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This invention relates to a device, system, and method for cleaning the interior of the tubes in air-cooled heat exchangers.
This invention further relates to a cleaning method that uses dry abrasive blasted through the tube using high pressure air to remove any accumulation in the tube or on the tube walls resulting in a bright metal finish suitable for inspection or coating or a predetermined level of cleanliness for return to service.
This invention still further relates to a device that is electromagnetically secured to the outside of a tube header to temporarily secure a grit-resistant nozzle assembly and position the nozzle for proper application of the air and entrained abrasive to facilitate cleaning, avoid tube damage, and provide for operator safety.
This invention still further relates to closed systems for cleaning the interior of the tubes with dry abrasive blasting using high pressure air, capturing the air, spent abrasive, and removed material, at the other end of the tube, separating the abrasive and removed material from the waste air, filtering the waste air, and then exhausting the filtered air to the environment; all without fugitive emissions.
Numerous types of heat exchangers are used in the chemical process industry. Among the more common types are shell-and-tube exchangers, plate-type heat exchangers, scraped-surface heat exchangers, and air-cooled heat exchangers. Among heat exchangers, the air-cooled heat exchanger is unique since it cools a liquid or condenses a vapor using induced-draft or forced-draft ambient air. The thermal energy contained in the tube-side liquid or condensing vapor is rejected directly to ambient air.
Increased use of air-cooled heat exchangers has resulted from ever diminishing cooling water, significant increases in water costs, concern for water pollution, and in cold climates the unlimited supply of cool air. The typical air-cooled heat exchanger includes a tube bundle, with tubes which have spiral-wound fins fixed to their outsides, and a fan to move air across the tubes.
An air-cooled heat exchanger typically has greater heat transfer surface area than its liquid-liquid counterpart. They can have large foot-prints and are generally elevated to provide room for the forced-draft fans and motors; which are located underneath the tubes.
The tubes in an air-cooled heat exchanger are usually arranged in a bundle of some 20-30 tubes. Numerous tube bundles may be assembled to create air-cooled heat exchangers of enormous size.
A complete tube bundle is an assembly of finned tubes, inlet and outlet headers, side frames, and tube supports. There are generally two types of headers; plug-type and plate-type.
Tubes and headers wetted by the process fluid may be made out of ferromagnetic or non-ferromagnetic materials. Non-ferromagnetic materials include aluminum and aluminum alloys, stainless steels of numerous compositions, titanium, hastelloy®, brass, bronze, monel®, and other alloys that do not contain iron in appreciable amounts. Ferromagnetic materials are typically carbon steels and high nickel alloys.
Most tubes in air-cooled heat exchangers in use in the chemical process industry are 1 inch, 1¼ inch, or 1½ inch outside diameter. Tube wall thickness is based on the material of construction, the design pressure and temperature of the tube-side fluid, and the corrosion characteristics of the process fluid. Fins are almost always aluminum.
The tube-side and fin-side of the tubes in an air-cooled heat exchanger predictably foul over their life. The fouling mechanisms encountered in the tube-side are the same as those found in all heat exchangers; deposition of insoluble matter; corrosion, biological growth, crystallization, side reaction products, freezing, or a combination of one or more of them. Fin-side fouling in air-cooled heat exchangers occurs from air-borne contaminants such as dirt, dust, debris, pollen, leaves, insect accumulations, and bird carcasses. The fin-side is typically cleaned by flushing with compressed air or water under moderate pressure.
The most common method of cleaning the tube-side of air-cooled heat exchanger tubes is mechanical cleaning. For safety, most, if not all, tube-side mechanical cleaning is performed during maintenance turn-arounds with the air-cooled heat exchanger off-line, tubes purged of process fluid and prepared for cleaning, headers flushed and blanked, and all rotating equipment locked out from sources of energy.
Mechanical cleaning removes tube-side fouling by physical means. The most common methods are; (1) pulling brushes through the tube, (2) high pressure water jet cleaning, (3) high pressure air blasting without abrasive, or (4) a mix of high pressure air and finely divided abrasive to scour the inside of the tube wall. Cleaning methods that involve pulling brushes through the tube and using high pressure air without abrasive do not clean the tube to near new condition. Using high pressure water jet cleaning results in substantial amounts of waste water that must be disposed of. In cold climates, outdoor water use results in ice that creates safety issues both for its weight and its near frictionless surface. Other than the mix of high pressure air and finely divided abrasive, none of the other mechanical cleaning methods result in tubes cleaned to near new or bright metal condition. This condition is necessary if the inside of the tube is to be inspected using the Internal Rotary Inspection System (IRIS) or coated after cleaning. A valid IRIS inspection can only be performed if the tubes are cleaned to a bright metal finish. The same level of cleaning is required if the tubes are to be coated with a corrosion-resistant material.
In this invention, the mechanical cleaning method is a mix of high pressure air and finely divided abrasive. In this disclosure, finely divided abrasive and grit mean the same thing and are used interchangeably. The most commonly used abrasive is garnet. Garnet for dry blasting is typically available in sizes ranging from 16 to 80 mesh, nominal 177 to 1190 microns with a Mohs' Hardness of 6.5 to 8.5. The preferred size range for cleaning tubes in air-cooled heat exchangers is 30 to 60 mesh, nominal 250 to 595 microns, and Mohs' Hardness of 7.5 to 8. Other materials such as steel shot may also be used. The air pressure ranges from 100 to 150 pounds per square inch gauge (PSIG), with a preferred pressure of 125 PSIG. The quantity of supplied air is 350 to 400 actual cubic feet per minute (ACFM), with a preferred amount of 375 ACFM. Abrasive loading ranges from 1 to 10 pounds (LBS) per 100 actual supplied cubic feet (ASCF) at 125 PSIG, with a preferred amount of about 3 LBS per 100 ASCF at 125 PSIG.
Although this method overcomes the limitations of other mechanical cleaning methods, issues of waste disposal and safety have arisen. For safety and environmental considerations, the high pressure abrasive tube-cleaning method described here is conducted in a closed system in which there are no fugitive emissions. In the closed system, two workers are required to be on the landing shown in
In most instances, the workers at each end of a tube cannot see each other and sometimes find themselves positioning their nozzles on different tubes. If this occurs, the worker capturing the waste air, abrasive, and removed fouling material, can be seriously injured by being hit by the spent abrasive ejected at high velocity.
The invention described herein eliminates the need for workers to manually hold their grit-resistant nozzles while tube cleaning. The invention describes a device which holds the grit-resistant nozzles in place, a system for cleaning the inside of air-cooled heat exchanger tubes using the device, and a method for cleaning the tubes utilizing the device and system.
While the prior art discloses numerous devices, systems, and methods for cleaning heat exchanger tubes, there has been no motivation or suggestion in the art for an electromagnetic grit-resistant nozzle support and a system and method for using it.
Although there are many devices, systems, and methods for cleaning the inside of tubes in air-cooled heat exchangers, there is a need in the art for increased environmental protection and operator safety.
Although U.S. patents and published patent applications are known which disclose various devices, systems, and methods for cleaning the interior of air-cooled heat exchanger tubes, none of them disclose using electromagnetically attached and positioned grit-resistant nozzles to clean such tubes using high pressure air with entrained finely divided abrasive. No prior art anticipates, nor in combination renders obvious, the invention described herein.
U.S. Pat. No. 5,897,456, Curran, E., discloses a tube coating system that can be converted to an assembly for sandblasting or hydro-blasting to clean the inner wall surfaces of heat exchanger tubes by removing deposits and corrosive blisters. The invention described in Curran neither anticipates nor, when combined with other prior art, renders obvious the invention described herein.
U.S. Pat. No. 5,375,378, Rooney, J., discloses a method and devices for hydro-blasting using a hydrolyzed solution of a silica compound and water, the hydrolyzed solution containing solid particles of the silica compound, is ejected at the surface to be cleaned. Rooney further discloses that process may be employed for cleaning a variety of surfaces including the inside surfaces of tubes and heat exchangers. The invention described in Rooney neither anticipates nor, when combined with other prior art, renders obvious the invention described herein.
It is an object of this invention to disclose a device, system, and method that, safely, efficiently, economically, and protective of the environment, cleans the inside of the tubes in air-cooled heat exchangers using high pressure air with entrained finely divided abrasive, captures the waste air, spent abrasive, and removed fouling material, and separates the spent abrasive and removed fouling material from the waste air, before the waste air is exhausted to the atmosphere.
After the plugs are removed from a ferromagnetic plug-type header, it is a further object of this invention to disclose a device that electromagnetically attaches to the face of the ferromagnetic plug-type header that permits workers to secure and position the supply and capture grit-resistant nozzles. Workers can thereby operate the nozzles without holding them by hand.
It is still a further object of this invention to disclose a ferromagnetic plate with securing apparatus that can attach to at least two of the threaded plugs in a non-ferromagnetic plug-type header or two of the threaded bolt holes in a ferromagnetic or non-ferromagnetic plate-type header thereby providing a surface upon which the electromagnetic nozzle support may be attached.
The invention described herein will substantially increase the safety for workers performing the cleaning of the interior of the tubes in air-cooled heat exchangers without sacrificing efficiency, economy, and environmental protection.
1. Detailed Description of the Preferred Embodiment of the Electromagnetic Nozzle Support
An electromagnetic nozzle support is disclosed in detail that alleviates the need for inlet technician 606 and outlet technician 620 to manually hold their grit-resistant nozzles 106 and nozzle holders 108 against the tube ends during cleaning.
100 in
As depicted more clearly in
Returning to
2. Detailed Description of the Preferred Embodiment of the System Incorporating the Electromagnetic Nozzle Support
600 in
When tubes 602 are to be cleaned and Items 604 and 622 are plug-type headers of ferromagnetic material, they are prepared by removing plugs 700 shown in
Additional items not shown in
100 in
100 in
It is understood that ferromagnetic plate 1000 will attach to a ferromagnetic or non-ferromagnetic plate-type header in the same fashion as depicted in
3. Detailed Description of the Preferred Embodiment of the Method of Using the Electromagnetic Nozzle Support to Clean Tubes Supported by a Ferromagnetic Plug-Type Header
It is understood that the air-cooled heat exchanger represented by 600 in
Referring to
Referring to
Continuing to refer to
A battery back-up power supply 122 is located adjacent to each of headers 604 and 622. Power cord 124 is connected to a nominal 120 VAC single-phase power source to energize each of 122. Switch 300 shown in
Inlet technician 606 pushes nozzle holder with 106, 112, and 900 in their proper pre-selected places through a hole 132 until it communicates with the end of the tube 602 corresponding with 132. Outlet technician 620 performs the same task as inlet technician 606 but at outlet header 622. Sleeve 112 holds nozzle 106 and nozzle holder 108 in place. Ring 110 previously left loose is permitted to slide along 108. Inlet technician 606 positions 134 against the face of header 604 while simultaneously elevating it so that the edge of saddle 200 facing header 604 communicates with the edge of ring 110 facing away from 604. The same is performed by outlet technician 620 at 622.
Once Item 134 is properly positioned on the face of 604 and face of 622, inlet technician 606 and outlet technician 620 each select 300 on their respective 134 to the On position. Electromagnet 102 is energized magnetically coupling each 134 to the face of 604 and 622. By rotating handle 128, inlet technician 606 causes rack and pinion to move ring 110 towards saddle 200 until it communicates tightly against 200. Pawl 408 communicates with 118 via spring 402 to hold ring 110 snug against saddle 200. Inlet technician 606 then tightens pinch bolt 500 to cause ring 110 to communicate tightly around nozzle holder 108. The same is performed by outlet technician 620 at 622.
Inlet technician 606 connects grit-resistant hose 116 to nozzle holder 108 using hose connection 114. The same is performed by outlet technician 620 at 622. Inlet technician 606 and outlet technician 620 at each end of tube 602 communicate via walkie-talkie to confirm each are ready to begin tube cleaning. After confirmation, portable air compressor 610 is energized. Inlet technician depresses a dead-man control valve or dead-man switch known to persons of skill in the art. Once depressed, high pressure air flows through 612 to 614, picking up grit, then through 116, through 106, through tube 602, exits through the 106 at 622, then flows through 116 to 618, then through 618 to 616. Spent grit and debris removed from the interior of tube 602 is grossly collected in drum 618. Fines entrained in the waste air and passing through 618 are captured in 616 and collected in 624. The time required to clean a tube 602 may range from 10 seconds to 10 minutes.
After the pre-selected time for cleaning tube 602 is met, inlet technician 606 releases the dead-man valve or switch; thereby shutting off high pressure air and grit flowing from 614. Inlet technician 606 and outlet technician 620 communicate again by walkie-talkie. Inlet technician depresses arm 404 pulling pawl 408 away from sprocket 118. Handle 128 is rotated to cause rack and pinion to retract away from 604. The same is performed by outlet technician 620 at 622. The Item 134 at each of 604 and 622 is taken by hand and then de-energized by selecting 300 to the Off position. The Item 134 is allowed to safely fall away from the face of 604 and 622. Inlet technician 606 pulls nozzle holder with 106, 112, and 900 from hole 132 and reinserts it in the next 132 until it communicates with the end of the tube 602 corresponding with another 132. The same is performed by outlet technician 620 at 622. Inlet technician 606 again takes 134 by hand, repositions it against nozzle holder 108 and then re-energized by selecting 300 to the On position. The same is performed by outlet technician 620 at 622. Inlet technician 606 and outlet technician 620 communicate by walkie-talkie to confirm each is ready for tube cleaning. After confirmation, inlet technician 606 depresses dead-man control valve or switch to initiate tube cleaning. The process is repeated until all tubes 602 are cleaned.
4. Detailed Description of the Preferred Embodiment of the Method of Using the Electromagnetic Nozzle Support to Clean Tubes Supported by a Non-Ferromagnetic Plug-Type Header or a Ferromagnetic or Non-Ferromagnetic Plate-Type Header
When inlet technician 606 and outlet technician 622 are confronted with a non-ferromagnetic plug-type header or a ferromagnetic or non-ferromagnetic plate-type header he or she must first attach ferromagnetic plate 1000 shown in
Inlet technician 606 and outlet technician 620 each prepare their ferromagnetic or non-ferromagnetic plate-type headers as shown in
Referring to
Referring to
It is understood that ferromagnetic plate 1000 will attach to a ferromagnetic or non-ferromagnetic plate-type header in the same fashion as depicted in
5. Variations of the Preferred Embodiment can Still Remain Within the Scope of this Invention
Persons of skill in the art of selecting, connecting, and modifying a portable electromagnetic drill guide would understand that the device, system, and method of using the device described in the preferred embodiment can vary and still remain within the invention herein described. Variations obvious to those persons skilled in the art are included in the invention.
This written description uses examples to disclose the invention, including the preferred embodiment, and also to enable a person of ordinary skill in the relevant art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those person of ordinary skill in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
Further, multiple variations and modifications are possible in the embodiments of the invention described here. Although a certain illustrative embodiment of the invention has been shown and described here, a wide range of modifications, changes, and substitutions is contemplated in the foregoing disclosure. In some instances, some features of the present invention may be employed without a corresponding use of the other features. Accordingly, it is appropriate that the foregoing description be construed broadly and understood as being given by way of illustration and example only, the spirit and scope of the invention being limited only by the appended claims.
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3139704 | McCune | Jul 1964 | A |
3448477 | Mior | Jun 1969 | A |
5800246 | Tomioka | Sep 1998 | A |
20020130140 | Cote | Sep 2002 | A1 |
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Number | Date | Country |
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60006354 | Jan 1985 | JP |
62162900 | Jul 1987 | JP |
Number | Date | Country | |
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20190039209 A1 | Feb 2019 | US |