US2857922A - Apparatus for cleaning tube bundles - Google Patents

Description

Oct. 28, 1958 R. 1'. EFFINGER 2,857,922

APPARATUS FOR CLEANING TUBE BUNDLES Filed Oct. 9, 1951 2 Sheets-Sheet 1 .lnveni'or Oct. 28, 1958 R. T. EFFINGER 2,857,922

APPARATUS FOR CLEANING TUBE BUNDLES Filed Oct. 9, 1951 2 Sheets-Sheet 2 29 w I00 4 7mm Valve Clzanin l8 9 Vzsszl X.

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lnvenror is AHor rwq States Patent IO APPARATUS FOR CLEANING TUBE BUNDLES Robert T. Eliinger, Lafayette, Califl, assignor to Shell Development Company, Emeryville, Caliil, a corporation of Delaware Application October 9, 1951, Serial No. 250,480

2 Claims. (Cl. 134-133) This invention relates to an apparatus for cleaning deposits from objects by means including the application of solvents to the deposits. It involves an apparatus for removing deposits consisting essentially of solids bound by resinous binder that are built up during prolonged exposure to petroleum liquids-by subjecting such objects to the action of a cleaning liquid, specifically a solvent. Although certain features of the invention have other applications and the invention may be applied to cleaning other objects, it will be described as applied to cleaning the shell side of heat exchange tube bundles.

Due to the layout and pitch, it is often exceedingly diflicult, if not impossible, to scrape the outside of tubes of such tube bundles by mechanical means; furthermore, satisfactory cleaning is not always obtained by mechanical means even where it is possible to use them.

Attempts have heretofore been made to avoid mechanical removal of deposits by recourse to solvents or detergents. However, deposits resulting from prolonged exposure of tubes and the like to petroliferous streams are difiicult to remove by prior techniques employing solvents or detergents. Moreover, the handling of heavy and bulky objects such as tube bundles to introduce them into the cleaning vessel and the movement of such objects within the vessel during the cleaning operation have presented difficulties and required expensive equipment.

Among the objects of this invention are the provision of an improved apparatus for removing deposits of petroleum origin from objects, such as the exterior surfaces of heat exchange tubes assembled as tube bundles, including a vessel with means for supporting the object rotatably therein and for rotating the object while it is subjected to the action of a solvent or other cleansing liquid; and the provision of an improved apparatus for facilitating the introduction and withdrawal of elongated objects into and removal of such objects from the vessel. Further objects will become apparent from the following description.

The improved method is founded upon the fact that deposits of the character described consist of two types of materials, viz., solids and binding material, and that the great majority of deposits formed on surfaces of heat exchange tubes and the like are of this character. The solids are primarily solid corrosion products derived from the tubes themselves or from other equipment with which the process stream has come into contact, or other solids such as carbon or carbonaceous material that is carried in suspension in the process stream. The binding material is resinous in nature and consists of hydrocarbons or polymerized resins derived from the petroleum liquid; it cements the solids together. No single detergent or solvent was found to be effective for removing both the binding material and the solids within a reasonable time period.

According to the invention such deposits are removed preferably by a two-step process, the first of which in-' ,volves extracting the binding material with a suitable solvent under conditions insuring uniform contact of Patented Oct. 28, 1958 the solvent with all parts of the surface of the object and insuring contact under conditions insuring the use of the solvent in a state of cleanliness and at a temperature promoting high solvent power. This step leaves a residual deposit that consists essentially of the solids. The second step involves the removal of the residual deposit by mechanical means, such as the application of a blast of air or jet of water, or by the use of a detergent solution; this may be performed within the vessel used in the first step.

The invention further resides in the improved apparatus for applying clean solvent to the deposit by exposing the object to a bath of vapors of the solvent while cooling the object by applying cooled liquid thereto, e. g., liquid solvent.

The apparatus according to the inventionincludes, in one aspect, a pressure vessel having means for providing vapors of the solvent and for cooling the: object within the vessel by applying a coolant thereto, e. g., cooled solvent or another liquid such as water, to cause condensation of vapors as clean solvent on the surface of the object during the first step of the method. The invention further provides a vessel provided with a bearing support for a pair of circular supports that are fixed to the object to be cleaned whereby the object may be rotated while undergoing treatment, together with drive means within the vessel for causing such rotation. Moreover, the invention provides a cleaning system including a carriage, movable on a track .exteriorly of the vessel and supporting a dolly that may be moved to the vessel on the carriage, the said bearings for supporting the circular supports being mounted on the dolly. In the preferred arrangement, the carriage and vessel are provided with tracks that may be brought into juxtaposition by movement of the carriage, and the dolly has wheels on which it may be rolled from the carriage onto the tracks in the vessel.

Having thus indicated the general nature of the invention, reference is made to the accompanying drawings forming a part of this specification and showing one illustrative embodiment of the invention, wherein:

Fig. 1 is an oblique projection of the apparatus showing the carriage and dolly in front of the pressure vessel;

Fig. 2 is a transverse sectionalview taken on line 22 of Fig. l with a dolly and tube bundle within the vessel;

Fig. 3 is an elevation view of the inner bundle rotating plate secured to a tube bundle; and

Fig. 4 is a schematic diagram showing the pressure vessel and associated tanks and pipes.

The cleaning vessel 10 is constructed as a pressure vessel, supported on pedestals 12'and having a hinged door 14 that may be bolted to the end of the vessel. It has a plurality of steam jackets 16 to which steam may be admitted from a pipe 18 through valves 20 and inlet pipe 17 for heating solvent placed within the vessel. Condensate may be drained through outlet pipe 19. A distributing pipe 22 having perforations along the length thereof extends the full length of the vessel near the top thereof and is connected at one end to a liquid supply pipe 24. A safety blow-off conduit 26 connects a pressure relief valve 29 to the vessel. A large vapor drawotf pipe 28 communicates with the top of the vessel. A drive shaft 30 having a non-circular end is rotatably mounted slightly above the center of the rear wall of the vessel and extends through a stufling box in the latter; the outer end of the shaft may be driven by any suitable means such as pulley and drive belt 32. The end and side wall of the vessel 10 and the door 14 are advantageously thermally insulated, e. g., by covering with glass wool, not shown.

For moving the object to be cleaned into thevessel and for supporting the object rotatably within the vessel,"I

provide a dolly 34 having flanged wheels 36 movable on a pair of tracks 3'8which are'fixed withinthe vessel and on a pair of tracks 40 in alignment therewith and outside of the vessel. The latter tracks are preferably carriage-borne, :i. e.,"theyare mountedon'a carriage 42 having flanged wheels 44 "that move on tracks 46, these tracks being 'laid 'on .theground exterior to the vessel and"extending{longitudinally -away-from the front end thereof. By this arrangement, the carriage 42 may be r'olledto place ithe tracks 40 into abutment with the tracks 38, permitting the dolly 44to be-rolled into the vessel. The'carriage "42maybethen rolled away permitting the door '14 to be closed.

The dolly 34 has a pair of supports 48a, 48b, "the latter being longitudinallyadjustable, as by means of bolts '50 extending through slots '52. These supports comprise double-flanged rollers'54 having stellited shafts extendinglong'itudinally'withrespect to thedolly to form roller nests adapted to receive circular rotating supports 56a and 56b. These plates, constituting bundle rotating plates, have radial slots 58 for securing the object to be cleaned, such as a heat-exchange tube bundle 60, by means of clamps 62. Thus, thebody portions of these clamps may engage the margins of the tube sheets 64 at the end of the tube bundle and the clamp bolts may extend through 'these slots. Additional radial slots 66 receive tie rods 68. As is shown'in Fig. 3, the inner plate 56a has a pair .of lugs 70a, 70b, bolted thereto at the center; these lugs are spaced apart for receiving between them the end 'of "the drive shaft 30 when the dolly and'the support assembly are moved into the vessel. A hole 74 in a forwardly projecting arm 76 of the dolly is located to be over a threaded nut 78 when the dolly is in position within the vessel; the nut '78 is fixed to the=bottom of the vessel. has 'aifloor, as shown, the' latter is provided with openings '80 to permit -liquid "to drain.

'lItis evident'that the dolly, when positioned within'the vessel and secured'theretoby a bolt'extending through the hole 74 into the nut '78forms a support for rotatably supporting the object to be cleaned. By virtue of the fixed position of the inner support 48a and sizes of the circular plates 56a and 56b which bring their centers to the axis of the vessel,;driving engagement of the drive shaft 30 with the drive lugs "70a and 70b is assured.

Tube bundles of various lengths'may be accommodated by adjustment of thesupport 48]; while the radial slots 58 permit'tube bundles of different diameters to be supported.

Considering next the piping, any desired number of 2 90. The discharge of thelatter is connected through a valve 92 and the pipe .24 to the distributing pipe .22. The vapor draw-off line28 is;connected through a valve "94 to a water cooled condenser 96 which may have a vent valve 97; condensate from thelatter may be returned to tank82a via'a valvef98, pipe 100 and valve 114 or to the cleaning vessel through a valve 102 and the pipes 24 and 22. A further return flow pathto the vessel via a 'valve 126and pipe.26 may be provided if .desired.

Liquid from the bottom of the vessel may be withdrawn through a pipe 104 and valve 106.and discharged from the system through a drain valve 108 or fed to the suction side of the .pump'90 through a valve 110; from the latter it may bereturned through the valve 112 to any tank by manipulation of the valves 114, 116 and 118. When valve 118 is closed, it is possible to return condensate to the tank 82a while returning liquid from pipe 104 to the tank 82b. Fresh make-up solvent may be ad- -mitted to the system through valve 120, and steam may,

if desired, be admitted into the vesselthrough a'valve "122 and to the" solvent piping through 'a valve 124.

When the dolly 56b by the clamps 62 and tie rods 68, and the outer support 48b is adjusted longitudinally by means of the bolts 50 extending through the slotted holes 52 to space the supports 48a and 48b apart the required distance to permit the circular plates to he supported on the edges of the flanged rollers 54. These preparations being made in a'service area provided with suitable hoisting equipment, and the carriage. with the dolly,34. thereon being at that area, theassemblypfrthe ,tube bundle andcircular rotating plates are placed on the supports. The ,door 14 being open, the carriage and dolly are moved on tracks 46 up -to-=the vessel 10 and'the'dolly is rolled from the carriage-borne track :40 onto ;.the interior tracks 38 within the vessel, the drive shaft 30 being turned slightly if necessary to enter the space between the lugs 70a, 701) on the'support plate 56a. A bolt is then passed through the hole- 74 at the outer end'of the dollyand-into the fixed-nut 78 -to.-hold the dolly-implace. The door 14 is then shut and bolted-"fast.

=All valves being-initially closed, a suitable solvent for the resinousbinding material that holds together the solids-of-the deposit on theexternal-surfaces of the tubes is admi'tted frOm one of the-storage tanks. Thus, to admit a volatilesolvent frorn --the --tank =82a,- the valves $441988 and 92 are opened-and the pump is operated to force liqu'id -to'the perforated pipe '22, from which it flows onto the heat exchange tubes, from which it drains tothe :bottom of the vessel. -Steam-is admitted -to the -jacket16-fmm thepipe -18 through valves 20 and inlet pipes -17, 'water condensate being discharged through pipes'19. The drive shaft 30 is rotated-slowly, thereby rotating the tube bundle "on the rollers 54. When the 'steamvapor'izes thesolvent, the'resulting vapors form a vapor bath' that-envelops 'the rotating .tube bundle. The tubes-are cooled by thesolvent-admitted' continuously all along the length of'the pipe 22, causing vapors to-condense overextended-areas of'thetubes -as-clean,--warm solvent, having a high solvent'power for the resinous material. This forms-an'extract solutionofresinous-materialinthe condensed solvent that drains-down-to the bottom of the vessel.

Cooling waterisysupplied to the condenser 96 and tubes; evenhighenpressure are at times desirable to per- 'mit'operation at higher-temperatures and cause condensation of the solvent: at temperatures at which it has a greater selveutaction- The rate of admission ofliquid solvent through the pipe 22 may be regulated byoperation of thepump-90or throttling the valve 92 to'maint ain a desiredquantity--of solvent within the vesselythus, it was found convenient tosupply about 50 to 150 gallons of liquid-solvent'for every cu. ft. of capacity of the vessel at" the start a-nd'thereafter-to maintain the-total quantity of solvent-within the vesselconstant by maintaining the liquid .level withinthe tank 82a constant, e. g, by an automatic device,not shown, responsive to the level in the ta-nk. As a'variant, condensate may be returnedby gravity flow from-the condenser through the valve lb-'2 and pipe 24,- the- valves 98, 114, 84a, 88 and -92 being closed and the pump'being stopped. iBy rotatiug the tube bundle difierentparts thereof are successively cooledto-r-the condensation-of solvent vapors,

whilst, moreover, the-direction of drainage relatively to the tubes is altered. Extracted resinous material ac dates in the bottom of a the vessel. 'iheabove treatment is continued for atime dictated by the natureof=the-'deposit, the type of solvent, and the temperature of operation, e. g., from 4 hours to 4 days. At the end of this cleaning period, the valve 84a is shut off and the pump 90 is stopped, and the solvent in the vessel is distilled overhead, condensed and returned to the tank 82a by continued heating. The vessel is steamed out by admitting steam through valve 122 and opening drain valves 106 and 108 prior to being opened.

The vessel may then be opened and the bundle pulled out with the dolly onto the carriage and immediately washed with hot water. The inside of the vessel is then also washed down to remove resinous material and other impurities removed from the tubes. By removal of as much solid material as possible at this stage, the effectiveness and useful life of the secondary stage cleansing liquids, when used, are greatly increased.

The residual deposit remaining on the tubes after the first stage treatment is porous and consists mainly of solids. These may be removed by mechanical means, such as by applying a blast of air or a jet of liquid against them, or by applying a liquid detergent that separates the solid particles from the tube surface. Treatment with liquid is advantageously carried out in the same vessel by again moving the tube bundle into the vessel and shutting the vessel and admitting a suitable cleansing liquid, such as a detergent solution, from the tank 82b through valves 84b, 88 and 92 and the pump 90 until the -vessel is filled to a level at which the tube bundle is at least partially immersed, preferably to or slightly above the mid-level. Steam may be admitted to steam jackets 16 if desired, and rotation of the shaft 30 is started. The condenser 96 in this case is used as a knockback unit and all condensate is returned directly to the vessel through the valve 126 and pipe 26, the valves 98 and 102 being shut. As soon as the desired temperature, such as 100 to 200 F., is reached, steam flow is reduced to maintain the temperature. The residual deposit is efiectively removed from the tubes by continuing this treatment for a period of about one to ten hours by the movement of the liquid over the surfaces of the tubes. Steam flow is then shut off and the liquid is discharged through the pipe 104 and valve 106, being either discharged through the drain valve 108 or passed through valve 110, pump 90 and valves 112 and 116 to the tank 82b.

Volatile solvents suitable for use in the first step include hydrocarbon liquids, particularly a fraction rich in aromatics, such as benzene and toluene, and having a boiling point range at atmospheric pressure within the limits of about 150 and 300 F. Other solvents are halogenated hydrocarbons, such as chloroform, car bon tetrachloride, etc. Usual operating temperatures are from 120 to 300 F., e. g., 220 F., when working with a hydrocarbon fraction of the type indicated.

Suitable cleansing liquids suitable for use in the second step include caustic soda, sodium salt of alkyl phenols, and the like.

The invention is not limited to any of the solvents and cleansing liquids indicated by way of specific examples. As a variant, water may be used as a coolant during the first step and supplied to the pipe 22 instead of solvent; rich water, upon being vaporized in the cleaning vessel and condensed in condenser 96 flows to the tank 82a wherein it settles from the hydrocarbon solvent.

I claim as my invention:

1. In apparatus for cleaning bundles of heat exchange tubes, the combination of a horizontally elongated pressure vessel having a removable closure at one end thereof to provide an access opening when the closure is removed; exterior track means exterior to said vessel having a part thereof situated adjacent to said opening; a wheeled carriage adapted to move on said exterior track means; carriage-borne. track means on said wheeled carriage disposed to be opposite the said opening and to extend longitudinally away fromthe vessel when the carriage is in front of the opening; a dolly adapted to sup port said bundle of heat exchange tubes and to enter the vessel through said opening and having wheels adapted to move on said carriage-borne track means; and interior track means within said vessel adapted to support wheels on the dolly and extending longitudinally inwardly from said opening, whereby the dolly may be rolled into the vessel from the truck on said carriageborne and interior track means.

2. In apparatus for cleaning bundles of heat exchange tubes, the combination of a horizontally elongated pressure vessel having a removable closure at one end thereof to provide an access opening when the closure is removed; exterior track means exterior to said vessel having a part thereof situated adjacent to said opening; a wheeled carriage adpated to move on said exterior track means; carriage-borne track means on said wheeled carriage disposed to be opposite the said opening and to extend longitudinally away from the vessel when the car riage is in front of the opening; a dolly adapted to enter the vessel through said opening and having wheels adapted to move on said carriage-borne track means; interior track means within said vessel adapted to support wheels on the dolly and extending longitudinally inwardly from said opening, whereby the dolly may be rolled into the vessel from the truck on said carriageborne and interior track means; means on said dolly for supporting said bundle of heat exchange tubes in horizontal position for rotation about a horizontal axis; and drive means within said vessel for rotating said bundle of tube about said horizontal axis when the dolly and bundle are within the vessel.

References Cited in the file of this patent UNITED STATES PATENTS 318,205 Rau May 19, 1885 512,683 Cochrane Jan. 16, 1894 958,812 Judge May 24, 1910 1,414,928 Backus May 2, 1922 1,559,346 Moore Oct. 27, 1925 1,753,243 Liddle Apr. 8, 1930 1,834,872 Rosenberg Dec. 1, 1931 1,934,677 Ash Nov. 14, 1933 2,202,344 Hamilton May 28, 1940 2,231,087 Protin Feb. 11, 1941 2,273,039 Hudson Feb. 17, 1942 2,295,912 Pagenkopf Sept. 15, 1942 2,349,000 Phillips May 16, 1944 2,366,949 Woppman Jan. 9, 1945 2,371,644 Petering Mar. 20, 1945 2,371,645 Aitchison Mar. 20, 1945 2,371,647 Petering Mar. 20, 1945 2,409,402 Thompson Oct. 15, 1946 2,538,457 Hudson Ian. 16, 1951 2,685,293 Dauphinee Aug. 3, 1954

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