Patent Publication Number: US-8974607-B2

Title: Cleaning apparatus for heat exchange tubes of air cooled heat exchangers

Description:
I. CROSS REFERENCES TO RELATED CASES 
     This is a non-provisional application claiming priority under 35 USC §119, 120 and/or 365 on provisional application Ser. No. 61/580,821 filed Dec. 28, 2011, a copy of which is incorporated herein by reference. 
    
    
     II. FIELD OF THE INVENTION 
     This invention is in the field of air cooled heat exchangers and particularly methods and apparatus for cleaning the outer surfaces of bundles of heat exchange tubes of air cooled or other heat exchangers. 
     III. BACKGROUND AND PRIOR ART 
     In certain large scale facilities for production, treatment, storage and distribution of gas and liquid products there are a large number of conventional air cooled heat exchangers. These facilities sometimes experience substantially excessive high power consumption and low performance due to fouling accumulation on external surfaces of cooling fins as heat exchange tubes. This is particularly true in an environment like that of Saudi Arabia where the air is filled with heavy dust so that tube bundles of air cooled heat exchangers become externally plugged in a short period of time and require frequent and extensive cleaning. Existing cleaning methods are known to be both expensive and not fully successful because of heat exchanger construction where many tubes with their closely spaced fins are packed in relatively tight bundles. Many surfaces are not reached by the cleaning liquid or spray since many are below or otherwise blocked by others closer to the source of the cleaning spray. The same problem exists even with mechanical brushing or scraping, as there are such a great many areas that are simply not accessible. 
     In applicant&#39;s various facilities there are together more than 15,000 air cooled heat exchangers that are regularly fouled and require frequent and repeated cleaning. The estimated cleaning cost by a company-wide survey was $12 million annually, without even considering other costs from slowdown or (operation bottlenecking) or other process interruptions. The above-noted cost does not include other mechanical damage caused by conventional types of cleaning to the fins and heat exchange tubes. 
     The present invention seeks to provide a new and improved apparatus and method for cleaning the external surfaces of finned tubes of air cooled heat exchangers. 
     IV. OBJECTS AND SUMMARY OF THE INVENTION 
     A first object is to provide a new apparatus and method for cleaning the external surfaces of heat exchange tubes in air cooled heat exchangers which provides more effective cleaning and without additional power consumption and with less damage to the cooling fins and heat exchange tubes. 
     Another object is to provide a method and apparatus where the cleaning spray heads are carried by a central body and moved laterally between layers of tubes and/or moved axially along the tubes between said layers, to position the spray heads in the closest possible proximity to the outer surfaces of the heat exchange tubes. 
     A further object of the invention is to provide a great plurality of spray heads carried by a laminate sheet that is movable between layers of tubes of the tube bundles and to thereby spray large areas simultaneously with spray directed at short range onto the external surfaces. 
     A still further object of the invention is to provide a structure to hold and transport the great many spray nozzles, the structure being in the form of a sheet which is movable axially or transversely of the space above a top layer or between adjacent layers of tubes. 
     It is a still further object for the nozzle carrying element to have an air mattress type structure comprising upper and lower sheets welded together in designated areas to define liquid flow passages from a fluid inlet to the multiple outlet spray nozzles. 
     An additional object is to provide a transport mechanism for moving a sheet as described above, in said transverse and axial directions for cleaning, and to subsequently fully remove such sheet from the area adjacent said tubes. 
     An additional object is to provide rollers and drive means for rolling up said sheet in an area external of the tube bundle when the sheet is not in use, and later for facilitating delivery of the sheet to the areas above or between rows of tubes. 
     A still further object is to provide in said sheet, outlet nozzles which will pop out externally of the sheet surface under the influence of cleaning fluid pressure being directed through said sheet and to said nozzles, for the purpose of moving the nozzles outward of the sheet surface and closer to the surface areas being cleaned. 
     Another object is to provide a spring element in the above-described nozzles biasing them to their retracted position when they are not being urged by the fluid pressure, so that the sheet with its retracted nozzles will be as thin as possible for maneuvering into the spaces between rows and layers of said tubes. With the above type of new structure and method, the sheet with its outlet nozzles can be rolled up for storage or can be unrolled and slid into the narrow spaces between layers of tubes of the tube bundle. 
     A still further object is to provide a secondary sheet generally parallel to and spaced below the primary spray sheet and movable essentially at the same time in the same way as the spray sheet, but positioned below the row of tubes being spray cleaned. Thus, if the spray sheet is above the top row, the collection sheet would be below the top row. If the spray sheet is between the top row and the second row down, the collection sheet would be between the second and third rows. In this manner the purpose of the collection sheet is to collect the soiled water and cleaned-off fouling substances from the row of tubes cleaned, and to drain same off to an external area, so that it does not drip down and further foul the heat exchange tubes below the ones that have been cleaned. The collection sheet is also called the sink while the spray sheet is also called the source. Alternately, the collection sheet may e positioned to collection drainage independently of movement of the spray sheet. Some examples of embodiments of the present invention are described below. 
     A first embodiment exemplified by an apparatus, operable with a source of cleaning fluid under pressure, for cleaning external surfaces of heat exchange tubes of an air cooled heat exchanger which tubes are situated in generally horizontal rows that are vertically separated from each other, thus defining a generally horizontal zone between each two adjacent rows, which space has a height defined by the distance between each of said two adjacent rows, comprising:
     a. a spray mat having:   

     i. top and bottom fluid impermeable sheets sealed at their mutual peripheral edges defining at least one chamber between said sheets, with at least one fluid inlet into said chamber for receiving a flow of said cleaning fluid under pressure, 
     ii. a plurality of laterally spaced apart apertures in at least one of said top and bottom sheets, said apertures being in fluid communication with said at least one chamber, and 
     iii. a spray nozzle coupled to each of said apertures for outward spraying of cleaning fluid received from said chamber, and
     b. a positioning mechanism for moving said spray mat transversely into one of said zones between two adjacent rows of said heat exchange tubes, where said cleaning fluid can be sprayed onto the external surfaces of said heat exchanger tubes in said zone, and for moving said spray mat out of said zone.   

     A second embodiment according to said first embodiment which has said plurality of spaced apart apertures in both said top and bottom sheets. 
     A third embodiment according to said first embodiment where said top and bottom sheets have mutually facing inside surfaces that are sealed together at predetermined locations to define:
     a. said chamber and   b. a plurality of fluid flow channels communicating said inlet with said plurality of outlet apertures.   

     A fourth embodiment according to said second embodiment where said top and bottom sheets are formed of plastic and are heat sealed together at their peripheral edges and at other areas for defining said flow channels within said chamber between said sheets. 
     A fifth embodiment according to said first embodiment where said positioning mechanism is adapted to move said spray mat to selected elevations for positioning said spray mat into different ones of said zones. 
     A sixth embodiment according to said fifth embodiment where said positioning mechanism includes a roller onto which said spray mat is rolled and stored until said spray mat is unrolled and inserted into one of said zones. 
     A seventh embodiment according to said first embodiment where each of said spray nozzles has an outer surface and has a retracted position where its outer surface is generally close to the external surface of said top or bottom sheet where it is situated, and has an extended position extending outwardly from the plane of said surface, further comprising a spring biasing said spray nozzle to its retracted position, said nozzle being pushed to its extended position when cleaning fluid under pressure is flowed from said source of cleaning fluid through said chamber to said nozzle. 
     An eighth embodiment according to said seventh embodiment where each of said springs has force F, and said cleaning fluid exerts a pressure greater than force F, which thereby pushes said spray nozzle to its extended position when said cleaning fluid is flossing under pressure to said spray nozzles. 
     A ninth embodiment according to said first embodiment further comprising a collection sheet having leading and trailing edges and a generally central area with a drain aperture therein,
     said positioning mechanism further including coupling for inserting said collection sheet into one of said zones below a zone where said spray mat has been inserted, and   where said collection sheet receives cleaning fluid dripping down from said spray met and from external services of heat exchange tubes which received cleaning fluid from said spray mat, said cleaning fluid being discharged from said drain aperture in said collection sheet.   

     A tenth embodiment according to said ninth embodiment where said collection sheet comprises a frame maintaining it in a generally horizontal plane except for said central drainage aperture which is at a lower elevation. 
     An eleventh embodiment according to the ninth embodiment where said positioning mechanism positions both said spray mat and said collection sheet simultaneously into and out of each of said zones. 
     A twelfth embodiment according to said first embodiment where each of said spray nozzles distributes cleaning fluid in a flow pattern substantially greater than the inlet diameter of said spray nozzle. 
     A thirteenth embodiment according to said second embodiment where the height of said spray mat with said spray nozzles in their extended state is less than the height of said zone between two adjacent rows of said heat exchange tubes. 
     An embodiment exemplified by a method operable with a source of cleaning fluid under pressure, for cleaning external surfaces of heat exchange tubes of an air cooled heat exchanger which tubes are situated in generally horizontal rows that are vertically separated from each other, thus defining a generally horizontal zone between each two adjacent rows, which space has a height defined by the distance between each of said two adjacent rows, comprising:
     a. providing a spray mat having:   

     i. top and bottom fluid impermeable sheets sealed at their mutual peripheral edges defining at least one chamber between said sheets, with at least one fluid inlet into said chamber for receiving a flow of said cleaning fluid under pressure, 
     ii. a plurality of laterally spaced apart apertures in at least one of said top and bottom sheets, said apertures being in fluid communication with said at least one chamber, and 
     iii. a spray nozzle coupled to each of said apertures for outward spraying of cleaning fluid received from said chamber, and
     b. positioning said spray mat transversely into one of said zones between two adjacent rows of said heat exchange tubes and spraying said outer surfaces of said heat exchange tubes in said zone with said cleaning fluid.   

     A further embodiment comprising the step of inserting a collection sheet onto one of said zones below a zone where a spray mat is inserted to collect cleaning fluid that drips downward from heat exchange tubes onto which it had been sprayed. 
    
    
     
       V. BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1-10  illustrate a first embodiment of the new invention, and  FIGS. 11-14  illustrate a second embodiment. For convenience and clarity similar components in the two embodiments have been given the same reference numbers. 
         FIG. 1  is a front perspective exploded view partially cut-away of a prior art air cooled heat exchanger (ACHE), 
         FIG. 2  is a top plan view of the heat exchanger of  FIG. 1 , 
         FIG. 3  is an elevation view in section taken along line  3 - 3  in  FIG. 2 , 
         FIG. 4  is a fragmentary top plan view of an ACHE with a first embodiment of the new cleaning apparatus of this invention, 
         FIG. 5  is a sectional view taken along line  5 - 5  in  FIG. 4  of the heat exchanger and cleaning apparatus of  FIG. 4 , 
         FIG. 6  is a schematic top plan view of the spray pad of the new invention, 
         FIG. 7  is a fragmentary top perspective view partially in section of the spray pad of  FIG. 6 , 
         FIG. 8  is a fragmentary view partially in section taken along line  8 - 8  in  FIG. 7 , 
         FIG. 9A  is a fragmentary sectional view of the spray pad of  FIG. 6  showing the spray nozzle, 
         FIG. 9B  is a top front perspective view of the spray nozzle of  FIG. 9A , shown in its extended state, 
         FIG. 9C  is a top front perspective view of the spray nozzle of  FIG. 9A , shown in its retreated state. 
         FIG. 9D  is a top front perspective view of the nozzle spring of said nozzle in its extended state, 
         FIG. 9E  is a view similar to  FIG. 9D  showing the nozzle spring in its retracted state, 
         FIG. 10  is a plan view of the collection pad, 
         FIG. 11  is an elevation view in section similar to  FIG. 5  showing a second embodiment of the new cleaning apparatus, 
         FIG. 12  is a schematic top plan view of the spray pad associated with the cleaning apparatus of  FIG. 11 , 
         FIG. 13  is a top plan view of the collection pad associated with either cleaning apparatus of  FIG. 4  or  11 , and 
         FIG. 14  is a bottom plan view of the collection pad of  FIG. 13 . 
     
    
    
     VI. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention is a method and apparatus for cleaning corrosive material, dirt and/or other material accumulated on the outer surfaces of ACHE heat exchanger tubes and accumulated particularly between and about the heat exchanger tube fins.  FIGS. 1-3  illustrate a conventional ACHE  10  including a header or manifold  12 , tubesheet  14 , heat exchange tubes  16  within the outer surfaces  18 , inlet  20  and outlet  22 . 
     As seen in  FIGS. 1-3  a conventional ACHE has heat exchange tubes situated in rows  24  comprising a tube bundle  26 . Cleaning the outer surfaces and fins of these tubes is extremely difficult because most rows of tubes are beneath or hidden by other rows, and because many tubes are packed in a relatively compact bundles for design and space reasons. Furthermore, the fins are necessarily thin for heat exchange design reasons and are susceptible to damage if impacted by cleaning equipment. The above problems are multiplied when the ACHEs are in a desert or dusty environment as is the case with applicant&#39;s many gas and petroleum processing plants in Saudi Arabia. 
       FIG. 4  shows in a top plan view a general layout of a ACHE  30  with the new tube cleaning apparatus  37 .  FIGS. 5 and 6  show further structural details of tube cleaning apparatus  37  with a heat exchanger  30 , its header  32 , inlet  33 , and a bundle  34  of heat exchange tubes arranged in rows, namely top row of tubes  34 A, second row down of tubes  34 B, next row below that  34 C, etc. Shown schematically are thin fins  35  on the external surfaces of the heat exchanger tubes. 
     As seen in  FIGS. 5 and 6  the cleaning apparatus  37  comprises: (a) a source of cleaning fluid in the form of a spray mat  38  that has the form of an inflatable sheet having some similarity to an air mattress, and (b) a sink  40  or collection sheet that collects the soiled cleaning fluid and directs it away from the tube bundle. Spray mat  38  is an inflatable laminate sheet which includes a substantial number of spray nozzles  38 N distributed on its upper and lower surfaces. Interspersed between spray nozzles  38 N are a plurality of drain holes  38 D through which cleaning fluid particularly soiled cleaning fluid dripping down onto spray mat  38 , can pass through the mat and onto the collection sheet or sink  40  below. Spray mat  38  has a similar array of spray nozzles  38 N on its lower side which direct fluid downward to heat exchange tubes  34 B of the second row, while the nozzles on the top surface spray direct cleaning fluid onto the bottom surfaces of heat exchange tubes in the top row  34 A of the tube bundle. 
     As seen in  FIG. 6  (and generally similarly in  FIG. 12 ), cleaning fluid is applied from a high pressure source (not shown) via a flexible tube  41 A to an inlet  41 B in a side region of spray mat  38 . This fluid flows through channels in the interior of spray mat  38  to the above-mentioned spray nozzles  38 N. The soiled cleaning fluid that drips downward from “cleaned” row  34 A tubes onto the top surface of spray mat  38 , drips through drain holes  38 D, then drips onto collection mat  40  which is generally concavely curved or inclined downward in its center, to drain hole  40 A and drain duct  40 B which discharges the soiled fluid away from the tube bundle. 
     An object of the present invention is to provide an apparatus and method that can deliver cleaning fluid sprayed from above and below the rows of heat exchanger tubes, in a way that has not previously been possible. As opposed to prior art methods which spray only from the top downward and/or from the bottom upward, and which fails to adequately impact onto the many tubes in the bundle inward of the exposed outer rows, the new spray mat is thin enough to be pulled into the space between two rows and to be closely adjacent substantially all of the exposed upper and lower surfaces of said heat exchange tubes. 
     As seen in  FIGS. 4 and 5 , spray mat  38  can be rolled onto roller  38 R which is carried by a transport mechanism  42 . When properly positioned by transport mechanism  42 , spray mat  38  is pulled off its roller  38 R into the space between adjacent rows, which may be between top row  34 A and second row  34 B (as shown in  FIG. 5 ), or may be between second row  34 B and third row  34 C, or may be above first row  34 A, etc. Spray mat  38  is pulled into such location by a pulling element  38 P which may take many alternative forms. Mat  38  is subsequently withdrawn by being rolled back onto roller  38 R by a roller mechanism on transport mechanism  42 . 
       FIG. 5  shows the transport mechanism  42  positioned along the side edge of the tube bundles  34 . This transport mechanism can be moved by drive means  42 D in the direction of the arrow X (see  FIG. 4 ) towards the far end of the tube bundle or positions in between. Also transport mechanism  42  can be moved in the vertical direction of arrow Y (see  FIGS. 4 and 5 ) to re-position spray mat  38  at appropriate elevations to be inserted between selected rows  34 A,  34 B,  34 C, etc. of heat exchange tubes of the tube bundle  34 .  FIG. 5  shows spray mat  38  positioned between rows  34 A and  34 B of heat exchanger tubes, and cooperating collection sheet  40  positioned below row  34 D of tubes, with its drain tube  40 B extending out of the bottom of collection sheet  40 . Also in  FIG. 5  is seen roller  38 R for withdrawing and rolling up spray mat  38 , and roller  40 R for withdrawing and rolling up collection sheet  40 . These two rollers are mounted on transport apparatus  42  which, as discussed before, can move vertically in the Y direction or transversely in the X direction. 
       FIGS. 6 ,  7 , and  8  illustrate the structure of the spray mat  38  which comprises (a) upper sheet  50  and lower sheet  51  sealed together in selected areas, and not sealed and other areas to define fluid flow ducts  52 , (b) a multiplicity of spray nozzle openings  53  on top and bottom surfaces where each spray opening communicates with a fluid flow duct, and (c) a spray nozzle  60  associated with each opening  53 . The many ducts  52  are fed cleaning fluid by one or more inlets  41 B as seen in  FIG. 6 . An alternate method of providing fluid to the spray nozzles would be to have small tubes distributed over the top or bottom surface of the spray mat, instead of having ducts formed by a pattern of sealed areas between the top and bottom sheets forming the mat. 
     Spray mat  38  also has a plurality of through holes  38 D which serve as the previously described drain holes for fluid to drip down onto and through spray mat  38 , and thence to be collected by collection sheet  40  below. 
       FIGS. 9A-9E  illustrate one of the many spray nozzles  60  in spray mat  38 . Each spray nozzle is formed by a generally conical piece of flexible material  61  having a plurality of openings  62  which communicate with the above-mentioned fluid channels  52 . 
     In this preferred embodiment it is desired that the nozzles have a normally compressed state as seen in  FIG. 9C , and be extendible axially to their extended state as seen in  FIG. 9B . Accordingly, the spray mat, when the nozzles are compressed, can be as thin as possible for negotiating it between tight spaces between rows of heat exchange tubes. Then, when cleaning fluid is directed through channels  52  to these nozzles, the pressure of the cleaning fluid will cause the nozzles to pop out into their extended configuration as seen in  FIGS. 9A and 9B . Within the flexible material  61  of each nozzle is a coil spring  64 , incorporated into the flexible material  61  of the nozzle, where the spring has a normal relaxed and retracted state as seen in  FIGS. 9C and 9E . The spring will bias the nozzle to remain in the closed retracted state at all times including during movement of spray mat into or out of spaces between heat exchange tubes and when it is rolled onto roller  38 R. However, when spray mat  38  is extended into the space between upper and lower rows of tubes, and when cleaning fluid under pressure is directed through channels  52 , the fluid will force the nozzles to pop out into their extended and generally conical shape, so that the holes  62  in the nozzles&#39; conical surfaces, facing many different directions will direct cleaning fluid in a great multiplicity of directions and will clean the maximum area of the heat exchange tubes and the fins thereof. 
     Also seen in  FIGS. 7 and 8  are drain holes  38 D extending between top and bottom sheets  50 ,  51  of the spray mat  38 . These drain holes extend through the mat in areas that are otherwise seal together and thus do not interfere with the joined areas that define the fluid flow ducts. 
       FIGS. 10-14  illustrate in more detail the collection sheet  40  which is constructed to have or take a generally concave shape or inclined downward which descends in a central area to its drain hole  40  and drain duct  40 A for disposing of soiled cleaning fluid that has dripped onto the top surface of collection sheet  40 . At corners or other edges of collection sheet  40  are apertures  40 P or other means for engaging and pulling collection sheet  40  into the space between, above or below rows of heat exchange tubes and then back out and on onto roller  40 R. Collection sheet  40  may be constructed to have a memory to take the above-mentioned concave or inclined shape after it is expanded, or it may have elastic members which form the mat into the above-mentioned shape after it is positioned in its fluid collection capacity. 
     As seen in these illustrations of the preferred embodiment, the new ACHE tube cleaning apparatus can be maneuvered into very close quarters between rows of heat exchange tubes in a bundle, which allows cleaning from nozzles positioned very close to the areas to be cleaned, that could never be done before. The results and benefits of this new invention are seen to a greatly enhance heat exchanger operation by rendering the heat exchange apparatus more efficient, by reducing downtime during the cleaning process, by reducing damage to heat exchangers and/or by providing all of the above at a greatly reduced cost as compared to prior art. 
       FIGS. 11 ,  12  and  13  illustrate a second embodiment of the present invention, whereby spray mat  30  that can be rolled up in  FIG. 5 , is replaced by spray mat  70  that remains generally planar in  FIG. 11  and cooperates with heat exchanger  69 . This alternate spray mat  70  is supported by transporter  72  which moves in the Z direction to withdraw mat  70  from between row  71 A and row  71 B of heat exchange tubes. Subsequently, transporter  72  can lower and insert mat  70  between row  71 B and  71 C of heat exchange tubes. The alternate spray mat  70  may have a peripheral or other frame  79  to maintain its shape, and may utilize supportive guide elements, such as brackets or shelves  75  shown in  FIGS. 11-13 , While this second embodiment arrangement requires more floor space for transport  72  to move away from heat exchanger  69 , it enables a simple fluid connection  74  to the fluid ducts in mat  70  which is no longer being rolled up, and enables a simple translation of mat  70  in and out in the Z direction with omission of the pulling means  38 P and the rollers in the embodiment of  FIG. 5 . 
       FIG. 11  further illustrates how transporter  72  in its laterally displaced position indicated in dashed line  72 A, can lower spray mat  74  to its partially descended elevation indicated by reference number  74 A and insert spray mat  74  between row  71 B and row  71 C of heat exchange tubes. 
     With this arrangement a sink or collection sheet  76  can be similarly supported and inserted between rows of heat exchange tubes, or such sink or collection sheet  76  can simply be positioned beneath the lowest row of heat exchange tubes, as in  FIG. 5 , and removed at the conclusion of cleaning all the rows above 
       FIG. 12  is a schematic top plan view of the spray mat  70  indicated by “ 12 ” in  FIG. 11 , showing the connection of spray mat  70  to transporter  72 , and showing the further fluid connection  74  to cleaning fluid that flows as indicated by arrows  78  into fluid flow ducts  80  distributed throughout mat  70 . 
       FIG. 13  is a schematic top plan view taken at level “ 13 ” in  FIG. 11  showing collection mat or sink  76  coupled to transporter  72 . As stated above, sink  76  could be inserted only at the lowest elevation and kept there until the cleaning between all the rows of heat exchange tubes is completed.  FIG. 13  further shows drain tubes  84  leading soiled fluid from central drain hole  86  in sink  76 . 
       FIG. 14  merely shows a bottom plan view of the collection sheet or sink  76  of  FIG. 13 . 
     The spray mats  38 ,  70  and collection sheets  40 ,  76  of said above referenced first and second embodiments respectively, may be made of various fabrics including nylon and other plastic. The nozzles are can be made of various similar flexible materials, and the coil springs within the nozzles may be made of plastic or metal, preferably materials not susceptible to corrosion or fatigue and obviously selected to have adequate strengths, memory and long life. The transport mechanism including the rollers and pulling means for directing the spray sheet and collection sheet to their desired positions would be made of from typical commercial materials and apparatus. 
     While the invention has been described in conjunction with several embodiments, it is to be understood that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, this invention is intended to embrace all such alternatives, modifications, and variations which fall within the spirit and scope of the claims.