US2669435A - Immersion heater - Google Patents

Description

Feb. 16, 1954 H. o. CORD ETAL IMMERSION HEATER 2 Sheets-Sheet 1 Filed April 27, 1951 INVENTORS:

Howard 0. Card TTY Feb. 16, 1954 H. o. CORD ETAL IMMERSION vHEATER 2 Sheets-Sheetv 2 Filed April 27, 1951 Bruce G. Merle/1 Char/es J. Rypm, Jr. BY v A TTORIVEY Patented Feb. 16, 1954 IMMERESIDN HEATER Howard 0. Cord Chicago, Ill Bi-ncaG: Merten,.- Munster lndg and"Charless,J..Ryant -Ji' Chi.- cago, 1112,; assignors. to StandardiOfilIGompany, .1 Chicago; 5111.; 8;. corporation .of .Indiana AnplicatiomAprilc232," 1951;.Serial N6: 223,40415-2- 6'5 G1ai'ins';.. (Cl. 257; 1'92il 1'1 Thist -invention: relates.- to heataexchangersl ands: mores particularly to" a am. improved. immersiom heater of. the fingemtype for. use inheating'tanks. and. the like;

Inrmanyrefinery, installations and. chemical.

plants,-. it: is desiredtto heat the contents of. a 1

tank-either. continuously. or intermittentlyfor. processing:- or for; simplesremovale of a. viscous 1 material. frommthe. tanks. For example in. petroleumsrefineny it is frequently desired'toheat hydrocarbon stocks such as heavy lube oilsand.

asphalt. A. convenient-1 way. for effecting. this. heating; isrtotproyide :atplurality. Dfh steam coils. j of; .thefinger; or. bayonet type. These. heaters. I

are: ordinarily; mountedl near;- the bottom of a tank. and are: manifolded-.. units= which. may. be individually-mounted :and replaced. as necessaryl Eachfingerltype'unit comprises an. outer... con.

densate tube. on. jacket closed attxone end and;

open: at the... other. to. receive; a nestedifinger tube. *2

oilsr'naller diameter which discharges.within; and-l adjacent the.elosed-endkofithe. outer. tube. Steam... is. passed ithroughihe iinnen tube. and into. the... annular spacebbetween themestedl tubesmwheren depending. uponthe extent ofiiheatitransir.from L.

the unit steam. may .or may; not condense.

Although. units oi.thissgeneralhtype'qare satis.,.-.

factory, for. some: purposes they... have; a .number.

oi deficiencies... The. prime. diffi'culty. is. that; the;

outer tube orajacket is;1ikely,..to.leak.andiconer densate or. steampassesintolthetanki Th'e.acs.-

oumulation oftwateninthe stock-tank .is; asvery: dangerouseondition and .mayresult in explosions. caused. by sudden... vaporization of. the. wat'eiu. This maybe-cur atftheitimeof. the initialilak or. at'wsome subsequent;stageswhenflhotrstockiis troduced'dnto. the; tank. containing. condensate...

Heretofore. in an attempt to. minimize; the; dangers. of...sudden vaporization. ofilcondnsate' water. fromimmersion heaters, at least .two..'cost.-,.

lyyexpedientsoliavebeentriedl- Oneis-to insulate;

the entire...ta-nk. sosassto. iIlSIlIfiJzthfitfiOIldBIlSfitfir does-.not "form. in. the stocks. Another. attempted" solution to the problemiis placing. the. steam. system. under. vacuum: sd thatacondensation not occur inthebayonet exchanger-s units Neither oft'theseexpedients; is satisfactory:

It isv therefore'an object:v ofz'this invention-r to: provide an immersion? type: heating. unitvzwhiohi' avoids the daTIgEY'TOf "6Xp10SiOnS jiI1? tanks: caused by leaks? in r the -heater; Anothen o'b'ject :is?* "t'o=; provideram apparatus? for continuously? indicat inglwhetlierron not flinfihgelff typet steamta coil detectiveavduringr, operatiom: KI. furthers b dicatingawhich of severaliheatingunitssis'leaklnga.. An;.-addit-ional..object.-is :to: provide an apparatus? which-makesit unnecessary to insulate the tankz or to place theswsteam;systemruunder vacuum-Atolprevent any condensate. formation jn steam heatedqtanks.

Briefly, by. our invention, an. immersion. heaten. is. modified) by-.-. providing; a spaced. proteetivee sheaths about. the. coil, and; by providing 1 a tell-.-:

talelat a .point 7 outside. the vesse1 .0rtank..- It; at 18Lk.-OC61HS;. steam; escapes from-l the heateninto the space. between it andathe. sheath,. .andlthence r. through the" tell-tale. and/0s Wateriromvthe :heater acketzzisn. confi-neda 1 bythe sheathand is not-permitted to enter. the.

stoclein the tank, Inasimilanmannengif thee sheath.shoulddeak ion example dueto the cor -u I provide. an. improved. immersion. type heater. which transfers-.as:.much heat as. the. originals unit: but; which. includes at positive: an.d..simp le means for. continuously determining whethen, there is a leak.

We have discovered that ifilwewfill the annular 5' space-between our sheath .and'. the. return. .tube= jacket..of Z.the-.heater wtihla fluids. substance. of I; high thermaL.-condnetivity;.; we. provideoas unit. which. overcomes the. objections. to. heat..ex.-.-,. ehangersaof I.this...type without any. sacrifice in;

theheat transfer. .Based upon...general1y.used..

capacity. calculations. of. heat. transfer. andtan... overall; coefiicient of about. 15' for theaters. of; this type, the transfer coefficient isireducedgless.

than. 05%. whena. materialmsuch as graphite..- is

packed.in.the. tell-tale annulus. This small re-. 3

deletion. inheat. transfer is: more. .than..-compen1-.;- sated: .for by the increased-surface area "of; the sheath" over: therai'ea ofthepriginal condensate:

! return. jacket;

Qther details.of our'.invention-and advantages? thereof. willxbesomeeapparent as the desoriptiom proceedstin" connectiongwith'st'he accompanying: drawingsnvhiulraformma partzhereof: and'iwhereimas Figure 1 is an elevation of .aetanlhinstallatiom Bye-this. means, .steamt.

employing our improved immersion type heater;

Figure 2 is a section taken along the line 2--2 of Figure l;

Figure 3 illustrates an automatic control applied to an installation similar to that illustrated in Figure 1; s

Figure 4 illustrates another embodiment of the heating unit and tell-tale duct; and

Figure 5 is a fragmentary view, partly in section, showing a modified form of a tell-tale indicator.

In the drawing a tank shell II] if provide with a port II through which the heating unit I5--I6 extends. An annular plate I2 about the port II supports the unit within the tank. A sheath or outer casing I3, which may be a tube about 3.5 inches in diameter, envelopes the heater unit I5-I6. The heating unit comprises an outer jacket I5 within the sheath I3 and it may be fabricated from a 2.5 inch pipe I5 inside of which is placed a 0.75 inch finger tube I6 The jacket I5 is mounted in an annular flange H which is bolted to end flange I l fixed to the exposed end Ida of the sheath I3.

The finger tube It passes through a tube sheet I8 welded to the end of return jacket I 5 and supplies steam from a steam header I9 by valved line 20. The inner end I3b of the sheath I3 is provided with a fill line 21 for introducing the fluid heat transfer medium 22, such as graphite or pelleted carbon black, into the tell-tale annulus 23. A return header 24 receives the steam and condensate from the return tube or jacket I5 via drain duct 25. The unit is completed by a telltale which in the illustrated embodiment is a 0.5 inch pipe 26 communicating through the wall of the sheath Il a with the tell-tale annulus 23. In the event a leak occurs, either in the return jacket I5 or in the sheath I3, the steam or stock as the case may be enters the tell-tale annulus 23 and escapes through the vent 2'! in the cap 23 threaded to the pipe 26.

If desired, a valve 3i in the line may be automatically controlled in response to the escape of fluid from thetell-tale 26. For example, a pressure sensitive control 30 may b actuated by an increase in pressure within the tell-tale annulus 23 as would result in the event that steam escapes from the return pipe I5 into the tell-tale annulus 23. Likewise, since the heatersare normally at a low point in a stock tank, the head of stock from above would cause the annulus 23 to fill with the stock and indicate an increased pressure on the tell-tale 26. l

' Referring to Figure 3, We may provide a diaphragm shutoff valve 3! in line 20 supplying steam to the finger tube IIiand a fluid pressure connection 29 from the tell-tale 26 to th diaphragm 3Ia of the diaphragm shutoff valve 3I. A-pressure switch 39 or its equivalent, adapted to operate-a solenoid or similar device, is inpressure communication with line 29 and may control a signal such as a light or an alarm a pump shutoff, or the like.

In operation, steam, Dowtherm, or other fluid heat transfer media enters line 26 through valve 3| and flows into finger tube I5 and condensate jacket I5. If the jacket I5 holes through allowing steam to pass into the tell-tale annulus 23, the line 25 will allow the escaping steam to enter the diaphragm chamber 3Ia of valve 3i. The pressure in line 29 will increase because of the entering steam, thereby causingjthe valve 3| to closeand shutoff the-flow of steam to the finger tube I16 from line '20.

In similar fashion, if a hole develops in the sheath I3, the liquid from the tank II) will increase the pressure in line 29 and cause the diaphragm of the shutofi valve to close the valve 3I, thereby shutting off the fiow of steam to the finger tube I6. ,I I

The shutoff valve 3| can be equipped with lights indicating a fully opened or fully closed valve or any other position between these two extremes. Similarly, the position of the valve diaphragm 3Ia in the valve can be used as a substitute for the pressure-responsive means 30 in actuating signals.

In another embodiment, the tell-tale 26 may be equipped witha visual indicator for displacement of fiuid within the annulus 24 due to a leak as illustrated in Figure 5. For this purpose, we may provide a piston slidable within the tell-tale pipe 26 and this piston 33 can operate a marked rod 34 which extends through the vent 21 in the cap 28. For example; this rodmay be'mark'ed with different colors so as to indicate any displacement of the piston due to the influx of either "stock from the tank or heat exchange medium from the heater into the tell-tale system; The tell-tale 26 is further modified by providing a fluid escape port 32 at a point normally above the initial position of the piston in the tell-tale 26 but below its uppermost position when it has been moved upwardly by the flow of fluid in the tell-tale annulus 23.

The packing 22 of high thermal conductivity which is used to fill the tell-tale annulus 23 may be such materials as Achesongraphite or furnace black such as sRF-Black marketed by the Witco ChemicalCompany. This black is in the form of it; inch pellets and can be'packed uniformly within the annulus 23 to provide the desired heat conductivity. Likewise the outer por tion I3a of the unit I3 can be packed with a heat insulating material if desired. In any event we have found that when such thermally conducting packing 22 is used the heat transferred is about 6 percent greater than the transfer withoutthe sheath I3, the heating unit without the sheath I 3 having an overall heat transfer coeflicient, of about 15 B. t. u./(sq. ft.) (l1r.) F.). On the other hand when the thermal packing 22 is omitted from the annular tell-tale chamber 23, the heat transferred by th apparatus, including the finger tube I6, the condensate jacket I5, and the sheath I3, wouldbe only about '7 percent of that which is transferred by the assembly without the sheath I3. Thus, the increased surfaceof the sheath I3 and the high heat conductivity of the carbon fill more than compensated for the expected heat loss due to the tell-tale sheath I3 and the annulus 23. v

The tell-tale duct has been described as comprisinga separate tube 26 attached, as by welding, to the sheath I3 outside the tank shell] 0. It is contemplated, however, that a tell-tale can be provided by other means, such as for example a radial channel 26a between the flanges I4 and I1, and communicating with the tell-tale annulus 23. Such channel 26a can be formed by registering grooves in the adjacent faces of the flanges I4 and I! or can be drilled through the bodyof the flange I 4 on the sheath I3.

A preferred immersion. heater apparatus is that shown in Figures 1 and 2 of the drawing which employs a finger-type unit including an inner steam inlet finger tube I6 and an outer concentric condensate return jacket I5; In'someinstanc'es', however; we may use a hairpin-type heater ltd-46a with a suitable sheath or casing l3, surround the hairpin tube with a material of high thermal conductivity as with the illustrated heater i5-it, and provide the sheath with a tell-tale duct as described. Such an embodiment is shown in Figure 4.

Although we have described a preferred embodiment of our invention in considerable detail, it should be understood that this is by way of illustration only and that many modifications and changes can be made therein by those skilled in the art without departing from the spirit of the described invention or from the scope of the appended claims.

We claim:

1. A tank heater of the reverse fioW type adapted to be mounted through a port in a tank shell, comprising a casing open at one end and closed at the other, a support flange about the open end of said casing, a heating unit within said casing, flange means carried by said heating unit and cooperating with said support flange to seal the open end of said casing, a fluent granular substance of high thermal conductivity substantially filling the volume of the casing not occupied by said unit, a fill duct communicating with the closed end of said casing for introducing said granular substance means for supplying steam to said unit, means for withdrawing condensate from another portion of said unit, and a tell-tale duct communicating with th interior of said casing exterior of said tank shell.

2. The apparatus or claim 1 wherein said substance of high thermal conductivity comprises pelleted carbon black.

3. An. immersion heater of the finger type adapted to be mounted through a port in a tank shell, comprising a cylindrical casing having an open end and a closed end, a support flange about the open end of said casing, a finger-type heater extending Within said casing through said open end, said heater comprising a single tube in telescoped arrangement with a condensate tube closed at the end extending Within said casing, a flange means on the exterior of said condensate tube adapted to cooperate with said support flange to seal the open end of said casing, a high thermal conductivity granular packing substantially filling the space in the casing not occupied by said heater, and a tell-tale duct communicating with the packed space between the interior of said casing and the exterior of said heater.

4. An immersion heater comprising a cylindrical outer sheath, a plug closing one end of said sheath, a fill line communicating with th interior of said sheath through said plug, an end flange about the open end of said sheath, a first tube of smaller diameter and greater length than said sheath, said tube being in a nested arrangement within said sheath, thereby providing an annulus between said outer casing and said first tube, an annular flange fixed about the exterior of said tube, means for joining said flanges, a finger tube nested within said first tube and discharging thereinto adjacent the closed end thereof, a drain from said first tube, heat conductive material in the annulus between said first tube and said sheath, and a tell-tale duct communicating with the said annulus at a point remote from said fill line.

5. A tank heater of the nested tube type comprising a cylindrical outer casing having a closed end and an open end, an end flange about said open end of said casing, a cylindrical condensate jacket of smaller diameter and greater length than said casing in nested arrangement therewith, said condensate jacket having a closed end and an open end, an annular flange fixed to the exterior of said jacket and adapted to engage said end flange thereby to position the said jacket in spaced arrangement within said casing, a tube sheet across the open end of said cylindrical condensate jacket, a finger tube nested within said condensate jacket and discharging thereinto ad- .iacent the inner end thereof, a drain from said condensate jacket exterior of said outer casing, a packing of high thermal conductivity within the annular chamber defined by the nested jacket and casing, and a tell-tale duct communieating with the chamber containing the said packing.

6. The apparatus of claim 5 including a steam line operatively connected to said finger tube, a valve in the said steam line and a control means for said valve actuated by fluid flow into said tell-tale duct from said chamber.

HOWARD O. CORD. BRUCE G. MERTECN. CHARLES J. RYANT, JR.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 572,020 Metz Nov. 24, 1896 1,305,365 Hopkins June 3, 1919 2,017,676 Girsewald et al. Oct. 15, 1935 2,360,094 Arvins et a1 Oct. 10, 1944 FOREIGN PATENTS Number Country Date 286,606 Germany Aug. 21, 1915

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