TUBE CLEANERS FOR CLEANING THE INSIDE OF A TUBE

Abstract: Recirculating tube cleaners (2) pass through inside diameters in a bank of heat exchanger tubes (3). Variable density tube cleaners are provided which are pressurized to compress and have a substantially neu­ tral buoyancy upon entry from an inlet manifold (12) to the inside diameter of the tubes. Upon exiting from a heat exchanger outlet manifold (13) the tube cleaners return to either positive or negative buoyancy de­ pending upon the embodiment. Skimmer means (25) inter­ cept tube cleaners having positive buoyancy from the upper portion of flow and direct them to a recircula­ tion system (6). Open cell elastomer tube cleaners having negative buoyancy may be intercepted at the bottom of the flow and then partially dewatered for adjustment toward neutral buoyance. As contrasted to prior art embodiments in which the entire outlet flow must be screened, here only a small percentage, for example one percent of the outlet flow, need be intercepted. The tube cleaners are re-entrained in a pumped stream and reintroduced for circulation through the tube bank under pressure. The tube cleaners are made to have a density such that they approach neutral buoyancy for equal distribution through upper and lower tubes. A tube cleaner may be formed of two components, a clean­ ing component and a buoyancy component. Variation in density in response to pressure may be limited.

Description: BACKGROUND OF THE INVENTION The present invention relates to a, tube cleaners for cleaning the inside of a tube according to the preamble of claim 1. A condenser utilized in applications such as steam generating power plants includes tubes arranged in a tube bundle. Water flowing through the condenser tube bundle picks up heat from condensing steam on a shell side or outside diameters of the tubes. Based on conventional design considerations, a plurality of condensers may be installed in one power plant, each condenser having a large number of tubes. The selection of number of tubes and number of condensers is a function of the design parameters for each system. These design parameters include the amount of water to be pumped through the tubes, the temperature of steam contacting the tubes and various flow rates. According to R. J. Stoker and E. F. Seavey, "The Selection of Large Steam Surface Condensers," Combustion , 1967, in a survey of fifty condenser units in a nominal 600 megawatt plant, a nominal flow through the condensers is very large and a large surface area is required. Since maximum surface area is provided by long, small diameter tubes, it is easy to see that individual condensers having 40,000 tubes in a bundle would not be uncommon. It will be readily apparent that any buildup of coatings inside these tubes or any other fouling will provide the highly disadvantageous effects of buildup and back pressure, making it more difficult to circulate the required large quantities of water through the tubes, and of creating a thermal insulation on the inner surface of the tubes, tending to defeat the very purpose of the heat exchanger itself. Since large quantities of water flow through the tubes and small buildups have a highly disadvantageous effect, online cleaning is very important in maintaining the efficacy and economy of the system. The continuous removal of deposited scale from the insides of the tubes will prevent pitting or concentration cell attack, a form of galvanic corrosion and will prevent further scale deposition. This will further prevent destruction of the tubes. Advantages of a cleaning program are further discussed in "Condenser Cleaning Improves Economics," Electrical World , December, 1969, page 31, and in A. F. Stegelman and R. Renfftlen, "Outline Mechanical Cleaning of Heat Exchangers, " Hydrocarbon Processing , January 1983, page 95. An established method of cleaning consists of circulating sponge rubber balls through the heat exchange unit. The balls are forced by pressure to traverse the tubes and each wipe the inside of the tube. While a sponge rubber ball will have only a minor effect on one pass, the balls are commonly maintained in circulation through several hundred or several thousand passes with the objective of cleaning the interior diameter of the tubes. Apparatus must be provided for collection the sponge rubber balls after they exit from the tubes, conducting them through a recirculation path and reinjecting them into a liquid stream for reintroduction into the tubes. Therefore, the art has developed various forms of cleaners. Exemplary of many prior art systems is US-A- 2,801,824, issued on August 6, 1957, to J. Taprogge. In the apparatus disclosed therein, condenser tubes are automatically cleaned by cleaning elements comprising "rubbing bodies" which are carried along tube walls by a liquid medium such as the cooling water. The rubbing bodies are moved through the heat exchanger in continuous circulation and intercepted from the outlet of the spent medium by a suitable device and returned again into the fresh liquid medium supplied to and flowing through the heat exchanger. The suitable device comprises a funnel shaped strainer in this apparatus. Another such system is disclosed in US-A-4,351,387, issued on September 28, 1982, to L. Milia. In the disclosure therein, the suitable device is a sieve means which may be formed as a "V" to intercept the outlet flow from the condenser when the system operates in a mode for recirculating the cleaning means. Alternatively, each leg of the "V" may be rotated so that the two legs are parallel and flow without intercepting the outlet from a condenser when a cleaning opeation is not being performed. Many other arrangements are provided in which a means intercepting the entire outlet from the condenser is positioned to intercept the flow and in which the intercepting means may be "feathered" to permit the flow to pass without being screened. As to the cleaning balls themselves, many forms have been provided commonly utilizing sponge rubber of a slightly larger dimension than the inner diameter of the tube to be cleaned. Over a large number of recirculating passes through the tubes, the sponge rubber balls tend to remove undesired buildups in the interior of heat exchanger tubes. After separation from the outlet stream from the condenser, the cleaning elements are recirculated. A means for separating worn out balls which are decreased in size prior to delivery to the inlet stream to the condenser may be provided. The cleaning elements are normally unevenly distributed through the tubes within the banks in a condenser since the cleaning elements are heavier than water when recirculated and returned for introduction into tubes in a condenser. As stated above, there can be up to 40,000 tubes in a bank. Therefore, some tubes in a bundle will be much higher than others. Turbulence normally encountered in an inlet manifold at the entrances to the tubes will not overcome the effects of gravity on the heavier-than-water cleaning elements in terms of providing for uniform vertical distribution of cleaning elements. Tubes which are vertically above other tubes will therefore tend to have fewer cleaning elements circulating therethrough with uneven cleaning resulting. Consequences can be significant. Upper tubes may not be cleaned effectively and eventually must be mechanically and/or chemically cleaned. Acid cleaning is a known form of cleaning. There is the attendant expense of the cleaning operation and significant "downtime" for the condenser, which often results in the shutting down of the power plant itself. In circulating, the cleaning elements must strike against the screens, separating sieves or the like, to be removed from the outlet flow and recirculated. The necessary action of this separation reduces the useful life of the cleaning elements. It is desirable to have a system in which separation does not require the rolling of cleaning elements against a screen. The geometry of the cleaning elements can provide for difficulty and expense in their construction. It is desired to provide for the option of simplifying construction. Prior art refers to means used for cleaning inner diameters by many differnt terms, e.g. plug, pig, ball, etc. Such names will be referred to herein as tube cleaners. US-A-4314604 and 4550466 disclose sponge like tube cleaners and DE-A-3233941 and EP-A-0053355 disclose two component cleaners. DE-A-3233941 discloses a tube cleaner for cleaning the inside of a tube having a given internal diameter, said tube cleaner comprising two parts, one of said parts being a flotation member, the other of said parts being a cleaning member, said two parts being connected together, the flotation member having a maximum transverse dimension slightly less than said given diameter, said cleaning member being resilient and dimensioned to engage and rub against the interior wall surface of the tube, the tube cleaner having neutral or positive buoyancy in water. It is an aim of the invention to improve on these cleaners. According to the present invention there is provided a tube cleaner of this type in which the cleaning member comprises an annular disc. In one such construction, the flotation member comprises a truncated spheroid, the cleaning member meets with the truncated portion thereof and fastening means extend through the centre of the disc and into the flotation member along a diameter thereof. In another construction, the flotation member comprises a spheroid surrounded by said cleaning member and said cleaning member comprises a disc having an annular peripheral portion extending radially outwardly of said flotation member. With this construction, the cleaning member may have a diameter proportioned with respect to said tube inside diameter such that in use said cleaning member is disposed at an angle other than perpendicular to the axis of the tube and is positioned for rotation about the axis. In another construction the cleaning member disc is formed into cup convex in the direction of travel, when, in use, said tube cleaner is positioned in the tube. The tube parts of the cleaner may be connected together by a fastener extending through the cleaning member and into said flotation member this being tightened sufficiently to induce deformation of the cleaning member. In either of the last two constructions the flotation member may be at least partly spheroidal. Preferably the cleaning member has negative buoyancy and the flotation member has positive buoyancy, said members being proportioned to provide said cleaner with neutral buoyancy. The flotation member may be compressible and may include cells which are closed. The invention will be more clearly understood from the following description which is given by way of example only with reference to the accompanying drawings in which: Figure 1 is a mechanical schematic illustration of a system for using tube cleaners in accordance with the present invention and incorporating a condenser stage for cleaning inner diameters of tubes in the heat exchanger. Figure 2 is a partial elevation in cross-sectional form taken along lines II-II of Figure 1 illustrating means for separating cleaning elements from the outlet flow from the heat exchanger. Figure 3 is a sectional plan view of the means illustrated in Figure 2 and is taken along lines III-III of Figure 1; Figures 4 to 6 are isometric illustrations, in some cases broken away of tube cleaners in accordance with the present invention; Figure 1 is an elevation in schematic and partially in cross-sectional form of a system 1 in which tube cleaners elements 2 are circulated to clean inside diameters of tubes 3 in a condenser 4. A recirculation system 6 is operable to selectively return tube cleaners 2 which exit from the condenser 4 to the inlet thereof. The supply of cooling water is provided from an inlet conduit 10. The inlet conduit 10 can supply cooling water from a river, lake or other source. It should be realized that cooling water is an example of one suitable form of cooling fluid medium which can be circulated through the present system. Other media may be utilized. However, water will most commonly be provided in embodiments in which the condenser 4 is included in a steam power generating plant. Cooling water enters an inlet distribution head 12 communicating with the entry to each tube 3. An outlet conduit 11 receives cooling water from an outlet collection head 13 communicating with the tubes 3 and discharges the cooling water. The outlet conduit 11 also communicates with the recirculation system 6. The outlet conduit 11 may comprise a pipe, tunnel or an open trough or flume. The illustration in Figure 1 is intended to be representative of either. The cross-section of the outlet conduit 11 at Figure 1 may be either square or circular. Commonly, an open trough or tunnel will have a rectangular cross-section, and a pipe will have a circular cross-section. Figures 2 and 3, which are partial cross-sectional illustrations of an elevation and a plan respectively along Lines 2-2 and 3-3 of Figure 1 illustrate one form of the interface between the outlet conduit 11 and the recirculation system 6. The interface means 20 comprises a barrier 25 for intercepting flow in the outlet conduit 11 in a manner described in further detail below and directing a portion thereof to a conduit 30 having an outlet 31 terminating in a deaeration tank 34. The deaeration tank 34 is of conventional construction including a liquid level controller 36 for controlling water level in the tank 34 by controlling valve means 37 operating pressure means 38. The deaerating tank 34 is operated in a conventional manner. The pressure means 38 is operated in a conventional manner. The pressure means 38 which may supply negative pressures such as a vacuum is operated to draw air off from the tank 34. In this manner, air is removed from the flow that is to be returned through the remainder of the recirculation system 6. Within the aerating tank 34 is an inlet 40 to a conduit 41 which conducts water and material entrained therein (such as tube cleaners 2) from the deaerating tank 34 pumped by a pump 43 to a conduit 44. A source 42 of make-up water is provided to provide a sufficient stream into which to entrain, pressurize and reinject the tube cleaners 2. The conduit 44 has an outlet 45 for injecting tube cleaners 2 in the flow path to the inlet 10 of the heat exchanger 1. Referring to Figures 2 and 3, the interface means 20 is discussed in greater detail. As illustrated variable buoyancy tube cleaners 2 are utilized which will have positive buoyancy upon reaching the outlet manifold 4 and outlet 11. In the prior art systems wherein the exiting tube cleaners have negative buoyancy, it is the standard practice to intercept the entire flow in an outlet analogous to the outlet 11 to remove tube cleaners therefrom. The barrier 25 is formed to provide skimmer means positioned for intercepting a vertical extreme portion of flow in a horizontal component of the flow direction from the outlet collection head 13. The barrier 25 is preferably a straight, rectangularly shaped wall member. Where fitted into a circular pipe, however, the barrier 25 may be a V-shaped barrier when viewed in a direction normal to outlet flow and comprising first and second radial flanges. In the present embodiment in which tube cleaners 2 are expected to float upon exiting from the outlet collection head 13, the barrier 25 is positioned extending across a top portion of the outlet 11. As used here, "top portion" contemplates a depth which corresponds to the expected depth to which tube cleaners are expected to be encountered. The barrier 25 is preferably positioned a distance from the outlet collection head 13 such that tube cleaners 2 will have an opportunity to float to the top of the water flow. It is significant that the barrier 25 and outlet conduit 30 may be formed to provide a minor portion, for example, as little as one or two percent of the outlet flow in the outlet 11 to the recirculation system 6. This proportioning provides for a number of highly beneficial results. The barrier 25 may be of solid construction, such as a solid piece of steel. The barrier may be made at minimum cost to provide maximum strength. This is to be contrasted with extremely expensive and complex screen systems of the prior art. A screen system is of necessity difficult to provide in that a screen must be open enough to permit flow therethrough and yet must be strong enough to withstand the differential pressure thereacross. A screen also necessarily creates a back-pressure. Such a back-pressure is not produced by the present barrier system in an open flume. The back-pressure produced in a closed pipe embodiment is not significant since only a minority of the area of the cross-section of the pipe need be blocked, (140,000 gallons). The barrier 25 preferably extends to a point at which the conduit 30 intersects the outlet 11. From that point, the barrier 25 is angled with respect to the horizontal component of flow in the pipe 11. As the tube cleaners 2 are carried along in the flow and impact the barrier 25, the tube cleaners 2 are directed to the conduit 30. The angle at which the barrier 25 is placed with respect to the flow may be, for example, 45°. An optimal angle may be selected as a function of the geometry or geometries of the tube cleaners 2. Different geometries of tube cleaners may be used. The optimum angle is a function of the combination of tube cleaners 2 provided in the flow. One skilled in the art will know when the optimum angle is achieved in that the maximum number of tube cleaners reach the conduit 30 after striking the barrier 25 in a minimum time. The conduit 30 receives a flow of water and tube cleaners 2 and provides the flow to the deaeration tank 34. The pump 43 pumps flow therefrom. The tube cleaners 2 as entrained in the flow are then injected from the outlet 45 into the stream entering the inlet 10. Tube cleaners 2 are then dispersed throughout the inlet distribution head 12. The pressurization of the tube cleaners 2 to substantial neutral buoyancy is highly useful in that it helps assure a substantially even distribution of tube cleaners to all the tubes 3 in the heat exchanger 4. Turbulence in the inlet distribution head 12 further disperses the tube cleaners 2. (20 feet) The tube cleaners 2 are forced under pressure through the tubes 3. The tube cleaners rub thereagainst. Only a minimum amount of cleaning takes place on one pass. It is contemplated that the tube cleaners 2 will be recirculated continuously through the heat exchanger except during cleaning system outages. Cleaning members described below may comprise medium durometer elastomer. Figure 4 is an isometric illustration of an embodiment in which a compressible flotation member 88 and a relatively incompressible cleaning member 89 affixed thereto by fastening means 90 is provided. The flotation member 88 is shaped to fit for travel through a tube 3. In the embodiment of Figure 4, the flotation member 88 comprises a truncated spheroid having the annular member 89 mating to the truncated portion thereof. The fastening means 90 extends through the center of the cleaning member 89 into the flotation member 88 along a diameter thereof. Edges of the outer diameter of either annulus 89 may be rounded. Alternatively, they may be rounded upon progressing through repeated passes through the heat exchanger tubes 3. In the embodiment of Figure 5, the flotation member 88 may be bifurcated to abut opposite surfaces of the cleaning member 89 which is mounted in a plane on a diameter of the member 88, e.g. as to resemble the planet Saturn. To provide for the same result, the flotation member 88 may have a groove formed in its circumference. The cleaning member 89 may be stretched over the flotation member 88 and snap into place in the groove. The cleaning member 89 is supported in the flotation member 88 and has only an annular peripheral portion projecting in a radial direction from the spheriod defined by the flotation member 88. In the embodiment of Figure 6, the flotation member 88 is a sphere, and the cleaning member 89 is a deformable disc attached to and depending from the flotation member 88. The disc comprising the cleaning member 88 is deformable to form a convex surface in the direction of travel. Both embodiments are oriented in each tube 3 by hydraulic forces. Fastening means 92 maintain the members 88 and 89 in engagement. In Figure 6, the fastening means 92 is engaged to the flotation member 88 sufficiently tightly to initiate the above-described cup-like deformation of the disc i.e., the cleaning member 89. The fastening means 92 need not be a screw; it could comprise a molded retaining means integral with the flotation member 88. In both cases, the flotation member 88 has a longest dimension less than an inside diameter of a tube 3 through which it is intended to travel and the cleaning member 89 has a greater diameter. The cleaning member 89 is sufficiently elastomeric such that a side 91 seals thereof the inside diameter of a tube 3 and provides a wiping motion of its periphery against the inside diameter as the tube cleaner 2 moves in response to the pressure differential thereacross. The cleaning member 89 thus engages the tubes in a cleaning relationship. The side 91 may initially be squared and eventually become rounded due to wear. The diameter of the cleaning member 89 in the embodiment of Figure 5 is chosen so that the cleaning member 89 will be other than normal to an axis of a tube 3, illustrated as axis A in Figure 5, and will assume differing orientations in successive passes. Ideally, the tube cleaner 2 will rotate about the axis of the tube 3. In the embodiment of Figure 6, greater deformability of the cleaning member 89 is provided for, and the cleaning member 89 forms a cup upon entry into a tube 3. The material and the diameter of the cleaning member 89 are selected so that the cup "wobbles" in its travel through the tube 3 so that cleaning action is enhanced.

Claims: A tube cleaner for cleaning the inside of a tube having a given internal diameter, said tube cleaner comprising two parts, one of said parts (88) being a flotation member, the other of said parts (89) being a cleaning member, said two parts being connected together, the flotation member (88) having a maximum transverse dimension slightly less than said given diameter, said cleaning member (89) being resilient and dimensioned to engage and rub against the interior wall surface of the tube, the tube cleaner having neutral or positive buoyancy in water, characterised in that the cleaning member (89) comprises an annular disc. A tube cleaner according to claim 1, characterised in that said flotation member comprises a truncated spheroid (88), in that the cleaning member (89) mates with the truncated portion thereof and in that fastening means (90) extend through the centre of the disc and into the flotation member along a diameter thereof. A tube cleaner according to claim 1, characterised in that said flotation member (88) comprises a spheroid surrounded by said cleaning member and said cleaning member comprises a disc having an annular peripheral portion (91) extending radially outwardly of said flotation member. A tube cleaner according to claim 3, characterised in that said cleaning member has a diameter proportioned with respect to said tube inside diameter such that in use said cleaning member is disposed at an angle other than perpendicular to the axis of the tube and is positioned for rotation about the axis. A tube cleaner according to claim 1, characterised in that said cleaning member disc is formed into a cup convex in the direction of travel, when, in use said tube cleaner is positioned in the tube. A tube cleaner according to claim 5, characterised in that said parts are connected together by a fastener (92) extending through said cleaning member and into said flotation member and tightened sufficiently to induce deformation of said cleaning member. A tube cleaner according to claim 5 or 6, characterised in that said flotation member is at least partly spheroidal. A tube cleaner according to any preceding claim, characterised in that the flotation member is compressible. A tube cleaner according to any preceding claim, characterised in that the cleaning member (89) has negative buoyancy and the flotation member (88) has positive buoyancy, said members being proportioned so that together they provide said cleaner with neutral buoyancy.

Inventors: ECHOLS, MARVIN
Applicants: SUPERIOR I.D. TUBE CLEANERS INC.
Application year: 1985
Main classification: F28G1
IPC codes: B08B9, F28G1