US2499105A

US2499105A - Apparatus for determining initial boiling point of liquids

Info

Publication number: US2499105A
Authority: US
Inventors: William M Mercer
Original assignee: Individual
Current assignee: Individual
Priority date: 1945-09-17
Filing date: 1945-09-17
Publication date: 1950-02-28
Anticipated expiration: 1967-02-28

Description

w. M. MERCER 2,499,105 APPARATUS FOR DETERMINING INITIAL BoILING POINT oF LIQuIns Feb. 28, 1950 k WA-I I QQ .y B3 g (1R 3 INVENTOR -W/aL//z/vf MME-ecs@ B Y f ff/"1 ATTORNEY Feb. 2s, 195o w M MERCER 2,499,105

APPARATUS FR bETERMINING INITIAL BOILING POINT oF LIQUIDS Filed sept. 17, 1945 2 sheets-sheet 2 INVENTOR .93 WiL/AM Jil. Mts/@$52,

BY f I ,n/

f TTORNEY meme ret. ze', 195o APPARATUS FOR DTEBMINING INITIAL BOILING POINT F LIQUIDS william M. Mercer, Los Angeles, cam. Application September 17,1945, Serial No. 618,884

reclaim. l

My invention relates to apparatus for deter (cias-11) mining the initial boiling points of liquids andl has particular reference to an' apparatus for accurately measuring the initial boiling' point of a desired low boiling point fraction of a mixture of liquids such as a mixture of hydrocarbons.`

In many industries, for example, the oil reining industry, it is the common practice to heat a. mixture of a number of hydrocarbons' to separate certain of the hydrocarbons from the remainder of the oil. In the production of gasoline, for example, it is the practice to treat the crude oil by heat to vaporize the lighter fractions and then to condense the gasolines to produce a gasoline hydrocarbon mixture having the desired characteristics for the type of gasoline to be produced. A desirable characteristic of such gasoline is that all undesirable highly volatile hydrocarbons should be removed, leaving only a mixture of selected hydrocarbons, the lightest desirable fraction of which determines vthe kind or quality of the gasoline to be produced.

Heretofore it has been the practice to attempt to maintain a uniform gasoline product by passing the gasoline mixture through a kettle where it is heated suillciently to drive off thefundesirable lighter fractions butin which an attempt is made not to heat the-mixture suiciently to drive oi the lightest of the fractions desired to be kept in the iinished product. In order to properly control the heat of the kettle, it has been the practice to from time to time remove Aa spie of the outgoing product from the kettle, the sample being conveyed to a laboratoryat which the sample is brought to a temperature at which the lightest of the desired fractions starts to vaporze. That temperature is then notediand is passed back to the renery and such alteration in the quantity of heat applied to the kettle is made in the hope that the product from the kettie will contain the lightest desired fractions and will not contain still lighter undesired fractions. In order to maintain uniformity of product, itv is apparent that the correction of the kettle temperature should be made substantially instantaneously upon the kettle heat becoming either insuflicient to drive off the undesirables or becoming so great as to not only drive oi the undesirables but to tend to drive off the lightest desirable fraction. n

It is therefore an object of my invention t provide an apparatus in which the outgoing stream from lthe kettle is continuously sampled and tested for its initial boiling point (that is, the temperature at which the lightest of the desirable fractions tends to'yaporize) and to permit this-determination@ b""instantly available to the operator in' control of the kettle. y

Another object of my invention is to provide an apparatus ofthe' character described in which the variation in temperature required to initially vaporize the lightest of the constituents of the hydrocarbon mixture may be employed to automatically control the heat applied to the kettle to therebyautomatically maintain the quality of the resultant product uniform.

Another object of my invention is to provide an apparatus which may be connected directly to the outgoing stream from the kettle to continuously pass a sample of such stream through a testing apparatus andatwhich apparatus the temperature is automaticallyI varied to cause the lightest of the desired. fractions to start to va porize and in which such temperature is so registered as to be immediately' available to the opere ator of the kettle.

Another object of my invention is to provide an apparatus of the' characterdescribed wherein the initial vaporizaytion of the lightest of the fractions of the sample is employed to automatially heat or cool the sample to maintain a predetermined vapor pressure and inv which the tem- `perature ofthe sample. required'to maintain such iixed vapor pressure is automatically registered as the temperaturev at which the kettle must be maintained in order that the lightest of the fractions of the production stream should not be boiledoff.

Other objects and' advantages of my invention will be apparent from astudyof the following speciiicationsread inconnection with the accompanying drawings, wherein Fig. 1 is a diagrammatic viewof apparatus which may be employed to practice my invention,

the various elements of which are shown in vertical section;

Fig. 2 vis avdetail elevational View of a temperature registering or recording chart and pen constituting a part of the apparatus shown in 3 comprise the continuous am, i or s. predetermined volume ci a sample s into a closed vessel in which the pie is subjected to either the application ci heat or the application of a cooling medium sunlcient to vaporize a portion of the lightest o! the hydrocarbon fractions in the sample mixture, sumcient also to maintain within the closed chamber a predetermined pressure value and in utilizing any tendency oi the pressure value to' increase or decrease to automatically control the application of the heat or the cooling medium to raise or lower the temperature of the sample to cause the vaporized portion thereof to remain at the predetermined selected pressure value. Thus by measuring the temperature of the sample and noting the temperature required to maintain the predetermined pressure value within the vessel, the initial boiling point of the sample mixture will be deteru mined and this information may be utilized to control the main rennery kettle and to thus maintain the product from the kettle at a uniform value.

I accomplish this result by employing a sample vessel I, into which is passed a continuous stream of the mixture to be measured, the quantity or volume oi the sample retained within the chamber! being controlled by means of a valve 2 actuated by a iioat 3 adapted to oat in the liquid of the sample within the vessel i. The valve 2 controls the exit passage 4 from the vessel I.

Within the vessel I, I dispose a pressure rcsponslve apparatus indicated generally by the reference character 5 as comprising a bellows 8 secured to the cover plate 'I oi the vessel I in such fashion that gas pressures existing within the vessel I will cause the bellows to expand or contract. Within the bellows 6 I dispose a pair of valves 8 and 9 (Fig. 3), the valve 4 being utilized to control the application of heat to the vessel l to raise the temperature of the sample therein while the valve 8 is employed to control the application of a cooling or refrigerant medium to reduce the temperature of the vessel and the sample contained therein. In this connection it should be noted that valve 8 may have a construction similar to valve 9.

Since it is desired to determine the initial boiling point of the sample, that is, the temperature at which the lightest of the hydrocarbon fractions contained within the sample will start to vaporize, I prefer to permit a sufllcient quantity of the lighter fraction to vaporize to achieve within the vessel I some predetermined ilxed pressure value, for example, live pounds per square inch. I prefer to eliminate from the mechanism employed any necessity for measuring the pressure of the sample and to depend for the creation of pressure within the vessel I solely upon the quantity of the sample vaporized within the vessel I.

To accomplish this purpose, I lead the sample stream from a pipe III connected to the output end of the refinery kettle through a filter Il and thence through a pressure reducing valve I2 to insure that the incoming stream. of sample will be passed into the vessel i at some fixed predetermined pressure value. Since it is desirable .to maintain a predetermined volume of the sample within the vessel I, I pass the sample 'stream through an oriiice member I3, the opening through which is smaller than the exit opening through the iloat controlled valve 2. Thus the volume oi' the sample within the vessel I and the pressure of the incoming sample are bo y maintained at constant values. ,1 In order to vaporize a portion of the lighter fractions oi the sample stream within the vessel l, it may be necessary to apply heat to the vessel I and this may be readily accomplished by any suitable means such as a heating coll I4 adapted to be supplied with electric current through a control switch i6. The coil I4 is disposed about the lower` portion of the vessel I immediately adjacent the neat 3. On the other hand, it may be 1 that the incoming sample stream is at a temperature sumcientiy high to vaporize 'a portion of the lighter fractions of the sample, in which event it may be necessary to apply a cooling o1" refrigerant medium to the vessel I to lower'the temperature or' the sample under test. This would be particularly true of liquids to be tested which have desirable fractions which would boil at atmospheric temperatures requiring cooling, which may be readily accomplished by.` providing a cooling chamber le between the vessel I and an outer Jacket ll, through which chamber a cooling refrigerant medium from a suitable source, indicated at i8, may be circulated under the control oi' a refrigerant valve I9 and an oriiice 2u. The cooling medium is permitted to enter the chamber Ic through a suitable entry port 2l and to be exhausted through an exhaust or return pipe 22.

'io eilectiveiy control the switch I5 for the heating element le, I mount the switch l5 to be actuated under the innuence of air pressure from a suitable source of air pressure indicated by the pipe 23. 'lhe air pressure from such source is passed throughs. nlter 24, a pressure regulator valve and a ow limiting oriice 2liv to a distribution pipe 2, one branch of which is connected to a Bourdon tube 28 operatively con- -nected to the switch I5 to hold switch i5 in circuit closlng position whenever pressure from the source 23 is applied thereto and permitting the switch l5 to move to its open position when the pressure in the Bourdon tube 28 is released.

The control of the switch I5 is accomplished by the valve 8 which. as will be noted from an lnspection of Fig. 3, comprises a valve tube 29 having upon its upper end a head 30 slidably mounted upon guides 3l in a valve housing 32, the tube 8 being normally urged upwardly in the housing 32 by means of asprmg I3 but limited in its upward movement by means of an adjusting screw 34 threaded into a plug 3l in the upper end of the housing 32 in such manner that the lower end of the screw 34 will bear upon the head 30 and hold the valve tube 8 at some fixed predetermined level with respect to an operating plates disposed upon the bottom of the belows a0 By adjusting the position of the tube 8 relative to the plate 36, the valve stem 31 in the lower end of the tube 8 will be caused to be lifted when the bellows 6 is subjected to a predetermined value of vapor pressure within the vessel I, the es pressure required to operate the valve stem 31 being adjusted by raising and lowering the ad- Juting screw 34 to select the desired operating v ue.

The valve stem 31 is arranged to operate a 7o poppet valve. such as that illustrated at 3l, the poppet valve being normally closed to prevent the escape of air pressure from the source 23 'extending through the branch pipe I9 to the interior of the valve tube 29 but adapted, when actuated 76 by engagement with the plate 38. to exhaust the duction in pressure of the air effective upon the Bourdon tube 29. By making the valve'll of larger ow capacity than the orice 29, it will be apparent that the opening of the valve'3'l willl result in the substantial exhaustion of air pres- 'sure from the ABourdon tube 2l and the consequentopening of the switch I9. v

Thusit will be observed that the necessaryv heat will be applied to the sample within the vessel I to vaporize a portion of the lighter fractions of the sample mixture until the predetermined fixed vapor pressure has been attained and there.-

after the application of heat will be stopped un- VVtil the vapor pressure within the vessel I tends t reduce below the selected pressure, at which time the valve 31 will again close and the air pressure from the source 23 will be effective to reclose the switch i5. to supply additional heat to the sample within the vessel I. By properly selecting the pressure value for the setting of the valve 8-31, only a portion of the lightest of the desired fractions in the sample will be vaporized and the quantity of heat necessary to cause this partial vaporization will be supplied to the vessel I.. Thus by measuring the temperature within the vessel I, the temperat'ureat which the lightest of the fractions will start to vaporize i's determined and this value is the initial boiling point erate the reduction in temperature by the application of the cooling or refrigerant medium, particularly in instances in which the incoming sample stream is at a relatively high temperature .as it enters the vessel and the regulation of the application of the cooling or refrigerant medium to the vessel I may be readily controlled by means of the valve 9 Within the bellows 6 by setting the position of the valve tube 40 to a position relative to the plate 36 as to cause the valve 33 in the valve tube 9 to be opened by a -minute increase of vapor pressure within the vessel I over the pressure at which the valve 31 operates. The differential between the pressure values required to operate the valve 3l and to operate the valve 39 may be extremely small, for example, .02 pound per square inch, so that any tendency of the pressure within the vessel I to rise above the value selected by the setting of the valve 9--31 will immediately result in the application of the cooling or refrigerant medium to the vessel.

`.'Ihe operation of the valve 38 in valve tube 9 is employed to control the refrigerant valve I9 (Fig. l) as by extending a branch 4I of the air pressure supply pipe through a pilot valve 42 and thence by way of a pipe 43 to a control chamber 44 associated with the valve I9 in such manner that the air pressure is exerted upon a bellows 45 to cause a movable valve member 46 to normally close upon a valve seat 4l and prevent the passage of refrigerant medium to the vessel 4I The pilot valve 42 is a normally open valve adapted to be closed by the application of air pressure to an actuating bellows 48 which will andthroughaventu tothe v j valve 42 may be used to control the main refrigerant valve Ildirectly.. a more rapid and sensitiveoperation of the valve II will be eccome plished by interposing an auxiliary control valve I3 immediately ahead of and adapted to control v the pilot valve 42. The auxiliary valve I3 is subjected to ypressure from the air pressin'e source through an oriilce member 34 connected in a pipe line,.one branchl 65 of which extends to l a bellows chamber in the valve I3 to normally hold the movable valve member I59 thereof in closed posit tion, as shown in Fig. l, while the other branch 31 ot the pipe line extends to the valve! through the bellows 0. y

It will be apparent that as' long as the valve member 38 in the valve 9 remains in its closed the valver member 38 by an increase in vapor pressure within the vessel I above the selected pressure value. the air pressure from the source- 23 will be exhausted from the bellows within the auxiliary valve 53, allowing the movable valve member 56 thereof to move to open positionr and to supply the necessary air pressure to the bellows 43 of the pilot valve 42 to close the valve member 49 and to thereby permit exhaustion of air from the main control valve I9.

Thus the operation of the main valve I9 will supply cooling medium to the vessel fl to cause f a rapid reduction in the temperature thereof until iliary seat 5I, permitting the exhaustion of air pressure through the pipe 43 and valve seat 5I 75 the temperature within the vessel I is just sufllcient to maintain vaporzed a portion of the lightest of the fractions of the sample stream.

From the foregoing it will be apparent that a continuous sample stream passing throughthe vessel I is automatically regulated as to temperature to cause the vaporization of only the lightest of the lighter fractions and that fluctuations in' the temperature necessary to maintain this portion of the lighter fractions vaporized will be automatically recorded by a temperature recorder 60 which may be of any suitableconstruction. As illustrated in Figs. l and 2, the temperature recorder comprises a temperature responsive instrument BI which may be a helix of' thermometal coupled to a shaft A62 in such fashion as to rotate thet shaft 62 in response to .variations in temperature within the vessel zigthe shaft 62 having secured thereto an arm 63 Iadapted to sweep across a record chart or disk 4 to draw a curve corresponding to temperature variations within the vessel I.

By noting the position of the pen on the chart, an operator may readily adjust the temperature applied to the renery kettle to raise or lower the temperature of the kettle so as to eiectively drive of! the lighter undesirable fractions and to insure the retention of the lightest desirable fractions in the product from the kettle.

Since most volatile liquids contain minute amounts of components which cannot be readily condensed, or re-absorbed, in theordinary processes of distillation, I prefer to provide a vent connected to the upper portionv of vessel I and having` connected thereto an orifice member having an extremely small orifice therein which If desired, a pressure gauge 18 may be connected in the sample line between the pressure regulating valve Iz and the vessel i to'give a continuous indication of the pressure in the sample stream while pressure gauges 1i and 12 interposed in the air pressure lines 51 and I8 may be of the valves 9 and 8, respectively. Similarly, if desired, pressure'gauges 18 and 18 may be interposed in the air pressure line immediately in advance of the pilot valve l2 and the cooling medium control valve i8 to eiectively register the operativeness of these valves.

While the switch I8 may be of any suitable construction, it is desirable to'employ a nonarcing switch such as a mercury switch such as illustrated in Fig. l, and it is further desirable to enclose the same in a suitable vapor-proof housing such as is illustrated at when the instrument is to beemployed in connection with highly volatile and inflammable materials such as gasolines and the like.

It may also be desirable to add a safety feature to the ves-sel I to prevent the inadvertent overheating thereof. One form of such safety device is illustrated in Figs. 1 and 4 as comprising a temperature measuring instrument 18 of the helical thermo-metal type, the shaft 11 of which has a flanged head 18 secured thereto and disposed below the bottom of the vessel I. The shaft 11 is preferably guided through a bearing member 18 threaded into the lower end of the vessel l and has a groove 80 formed upon its periphery for the reception of a plurality of screws 8l or other supports for a housing 82. The housing 82 has at its lower end a valve 83 normally closed by means of a spring 84 but adapted to be opened by a weight 85 when the weight is released by Y Memos 8 ingthvalveag'ainsttheforceofitsbiasing springll.' a,

.Itwillbenotedthatthehousingliisprovided with a pair of openings Il and 8|,the openemployed to effectively register the operativeness ing 88 being connected by means of a suitable piping 82 tothe same branch pipe 21 as is employed to supply air under pressure to the Bourdon tube 28 controlling the switch Il, while-the opening 8| constitutes a vent to the atmosphere 8o that upon the opening' of the valve 88 the Bourdon tube 28 will be vented to atmospheric pressure and the switch Il will be moved to its open circuit position, as was described with re!- .erence to the operation o f the main control From the foregoing it will be apparent that I have provided an apparatus in which a sample stream of any mixture of liquids may be tested continuously to determine the initial boiling point the flanged head 18. The weight is illustrated as being in the formA of a cup, upon opposite side walls of which are mounted pins 86, one end of each -of the pins 4being slidably guided in longitudinal slots 81 formed upon the interior of the housing 82 while the opposite ends of each of the pins overlie the flanged head 18 at all times except when the flanged head 18 is rotated under the influence of the temperature measuring element 18 to a position to align a with the pins 86.

pair of slots 88 By rotating the hou-sing a2 relative te the-beari ing member 18, the position of the pins88 rela,- tive to the slots 88 may be adjusted so that the predetermined temperature which must be attained by the temperature measuring device 18 before sufficient rotation of the head 18 will occur to align the slots 88 with the pins 88 may be readily adjusted.

It will be apparent therefore that by setting the housing 82 at some desired position relative to index marks 89 on the bearing member 19, the maximum heat which can be attained by the vessel l 'will be predetermined, the attainment of such predetermined heat resulting in the rotation of the shaft 11 and the head 18 to align the slots 88 and the pins 88 in such position that the cup weight 85 which has been previously supported by the hanged head 18 will be released and will be urged by spring 88a upon the valve 88, openlill IlA

of the liquid' or liquid mixture under test and by which the initial boiling point is detected by reason of the start of the vaporization of the lightest of the fractions in the liquid under test.

It will also be apparent that by utilizing a predetermined pressure responsive mechanism in connection with the testing of the sample stream, the initial boiling point will be denoted by the temperature which is required to start the vaporization of thelightest fraction of the liquid. Hence by noting the required temperature t0 start such vaporization. not only is the information obtained as to what is the initial boiling point but the temperature information is available to be employed for the purpose of controlling the refinery kettle to insure the production from the rennery being maintained at a constant value of initial boiling point.

While I have shown and described the preferred embodiment of my invention, I do not desire to be limited to any'of the details of construction shown and described herein,- except as defined in the appended claims.

I claim:

1. In an apparatus for determining the initial boiling point of liquids, a vessel, n ow control means for maintaining a continuous stream of the liquid to be tested passing through said vessel and including an automatic valve for maintaining within said vessel a predetermined volume of the liquid under test. thermal transfer means for maintaining the vapor pressure within said vessel at a predetermined fixed value, and means for measuring the temperature of the vessel required to maintain said predetermin vapor pressure.

2l In an apparatus for determining the initial boiling point of liquids, a vessel, means for main.. taining a continuous stream of the liquid to be tested passing through said vessel, means in said vessel for maintaining within said vessel a predetermined volume of the liquid under test, a vapor ilow control device for maintaining the vapor pressure within said vessel at a predeter- Y mined fixed value, means for measuring the tem- 'perature of the vapor maintained at said predetested passing through v said vessel, means in said vessel for maintaining withinjsaid vessel a presaid valve means for venting said pressure iiuid j from said heat control means to cut oi! the ap'- determined volume o! the liquid. under test, a v

vapor control mechanism -for maintaining the vapor pressure within said vessel at a predetertherein to vaporize sufficiently to attain said predetermined vapor pressure and including' a source of heat and av heat absorber, and means Y responsive to changes in the vapor pressure within said vessel for controlling the quantity of the heating medium and cooling medium applied to said vessel.

4. In an apparatus for determining the initial boiling point of liquids, a vessel, means for maintaining a continuous stream of the liquid to be tested passing through said vessel, valve means in said vessel responsive to vapor pressure existing within said vessel, means for supplying a heating medium and a cooli'ng medium to saidv vessel to cause the liquid therein to become partially vaporized, means actuated in response to operation of said'valve means when the vapor pressure Within said vessel reaches a predetermined iixed value for controlling the application of the heating medium to said vessel, means actuated by said valve means when the pressure within said vessel reaches a predetermined value in excess of said iirst named value for controlling the application of the cooling medium to said vessel, and means associated with said vessel for registering the temperature of said vessel required to attain said predetermined vapor pressure values.

5. In an apparatus for determining the initial boiling point of a liquid, a vessel, means for passing a continuous stream of the liquid to be tested passing through said vessel, means forregulating the pressure of the liquid entering said vessel at a predetermined xed pressure value, means for maintaining the rate of flow of the incoming stream of liquid at a fixed value, iioat actuated vplication of heat to said vessel.

7. In an apparatus for determining the initial boiling-point of a liquid, a vessel, means for passing a continuous stream of liquid under test through said vessel, means associated with said vessel for maintaining within said vessel a predetermined volume oi' a stream of liquid under test, means for applying heat to said vessel, control means for controlling the quantity of heat supplied to said vessel, valve means in said vessel responsive to the attainment of a predetermined pressure within said vessel, a source of iiuid under pressure, means for supplying iluid from said source to said temperature control means to valve means in said vessel having a capacity in -temperature regulating means to-maintain the vapor pressure within said vessel at a predetermined iixed value, and means for registering the temperature of said vessel required to maintain said predetermined vapor pressure.

6. In an apparatus for determining the initial boiling point of a liquid, a vessel, means for passing a continuous stream of liquid under test into said vessel, flow control means associated with said vessel for maintaining within said vessel a predetermined volume of said stream of liquid under test, means for applying heat to said vessel, control means for controlling the quantity of heat supplied to said vessel, valve means in said vessel responsive to the attainment of a predetermined pressure within said vessel, a source of iluid under pressure, means for supplying iluid from said source to said heat control means to actuate said control means to apply heat to said vessel, and means responsive to actuation of actuate said control means to apply heat to said vessel, means 'responsive to actuation of said valve means for exhausting said pressure -fluid from said temperature control means to cut oil the application of heat to said vessel, means for supplying a cooling medium to said vessel, a second valve means responsive to the attainment of a vapor pressure within said vessel in excess of that required to operate said first valve means, a control means lor controlling the supply of said cooling medium to said vessel, means for applying the pressure fluid to said control means for actuating said control means to cut off the supply of cooling medium to said vessel, and means responsive to actuation of said second valve means for exhausting said pressure iluid from said cooling medium control means to cause said control means to apply cooling medium to said vessel during such periods as the vapor pressure within said vessel exceeds said iirst named predetermined value.

8. In an apparatus for determining the initial boiling point of a liquid, a vessel, means for passing a continuous stream of liquid under test through said vessel, means associatedwith said vessel for maintaining within said vessel a predetermined volume of a stream of liquid under test, means for applying heat to said vessel, control means for controlling the quantity of heat supplied to said vessel, valve means in said vessel responsive to the attainment of a predetermined pressure within said vessel, a source of iiuid under pressure, means for supplying fluid from said source to said heat control means to actuate said control means to apply heat to said vessel, means responsive to actuation of said valve means for venting said pressure fluid from said heat control means to cut oil the application of heat to said vessel, and a safety device responsive to the attainment of a predetermined temperature in said vessel for actuating said temperature con= trol means to cut off further supply of heat to said vessel.

9. In an apparatus for continuously determining the initial boiling point of a liquid mixture, a vessel adapted to receive a sample of the mixture, a metered liquid inlet for the vessel, a metered vapor outlet for the vessel, a oat valve to maintain a pool of liquid within the Vessel and to'regularly eject a portion of the liquid, a thermal-transfer mechanism for the vessel, a pressure responsive control for the thermal transfer mechanism whereby excessive pressure causes subtraction of heat and deficient pressure causes addition of heat, and a temperature indicator for the vapor within the vessel.

l0. In an apparatus for continuously determining the initial boiling point of a liquid mixture, a vessel adapted to receive a sample of the l1 mixture, a metered la' the liquid sample. a metered outlet 10i' Por from the sample, a noat valve to maintain c pool'o! liquid in the vessel.

a heater for the vessel. s. cooler for the vessel'. a

pressure operated control for actuating the heater, s control for the cooler operable upon release of pressure, a member movable in response to the vapor pressure within the vessel, and a valve associated with the heater control and the cooler control and adapted to be operated by the lo movable member. whereby' excessive pressur within the vessel will actuate the heater control valve to release pressure in the heater control and thereby de -enerzise the heater, and whereby excessive within the vessel will actuate the cooler control valve for enerzizins the cooler.

thereby eiIectinc automatic subtraction or additionoiheatinrespcnsetothepressmewithin thevelsi.

Number Name Date 1,789,339 Lewis Jan. 20, 1931 2,086,808 Kallam July 13, 1937 2,119,786 Kallam June 7, 1938 2,339,026 Mercer Jan. 11. 1944 OTHERREFERENCES Stewart, Oscar M., "Physics, s. Textbook for Colleces," revised edition, pgs. 291 to 296, pub- ,13 lished by Ginn 8nd 00.

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