US3580047A

US3580047A - Pour and cloud point analyzer

Info

Publication number: US3580047A
Application number: US685587A
Authority: US
Inventors: Samuel W Simpson
Original assignee: Shell Oil Co
Current assignee: Shell USA Inc
Priority date: 1967-11-24
Filing date: 1967-11-24
Publication date: 1971-05-25
Anticipated expiration: 1988-05-25

Abstract

Apparatus for determining the pour point of an oil sample by observing the temperature at which the solidified constituents in the oil sample, upon being heated, will no longer support a small object. This point is indicated by discontinuance in an automatically recorded time/temperature curve during the warning portion of the cycle. The inception point of a plateau in the time/temperature curve during the cooling portion of the cycle is the crystal point. This crystal point correlates with the ASTM cloud point. Modification of the apparatus for continuous service can be accomplished by automatically introducing the sample, then cooling, heating, removing the sample and recirculating a fresh sample.

Description

United States Patent [72] Inventor Samuel W. Simpson Florissant, Mo. [21] Appl. No. 685,587 [22] Filed Nov. 24, 1967 [45] Patented May 25, 1971 [73] Assignee Shell Oil Company New York, N.Y.

[54] POUR AND CLOUD POINT ANALYZER 6 Claims, 12 Drawing Figs.

[52] US. Cl 73/17 [51] Int. Cl .....G01n 25/02 [50] Field ofSearch 73/17, 79

[56] References Cited UNITED STATES PATENTS 2,423,687 7/1947 Davis et a1. 73/17 3,187,556 6/1965 Ehlers... 73/17 3,233,446 2/1966 Ceglia 73/17 3,289,460 12/1966 Anderson 73/17 RECORDER Primary ExaminerJames J. Gill Assistant Examiner-Herbert Goldstein Attorneys-Louis J. Bovasso and J. H. McCarthy ABSTRACT: Apparatus for determining the pour point of an oil sample by observing the temperature at which the solidified constituents in the oil sample, upon being heated, will no longer support a small object. This point is indicated by discontinuance in an automatically recorded time/temperature curve during the warning portion of the cycle. The inception point of a plateau in the time/temperature curve during the cooling portion of the cycle is the crystal point. This crystal point correlates with the ASTM cloud point. Modification of the apparatus for continuous service can be accomplished by automatically introducing the sample, then cooling, heating, removing the sample and recirculating a fresh sample.

Patented May 25, 1971 3,580,047

' e Sheets-Sheet 1 RECORDER 2 23 FURNACE A OIL 22 -49 I 20 0 5 CRYSTAL E POINT AND 5 4 PLATEAU Q T 3 o U I LPOUR START m TIME FIG. 2

FIG. I

DEWAXED DEWAXED LUBRICATING LUBRICATING OIL FURNACE OIL OIL WITH POUR WITH POUR DEPRESSANT DEPRESSANT g CRYSTAL o o 2 33 2 Z 2 POINT 2 2 .J l E POUR O E PouR O E PONT 8 POINT 8 g START START & START TIME -TIIvIE *-TII II FIG. 3 FIG. 4 FIG. 5

INVENTOR'.

s. w. SIMPSON 4M HIS TTORNEY Patented May 25, 1971 3,580,047

6 Sheets-Sheet 2 FIG. 7

|5- a. Q -'-*-l4 A ($1 g INVENTOR'.

s. w. SIMPSON BY. m. 6 z

HIS ATTORNEY Patented May 25, 1971 6 Sheets-Sheet 3 RECORDE R swe L/ FIG. 8

INVENTORI S. W. SIMPSON BY: W

M HIS ATTORNEY Patented May 25, 1971 3,580,047

6 Sheets-Sheet 4 INVENTOR:

S. W. SIMPSON H IS ATTORNEY Patented May 25, 1971 6 Sheets-Sheet 6 FIG.

TI ME FlG.

INVENTOR'.

S. W. SIMPSON H l S ATTORNEY POUR AND CLOUD POINT ANALYZER BACKGROUND OF THE INVENTION 1 Field of the Invention This invention relates to apparatus for determining the pour and cloud points of liquid compositions; In particular, the invention relates to apparatus for determining our points by heating a cooled sample of a liquid composition until a plate supported solely by the solidified constituents in the cooled sample moves downwardly.

2. Description of the Prior Art When liquid petroleum products are cooled, a point is reached at which some of the constituents begin to solidify; and if cooling is continued, the oil eventually possesses a viscosity at which it would not fiow. The temperature at which this occurs under certain conditions is recorded as the setting or solid point and the pour point is defined at the temperature F. above it. One conventional method to determine the pour point of a liquid composition is to heat a sample in a cylindrical glass jar with a fiat bottom to 1 F. or a temperature 15 F. above the expected pour point if this is above 90 F. The sample is then cooled at a specified rate until there is no apparent movement of the surface of the sample when the jar is held horizontally for 5 seconds. This is the setting point; and the pour point, as discussed above, is 5 F. above it. In modern day practice in oil refineries, hundreds of such pour point tests are carried out daily more or less manually and require the constant presence of an operator whose judgment and skill are relied upon for a determination of the pour points. Manipulations are generally made by hand and there is a high variance from sample to sample and from operator to operator so that,'for any particular oil under test, the results obtained by several operators may vary as much as 15 F.

' SUMMARY OF THE INVENTION It is an object of this invention to provide more accurate apparatus for determining the pour point of a liquid composition, such as a lubricating oil.

It is a further'object to provide means for automatically measuring the pour point of lubricating oil base stocks and other oils containing chemical pour depressants. Presently known automatic pour point instruments are not usable on most lubricating oils.

It is a still further object of the invention to provide a continuous automatic instrument for process control or for lubricating compounding.

The teachings of the invention are carried out by disposing a cooled sample of a normally liquid composition, having constituents which solidify upon cooling, into a container. A thermistor probe is then inserted into the container and below the level of the sample in order to measure the temperature of the sample. Means for recording changes in temperature of the sample are connected to the probe. A movable plate is disposed within the container and is supported solely by the solidified constituents within the sample. The plate has an opening to accommodate the lower end of "the probe. The liquid constituents directly below the plate are supported within the container by means of a second plate rigidly fastened in the container. Movement indicating and recording means are attached to the first-named plate for detecting any downward movement when the sample is heated until the softening point in the vicinity of the probe is reached and the plate moved downwardly since it can no longer be supported by the solidified constituents.

The information derived from the apparatus of this invention can be further used to determine the cloud point of the liquid sample since the crystal point of the sample correlates directly with the ASTM cloud point. The thennistor crystal point derived at by the preferred method has been found to be 3 the most accurate tool to predict the low temperature characteristics of fuel oil.

The apparatus described herein is suitable for use with any liquid composition which contains solidified constituents when cooled. However, it is particularly applicable to oils, including synthetic lubricating oils, mineral hydrocarbon oils, and fuel oils, since the pour and cloud points of these oils is an important aspect of quality evaluation in the oil industry.

Theseand other advantages will be further apparent from the following description of a preferred embodiment, taken in connection with the attached drawings, which form a part of this specification.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a partly diagrammatic vertical sectional view of an arrangement of apparatus for carrying out the invention;

FIG. 2 through 5 are graphs showing typical cooling-warming curves of various oils utilizing the apparatus of FIG. 1;

FIG. 6 is a diagrammatic view, partly in section, showing the apparatus of FIG. 1 adapted to an automatic assembly;

FIG. 7 is a diagrammatic view, partly in section, of a cooling bath assembly to be utilized with the automatic apparatus of FIG. 6;

FIG. 8 is a wiring diagram for the automatic apparatus of FIG. 6;

FIG. 9 is a partly diagrammatic vertical sectional view of an automatic-filling and -discharging assembly to be used with the apparatus of FIG. 6;

FIG. 10 is a wiring diagram for the automatic-filling and discharging assembly of FIG. 9;

FIG. 11 is a schematic view of a simplified method and apparatus forestimating automatically certain properties of an oil sample; and

FIG. 12 is a typical cooling curve of the oil sample of FIG. 1 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning to the drawings, FIG. 1 shows a standard pour and cloud point test jar 11, preferably of glass, for automatically measuring the pour point of an oil sample 12 by observing the temperature at which the solidified constituents in the oil sample 12, after being heated, will no longer support a small ob- I ject. A measuring device,- such as a thennistor probe 13, for making temperature measurements at a point source is disposed in jar.ll and below the level of sample 12. A thermistor probe is a very small solid-state semiconductor with a negative coefficient of resistivity which is used to sense temperature by measurement of resistance. The probe 13 is coupled to both a bridge circuit and a strip chart recorder for making profiles of time versus temperature in a manner to be discussed more fully hereinbelow.

A small, preferably circular, movable plate 14 having a hole or opening 15 in its center is placed around the lower end of probe 13, as can be seen in FIG. I. A wire adjusting rod 16 is attached to plate 14 to indicate any slight downward .movement of plate l4 as will be discussed in more detail below. A supporting device such as a plate .17 is rigidly supported below the lower end of probe 13. Plate 17 supports any solidified constituents in the cooled oil sample immediately surrounding and directly below the probe end of thermistor probe 13. This support plate 17 is necessary to prevent the solidified constituents surrounding plate 14 and the lower end of probe 13 from sinking into the warmer surrounding liquid of sample 12 when the sample is being heated, thereby indicating downward movement of plate 14 before the pour point of sample 12 is reached at the lower end of probe 13. In other words, the property being measured is the temperature .when plate l4 sinks in sample I2 through the solidified constituents and not the temperature when the solidified constituents begin to liquefy and sink within the surrounding liquid of sample 12.

Jar 11 is closed by a resilient stopper 18 which has a plurality of openings extending therethrough to allow the various components of the apparatus to pass. Supporting plate 17 is preferably rigidly mounted in jar 11 by a pair of rigid means such as wires 19, 20: Wires l9 and 20 are preferably attached at one end to stopper I8 and at their free end to supporting plate 17. Wire rod 16 is freely slidable in glass bushing 22 which bushing is fixed in stopper 18. The upper portion of wire rod 16 extends beyond stopper 18 and is angled at 23 for a purpose to be described hereinbelow. A switch 24 consisting of a pair of

wires

25 and 26 is rigidly mounted in a glass housing 27 fixed in stopper 18. One end of wire 25 is connected to the positive terminal of a strip chart recorder 28 and passes through stopper 18 and out of the top of glass housing 27 where it is angled at 29 to form one-half of a seat for angled portion 23 of wire rod 16. One end of wire 26 is connected to the negative terminal of strip recorder 28 and passes through stopper 18 and out of the top of glass housing 27 where it is oppositely angled at 30 to angled portion 29 of wire 25 to form the other half of a seat for angled portion 23 of rod 16 as can be seen in FIG. I. The purpose of

wires

25 and 26 is to short out strip recorder 28 when contact is made with the adjusting wire rod 16 which moves downwardly whenever plate 14 is sinking in sample 12. The

wires

25 and 26, at least adjacent

angled portions

29 and 30, thus must necessarily be extremely close to each other so that angled portion 29 can readily bridge the gap between them.

In a preferred embodiment of the invention, an electromagnet 31 automatically lifts and holds the angled portion 23 of rod 16 in spaced relation from switch 24 until the sample 12 is cooled beyond its solid point. When this point is reached, the sample 12 in its jar 11 is moved to a warmer bath, the electromagnet 31 is removed and the sample 12 is allowed to soften while being heated. The electromagnet 31 is supported by any known means and can be removed either manually or automatically as will be discussed hereinbelow.

Alternately, a small section of wire insulation (not shown) can be placed on angled portion 23 of rod 16 and removed when desired.

Accordingly, 'after actuating strip recorder 28 to record changes in the temperature of the sample 12, the solidified constituents in sample 12 will support the adjusting rod 16 and plate 14 until the softening point of the sample 12 in the immediate vicinity of thermistor probe 13 is reached. At the softening point, the plate 14 and adjusting rod 16 will begin to moveslowly downwardly. Experiments have shown this rate of movement to be approximately 1 millimeter per degree Fahrenheit i.e., the rate of downward movement of plate 14 and rod 16 is for a distance of approximately I millimeter for each degree Fahrenheit of temperature change. After approximately 1 millimeter of downward movement, the angled portion 23 of adjusting rod 16 comes into contact with switch 24 thereby shorting and thus stopping the strip recorder 28 at the temperature shown experimentally to correspond to the pour point of the oil sample 12. Comparative data have demonstrated the disclosed method to give more accurate pour point values than the conventional manual method. The preferred method is not influenced by tester bias, nor are the determinations restricted to products which do not contain pour point depressants since the test is made on a static sample.

FIGS. 2 through show typical cooling and warming curves resulting from tests performed on different types of samples as indicated using the preferred method. The pour point is indicated by discontinuance of the time versus temperature curve when the plate begins to sink in the sample. The crystal point of the furnace oils is indicated by the portions of the curves in FIGS. 2 and 3. In other words, the inflection point of a plateau in the time versus temperature curve during the cooling or chilling portion of the cycle is the crystal point. The crystal or cloud points determined here are directly equivalent to the ASTM (D-97) cloud point (i.e., the American Society for Testing and Materials standardization of cloud points) as a definite correlation exists.

FIG. 6 shows the preferred method of FIG. 1 adapted to an assembly for automatic operation. The assembly of FIGS. 6 is to be used in conjunction with the cooling bath assembly of FIG. 7. In FIG. 6, like elements refer to like parts of FIG. 1.

A resilient stopper 32, having a preferably plastic integral housing 33 on its upper end, has been substituted for the stopper 18 of FIG. 1. The electromagnet 31 of FIG. 1 is mounted in the upper portion of housing 33 and the extreme upper portion of housing 33 is closed by resilient stopper 34. A plate 35 is magnetically retained in position by electromagnet 31. The plate 35 is preferably of soft iron and covered with aluminum foil to overcome any residual magnetism and insure release by the electromagnet 31 whenever desired. Wires 36 couple the electromagnet 31 to conventional releasing means (not shown in FIG. 6). Wires 37 couple the thermistor probe 13 to both a bridge circuit and the strip recorder 28 as will be discussed more fully hereinbelow. Wires 37 and

switch wire

25 and 26 extend out of an opening 38 in housing 33. An adjusting rod 39 is fixedly attached at its upper end to plate 35 and at its lower end to plate 14. Rod 39 passes through an opening in stopper 32. Thus, rod 39 has been substituted for the rod 16 in FIG. 1 embodiment and the release of electromagnet 31 allows iron plate 35, attached rod 39, and plate 14 to move downwardly as the liquid sample is heated. Rod 39 has an angled portion 40 adapted to engage switch 24 as it moves downwardly. Extension portion 40 is formed of a horizontal leg portion 40 having an end attached to vertical rod 39 and its free end attached to an angled portion 40', the free end of which is also attached to rod 39 as can be seen in FIG. 6. Both switch 34 and extension 40 are preferably of platinum and can contact each other under a force of less than 4 grams. Conventional leaf spring switches having platinum contacts may be substituted for the

switches

24 and 40 if desired.

After a specified volume of sample 12 is introduced into the test jar 11, the glass lower portion (below stopper 32) is lowered into the cooling bath assembly 41 of FIG. 7. The cooling bath assembly 41 shows three adjustable thermoswitches Fl through F3 mounted in the upper portion of assembly 41 which have been preset to control (i.e. make and break) at temperature of 0 F -30 F. and 60 F., respectively. A hollow chamber 50 surrounds bath portion 51 of the apparatus. This chamber 50 allows for expansion for a cooling agent, such as Freon, which is introduced through solenoid 46 as will be explained hereinbelow. Solenoid 46 is coupled to chamber 50 of bath portion 51 by any known means, such as tubing 52. Vent 53 at the upper portion of cooling bath assembly 41 and communicating chamber 50 allows for the relief of pressure of the cooling agent introduced into chamber 50. Thermoswitch F4 is coupled to a pair of lamps 47 in lamp housing 54 and to the automatic-cooling circuit as will also be discussed below. The cooling bath assembly 41 can be programmed to first cool to 0 F and then to 30 F and then either stop or proceed to 60 F. (as required to simulate the ASTM (D-97 method) or it can cool directly to -60 F. without stopping at the 0 F. or 30 F. points. The use of the rapid cooling rate whenever possible is advantageous because it reduces the total testing time. Distillate fuels such as gas oils and furnace oils can be tested with a rapid cooling rate. However, pour points of some lubricating oil base stocks are affected by cooling rate when they contain chemical pour depressants. This precludes the use of the fast cooling rate of all compounded lubricating oils containing these base stocks. Also, in order to conform to the ASTM (D-97) method, prescribed cooling methods must be used.

Referring now to FIG. 8, current from any preferred source, such as AC source 42, to the circuit is controlled by main power switch SW-8 and fuse 43.'A transformer T1 energizes light source 11 and also energizes latching relays R1 and R2, relays R1 and R2 being controlled by starting switch SW-l and stopping switch SW-2. Power source 42 also energizes transformer T2 which supplies a rectifier bridge 44 for the voltage supply to electromagnet 31 which is in circuit with the latching coil 1 of relay RI. Switches SW-9, SW-3, and SW-7, respectively, control thermoswitches F-l through F3 through the primary windings l of relay R-l. Switch SW-9 is preferably mounted on the control box (not shown), switch SW-3 is coupled to strip chart recorder 28 and is preferably preadjusted to be actuated at +20 F., and switch SW-7 is a double-pole, double-throw switch for bypassing the lower limit switch and stopping the cooling cycle at 1 0 F. as will be explained in detail later. Switches F-l through F3 are thermoswitches which are normally closed at above control temperature and are adjustable. F-l is preferably normally preset to control at a temperature of 0 F., F2 at30 F., and F3 at 60 F. A motor driven interrupter 45 is in circuit with thermoswitches Fl through F3 and is controlled by solenoid 46, an electrically operated valve which opens on signal from the device and admits the cooling agent to initiate the cooling cycle as will be explained hereinbelow. Lamps 47 in the cooling chamber are energized by a small thermoswitch F-4, preadjusted to +40 F., through the delatching coil 2 of relay R-l. The latching coil 1 of relay R-2 energizes the temperature-measuring bridge circuit 48 coupled to both strip recorder 28 and thermistor probe 13. The delatching coil 2 of relay R-2 is coupled to a motor driven interrupter 49 for the balancing motor 50 of recorder 28. SW-6 is preferably of platinum and is a contact switch energized by the secondary winding 2 of relay R-2 and refers to the probe contacts (for example, 23 and 24 in FIG. 1) that close when the pour point is reached.

The programming control of the wiring diagram of FIG. 8 is thus accomplished in the following manner. When the start switch SW-l is pressed, it energized the two latching relays R-1 and R2 which in turn energize the separate circuits that control the adjusting rod 16 and plate 14, the temperaturemeasuring bridge circuit 48, and the cooling cycle. The cooling cycle is initiated when the start switch SWl energizes therrnoswitch F-l which is preferably preset to a control at a temperature of 0 F. through the latching relay R-l. Recorder switches SW-3, SW-4, and SW-S, coupled to the strip chart recorder 28, are normally openand are adjusted to close when the recorded sample temperature reaches +20 F., -l0 F., and 40 F., respectively. Recorder switches SW-3, and SW-4, when closed, will complete the circuit to thermoswitches F2 and F3 which are preferably preset to control at 30 F. and 60 F., respectively. Switch SW-S ends the cooling cycle by deenergizing relay R-l when the recorded sample temperature reaches 40 F. Double pole, double throw switch SW-7 has two positions. In the B" position, it will end the cooling cycle by deenergizing relay R-l when the sample temperature reaches 1 0 F. In the A position, switch SW-7 allows the cooling cycle to proceed to a sample temperature of 40 F. This cooling sequence which conforms to the ASTM (D-97) method can be summarized as follows:

solidified constituents of sample 12, stops the cooling cycle and turns on thermoswitch-controlled heating lamps to speed the melting or softening cycle. When the sample 12 softens in the immediate vicinity of the temperature sensing thermistor probe 13, the plate 14 and adjusting rod 16 drop and close the probe contacts (SW-6) in the circuit. This energizes coil 2 of relay R-2 which turns off the bridge circuit 48 and balancing motor of the recorder 28, tracing a straight line on the strip recorder 28 at the pour temperature.

A continuous chart advance is used to record the temperature in this embodiment; however, the use of a continuous recorder is not necessary where only the pour point is to be measured. In these cases, a simple modification would allow the chart drive motor to be actuated after recording the pour point. This feature would be more desirable on a process instrument because it presents graphically essential points for easy surveillance by the operator.

A sample introduction and removal system for converting the apparatus of FIG. 6 to a continuous processing apparatus is shown in FIG. 9 wherein like numerals refer to like parts of FIG. 6. Here, glass jar 11 has been replaced by a housing 55, preferably of copper, having a funnel portion 56 at its lower end communicating with a sample discharge tubing 57. In other words, the test jar 11 of FIGS. 1 and 6 has been eliminated and the metal wall of the cooling bath itself performs this function. In this embodiment of the invention, if desired, stopper 32 may be eliminated and housing 33 may be connected directly to assembly 41. The method of programming the cooling cycles will be the same as in the apparatus of FIG. 6. If necessary, a heat exchanger can be used to precool the materials before charging to the test cell through the solenoid valve 46. Pipe 58 communicates with the sample 12 in housing 55 and drains off any overflow to a drain (not shown) common to discharge tubing 57 as shown in FIG. 9. A sample discharge solenoid 59 coacts with sample discharge tubing 57 for purposes to be explained below. A small heater 60 coacts with discharge pipe 57 to heat the drained fluid sample 12. A pair of heaters 61 are used to heat the sample 12 in housing 55. The sample 12 is introduced into housing 55 through pipe 62 which communicates with both housing 55 and a sample introduction solenoid 63 which cooperates with a continuous sample bypass 64 for storing sample 12 prior to introducing it in the assembly. A plate 64, of suitable material that will not be attacked by aromatics present in certain oils, such as Teflon, is preferably attached to the underside of resilient stopper 32 and retains the

elements

13, 19, 20, and 39 in place in housing 55.

Temperature, F.

Switch positions Bath Sample SW-l SW-3 SW-4 SW-5 Fl F2 F3 SW-7 Ambient Ambient O l 0 O O C C C 0 Approaching +20 0 0 O O 0/0 C C 0 20 O C O O 0/0 C C 30 Approaching -10... O C O O 0 C -30 0 c c 0 0 c/o c B pos1it)i0n (en f cooling cyc e A roachtn 40 O C C O O O 0/0 o c o 0 o 0 0/0 p g o s eye 8 1 Closed momentarily to energize latching relays R-1 and R2.

NOTE: 0 denotes closed switch position; 0 denotes open switch position; C/O denotes controlling point.

below the expected solid point. When the programmed v switching point for stopping the cooling cycle or the manually controlled stopping point is reached, the completion of the circuit through coil 2 of R-l deenergizes the relay R-1 and allows the adjusting rod 16 and plate 14 to rest freely on the The wiring circuit for the continuous processing apparatus of FIG. 9 is shown in FIG. 10 where again like numerals refer to like elements of the circuit of FIG. 8. The circuit of FIG. 10 is essentially the same as the circuit of FIG. 8 with addition of the continuous processing feature. Initial flushing and filling of the sample cell 55 will be accomplished manually by closing both inlet solenoid switch SW-12 and discharge solenoid switch SW-13 which are coupled to the power supply 42 and the recorder 28 as can be seen in FIG. 10. This will energize both the sample introduction solenoid valve 63 and the sample discharge solenoid valve 59. After approximately 1 minute,

the sample discharge solenoid valve 59 will'then be closed by opening switch SW-l2 to trap the initial sample 12. Depressing the switch SW-l will start the cooling cycle and the apparatus will automatically initiate and proceed through repeated cycles of sample analyses.

The functioning of the continuous processing instrument will be identical to the apparatus of FIG. 6 until the pour point is reached. At this point, coil 2 of relay R-2 (see FIG. 10) will be energized which in turn starts a multicam timer 65. Four contacts, numbered A through D in FIG. 10, control four circuits: A interrupts power to the recorder balancing motor 50, B energized the heater 60 located on the sample discharge tube 57 and the heaters 61 located between the concentric walls of the cooling chamber for a period of time sufficient to assure sample fluidity, C energizes the sample discharge solenoid valve 59 for a period of time sufficient to drain off the sample 12, and D energizes the sample introduction solenoid valve 63 for a period of time sufficient for flushing and filling the sample housing 55. This sequence of opening and closing, the

valves

59 and 63 will drain and refill housing 55 with a' 2c fresh sample 12. Subsequently, the recorder motor 50 will be energized and the recorder 28 will proceed to the warm tem-' perature end of the chart. When the recorder 28 reaches this point, microswitch SW-ll coupled to recorder 28 will energize latching relays R-1 and R-2 again initiating the analysescycle.

A further embodiment of the invention involves an apparatus and technique for automatically making precise temperature versus time cooling curve measurements from which a very accurate estimate of ASTM cloud point, solid point (i.e., the quasi ASTM solid point used to define the ASTM pour point), and ASTM freeze point of certain solvents such as paraffin-containing hydrocarbons can easily be made.

The technique involves the use of a thermistor probe 66 (FIG. 11) which is placed in approximately the center of a sample 67 of a solvent such as paraffin-containing distillates, disposed in container 68. The thermistor probe 66 measures the temperature of the sample 67 as it is lowered at a constant rate. Wax crystals eventually begin to form as the temperature is lowered. When these crystals begin to form around the lower end 69 of thermistor probe 66, heat is liberated and detected as a plateau on a time versus temperature curve. This plateau correlates with the ASTM cloud point, solid point (i.e., the quasi ASTM solid point), and the ASTM freeze point properties of the distillates. The apparatus illustrated in FIG. 11 for automatically measuring these properties thus consists of a strip recorder 70, a bridge circuit 71, the end 69 of thermistor probe 66, test jar or container 68, and a cooling bath 72. The sample 67 is disposed in a standard cloud and pour point test jar or container 68. Therrnistor probe 66 is coupled to a bridge circuit 71 which gives a millivolt signal within the span of a multipoint strip chart recorder 70. The

thermistor probe 66 is inserted into the center of the sample 67. The test container 68, thermistor probe 66, and sample 67 are then placed in a low temperature cooling bath 72. The temperature is lowered at a constant rate by any conventional means and when wax crystals begin to form around the end 69 of thermistor probe 66, a plateau appears on the time versus temperature curve recorded by the strip chart recorder 70 as shown graphically in FIG. 12. The apparatus disclosed is capable of running a plurality of samples simultaneously. It has found use in controlling the cut point in the fractionation of catalytic cracked and straight run gas oils and in controlling the cloud point of finished furnace oils. This apparatus provides for more precise measurements and allows closer regula tion of processing to maximize yield without sacrificing qualithat such modifications and alterations fall within the spirit and scope of the appended claims.

I claim: 1. Apparatus for determining the pour and cloud points of a 15 normally liquid composition having constituents which solidify upon cooling comprising:

a casing adapted to contain a cooled sample of said liquid composition containing solidified components; temperature-measuring means disposed within said casing for measuring the temperature of said sample as a function of time; temperature-indicating means connected to said temperature-measuring means for indicating the temperature of said sample; a vertically movable plate means carried within said casing and adapted to be supported therein solely by said solidified constituents disposed within said casing and surrounding the lower end of said temperature-measuring means;

movement-indicating means attached to said plate means and connected to said temperature-indicating means for indicating any downward movement of said plate;

sample supporting means rigidly carried by said casing below the lower end of said temperature-measuring means to support the solldlfied constituents of said sample immediately surrounding and directly below said temperature-measuring means;

heating means operatively engaging said casing for heating said sample;

cooling means operatively engaging said casing for cooling said sample;

retention means connected to said casing for maintaining the movement-indicating means in spaced relation from said temperature-indicating means; and

means responsive to a predetermined temperature cooperating with said retention means for releasing said movement-indicating means after the sample has solidified.

2. Apparatus as in claim 1 wherein said plate means has an 50 opening therein to accommodate the lower end of the temperature-measuring means.

3. Apparatus as in claim 1 wherein the weight of said plate means is approximately 4 grams.

4. Apparatus as in claim 1 wherein said cooling means comprises electrically operated solenoid valve means connected to said casing adapted to open to admit a colling medium therein to initiate the cooling cycle of said sample.

5. Apparatus as in claim 4 wherein said cooling means includes electrical circuit means connected to said valve means for actuating said cooling means.

6. Apparatus as in claim 1 including sample refilling means connected to said casing for draining any sample within said casing, flushing said casing after draining and refilling said casing with a fresh sample.

Claims

2. Apparatus as in claim 1 wherein said plate means has an opening therein to accommodate the lower end Of the temperature-measuring means.
3. Apparatus as in claim 1 wherein the weight of said plate means is approximately 4 grams.
4. Apparatus as in claim 1 wherein said cooling means comprises electrically operated solenoid valve means connected to said casing adapted to open to admit a colling medium therein to initiate the cooling cycle of said sample.
5. Apparatus as in claim 4 wherein said cooling means includes electrical circuit means connected to said valve means for actuating said cooling means.
6. Apparatus as in claim 1 including sample refilling means connected to said casing for draining any sample within said casing, flushing said casing after draining and refilling said casing with a fresh sample.