US3319710A - Apparatus for cleaning surface condenser and heat exchanger tubes - Google Patents

Description

May 16, 1967 H. HEEREN ETALL. 3,319,710

APPARATUS FOR CLEANING SURFACE CONDENSER AND HEAT EXCHANGER TUBES Filed May 31, 1962 5 Sheets-Sheet 1 4 INVENTOR5 F2" 5 Hermann Heer'en 110/19 Kmzzen Bern/10m D699 May 16, 1967 H. HEEREN ETAL 3,319,739

APPARATUS FOR CLEANING SURFACE CONDENSER AND HEAT EXCHANGER TUBES Filed May 31, 1962 5 Sheets-Sheet 2 INVENTORS Hermann flee/"en Hans Kmzzer' fiernhard D699 May 16, 1967 H. HEEREN ETAL 5 9 APPARATUS FOR CLEANING SURFACE CONDENSER 7 AND HEAT EXCHANGER TUBES Filed May 51, 1962 5 Sheets-Sheet Z5 INVENTORS Hermann H ee/"en Hans K razzer BY Bern/1am Daze MMAFTZIZORNE J y 1957 H. HEEREN ETAL 3,319,710

APPARATUS FOR CLEANING SURFACE CONDENSER AND HEAT EXGHANGER TUBES Filed May 31, 1962 5 Sheets-Sheet 4 INVENTOR5 #ermann Heeren 740/15 Krazzer' Bernhard Deye 4% 0 ATTORNEYS May 16, 1967 H. HEEREN ETAL 3,319,710

APPARATUS FOR CLEANING SURFACE CONDENSER AND HEAT EXCHANGER TUBES Filed May 31, 1962 5 Sheets-$heet 5 Fay 12 Fq'yr 14:

Fay 15 INVENTORS Hermann Heeren Hans Kmzzer fiernham' De 9 United States Patent 6 Claims. (Cl. 165--95) This invention relates to an apparatus for cleaning the tubes in surface condensers and other heat exchangers which utilize raw water for the cooling fluid. In particular, the invention is directed to the use of cleaning instruments which are pushed through the tubes or tube 'c-oils by means of the flow of the raw cooling water.

The efliciency of a common condensation turbine depends in a large part to the vacuum produced in the steam condenser. One feature, amOng others, substantially influencing the inefficiency of the vacuum is the amount of scale formed by the cooling Water in the tubes or tube coils. Several methods have been used for cleaning the tubes. The ones that use brushes have the disadvantage in that the condenser either has to be shut down or one side emptied. Obviously such method is not comparable in effectiveness to a method that can be used while the condenser is operating. A so-called self-cleaning method is known which does not require at least a partial shut down of the condenser. In this method, spherical cleaning members are pushed continuously through the tubes by the cooling water using a special pump. By using a plurality of spherical members, all tubes are periodically cleaned, one by each spherical member. However, difliculty occurs in the movement of the spherical members when the tube sheets in the water boxes are not water-tight, and when dead corners exist in the water boxes. The spherical members get stuck at these points and become inoperative.

The objects of this invention are to produce an apparatus by means of which all tubes are positively cleaned. In general, these objects are obtained by providing each tube with a cleaning brush, and these cleaning brushes are moved back and forth in their respective tubes by reversing the direction of the flow of the cooling water. A brush catching chamber is provided at each end of a cooling tube, said chamber having openings for the passage of the water. Preferably the reversal of the direction of flow of the cooling water is achieved by means of valves positioned at the inlet and outlet openings for the cooling water, said valves being coupled so that there is no turbulence in the flow of the water through the tubes,

An apparatus is known for condensing the waste steam of steam turbines in which air is used as the cooling medium and flows through tubes having inserted interior fins in order to achieve the maximum heat conductivity through the tubes. These inserted fins are costly to fabricate in that they are composed of thin sheets of folded white metal. The interior of the tubes are zinc coated and the inserted fins are soldered to the inner wall of the tubes by heating the outside of the tubes. Consequently, fins are formed which extend radially almost to the longitudinal axis of the tubes and form circular segments in the cross-sectional area of the tubes. Although such construction may be adequate when using air as the cooling fluid, it would be objectionable when using water cooling as the passages between the fins would quickly accumulate scale which would be difficult to clean, and would result in a poor coefficient of heat transfer.

3,319,710 Patented May 16, 1967 In another known tube-like type heat exchanger in which heat exchange takes place through a rigid wall, the condensation side of the wall and, in the case of a tube, can be either on the interior or exterior wall of the tube. These projections have such a form that the surface tension of the vapor being condensed forces a decrease in the thickness of the film of vapor in the vicinity of the apex of the projections.

Also known is a vertical tube cooler for corrosive gases in which lead tubes have an interior fin extending longitudinally of the tube in order to increase the rigidity of the tube,

These known heat exchangers cannot use raw water as the cooling element inasmuch as the raw water is easily oxidized and forms scale so that the tubes would have a poor coefiicient of heat transfer and would incur high cost in time and labor for cleaning. Because of this, it has heretofore been impractical to produce watercooled heat exchangers having interior fins for giving a maximum heat exchange area within the tubes in order to improve the coefficient of heat exchange because of the expense of fabrication and the lack of means for economically cleaning the tubes during the operation of the heat exchanger.

According to a principal feature of this invenion, an automatically working and inexpensive cleaning apparatus exists for heat exchanger tubes having smooth interior walls and also for tubes having longitudinal ribs or fins in the form of rounded ribs separated by rounded recesses extending parallel to the axis of the tube, and at all times engageable by the cleaning instrument with the tube.

Also, heretofore known is a cleaning device for a heat exchanger composed of tube bundles and water cooled. In this case, the tubes have smooth cylindrical inner walls, with the customary coefficient of heat transfer which necessitates a large-sized unit. In this case, each tube is provided with two scrapers or brushes attached to a rod, and the scrapers or brushes are moved longitudinally in the tube. This is disadvantageous in view of the expense involved in the numerous rods needed, and also the presence of the rods in the tubes reduces the effective crosssectional area of the tube for the passage of the cooling water.

In contrast to the prior art, this invention uses a new construction for the inner fins of the heat exchanger tubes which give a higher coeflicient of heat transfer for each tube than has been heretofore available. Consequently, it is possible to make the cooling system for shell and tube condensers with considerably less cooling tubes, but maintaining the same high capacity. Consequently, the structural height of a tube condenser can be half of that of previously known units. This means that the building height for the power plant housing the turbine with the condenser thereunder can be substantially descreased. In addition, the tubes are easily cleaned, even though they contain inner fins, and the operational safety of the condenser is maintained.

Another feature of this invention is that the cleaning instrument used has an axial core carrying brush, material, such as bristles or foam rubber, which frictionally engages the inner surface areas of the tube, and this frictional engagement continues as the cleaning instrument is moved through the tube to clean the same. A further feature of this invention lies in that the cleaning instrument has a periphery complementary in shape to the inner surface of the tube so that all the surface portions of the tube are frictionally engaged by the cleaning instrument. The brush material can be cemented to the core, or it can be in the form of a sleeve pulled onto the core.

The means by which the objects of the invention are obtained are described more fully with reference to the accompanying drawings, in which:

FIGURE 1 is a schematic cross-sectional view through the water boxes of a condenser;

FIGURE 2 is a longitudinal cross-sectional view through a heat exchanger tube having a smooth inner wall and catching chambers at each end of the tube;

FIGURE 3 is a view similar to FIGURE 2 of a modified form of the invention;

FIGURE 4 is a cross-sectional view through a heat exchanger tube having ribs alternated by recesses and serving as heat exchanging fins;

FIGURE 5 is a view similar to FIGURE 4 of a modified form of the cleaning instrument;

FIGURE 6 is a longitudinal cross-sectional view through the end of a tube having a modified form of cleaning instrument therein;

FIGURE 7 is a front view of a further modified form of the invention;

FIGURE 8 is a side view of FIGURE 7;

FIGURE 9 is a longitudinal cross-sectional view through a further modified form of cleaning instrument;

FIGURE 10 is a side view of FIGURE 9; and

FIGURES 11 to 16, respectively, are front views of further modified forms of the cleaning instrument of this invention.

As shown in FIGURE 1, in order to move the cooling water through the two-part condenser 1 for a steam turbine, the water boxes 2 and 3 are sub-divided, as is customary, by means of partitions 4 and 5 into two boxes I and II, respectively. The cooling water flows through inlet 6 and is drained from outlet 7. Valves 8- and 9 are mounted in the inlet 6 and outlet 7, respectively, in order to reverse the flow of the cooling water through the tube bundles. Each pair of valves is actuated by a servo-motor 10. Each motor is periodically actuated by means of a common switch 11. The valves may also be manually actuated. The frequency of actuation depends on the rate scale forms in the tubes.

In FIGURE 2, the heat exchanger tube 12 contains a cleaning instrument 13 which is shown in a catching chamber or basket attached to the end of the tube, which chamber has openings for the passage of water. Chambers 14 are preferably made of an inert synthetic material. The chambers 14 are either attached directly to the end of the tubes or, as shown, are mounted in openings formed in the tube sheet and secured by any suitable means such as a slot and spring. The cleaning instrument 13 is formed as a brush with conical caps attached to each end of the core. The brush material can be either bristles or foam rubber. Brush 113 is held in the catching chamber as shown by water pressure. When the direction of the water is changed, the brush 13 is pushed by the water pressure into tube 12 and pushed through the pipe until it reaches the opposite catching chamber. This cleans the tube, and the cleaning is repeated when the water flow is again reversed to return the brush to its original position. This operation can be repeated as often as it is necessary to keep the tubes clean, and it does not impair the operation of the condenser. The valves 8 and 9 which are coupled to each other and mounted at the water inlet and outlet serve to control the exact reversal of the direction of flow of the cooling water.

In order to use better the water pressure gradient that exists in tube 12, according to FIGURE 3, a second smaller housing 15 is axially movably mounted in catching chamber 14. Housing 15 is longitudinally displaceable by the distance 16 and moves with the brush 13 toward tube 12. In its closed position, housing 15 seals the tube against the brush so that the full water pressure bears against the brush and thus pushes the brush safely through the tube.

In FIGURE 4, the heat exchanger tube 21 has longitudinally extending ribs 22 separated by recesses 23 on its inner wall. These ribs constitute longitudinal fins on the inner wall of the tube and the tfins, in turn, increase the coefiicient of heat transfer for each longitudinal increment of the tube. The ribs 22 and recesses 23 can be formed by corrugating the body of the tube during the fabrication of the tube. The connection between each rib and recess is rounded off so that the interior surface of the tube presents areas toward the longitudinal axis of the tube which are directly engageable by the cleaning instrument whose core 24, in this case, has a cylindrical cross-section. In this form of the invention, the brush material is composed of long bristles 25 for engaging the recesses 23 and by short bristles 26 for brushing the ribs 22 on the inner wall of the tube. The bristles are cut so that they are complementary in shape to the inner wall of the tube and ensure a continuous brushing or scraping of the inner surface of tube 21. According to this invention, the brush material carried'by core 24 can be foam rubber rather than bristles and the cross-sectional area of the foam rubber corresponds to the cross-sectional area of the bristles.

In the modification 0f FIGURE 5, the tube 21 is similar to that of FIGURE 4. Core 27 of the cleaning instrument has a peripheral shape complementary to the inner wall of tube 21, thus forming ribs 28 and recesses 29. The brush material 30 is evenly distributed around the surface of core 27 so that the brush material, either bristles or foam rubber, presents a surface for frictionally engaging the entire inner surface of tube 21 for the purpose of cleaning the same. The brush material can be in the form of a sleeve 31 pulled over core 27, with the bristles 32 secured to the outer surface of the sleeve. Other brush material can be used which forms a surface for frictionally engaging the inner wall of the tube. The brush material can be fastened to the core by glue or cement, or by any other suitable means. The catching chamber for a tube having interior fins likewise has corresponding fins for receiving the cleaning instrument used in the tube.

As shown in FIGURE 6-, each tube 12, preferably made of brass, is provided at each end with a catching chamber 42 having openings therein for the passage of water. This catching chamber is preferably made of non-water absorbent synthetic material and serves to receive the cleaning instrument after each passage through the tube. The cleaning instrument itself has non-absorbent conically shaped caps 43 and 44 at each end. These caps are of less diameter than the inner diameter of tube 12 so that the cleaning instrument will move through the tube at a slower rate than the cooling water. Consequently, the dirt particles that have been scraped off by the bristles are moved by the water ahead of the brush. Each cap 43 and 44 is provided on its base face 45, 46, respectively, which face each other with an axially positioned collar 48 and 49 in which the ends of the core is rigidly secured. Core 50 is composed of twisted wires, preferably made of brass. Each collar 48 and 49 has a length 52 which spaces the end bristles from the peripheral free edge of each cap 43 and 44, so that the peripheral ends of the bristles will not jam between the cap and the end of the tube inasmuch as the bristles 51 are somewhat resilient and 44 is provided on its base face 45, 46, respectively, which have a diameter slightly greater than that of tube 12. Also, when the cooling water flows through the openings in the chamber 42, the water first strikes the surface 45 and/ or 46 of the cap and thus moves the cleaning instrument out of the chamber into the tube. The flowing water advances faster than the cleaning instrument and creates a suction by reason of the pressure gradient which forces the cleaning instrument to move through the entire length of the tube 12.

As shown in FIGURES 7 to 10, the cleaning instrument is so made that it is composed, as shown in FIG- URE 7, of the core 50 and bristles 51 lying between the end caps 43 and 44. Core 50 also carries circular foam rubber brush members 53 and 54, each preferably being mounted adjacent an end cap 43, 44. In FIGURES 9 and 10, the foam rubber brush members 55 and 56 are formed as inserts positioned in the caps 43 and 44, respectively. The foam rubber members are preferably secured to the collars 48 and 49 of FIGURE 6, and these foam rubber members have a diameter sligthly greater than that of the tube into which the cleaning instrument is placed. According to this invention, the foam rubber members 53 and 54 are provided with channels 57, 58 in their peripheries for the passage of water, these channels being inclined with respect to the longitudinal axis of the cleaning instrument. In order to assure that the entire inner surface of the tube is contacted and brushed by the cleaning instrument, the channels are overlapped. Furthermore, in order to avoid the twisting of the cleaning element which would result in the uneven wear of the inner wall of the tube and the catching chambers, the channels extend in opposite directions at each endof the cleaning instrument. In FIGURES 9 and 10, the foam rubber members 55 and 56 which are formed as inserts in the caps 43 and 44 also have a diameter which is at least equal to or slightly larger than that of the bristles 51. These foam rubber members contain openings 59 and 60 for the passage of the cooling water, and these openings extend at opposite directions from each other.

The novel cleaning instrument of this invention is also usable in bent or curved heat exchanger tubes, or with hair-pin bent-type tubes, so formed to compensate for the expansion and contractions of the tubes and/or for avoiding stresses in the tube sheets. To clean these more or less curved tubes, a further feature of this invention is to replace the rigid core of the cleaning instrument which extends between caps 43 and 44 by two or more jointed core elements, as shown in FIGURES 11 to 14, or by making the core which carries the brush material pliable and elastic so that the cleaning instrument is able to move with the cooling water through the curved sections of the tubes and thus assures that the inner walls of these curved sections are also cleaned.

In FIGURES 11 to 16, the caps 43 and 44 are attached to the ends of the core which carries the cleaning material as represented by the bristles 51. In FIGURE 11, a flexible cleaning instrument is shown inside the curved portion of a tube 61. The axis of the tube is shown by the broken line 62 in FIGURES 11 to 16.

In FIGURE 11, the core is composed of two rigid elements 63 and 64 made of twisted wires and which are joined by a pair of connected rings 65 and 66 so that the caps 43 and 44 are movably connected with respect to each other.

In FIGURES 12 to 14, the core is composed of the same two rigid elements 63 and 64. The flexible joint connecting elements 63 and 64, in FIGURE 12, is a ball and socket joint composed of a ball 67 and a socket 68. In FIGURE 13, the elements 63 and 64 are joined by an elastic hose 69 which is telescoped over the ends of the core elements 63 and 64. Hose 69 could also be glued or cemented to the ends of core elements 63 and 64. As shown in FIGURE 14, a cylindrical cage-like flexible element 70 is snapped and/or cemented or glued onto the free ends of the core elements 63 and 64.

In FIGURES 15 and 16, the core carrying the bristles 51 is elastic and flexible, such as being composed of a helical spring 71. The circular brushes carrying the bristles 51 are fastened to this spring core. In FIGURE 16,

the caps 43 and 44 are connected by an entirely elastic circular rod 73 which carries circular brushes 72 at spaced intervals. Preferably elastic rings 74 are placed between brushes 72, or at least between the two outer brushes and the caps 43 and 44 in order to prevent the bristles 51 from being caught and jammed between the peripheral edges of the caps 43 and 44 and the inner wall of the tube being cleaned, and to assist in the strengthening of the cleaning instrument when it enters a straight portion of a heat exchanger tube.

A further feature of the invention is in that the flexible joints, such as the rings 65, 66 of FIGURE 11; the ball and socket joint 67, 68 of FIGURE 12; the hose connec tion 69 of FIGURE 13; and the cage 70 of FIGURE 14, as well as the brush elements 71 and 72 of FIGURE 15; are made of lightweight synthetic material so that the entire cleaning instrument weighs as little as possible and is inexpensive to make.

Having now described the means by which the objects of the invention are obtained,

We claim:

1. In a heat exchanger having a bundle of tubes extending between water boxes common to all the tubes, cleaning means comprising a cleaning instrument in each tube, respectively, an instrument catching chamber joined to each end of each tube and extending into its respective water box, openings in each chamber for the passage of water therethrough, and valve means in the raw water supply and discharge lines communicating with said openings for periodically reversing the direction of raw cooling water through the water boxes, each chamber and through the tubes to move each instrument back and forth through its tube and into the chamber at the end of the tube during normal operation of the exchanger.

2. In the heat exchanger of claim 1, wherein each catching chamber is composed of a synthetic material.

3. In the heat exchanger of claim 1, further comprising a housing longitudinally movable within each catching chamber for receiving the instrument and movable therewith within the chamber.

4. In the heat exchanger of claim 1, wherein said tubes have internal longitudinally extending ribs, and the instrument is a brush having a complementary shaped brush surface.

5. In a raw water cooled condenser having a plurality of parallel raw water cooling tubes reaching between water boxes, and raw water supply and discharge pipes connected to said water boxes, means for cleaning said tubes without shutting down the condenser comprising a catch basket joined to each end of each tube and extending into a respective water box, openings in each basket for the passage of water therethrough, a brush in each basket and composed of a core carrying brush bristles having a brush diameter greater than the tube and an outwardly pointed conical cap on each end of said core of less diameter than said tube, said brush being substantially buoyant in water, and valve means in said raw water supply and discharge pipes for reversing the direction of flow of water through the water boxes, the catch baskets and said tubes to move simultaneously all of the brushes from the baskets at one end of the tubes into the baskets at the other end of the tubes with the water flowing through the tubes faster than the passage of the brushes through the tubes so as to carry dirt swept by said brushes in the water flowing in advance of the brushes, and with the movement of said substantially buoyant brushes being restrained by the frictional contact of the tips of the bristles with the tubes.

6. In the condenser of claim 5, said tubes being separated into two tube bundles separated by a partition with the cooling water passing through a first tube bundle and then in a reversed direction through the second tube bundle, and said cooling water driving the brushes through the first bundle in one direction and simultaneously driving the brushes through the second tube bundle in the opposite direction.

References Cited by the Examiner UNITED STATES PATENTS 812,361 2/1906 Pickles et al. 15104.06 864,544 8/1907 Kessler et al. l5l04.06 1,049,012 12/1912 Weber et al. 15l04.06 X 1,165,455 12/1915 Schlemmer l5l04.06 X

(Other references on following page) 7 UNITED STATES PATENTS Sch1emmer 15-10406 X Penn 15-10406 Cook et a1 15-10406 Schmidt 16 5-95 Oberhubcr 15-10406 Irvin 15-10406 Giraud 15-10406 Schaer 15-10406 X Schaer 15-10406 X Schaer 15-10406 Crane 15-10406 Riney et a1 15-10406 Hall 15-10406 11/ 1951 Stephens 15-10406 9/1956 Redin 15-10406 8/1957 Taprogge 15-3.51 X 8/1961 Leach 99-134 8/1961 Leach 99-134 2/ 1962 Taprogge 165-95 1/1963 En Dean 15-10406 FOREIGN PATENTS 12/1953 Belgium.

8/ 1899* Germany. 6/1952 Great Britain.

MORRIS 0. WOLK, Primary Examiner.

Bailey 15-10406 X 15 J. ZATARGA, Assistant Examiner.

Claims (1)

1. IN A HEAT EXCHANGER HAVING A BUNDLE OF TUBES EXTENDING BETWEEN WATER BOXES COMMON TO ALL THE TUBES, CLEANING MEANS COMPRISING A CLEANING INSTRUMENT IN EACH TUBE, RESPECTIVELY, AN INSTRUMENT CATCHING CHAMBER JOINED TO EACH END OF EACH TUBE AND EXTENDING INTO ITS RESPECTIVE WATER BOX, OPENINGS IN EACH CHAMBER FOR THE PASSAGE OF WATER THERETHROUGH, AND VALVE MEANS IN THE RAW WATER SUPPLY AND DISCHARGE LINES COMMUNICATING WITH SAID OPENINGS FOR PERIODICALLY REVERSING THE DIRECTION OF RAW COOLING WATER THROUGH THE WATER BOXES, EACH CHAMBER AND THROUGH THE TUBES TO MOVE EACH INSTRUMENT BACK AND FORTH THROUGH ITS TUBE AND INTO THE CHAMBER AT THE END OF THE TUBE DURING NORMAL OPERATION OF THE EXCHANGER.

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