TUBE CLEANER

Abstract: A tube cleaner (42) for removing deposits from the inner wall of condenser and other types of tubes has scraper means (20) for contacting the inner wall of the tube. The scraper means (20) are adapted to contact the wall at an angle of 90 degrees or less when the cleaner travels through the tube, so as to achieve more effective cleaning. The scraper means (20) may consist of one or more split rings mounted in incomplete transverse channels (44) on a central core (32).

Description: TUBE CLEANER This invention relates to a tube cleaning device; more particularly, this invention relates to a device suited to cleaning condenser and heat exchanger tubes, inter alia. For the sake of brevity, this invention will generally be described in connection with tube cleaners for heat exchanger and condenser tubes. However, it is to be appreciated that the invention has application to a wide variety of tubes and that the scope of the invention is not limited to such cleaners. Condenser and heat exchanger tubes are normally manufactured from materials such as brass, aluminium-brass, copper-nickel, titanium, stainless steel and carbon steel. It is well known that the operating efficiency of heat exchangers and condensers in power plants is reduced and fluid flow is restricted when the condenser tubes become fouled by such deposits as scale, algae, mud, slime and the like. In addition, if tubes are not cleaned regularly, deposits may cause pitting or corrosion of the tubes, resulting in major damage and shortened tube life. Deposits in tubes can be classified loosely as two types: soft deposits, such as algae, mud and slime, and hard deposits, such as scale. The soft deposits may be loosened or even removed by using high pressure water alone, but removal is most effective if high pressure water is combined with some abrasive action. Hard deposits need a positive abrasive action; water is useful mainly to flush out the hard deposits once they have been scraped from the tube wall, and to remove acidic deposits found under pitting peaks. To clean the tubes, various systems have been devised. Many of these involve the propulsion of a cleaning projectile through the tubes. Propulsion is effected by means of an air, water or air/water gun which shoots the projectile through the tube. Over the years, the projectiles have included rubber scraper plugs, balls and brushes and may be propelled through the tubes. In recent years, more sophisticated propelled tube cleaners have been devised. One such tube cleaner, designed for use with a water gun, comprises a metal core on which are mounted a series of spring-loaded metal scraper blades. Each blade is designed to make contact with part of the arc of the tube wall's diameter, by forming an obtuse angle with the wall. The blades are fixed in position around the metal core so that their arcs overlap and all the circumference of a tube wall is intended to be contacted by at least one blade as the cleaner progresses through the tube. This cleaner is designed to remove obstructions and debris as well as all deposits, including soft deposits and hard scale from the tube wall. It will be appreciated that the cleaner has a certain degree of body strength and this is required in order to remove hard scale effectively. Material removed by the scraper blades is swept through the tube by the water used to propel the cleaner. This prior art cleaner may be reusable for up to 20 times; however, depending on the nature of the deposits, the life of the cleaner may be reduced to 8 to 10 uses. In addition, this cleaner suffers from the disadvantage that the metal blades may corrode unless cared for in a proper manner. Further, the fit between the tube wall and the scraper blades must be a close one for the cleaner to operate efficiently. There is very little tolerance for variations in the diameter of the tube. Therefore, this cleaner is not adaptable for use with tubes which vary in size, even within a small range of gauge. This can be a significant problem. Many tubes have a plastic or other lining running from the inlet into the tube for a short way, to prevent water erosion of the tube. If the prior art tube cleaner referred to above is chosen to fit the lined part of the tube, there may be insufficient contact between the scraper blades and the unlined length of the tube to effect proper cleaning. On the other hand, if the tube cleaner is chosen to fit the unlined length of the tube, there will be a tight fit between the cleaner and the lined part of the tube and use of the cleaner may damage the lining, especially in the case of plastic linings. In addition, many cleaners are not intended for use in other than straight tubes. Another type of tube cleaner now available consists of a scrubber made of semi-rigid plastic such as polyethylene and consists of a core body and a series of scraping discs integral therewith. This scrubber is designed for use with air and water guns: the scrubber channels the water through apertures in the scrubber, so that deposits may be loosened and swept out of the tube. The scraping discs which are designed to meet the tube at an obtuse angle, are relatively flexible and can adjust to the diameter of the tube. In a situation where the inlet and outlet of the tube is lined, as described above, the flexibility of the discs and the use of plastic rather than metal in the scraping discs means that there is little likelihood of damaging the plastic lining, while at the same time there is an adequate fit with the unlined part of the tube. While each scrubber is relatively inexpensive and adaptable to be used in tubes having a small variation in diameter, as indicated above, it is necessary to use different sized scrubbers if there is a larger variation in diameter. In addition, the scrubber may have a short life, especially if hard deposits are frequently encountered. The polyethylene scrubber suffers from a further disadvantage: some water contains a significant amount of mineral salts and leaves stubborn scale on tubes. It has been found that the polyethylene scrubber has insufficient body strength to remove this. Both the prior art cleaners described in detail above are vulnerable to damage if they hit a solid obstacle. The metal cleaners wear and riveting becomes loose, with the result that the cleaners are ineffective after about 10 uses. The plastic scrubbers break and must be discarded. The above description relates to heat exchange and conά;nser tubes. However, there is a different type of problem encountered in the case of some other types of tubes, such as chiller sets for air conditioning plant. The tube bores in these situations are not always of constant diameter. At present, it is common to use a brush driven by a flexible cable to clean these tubes, the cable causing the brush to rotate as it travels through the tube. However, these flexible brushes, whose bristles are dragged back against the wall of the tube during the cleaning operation, wear rapidly and require replacement frequently. It is an aim of the present invention to provide a tube cleaner which, in particular embodiments, substantially overcomes or at least alleviates some or all of the drawbacks presented by prior art tube cleaners and which incorporates other advantages not available with prior art cleaners. The present invention is predicated upon the discovery that tube cleaning is far more effective if scraper blades or bristles contact the inner wall of the tube at an acute angle or in a perpendicular manner, rather than at an oblique angle as is the case with prior art cleaners. Accordingly, the present invention provides a tube cleaner having at least one scraper means for contacting an inner wall of a tube, the scraper means being adapted to contact the wall at an angle of 90 degrees or less when the cleaner travels through the tube. The scraper means may take many forms. One preferred embodiment will now be described. The or each scraper means is mounted on a central core and the or each scraper means is capable of replacement without damage to the core. The core may be manufactured from any appropriate material, but preferably is made from a material which provides sufficient body strength to enable the cleaner to scrape hard deposits such as scale from the tube wall. It is also preferred that the core is made from a material which will not bend or break but which will retain its shape, even after hitting an obstruction at speed. One such suitable material is a plastic polymer, for example, some forms of polypropylene. Another is metal, such as steel. Others will be apparent to one skilled in the art, or will be apparent after suitable experimentation. The diameter of the core may vary according to the diameter of the tube to be cleaned. For example, the diameter of the core may range from 4.5 mm to 63.5 mm or even more. However, as will be appreciated from the description below, it is possible to use one size of core in conjunction with suitably-sized scraper means, to clean a relatively wide range of tube dimensions. The scraper means may be mounted on the core in any manner which permits the scraper to be effective in operation but replaceable without damaging the core. There are advantages in being able to replace the scraper means without having to replace the core. For example, if one or more scraper means becomes damaged or worn, each may be discarded in favour of a new scraper. In addition, the same core may be used for tubes of different gauges, by replacing the scraper means with other means of lesser or greater diameter. In one form, the scraper means comprises a split ring of resilient but relatively rigid material, mounted in a transverse channel in the core. If it is desired to replace the scraper means, for example because the scraper means has become worn or damaged, or so as to cater for a tube of different gauge, the existing scraper is pried away from the core and a replacement is snapped on to the core. The split ring configuration has the advantage that if the ring encounters an obstruction such as a scale build up, the pressure on the ring will cause the split to widen, which in turn will increase the diameter of the ring, thus enhancing the scraping action of ring. In addition, if the tube has an oval cross-section, due to sagging or other causes, the split can narrow and the ring may still pass through the tube. For most applications, the tube cleaner of the invention in this embodiment will include three or four scraper means mounted at intervals along the core. However, if it is desired that the tube cleaner can negotiate bends in the tubes, the cleaner may be relatively short, with only one or two scraper means. As to suitable material for the scraper means, this is preferably a plastic polymer. It is also contemplated that the scraper means may be made from metal, such as stainless steel, bronze or other suitable material. The tube cleaner of the invention may have on the same core scraper means of different materials - for example, there may be four scraper means, with the first being a plastic polymer, the second being metal, and so on. This form of the invention may have advantages in removing deposits of a wide variety of types. The scraper means preferably has a sharp edge which presents towards the front of the tube cleaner when in use, so that there will be excellent abrasive action between the scraper means and the wall of the tube and hard deposits will be removed from the wall. In cross-section, the scraper means may be rectangular, for example, or may have the leading edge sharpened via a taper or arc. This embodiment of the tube cleaner of the present invention preferably has openings to allow water to pass through the cleaner and to be forced through apertures aimed at the tube wall, so as to loosen deposits, especially soft deposits and to assist flushing of loosened material from the tube. This may be achieved by having a core which is hollow throughout its length but sealed (or substantially sealed) at the leading end. Each scraper means is mounted in an external transverse groove on the core. In each groove are one, two, three or four apertures, each of which communicates with the hollow bore in the core. (There need not be the same number of apertures in each groove - for example, the groove closest to the leading end of the cleaner may have four apertures, while the others may have only one or two. ) Each scraper means is fixed in its groove by a peg or other suitable means, and the scraper means are suitably shaped, so that in successive grooves one aperture is available for the emission of water and such apertures are staggered with respect to each other. In each groove, preferably there is at least one aperture opposite the peg or other suitable means fixing the scraper in the groove. In another preferred embodiment of the present invention, the scraper means comprises one or more longitudinal blades, the or each blade being adapted to form an arc to contact the inner wall of the tube in a tangential manner. The or each blade may be mounted around a central core made of suitable material such as metal, which is also the preferred material for the or each blade. There are preferably a plurality of blades - for example, eight or nine - spaced around the central core. For simplicity, the following description will refer to the case where there are two or more blades. Conveniently, the arc of the blades is adjustable so that the blades may be caused to bow out to a greater or lesser degree, thus permitting adjustment of the cleaner for bores of different diameter. This may be achieved, for example, by including means for permitting advancement of one or each end of the blades towards the other, as explained in more detail in connection with the drawings, below. The blades themselves may be manufactured from any appropriate material, which possesses the necessary degree of resilience. Metals coated with silicon carbide or phosphor bronze may be suitable, for example. The tube cleaner of the invention may be caused to travel through the tube in various ways. When the scraper means comprises one or more longitudinal blades, it will normally be more practical to propel the tube cleaner by means of an electrical or air motor driven flexible shaft or the like, so that the cleaner rotates as it travel through the tube. Where the scraper means are mounted transversely on a central core, the tube cleaner will normally be propelled through the tube by hydraulic or pneumatic means such as a water or air gun of sufficient force. A combined hydraulic and pneumatic means may also be used. The gun required may need to be able to exert a force greater than 400 psi to propel the tube cleaner. Where the tube cleaner of the invention is used in large-gauge tubes, such as calandria in the sugar refining industry, mains pressure water may be substituted for the gun employed for heat exchanger and condenser tubes. In this embodiment, the cleaner does not have openings to allow water to pass through the cleaner, but incorporates a piston to assist propulsion by means of the mains water pressure. The invention will now be described in greater detail in connection with the accompanying drawings, in which; Figs 1A, IB and 1C compare schematically the manner in which the scraper means of one embodiment of the tube cleaner of the invention and the prior art scraper means contact the inner wall of a tube; Fig. 2 represents a longitudinal sectional view of an embodiment of the tube cleaner of the invention; Fig. 3 is a transverse sectional view taken along the lines 3 - 3 of Fig. 2; Fig. 4 is a transverse sectional view taken along the lines 4 - 4 of Fig. 2; Fig. 5 is a transverse sectional view taken along the lines 5 - 5 of Fig. 2; Fig. 6 is a longitudinal sectional view of a second embodiment of the tube cleaner of the invention; Fig. 7 is a transverse half sectional view taken along the lines 7 - 7 of Fig. 6; Fig. 8 is a transverse sectional view taken along the lines 8 - 8 of Fig. 6; Fig. 9 is a transverse sectional view taken along the lines 9 - 9 of Fig. 6? Fig. 10 is a transverse sectional view taken along the lines 10 - 10 of Fig. 6; Fig. 11 is a transverse sectional view taken along the lines 11 - 11 of Fig. 6; Fig. 12 is a longitudinal sectional view of a third embodiment of the invention; Fig. 13 is a transverse half sectional view (enlarged twice) taken along lines 13 - 13 of Fig. 12; and Fig 14 is a plan view of one of the scraper blades in the embodiment of Figs 12 and 13. Referring first to Fig. 1A, scraper means 20 (attached to a central core of a tube cleaner of the invention, not shown) contacts tube wall 22 at an acute angle x, which is substantially maintained when the tube cleaner travels through the tube in the direction of arrow 24. In Fig. IB, bristle 26 of a tube cleaning brush, not shown, contacts tube wall 22 in an approximately perpendicular manner when the brush is at rest. However, when the brush travels through the tube in the direction of arrow 24, bristle 26 is forced rearwardly, to form an obtuse angle y with the tube wall 22. In Fig. 1C, blade 28 of a prior art scraper (not shown) contacts tube wall 22 at a right angle when the scraper is at rest. However, when the scraper is forced through the tube, blade 28 is bent rearwardly to form an obtuse angle z with tube wall 22. Turning now to Fig. 2, tube cleaner 30 consists of a central core 32 and four concentric scraper means 20. Core 32 also has a core head 34. Central aperture 36 in core 32 communicates with outlets 38 (see especially Fig.3). When this tube cleaner is propelled through a tube from a water gun, water is forced through aperture 36 and outlets 38 to assist flushing of the tube. As illustrated by Figs 4 and 5, scraper means 20 comprise blades 40, arranged so that each part of the inner circumference of tube wall 22 will be contacted by a blade 40. The embodiment of the tube cleaner 42 in Figs 6 to 11 has a central core 32 made of plastic polymer and incorporates four incomplete transverse channels 44, each terminating at tongue 46. In this embodiment, the scraper means 20 consists of a split ring of resilient but relatively rigid material (for example, a material which is harder that polyethylene) mounted in each of transverse channels 44. For ease of illustration, only one split ring is shown (see Fig. 8). Tongue 46 serves to maintain the split ring scraper means 20 in channel 44 and to prevent undue rotation. A portion only of split ring scraper means 20 is illustrated in Fig. 6, once again for clarity. It can be seen that forward edge 48 will form an acute angle with the tube wall (not shown) . Core 32 has a core head 34 and a central aperture 36 communicating with outlets 38, not only in core head 34 but also in channels 44, one such outlet being located opposite each tongue 46. It is of course possible to incorporate additional outlets 38 if desired. Referring now to Figs 12 to 14, tube cleaner 50 has a central core 32 comprising a metal rod screw threaded at each end 52 and 54. The scraper means consists of eight longitudinal blades 56 mounted about central core 32 between module 58 and block 60. Rotation of nut 62 will move end 52 towards or away from end 54, thus increasing or decreasing respectively the bow of blades 56. In this way, tube cleaner 50 can be adjusted for large or small diameter tubes, or for wear on blades 56. Fig. 13 includes tube wall 22 to show how scraper blades 56 bear against tube wall 22 in transverse view. Tube cleaner 50 is designed to be rotated by means of a flexible shaft or the like as it travels through the tube. It will be appreciated from Fig. 12 that blades 56 will contact the tube wall tangentially. It will be appreciated from the foregoing that the tube cleaner of the present invention may be capable of dealing with hard deposits as well as soft, that it may be made in a form which will not bend or break on collision with a solid obstruction, that it permits great flexibility as to the selection of scraper material and size and has economical advantages, and so represents a significant advance over the prior art. Other forms of the invention and methods of use will be apparent to one skilled in the art and the invention is not to be limited by the specific examples referred to herein.

Claims: CLAIMS 1. A tube cleaner having at least one scraper means for contacting an inner wall of a tube, the scraper means being adapted to contact the wall at an angle of 90 degrees or less when the cleaner travels through the tube. 2. A tube cleaner as claimed in claim 1, wherein the or each scraper means is mounted on a central core and the or each scraper means is capable of replacement without damage to the core. 3. A tube cleaner as claimed in claim 2, wherein the core is made from plastic polymer or metal. 4. A tube cleaner as claimed in claim 2 or 3, wherein the or each scraper means comprises a split ring mounted in a transverse channel in the core. 5. A tube cleaner as claimed in claim 4, wherein there are one, two, three or four scraper means mounted at intervals along the core. 6. A tube cleaner as claimed in claim 4 or 5, wherein at least one split ring is made of a plastic polymer. 7. A tube cleaner as claimed in claim 4 or 5, wherein at least one split ring is made of metal. 8. A tube cleaner as claimed in claim 4, wherein mounted on the core are two or more scraper means of different materials. 9. A tube cleaner as claimed in any one of claims 1 to 8, wherein the or each scraper means has a sharp edge which presents towards the front of the tube cleaner when in use. 10. A tube cleaner as claimed in 1, wherein the or each scraper means is integral with a central core. 11. A tube cleaner as claimed in claim 10, wherein there are four concentric scraper means on the core and each scraper means is adapted to contact the tube wall at an acute angle when the cleaner travels through the tube. 12. A tube cleaner as claimed in any one of claims 2 to 11, wherein the core has a hollow bore communicating with one or more apertures for the emission of water. 13. A tube cleaner as claimed in claim 1, wherein the scraper means comprises one or more longitudinal blades, the or each blade being adapted to form an arc to contact the inner wall of the tube in a tangential manner. 14. A tube cleaner as claimed in claim 13, wherein the or each blade is mounted around a central core. 15. A tube cleaner as claimed in claim 14, wherein the central core is made of metal and the or each blade is made of metal coated with silicon carbide or phosphor bronze. 16. A tube cleaner as claimed in any one of claims 13 to 15, wherein the blade arc is adjustable. 17. A tube cleaner as claimed in any one of claims 14 to 16, wherein there is a plurality of blades spaced around the central core. 18. A tube cleaner as claimed in any one of claims 1 to 12, which is adapted to be propelled through the tube by hydraulic means, pneumatic means or combined hydraulic/pneumatic means. 19. A tube cleaner as claimed in any one of claims 13 to 17, which is adapted to be propelled through the tube by means of an electrical or air motor driven flexible shaft, so that the cleaner rotates as it travel through the tube. 20. A tube cleaner as claimed in clairr; 1, substantially as herein described with reference to Figs 2 to 5, or Figs 6 to 11 or Figs 12 to 14.

Inventors: SMITH GRAHAM HUBERT, SMITH, GRAHAM, HUBERT
Applicants: SMITH GRAHAM HUBERT, SMITH, GRAHAM, HUBERT
Application year: 1991
Main classification: F28G1
IPC codes: B08B9, F28G1