US3735634A

US3735634A - Vapor-over-liquid temperature analyzer

Info

Publication number: US3735634A
Application number: US00150132A
Authority: US
Inventors: R Clinton; R Mator; J Condron
Original assignee: Gulf Research and Development Co
Current assignee: Chevron USA Inc
Priority date: 1971-06-04
Filing date: 1971-06-04
Publication date: 1973-05-29
Anticipated expiration: 1990-05-29

Abstract

An on-stream vapor-over-liquid ratio temperature (V/L) analyzer comprising a system wherein a constant volume of gasoline per unit time is supplied to a bomb, and pressure, temperature, and volume of vapors removed are held constant at some particular value simulating some particular V/L ratio and corresponding V/L ratio temperature. In the event of a change in the V/L ratio of the gasoline, only pressure will vary in response thereto, and this change in pressure is made to cause an inverse change in the temperature to bring the system back to the initial operating pressure. In general, the temperature required to maintain a fixed V/L ratio is measured.

Description

mite States Patent Clinton et al.

[54] VAPOR-OVER-LIQUID TEMPERATURE FOREIGN PATENTS OR APPLICATIONS ANALYZER 13,280 9 1963 Japan ..73/53 [75] Inventors: Russell M. Clinton, Gibsonia; James A. Condron, Freeport; Richard T. Primary Examiner-Richard C. Queisser Mator, Pittsburgh, all of Pa. Assistant Examiner-Joseph W. Roskos [73] Assigneez I Gulf Research & Development Attorney-Meyer Neishloss, Deane E. Keith and W1!- ham Kovensky pany, Pittsburgh, Pa. [22] Filed: June 4, 1971 i [57] ABSTRACT [21] Appl. No.: 150,132 A I An on-stream vapor-ove'r-liquid ratio temperature (V/L) analyzer comprising a system wherein a constant volume of gasoline per unit time is supplied to a [52] US. Cl. ..73/64.2, 73/36, 73/53 bomb, and pressure temperature and Volume of [51] [Ill- Cl. vapors removed are constant at some particular [58] Field of Search ..73/64.2, 53, 35, value Simulating some particular v/L ratio and 73/36 responding V/L ratio temperature. In the event of a change in the V/L ratio of the gasoline, only pressure [56] References d will vary in response thereto, and this change in pres- UNITED STATES PATENTS sure is made to cause an inverse change the temperature to bring the system back to the initial operat- 2,339,026 1/1944 Mercer v.73/36 ing pressure. In general, the temperature required to 2,119,786 6/1938 Kall m maintain a fixed V/L ratio is measured. 3,145,561 8/1964 Thmpson.. 3,276,460 10/ I966 Feld ..73/64.2 UX 23 Claims, 3 Drawing Figures 2a 5 100 H 24 ii VAPOR-OVER-LIQUID TEMPERATURE ANALYZER This invention pertains to an analytical device useful in the petroleum refining industry for determining the vapor-over-liquid (V/L) ratio temperature of light hydrocarbon liquids, particularly gasoline. The V/L, ratio is one of a large number of characteristics of gasoline which are controlled in the refinery in controlling the quality of the gasoline which is sold to the public. Essentially, the V/L ratio is a measure of the volatility of the gasoline. Generally, this ratio, usually a number on the order of about 20, indicates that under certain specific conditions of temperature and pressure a volume of liquid gasoline will produce 20 times that volume of vapor. More specifically, the V/L ratio is measured in the laboratory in accordance with ASTM method D 2533. This standard may be referred to for further background on V/L ratio.

The difference in the terms V/L ratio and V/L ratio temperature as used herein should be kept in mind. The V/L ratio is a characteristic of the material, and the V/L ratio temperature is simply the temperature at which the V/L ratio is determined, both as per ASTM D2533. The invention operates directly with the temperature but effectually with the ratio.

In the gasoline industry the refiner must accurately control the V/L ratio because it is varied both with the season of the year and with the geographical sales area. The general consideration is that for warmer marketing areas the gasoline has to be less volatile. The specific considerations for which and the ranges over which the ratio is varied is not essential to an understanding of the invention.

The present invention provides an inexpensive, foolproof, efficient, and accurate instrument for continuously controlling the V/L ratio temperature of a flowing stream of gasoline in the refinery. More generally,

- the invention could be used to determine the V/L ratio temperature of any substance having a vapor pressure. It is contemplated, however, that the lighter hydrocarbon substances, up to kerosine, would be the ones with which the invention would have the most utility. Therefore, the term gasoline as used in the specification and claims hereof should be understood to mean any substance with which the invention might be used. Less volatile materials would require a hotter bath, as will appear more clearly below.

The instrument of the invention includes a vessel to which pie-conditioned liquid gasoline is supplied at a constant volume per unit time. This pressure vessel is housed in a heat bath, preferably a closed heat bath. A vacuum pump is connected to the-vessel, and means are provided to cause the vacuum pump to withdraw a constant volume of vaporous material per unit timefrom the vessel. Therefore, volume supplied, volume removed, and pressure are all held constant at any given moment of time. If the gasoline stream being monitored should experience a perturbation in its V/L ratio, then this change in volatility would evidence itself as a change in pressure within the vessel. The invention provides means to control the pressure to a pre-set value, advantageously the ASTM test pressure. This change in pressure in the vessel is caused to conno] the temperature of the bath to correct for the change in volatility of the liquid to thereby return the pressure to its pre-set value. Thus, system temperature is precisely the V/L ratio temperature.

An important advantage of the invention is that the data produced is a direct and absolute measure of the V/L ratio temperature as per the above identified ASTM test.

The above and other advantages of the invention will be pointed out or will become evident in the following detailed description and claims, and in the accompanying drawing also forming a part of the disclosure, in which:

FIG. 1 is an overall somewhat schematic and somewhat mechanical showing of most of a system embodying the invention; v

FIG. 2 is a detailed showing of part of the apparatus of FIG. 1; and

FIG. 3 is a schematic diagram of an electrical circuit for the system shown in FIG. 1. Referring now in detail to the drawing, in FIG. l the apparatus 10 embodying the invention comprises a heat bath vessel 12 containing a heat conducting fluid 14 such as water, transformer oil, or a mixture of ethylene glycol and water. In the successfully constructed embodiment, a sealed system was provided with a mixture of about percent ethylene glycol in water as the heat transfer fluid. The criteria in selecting a heat exchange fluid are that it have a high thermal conductivity, and the lowest specific heat compatible with the particular on-off temperature control used.

Means are provided to circulate the fluid l4 and to control its temperature. To this end, vessel 12 comprises a downwardly extending leg 16, and a branching line 18 at the lower end thereof leading into a fluid circulating pump 20. The other side of pump 20 is connected to a line 22 which feeds the fluid into a heater jacket 24, the opposite end of which is connected by a line 26 back into vessel 12. An elongated electrical heater 28 is located within jacket 24 and is connected into the circuitry of the invention, as will be described below.

A vaporizing bomb or pressure chamber 30 is positioned in the fluid 14 in vessel 12. Means are provided to continuously supply a constant volume of gasoline per unit time from a process line or the like to bomb 30. To this end, a line 32 extends from any suitable sampling means, such as a bypass loop, not shown, to a constant displacement pump 34, of any suitable type. The constant volume of gasoline flows into the temperature bath 12 via a line 36 and through a coiled portion 38 thereof surrounding the bomb 30. Coil 38 serves the function of preheating the gasoline before it enters the top of the bomb 30 as at 40. Entrance 40 is in the nature of a bell end on coil 38, and serves to enhance the creation of a film of gasoline entering onto the top inside wall of chamber 30.

Means are provided to continuously withdraw a constant volume of vapor per unit time out of bomb 30. To this end, a line 42 is tapped into bomb 30 and extends to needle valve 44. A branching line 46 off of line 42 prior to the needle valve 44 leads to the reference side of a flow controller 48. The vertical leg of line 42 is larger than the horizontal leg containing valve 44 because of the specific components which were used. The desideratum is that line 42 be large enough to allow drain-back of any condensed liquid. A line 50 connects the opposite side of needle valve 44 to one end of a rotometer 52. The other end of rotometer 52 connects into the lower end of flow controller 48. The upper end of controller 48 is connected to a line 54 which includes a vacuum regulator 56 and a gauge 57, and which leads thereafter to a vacuum pump 58. The vapor drawn out of chamber 30 by pump 58 is exhausted via a vent 60. The needle valve 44 and the flow control 48, arranged as shown in the drawing, permits the withdrawing of a selectable constant volume of vapor out of the bomb, in a manner which will be de scribed below in the operation section and in conjunction with the description of FIG. 2.

Means are provided to constantly sense the pressure in bomb 30 and to operate an electrical contact in response to changes thereof. To this end, a line 62 extends from bomb 30 via a flashback arrestor 64 and terminates at a special mercury switch 66. Switch 66 may be thought of as a combination of a mercury manometer, a mercury barometer, and an electrical mercury switch. The switch includes a housing or mercury reservoir 68 and an elongated glass tube 70 extending thereinto. The tube is closed at its upper end and evacuated. An electrical contact 72 is sealingly fixed into the upper evacuated and sealed end of the tube 70. The open lower end of tube 70 is in the mercury in reservoir 68. A predetermined quantity of mercury is supplied in housing 68 and tube 70 so that pressure changes in the bomb 30 transmitted via the line 62 to the top surface of the mercury in housing 68 causes the level of mercury in tube 70 to change in response to said changes in pressure in bomb 30. In the successfully constructed embodiment, tube 70 was made of glass, 860 mm long, and had an outside diameter of one-fourth inch. Any absolute pressure sensing controller may be used in place of switch 66, such as a DP cell, but the apparatus shown is preferred because of its economic advantages and simplicity and reliability.

The line 62 passes through a wall of vessel 12, and means not shown are provided to make a fluid tight seal at that juncture. Line 62 also includes a T 74 including an on/off valve 76, which T and valve are convenient for start up, as will be explained in the operation section below. The line 42 enters the chamber 30 above the line 62, and both lines enter high on the bomb 30. This arrangement of the

lines

42 and 62 will protect the vacuum system in the event of an excessive liquid backup into bomb 30. Arrestor 64 serves to isolate the switch 66 to thus provide an explosion proof apparatus.

Any flow of the gasoline supplied to the bomb which does not vaporize, and any re-liquified gasoline, and any other liquid in the chamber 30, flow out via a leg 78 extending from the lower end thereof through the temperature jacket leg 16. The lower end of jacket 16 is sealed around leg 78 by any suitable means 80. Means 80 may comprise a compression fitting. A relatively long length of temperature jacketed leg 78 is provided because the gas/liquid interface location will vary with barometric pressure, and must be maintained at the bath temperature to prevent condensation of vapors in the system. After exiting from the temperature bath, the leg 78 connects to a horizontal portion 82, and then another vertical portion 84 extending back up towards bomb 30, and then yet another horizontal portion 86, terminating in a downwardly extending drain 88. Ambient pressure is provided over the liquid in vertical portion 84 via an atmospheric vent 90 joined to the pipe at the juncture of

portions

84 and 86. The presence of atmospheric pressure at this location is required to balance the pressure in the bomb via the leg 78, called a seal leg, and to prevent siphoning via drain 88. An enlarged portion or reservoir 85 is provided in portion 84 just below portion 86 to serve as an additional safety against loss of liquid in the seal leg 78. The length of vertical portion 84 is critical with regard to the ambient barometric pressure at the location in which a particular apparatus embodying the invention is to be used. Therefore, means will be provided, although are not shown for the sake of clarity, to adjust the length of portion 84 for this purpose. Such means could comprise simply replacing the entire pipe constituting portions 82 through 90, or providing a plurality of taps along an elongated portion 84, each marked with an elevation above sea level, or other means which will be obvious to one skilled in this art. Alternatively, a float trap could be provided in lieu of seal leg 78 to hold a constant liquid level.

Means are provided to sense and record the changing temperature of fluid 14. To this end, a thermocouple 92 located in fluid 14 is connected via a wire 94 to a recording device 96. Of course, the signal on wire 94 could be used for control purposes. The trace 98 shown in the drawing is exemplative of the type of result obtained. A safety thermostat 100 is positioned against jacket 24 to sense its temperature and is connected into the circuitry as shown in FIG. 3.

Referring now to FIG. 2, the controller 48 is shown in more detail, although still somewhat schematically. This is a commercial device, and comprises a housing 102 which is divided into two chambers by a wall 104 which is formed with a passageway 106. The right hand chamber communicates with line 54. The left hand chamber includes a diaphragm 108 which carries a closure member 110 cooperable with passageway 106 to open and close the passageway. A spring 112 extends between the wall 104 and the diaphragm 108 to normally urge the closure member 110 away from opening 106. The rotometer 52 communicates with the left hand chamber, i.e., the space between wall 104 and diaphragm 108. The operation of the controller appears below.

Referring to FIG. 3, the control circuitry is shown in detail. In the successfully constructed embodiment of the invention, ordinary l 10 VAC power was used, and the apparatus was plugged in via a three prong plug, not shown, one prong of which is grounded in the usual manner. The remaining two lines are indicated as L1 and L2 in FIG. 3. L1 includes a master fuse 114 and a master on/off switch 116. The heat bath fluid circulating pump 20 is connected across lines L1 and L2 by a line 118 which includes a fuse 120. Thus, the circulating fluid is pumped whenever master switch 116 is closed, as a safety precaution, and to prevent heater 28 from overheating. The coil 122 of a safety relay 124, is connected in series circuit with the normally open contacts of thermostatic device 100 across the lines L1, L2 by a line 126. A holding or latching circuit for said relay 124 is provided by means of a line 128 connected between device 100 and coil 122, and extending in series circuit through a pair of normally open contacts 130 on relay 124 and a normally closed manual reset device 132 back to line Ll. Thus, if regulator 100 should even briefly close thereby powering coil 122, therelay 124 will effectively latch because a circuit will be established through line 128, now closed normally opencontacts 130, and normally closed reset 132. The

other three

contacts

134, 136 and 138 on relay 124 are all normally closed, and are used as safeties. Contacts 134 are in a line 140 in series circuit with a fuse 142 and a manual on/off switch 144'all of which control the motor of the constant displacement gasoline pump 34. In a similar manner, a line 146 extends between the lines L1 and L2 and includes the contacts 136, a fuse 148, an on/off switch 150, and the motor of the vacuum pump 58 in series circuit. The last set of normally closed contacts 138 on the relay 124 is located in a line 152 extending from power line L1 and feeding both the normally open contacts 154 and the normally closed contacts 156 of a solid state relay 158. The coil 160 of relay 158 is connected in series circuit in a line 162 with a power supply 164 and the contact 72 of switch 66. The mercury in switch 66 is grounded via a linev 166. Because of its nature, power supply 164 must be connected across the AC power lines, and this end is accomplishedby a pair of

lines

168 and 170, as shown. Contacts 156 are in a line 172 which includes the heater 28 and a device 174 which responds to temperature, as by melting to break the circuit, to act as an additional safety. Contacts 154 are in a line 176 which includes a light 178. The light 178 or other resistance is required as a load by the nature of the solid state relay 158, and serves to visually indicate heater condition. Heater 28 is deactivated upon closure of switch 66 which occurs at a bomb pressure of 760 mm of mercury.

In the successfully constructed embodiment of the invention, the following commercially available components were used:

Name Supplier Part No. Comments Pump 20 Eastern D-l l Explosion proof Heater 28 Calrod 32 inches long 750W Pump 34 Milton RoyMilroyal-D Explosion proof Needle Valve 44 Brooks Elf 8502 Vacuum Controller Moore Products Intended for 48 Co. Spring pressure service House, Pa. 63BU-L as opposed to vacuum Rotometer 52 Fischer Porter Tube only Regulator 56 Pump 58 Tescom 44-2012-24 Teflon diaphragm Diapump G-4A Explosion proof Chemical resistant diaphragms Sintered stainless steel filter Flash Arrestor Hoke 64 Thermocouple 92 Standard Iron Constantan Thermocouple Rec0rder'96 Leads & Spedomax l-I Special ll0l60 Northrup F. range card Thermostat 100 Fenwall Relay 124 Potter &

Brumfield Three pole double throw l0 amps Relay 158 Ohmite SSB3SD-l Solid state Power Supply 164 Newark 66F354 Nicad Battery charger Temperature Fenwall Detect-al80F Melt link Fider Safety 174 OPERATION Prior to assembling the apparatus, the special mercury switch 66 is prepared for use by filling the closed end tube and its reservoir 68 with mercury. Then the assembly is uprighted and some mercury removed to thereby create a true vacuum or evacuated space above the mercury in the closed end of the tube. This vacuum space above the mercury is desired because absolute pressure is to be sensed. In starting up a new installation of an apparatus embodying the invention, the length of the vertical portion 84 of the vent apparatus 82 to is first adjusted to accommodate to the geographic location in which the apparatus is situated. In making this adjustment, the most important consideration is theheight above sea level.

The system is then filled with heat transfer fluid 14 and the analyzer is turned on by throwing main switch 116, and opening on/off valve 76 to vent to atmosphere. Pump 20 immediately starts circulating heat transfer fluid 14.

After these preliminary steps are completed, switch 144 is closed to start supply pump 34 to begin vaporizing gasoline in the bomb 30. Gasoline supply is set at some predetermined value, 5 ml/min for example, by use of the vernier adjustment means provided on the pump. Next, switch 150 is closed to start vacuum pump 58 to begin withdrawing vapors from the bomb 30 via the regulator 56, rotometer 52, and the flow controller 48. Regulator 56 is then adjusted to about 15 inches of mercury vacuum using gauge 57.

Referring to FIG. 2, it can be seen that line 46 dead ends at the left side of the diaphragm 108 and thus all flow is under the control of the needle valve 44. The controller 48 operates to maintain a predetermined vacuum pressure drop across valve 44, and thus a predetermined flow. Spring 112 of controller 48 is fixedat 3 psi tension against diaphragm 108. Any other pressure on either side of the diaphragm causes member 110 to open or close opening 106 proportionally, to thus hold the 3 pound drop across valve 44. The rotometer 52 gives a visual indication of this flow. Not shown but also provided is a viewing port in sealed heat bath vessel 12 through which the operator may see the rotometer 52.

The instrument may now be calibrated. When temperature approaches an operating value, such as about 1 10F, valve 76 is closed, and using a known V/L ratio gasoline, the valve 44 is adjusted until that V/L ratio temperature is reached and maintained. If no such calibration sample is available; then a bubble tube flow meter may be used to adjust the vapor flow out of chamber 30 to the calculated value which corresponds to the desired V/L ratio. Calibration is maintained by holding that value on rotometer 52.

It is a fact of the present day petroleum industry that a V/L ratio of 20 is very common, and therefore this value is frequently used. As described in the above steps, the system is at equilibrium. Assuming that the gasoline has a V/L of 20 at the system temperature, pump 34 is supplying a constant volume of gasoline per unit time, pump 58 via controller 48 is removing a constant volume of vaporous gasoline per unit time, pressure is constant at 760 mm of mercury, the ASTM test pressure, the entire system is being held at the V/L ratio temperature for a V/L ratio of 20 by the heat transfer fluid system, and the mercury in switch 66 is at some level in tube 70 near contact 72. Let it now be assumed that the gasoline supplied experiences a perturbation in its V/L ratio, for example, assume that it becomes more volatile. When the more volatile gasoline reaches the bomb 30 there will be more vapor therein, but this vapor cannot escape since the

components

44 and 48 are set to allow only a certain predetermined volume of vapor to be drawn out by the vacuum pump 58. The temperature of the heat bath remains unchanged up to this point. Therefore, the increased volume of vapor can only manifest itself by increasing the pressure within the bomb, thus raising the mercury level in the tube 70.

Referring now to the circuit of FIG. 3, the mercury in the switch completes the circuit of line 162, thus activating the coil 160 of relay 158, thus opening the normally closed contacts 156 of said relay, thus turning off the heater 28. The temperature of the bath then begins to fall, either naturally or with the aid of optional heat exchange means, not shown. The decreased temperature drives less of the gasoline into the vaporous state, thus re-establishing the test pressure at a new temperature. The change in temperature is detected by the thermocouple 92 and is recorded on the recorder 96. This change in temperature is a direct measure of the change in the V/L ratio temperature which the gasoline experienced, and that data may be used by the refiner in the usual manner. In the event the gasoline being tested experienced the opposite kind of perturbation, i.e., it became less volatile, the pressure would decrease in the bomb, the mercury level in the tube 70 would fall, and the temperature of the bath would continue to rise since the normally closed contacts 156 would continuously feed power to the heater 28. This process would continue until the temperature rose to a point where sufficient gasoline was driven into the vapor state to increase the pressure, incrementally only, to the point where switch 66 would be operated to turn off the heater, as described above. Again, the new increased temperature would directly be the V/L ratio temperature. The ASTM test mentioned above specifies 760 mm of mercury for the test pressure. The present invention operates by maintaining that pressure, permitting only slight changes sufficient to operate switch 66. During actual tests, using relatively large step changes in the V/L ratio of the test gasolines, the pressure in the bomb operates in the range of about 750 to about 770 mm of mercury in use. With only gradual normal changes in volatility, changes on the order of plus or minus 0.1 mm of mercury were experienced.

Thus, it can be seen that the invention operates on pressure changes away from the test pressure by using such changes to drive the heater to thereby correct for the change in pressure. The invention constantly corrects to maintain the test pressure.

In the event it was desired to operate at some V/L other than 20, this may be accomplished by operation of the valve 44, which valve in cooperation with the controller 48, in the manner described above, changes the volume of vaporous gasoline withdrawn. If, for example, more vapors are withdrawn, then the system effectively measures a higher V/L ratio, such as 25. Conversely, if less vapors are withdrawn then the opposite effect obtains. As is evident to one skilled in the art, a new operating V/L ratio could be obtained by changing the volume of liquid gasoline supplied rather than by changing the amount of vaporous gasoline removed via the

system including components

44, 48 and 58. The system shown in the drawing and described herein is preferred, however, because it is easier to monitor, more sensitive, and easier to adjust.

To complete this Operation portion, referring to FIG. 3, the relay 124 is provided for purposes of safety. The normally open contacts on thermostat will be closed in the event the temperature of the bath rises above a predetermined temperature. In said successfully constructed embodiment of the invention this temperature was 165F, and the general considerations in determining this temperature are the extremes experienced in the fuel specifications, and the limitations imposed by the bath fluid 14. In the event coil 122 should be operated, then, effectively, the analyzer shuts down. Contacts 134 open to stop the supply pump, contacts 136 open to stop the vacuum pump, contacts 138 open to shut off the heater 28, and contacts close to establish a holding circuit on the relay, all as is evident from the drawing. The circuit will remain latched until the temperature drops below the thermostat set point and reset switch 32 is manually operated. If the safety provided by relay 124 were not desired, this relay could be omitted, and the lines 140, 146 and 152 connected directly to line L1.

Yet another safety is provided by the device 174 which will be located physically close to the heater 28, in a conventional manner but not shown in the drawing, to detect the possibility of the heater itself running continuously. Device 174 is in the nature of a fuse which responds to a certain temperature, as by melting, to create an open circuit.

The possibility might suggest itself to one skilled in the art that the invention could as well be practiced by holding temperature constant and measuring the changes in vapor outflow rate, which changes would be somewhat proportional to changes in the V/L ratio of the gasoline being tested. Such a modified scheme is deemed much less desirable than that of the invention because, among other reasons, it would be necessary to correct for changes in ambient pressure. Also, the measurement of flow on a continuous basis is more difficult, more costly, and much less accurate than temperature measurement. From the refiners point of view, measurement of the V/L ratio temperature is more useful than measurement of the V/L ratio, since specifications are usually given as temperatures, (see specifications for Gasoline, ASTM D 439-70) rather than the latter.

While the invention has been described in detail above, it is to be understood that this detailed description is by way of example only, and the protection granted is to be limited only within the spirit of the invention and the scope of the following claims.

We claim:

1. A method for determining the V/L ratio temperature of a flowing stream of gasoline comprising the steps of constantly supplying a predetermined volume of gasoline per unit time from said stream to a pressure chamber, continuously sensing the absolute pressure within said chamber, continuously withdrawing a predetermined volume of vapor per unit time from said chamber, controlling the temperature of said chamber, and operating the means for controlling said temperature in response to sensed pressure changes within said chamber, whereby said absolute pressure is maintained at a predetermined value.

2. The method of claim 1, wherein said temperature controlling means are operated in such a manner that a change in the V/L ratio of the gasoline as determined by a sensed change in the pressure in said chamber will cause a change in the temperature of said pressure chamber, whereby changes in the temperature in said pressure chamber are changes in the V/L ratio temperature of said gasoline.

3. The method of claim 1, wherein said step of continuously withdrawing a predetermined volume of vaporous gasoline per unit time from said chamber is accomplished with a vacuum pump, and flow control means and a needle valve interposed in tandem between said vacuum pump and said chamber, and the step of supplying the pressure within said chamber to a reference portion of said flow control means to cause said vacuum pump to withdraw said predetermined volume per unit time, whereby said needle valve can be used to change said predetermined volume per unit time.

4. The method of claim 1, and preheating the gasoline supplied to said chamber.

5. The method of claim ll, wherein said temperature controlling step comprises circulating heat transfer liquid about said chamber.

6. The method of claim 1, wherein said step of sensing the absolute pressure in said chamber comprises exposing a reservoir of mercury in a mercury barometerlike device to said pressure, said device including a closed end tube positioned with its open end in said reservoir and extending thereabove, and wherein said step of operating the temperature controlling means includes causing the changing level of mercury in said tube to operate an electrical switch.

7. Apparatus for determining the V/L ratio temperature of gasoline comprising a pressure chamber, means for continuously supplying a predetermined volume of gasoline per unit time to said chamber, means for sensing the absolute pressure within said chamber, means for continuously withdrawing a predetermined volume of vapor per unit time from said chamber, means for controlling the temperature of said chamber, and means interconnecting said pressure sensing means and said temperature controlling means.

8. The combination of claim 7, said temperature controlling means comprising a bath of heat transfer fluid, means to circulate said fluid, a heater disposed in the circulation path of said fluid, whereby said means interconnecting said pressure sensing means and said temperature controlling means causes said heater to turn on and off in such a manner that a decrease in the V/L ratio of the gasoline in said chamber will cause said heater to increase the temperature of said heat transfer fluid, and whereby changes in the temperature of said heat transfer fluid are changes in the V/L ratio temperature of said gasoline.

9. The combination of claim 7, wherein said gasoline supplying means supplies gasoline from a flow stream of said gasoline, whereby the V/L ratio temperature is determined continuously.

10. The combination of claim 7, wherein said heat transfer fluid is circulated in a closed system.

111. The combination of claim 7, said means for continuously withdrawing a predetermined volume of vaporous gasoline per unit time from said chamber comprising a vacuum pump, flow control means and a needle valve interposed in tandem between said vacuum pump and said chamber, means to supply the pressure within said chamber to a reference portion of said flow control means, whereby said vacuum pump withdraws said predetermined volume per unit time, and whereby said needle valve can be used to change said predetermined volume per unit time.

12. The combination of claim 11, and a rotometer interposed between said flow control means and said vacuum pump.

13. The combination of claim 7, said means for continuously supplying a predetermined volume of gasoline per unit time comprising a constant displacement pump.

14. The combination of claim 7, wherein said pressure sensing means and a portion of said interconnecting means comprises a reservoir of mercury, a closed end tube positioned with its open end in said reservoir and extending thereabove, an electrical contact in said upper evacuated sealed end, and means to expose said mercury in said reservoir to the pressure within said chamber.

15. The combination of claim 7, and means to preheat the gasoline supplied to said chamber.

16. The combination of claim 15, said temperature controlling means comprising a bath of heat transfer fluid in which said chamber and said preheating means are immersed, and said preheating means comprising a coil of the conduit carrying said gasoline surrounding said chamber.

17. The combination of claim 7, said temperature controlling means including an electrical heater, said pressure sensing means including an electrical switch which is opened and closed in response to pressure changes within said chamber, said interconnecting means comprising a relay and an electrical circuit interconnecting said switch, said heater, and said relay; said circuit including a portion interconnecting the coil of said relay and said switch with a source of power, and a portion interconnecting a pair of contacts on said relay and said heater with a source of power.

18. The combination of claim 17, wherein said contacts are normally closed, whereby said heater is turned off wen the pressure in said chamber rises sufficiently to close said switch to operate said relay coil.

19. The combination of claim 17, said interconnecting means including a safety relay, means interconnecting the coil of said safety relay with a thermostatic normally open safety switch which senses the temperature of temperature control fluid in said temperature con trolling means, and said circuit portion for feeding power to said heater via said contacts of said first mentioned relay including a pair of normally closed contacts on said safety relay.

20. The combination of claim 19, said gasoline supplying means and said vapor withdrawing means each including an electrical motor, and said circuit including a pair of normally closed contacts on said safety relay in each of the circuits supplying power to each of said motors.

21. The combination of claim 19, said safety relay including means for latching said relay in the closed position once operated and manual reset means for unlatching said relay.

22. The combination of claim 17, and a meltable element disposed in the portion of said circuit feeding power to said heater, whereby power will be shut off to said heater in the event said heater reaches a temperature greater than the temperature at which said meltable element will melt and open said circuit portion.

23. The combination of claim 7, a thermocouple for sensing the temperature of said chamber and a recorder driven by said thermocouple.

10 I k i l

Claims

4. The method of claim 1, and preheating the gasoline supplied to said chamber.

5. The method of claim 1, wherein said temperature controlling step comprises circulating heat transfer liquid about said chamber.

6. The method of claim 1, wherein said step of sensing the absolute pressure in said chamber comprises exposing a reservoir of mercury in a mercury barometer-like device to said pressure, said device including a closed end tube positioned with its open end in said reservoir and extending thereabove, and wherein said step of operating the temperature controlling means includes causing the changing level of mercury in said tube to operate an electrical switch.

11. The combination of claim 7, said means for continuously withdrawing a predetermined volume of vaporous gasoline per unit time from said chamber comprising a vacuum pump, flow control means and a needle valve interposed in tandem between said vacuum pump and said chamber, means to supply the pressure within said chamber to a reference portion of said flow control means, whereby said vacuum pump withdraws said predetermined volume per unit time, and whereby said needle valve can be used to change said predetermined volume per unit time.

18. The combination of claim 17, wherein said contacts are normally closed, whereby said heater is turned off when the pressure in said chamber rises sufficiently to close said switch to operate said relay coil.

19. The combination of claim 17, said interconnecting means including a safety relay, means interconnecting the coil of said safety relay with a thermostatic normally open safety switch which senses the temperature of temperature control fluid in said temperature controlling means, and said circuit portion for feeding power to said heater via said contacts of said first mentioned relay including a pair of normally closed contacts on said safety relay.