the diaphragm. This fluid is more compressible than the test sample thereby reducing pressure changes on the test sample flow discharged from the sample drive pump  53 . The sample drive pump  53  is connected to auto pump priming valve  55 . During start-up, the closed auto pump priming valve  55  opens until all of the air contained in the pump and the lines are discharged into the waste container  57 . In case it is needed, a manual priming valve  161  is also provided. Additionally, the aeration pump  43  is turned ON to provide a slight pressure in the sample container  41  of about 2 to 3 psi. The sample vent valve  54  closes to prevent this pressure escaping to atmosphere. This pressure will help push the fluid sample from the sample container  41  to the inlet of the sample drive pump  53 . The 5 psi check valve  56  prevents the pressure in the sample container exceeding 5 psi. During the test, coil  163  also provides further dampening in addition to the pulse dampener  159 . Check valve  59  ensures there is no back flow of the sample fuel to the sample drive pump  53 . However, at the end of a test, flush check valve  89  receives air from flush air pump  87  to flush the test sample out of the system. 
         [0065]    During normal operation of a test, the sample fuel will flow through check valve  59  and through a prefilter  61  removing most solid particles. Following the prefilter  61 , the test sample flows into the heater tube test section  129  and then through the differential pressure filter  73 . Each side of the differential pressure filter  73  connects to the differential pressure sensor  75 . Also connected to the differential pressure filter  73  is the back pressure regulator  79 . The pressure on the system is continuously monitored through the system pressure transducer  81 . If for any reason pressure on the system needs to be released, system/safety vent valve  85  is energized and the pressurized test sample is vented through the four-way cross connection  165  to the waste container  57 . 
         [0066]    At the beginning of the test, to ensure there is no air contained in the system, the differential pressure plus vent valve  91  and the differential pressure minus vent valve  93  are opened to vent any pressurized fluid through the four-way cross connection  165  to the waste container  57 . 
         [0067]    In case the differential pressure filter  73  clogs so that the differential pressure exceeds a predetermined value, differential pressure bypass valve  77  will open to relieve the pressure. 
         [0068]    To determine the exact flow rate of the test sample through the system, the sample flow meter  83  measures the flow rate of test sample from the back pressure regulator  79  before being discharged through the waste container arm  167  and the waste container clamp  169  into the waste container  57 . The waste container  57  is vented all the time through vent  171 . 
         [0069]    Referring to  FIGS. 6A and 6B , a sample container  41  and the sample container arm  149  are illustrated in further detail. A glass frit  153  is located near the bottom of the sample container  41 . A glass frit  153  connects through aeration conduit  151 , elbow  400  in sample container arm  149  to sealing connector  402 . Sealing connector  402  will mate with a receiving connector in the sample container arm mounting clamp  147  (see  FIG. 4 ). As air is blown through the glass frit  153  by the air pump  43 , the air will form small bubbles and sparge through the test sample. Small bubbles are preferred as they have more surface area and more readily dissolve in the test sample. More detail will be given on the glass frit  153  herein below. 
         [0070]    Also extending to the bottom of the sample container  41  is a suction line  404  with a coarse filter  406  on the end thereon. While the coarse filter  406  can be of any particular type, it could be 10 um stainless steel sintered metal filter  153 . The coarse filter  406  is designed to remove larger solid particles that may be in the test sample. The suction line  404  connects through elbow  409  in sample container arm  149  to the suction connector  408 . The suction connector  408  connects to a mating connector (not shown) in the sample container arm mounting clamp  147  (see  FIG. 4 ). 
         [0071]    Also connecting through sample container arm  149  to the top of sample container  41  is vent line  410 . The lower end of vent line  410  terminates below sample container arm  149  but at the top of sample container  41 . The opposite end of vent line  410  connects to vent connector  412  which further connects to vent  157  (see  FIG. 2  and  FIG. 5 ). 
         [0072]    Located near the bottom of sample container  41  is a thermocouple  414  for measuring the temperature of the test sample. The thermocouple  414  sends a signal through thermocouple connection  416  to thermocouple plate  418  in sample container arm  149 . In the sample container arm mounting clamp  147 , an electrical connection with the thermocouple plate  418  will be made and the signal from the thermocouple  414  will be sent to the embedded computer  21  shown in  FIG. 2 . Also, if a signal is being received from the thermocouple  414  through thermocouple plate  418 , that indicates the sample container  41  is in position and the test can begin. 
         [0073]    Referring to  FIGS. 7A and 7B  in combination, the waste container  57  and waste container arm  167  are shown in more detail. The waste container arm  167  has a vent line  470  connecting to vent connector  472  the same as was shown in connection with FIGS.  6 A and  6 B of the sample container arm  149 . However, the vent line  470  and vent connector  472  in waste container arm  167  connects to the vent  171  for the waste container  57  (see  FIG. 5 ). 
         [0074]    During the operation of a test, test sample flow line  420  receives the spent sample from the test through sample connection  422 . Sample connection  422  connects with a mating connector (not shown) in the waste container clamp  169  to receive the spent sample after test from the sample flow meter  83  (see  FIG. 2 ). 
         [0075]    Either when starting up a test or shutting down a test, venting or purging of the system is necessary through vent/purge line  424  and vent/purge connector  426 . The vent/purge connector  426  has a mating connector (not shown) in waste container clamp  169 . The vent/purge line  424  and vent/purge connector  426  receive any fluid or air discharged from system vent valve  85 , differential pressure plus vent valve  91  and differential pressure minus vent valve  93 . Also any air or fuel from the auto pump priming valve  55  will be received through the vent/purge line  424 . The vent line  470 , test sample flow line  420  and vent/purge line  424  all terminate just below the waste container arm  167  in the top of waste container  57 . 
         [0076]    A shorting plate  428  is contained on the face of the waste container arm  167 . Two electrical connections extend through the waste container clamp  169  (see  FIG. 5 ) so that if the two connections are shorted by the shorting plate  428 , the embedded computer  21  will know the waste container  57  is in position. 
         [0077]    Sealing the top of the sample container  41  and the waste container  57  is a flexible washer  430 . It is important that the material of the flexible washer  430  is compatible with fuels or similar petroleum-based products. 
         [0078]    On the side of both the sample container arm  149  and the waster container arm  167  are indentations  432  that can be used for gripping the container arms thereto for installing or removing the respective clamps  147  or  169 . 
         [0079]    With the exception of providing a connection for the thermocouple  414  there through, the sample container arm  149  and the waste container arm  167  are essentially identical. However, the spacing on the connectors are different so that they cannot be mistakenly interchanged. While the sample container arm  149  and waste container arm  167  can be molded as an integral piece, in this preferred embodiment a fuel resistant epoxy is used to seal both the sample container arm  149  and the waste container arm  167  into a solid piece. 
         [0080]    The sample container arm  149  threadably connects in the bottom thereof to threads  434  in the top of the sample container  41 . Likewise, waste container arm  167  threadably connects to waster container  57  through threads  436 . When either the sample container  41  or the waste container  57  is threadably connected in the proper position, flexible washer  430  will seal against leakage. The sample container  41  and the waste container  57  are made from a fuel resistant plastic such as polyolefin or glass. 
         [0081]    Referring now to  FIGS. 8A and 8B , the glass frit  153  is shown in more detail. The aeration conduit  151  (see  FIGS. 6A and 6B ) is received in upper opening  438  of fitting  440 . Fitting  440  is a standard fitting for ⅛″ diameter tubing. The aeration conduit  151  is ⅛″ in diameter. Between the fitting  440  and the glass frit  153  is a frit cap  442 . The frit cap  442  is machined to receive the lower thread  444  to threadably connect with fitting  440 . On the upper part is inside passage  446  of frit cap  442 . The lower outside cylindrical portion  448  of the frit cap  442  is machined to fit just inside of glass frit  153  and has a shoulder  450  to abut the top of the glass frit  153 . The frit cap  442  is made from a fuel resistant material so it will not corrode. 
         [0082]    While many different types of glass frit  153  could be used, in this preferred embodiment, Applicant used a coarse frit made out of glass that has a 12 mm outside diameter, 6 mm inside diameter and 25 mm in length. To connect the glass frit  153  to the frit cap  442 , a fuel-resistant adhesive is used. The flexible washer  430  (see  FIG. 6B ) may be made of a Viton closed cell rubber gasket. 
         [0083]    The sample drive pump  53  is designed and built to pump liquid at high pressure. The sample drive pump  53  is not designed or built to pump air. Therefore any air in lines feeding the sample drive pump  53  can cause pump cavitation if the air reaches the sample drive pump  53 . In the past, this required the operator to manually insert a syringe into the manual priming valve  161  (see  FIG. 5 ) to draw air through the sample drive pump  53  until only the test sample was fed into sample drive pump  53 . 
         [0084]    In the present application, the priming process has been automated with a two step process. On the outlet side of the sample drive pump  53 , the auto pump priming valve  55  is open, allowing flow of any air or remaining test sample to the waste container  57 . This allows venting the sample drive pump  53  to ambient atmospheric pressure. 
         [0085]    Second, during aeration of the test sample in the sample container  41  by the aeration pump  43 , the sample vent valve  54  is closed (see  FIGS. 2 and 2A ). Now the sample container  41  is sealed but the aeration pump  43  continues to pump air into the sample container  41 . This causes a slightly higher than ambient pressure to be built up in the sample container  41 , which forces the test sample to the inlet side of the sample drive pump  53 . After about 30 seconds enough test sample will flow to the sample drive pump  53  to remove any air there from as well as the lines feeding the sample drive pump  53 . Any air or test sample that flows through the sample drive pump  53  at this time will flow through the auto pump priming valve  55  to the waste container  57 . After that occurs, the auto pump priming valve  55  is closed so the test sample will then flow through check valve  59 , prefilter  61  into the cylindrical heater tube test section  65 . The pressure on the sample container  41  is removed by opening the sample vent valve  54 . The sample drive pump  53  continues to draw the test sample from the sample container  41  and continues to pump the test sample at the required flow rate through a thermal oxidation stability tester  20 . 
         [0086]    Early in this process, it is important that the sample container  41  be pressurized for a short period of time with the aeration pump  43 . This is caused by the sample vent valve  54  being closed so the aeration pump  43  builds up a slight pressure inside of the sealed sample container  41 . Normally, the aeration pump will supply about 2-3 psi pressure, but the safety measure sample check valve  56  is located in parallel with sample vent valve  54  to prevent pressures in excess of 5 psi. This pressure in sample container  41  forces the test sample through coarse filter  406 , suction line  404 , elbow  409  and section connector  408  (see  FIG. 6A ) to the sample drive pump  53 . Once sufficient time lapses to allow this to occur, the sample vent valve  54  will again be open. 
         [0087]    Once the sample drive pump  53  is primed, it will continue to pump test sample so that any other air contained in the thermal oxidation stability tester  20  will be forced out. This ensures that the thermal oxidation stability tester  20  is liquid full at the time the thermal oxidation stability is started. 
         [0088]    After the thermal oxidation stability test is finished, system safety vent valve  85  is opened. Flush air pump  87  then pumps air through flush check valve  89  into the thermal oxidation stability tester  20 , including the cylindrical heater tube test section  65  at a flow rate of about 4.2 liters/minute at about 15 psi. This air that is being pumped by the flush air pump  87  pushes the test sample from the thermal oxidation stability tester  20  into the waste container  57 . The test sample is only removed from the thermal oxidation stability tester  20  after the sample drive pump  53  has been turned OFF. First, the flush air pump  87  with the 15 psi air pressure flowing there from at 4.2 liters/minute removes the test sample from the thermal oxidation stability tester  20 , but the continued air flow helps to remove any remaining droplets. The flush air pump  87  runs for about 40 seconds, the first 20 seconds being with the differential pressure bypass valve  77  being opened and the second 20 seconds with the differential pressure bypass valve  77  being closed. The differential pressure vent valves  91  and  93  are closed during the flushing process. Then, the flush air pump  87  is turned OFF so the cylindrical heater tube section  65  may be opened and the intelligent heater tube  69  removed there from as well as prefilter  61  and differential pressure filter  73 . The lines are then cleaned in preparation for the next test. Since the thermal oxidation stability tester  20  has been flushed, a minimal amount of test sample will be left in the thermal oxidation stability tester  20 . From the beginning of the flushing process, the system safety vent valve  85  is left open to insure the thermal oxidation stability tester  20  remains at atmospheric pressure.

Technology Category: 3