WO2008037755A1

WO2008037755A1 - Apparatus for the internal coating of pipes, and relative method

Info

Publication number: WO2008037755A1
Application number: PCT/EP2007/060239
Authority: WO
Inventors: Roberto Grassetti
Original assignee: G.M.A. Srl
Priority date: 2006-09-27
Filing date: 2007-09-26
Publication date: 2008-04-03
Also published as: ITUD20060217A1

Abstract

Apparatus (10) for the internal coating of pipes (12) in heat exchangers for boilers, condensers for cooling units or suchlike, comprising deposition members (30) insertable into the pipes (12) in order to deposit therein at least a processing substance able to achieve an internal coating layer. The apparatus (10) also comprises a first feeding unit able to feed a gas to the deposition members (30), and a second feeding unit able to fed the processing substance to the deposition members (30), which in turn comprise mixing elements (38) able to mix together the gas and the processing substance and disposed in correspondence with a terminal portion of the deposition members (30) which is inserted into one of the pipes (12).

Description

"APPARATUS FOR THE INTERNAL COATING OF PIPES,

AND RELATIVE METHOD" * * * * *

FIELD OF THE INVENTION The present invention concerns an apparatus and a relative method for the internal coating of pipes, such as for example the tube bundles of heat exchangers for boilers, condensers for cooling units, or suchlike, which normally have an internal diameter not exceeding 2 inches. In particular, the apparatus is able to achieve inside said pipes a coating layer comprising, for example epoxy resins, epoxy phenolic resins, phenolic resins, Teflon or suchlike, with an anti-corrosive or anti-rust function.

BACKGROUND OF THE INVENTION In the field of refineries and in the petrochemical industry, it is known to paint the inside of the tubes or pipes of heat exchangers, so as to render ineffective, on the material of which the tubes are made, which is generally carbon steel, copper alloys or suchlike, the corrosive effect of the cooling liquid, which is generally sea water, or water from a lake or river.

A known technique for painting the tube bundles provides to move the bundles to appropriate equipped plants where the painting is done, pouring paint directly into the tubes, or by immerging the tubes directly inside a bath of paint and subsequently dripping and drying the paint.

These known methods are very long and complex, however, they require equipped plants and furnaces to bake the paints, and entail high risks during the movement of the tube bundles, since the latter can reach weights of more than 50 tons.

Another known painting technique provides to use a transportable painting apparatus. The known painting apparatus is provided with a mobile probe which is inserted into the tubes, and paint is introduced at high pressure and without air, that is, in airless mode. This known painting apparatus has the disadvantage, however, that it allows to paint only one tube at a time, entailing long operations to complete the painting of all the tubes and consequent long periods when the machine on which the tubes are mounted is out of use. Moreover, given that the painting pressure is relatively high, the paint sprayed inside the tubes tends to run and solidify in the lower part of the tubes. The known painting apparatus therefore does not allow to obtain a homogeneous internal coating layer over the whole surface of the tube. From US-A-4, 368,219 it is known a method and apparatus for coating a long tube of small diameter by means of inserting a supplying hose of double structure, with a spray nozzle ahead and two separately extending inner and outer hoses for supplying paint and compressed air respectively therethrough, into the long tube from one end opening thereof toward the other end opening thereof, and retracting the spray nozzle, when it has reached the destination, while spraying the paint at a predetermined speed. The inner hose for the paint is made of flexible material as an elastic hose for being compressive in the diametrical direction under the pressure from the compressed air in the outer hose and again restorable to the original shape when the pressure is released. This known supplying hose can be fed out from and wound up on a drum of a winding up mechanism regularly and automatically, with the aid of a pinching roller mechanism which moves the supplying hose forwardly and backwardly by the rotating force of a pair of pinching rollers under some pressure for preventing the slackening of the same when it is moved in either direction. However, this known apparatus is not able to mix the paint and the gas (i.e. air) before they exit from the spray nozzle. One purpose of the present invention is to achieve an apparatus and perfect a relative method for the internal coating of pipes that allow to deposit in the latter a processing substance to define an internal coating layer which is homogeneous and which does not run, solidifying in the lower part of the pipes.

Another purpose of the present invention is to achieve an apparatus and perfect a method that allow to coat internally several pipes at the same time, in a rapid and reliable manner, obtaining a substantially homogeneous coating layer.

The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages . SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claims, while the dependent claims describe other characteristics of the invention or variants to the main inventive idea. In accordance with the above purposes, an apparatus according to the present invention is able to be employed for the internal coating of pipes in heat exchangers for boilers, condensers for cooling units or suchlike.

The apparatus according to the present invention comprises deposition means able to be inserted into the pipes in order to deposit therein at least a processing substance able to achieve an internal coating layer.

The processing substance comprises, for example epoxy resins, epoxy phenolic resins, phenolic resins, Teflon or suchlike, with an anti-corrosive or anti-rust function.

The apparatus according to the present invention, also comprises first feeding means able to feed to the deposition means a gas, such as for example air, and second feeding means able to feed to the deposition means the processing susbstance.

According to a feature of the present invention, the deposition means comprises at least a probe having at least a mixing chamber provided in correspondence with a terminal portion thereof, in which mixing chamber the gas and the processing substance are able to be mixed together.

According to the present invention, the gas and the processing substance are kept separate from each other substantially along the whole travel from the respective feeding means to the mixing chamber, in which only then are they mixed.

In this way, the present invention allows to obtain a correct and constant mixing substantially throughout the whole coating operation.

The present invention therefore allows to feed the gas and the processing substance at a relatively low pressure, respectively between about 2 bar and about 15 bar and between about 2 bar and about 12 bar, preferably between about 5 bar and about 8 bar and between about 5 bar and about 7 bar, guaranteeing good homogeneity in the deposition of the processing substance.

According to an advantageous solution of the present invention, the deposition means comprises a plurality of probes and guide and movement means, able to guide and progressively move each of the probes in a corresponding pipe to be lined, allowing to line a plurality of pipes substantially simultaneously. The apparatus according to the present invention allows to perform simultaneously an internal coating of several pipes in a rapid and reliable manner, obtaining a substantially homogeneous coating layer. The present invention also concerns a method for the internal coating of said pipes, comprising a first step in which a deposition means is inserted into the pipes, and a second step in which by means of the deposition means at least a processing substance is deposed in the pipes in order to achieve an internal coating layer.

In accordance with one characteristic of the method according to the present invention, in the second step a gas is fed to the deposition means, and the gas and the processing substance are mixed together in correspondence with a terminal portion of the deposition means which is inserted into one of the pipes in the first step.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics of the present invention will become apparent from the following description of a preferential form of embodiment, given as a non-restrictive example with reference to the attached drawings wherein:

- fig. 1 is a front view of an apparatus according to the present invention;

- fig. 2 is a left side view of the apparatus in fig. 1; - fig. 3 is a longitudinal section of a probe of the apparatus in fig. 1;

- fig. 4 is a block diagram of the apparatus in fig. 1. DETAILED DESCRIPTION OF A PREFERENTIAL FORM OF EMBODIMENT

With reference to fig. 1, an apparatus 10 according to the present invention is used for the internal coating of pipes 12 (fig. 3), such as for example the tube bundles of heat exchangers for boilers, or condensers for cooling units, by means of a processing substance. The processing substance, here and hereafter also called paint, comprises catalytic epoxy resins, phenolic based thermosetting resins, polytetrafluoroethylene (PTFE), for example comprising minerals, pigments, stabilizing substances, thixotropic substances and other additives, so as to guarantee maximum chemical resistance and heat stability.

The typical density of the processing substance before application with the apparatus 10 can vary from about 10 seconds to about 40 seconds with a Ford cup 4.

The apparatus 10 comprises (figs. 1 and 2) a frame 14 provided with wheels 16, a vertical support or column 18, a slider 20, able to slide in the vertical column 18, and a worm screw 22, inserted into the vertical column 18 and connected to a first motor 24 to move the slider 20 vertically.

The apparatus 10 also comprises, in the case shown here, a group of five pairs of movement rollers 26 connected to a second motor 28. Both the movement rollers 26 and the motor 28 are mounted on the slider 20. Moreover, the rollers 26 of each pair define a compartment into which a corresponding probe 30 is inserted.

Each probe 30 (fig. 3) comprises a first external tube 32, made of semirigid material, able to transport air, a second internal tube 34 able to transport a processing substance, a connection 36 and a terminal element 38.

The connection 36 is provided with a central pipe 40, able to be connected to the second tube 34, and with peripheral pipes 42, able to communicate with the first tube 32.

The terminal element 38 comprises a body 44, able to be connected to the connection 36 and defining inside a mixing chamber 46, in which the central pipe 40 and the peripheral pipes 42 terminate.

In the mixing chamber 46, the paint arriving from the central pipe 40 and the air arriving from the peripheral pipes 42 are mixed together. The terminal element 38 also comprises a nozzle 48 connected to the mixing chamber 46 and shaped so as to allow the radial spraying of the air/paint mixture.

According to a variant not shown here, inside the mixing chamber 46, the body 44 comprises a hollow cone spiral, able to guide the mixture towards the nozzle 48 to be sprayed with a spraying angle of less than 90° with respect to the longitudinal axis of the probe and 30.

The nozzle 48 is shaped so as to allow spraying at 360° on a plane substantially orthogonal to the longitudinal axis of the probe 30, thus allowing to coat the whole surface of the pipe 12.

In this way, the terminal element 38 allows to mix air and paint directly at the end of the probe, that is, in proximity with the point where the spray is delivered, thus guaranteeing the correct mixture of air and paint.

The apparatus 10 also comprises a reel 50 (figs. 1 and 2), on which the probes 30 are wound, and which is connected to a third motor 52 (fig. 2), an air/paint collector, or rotary distributor, 54 which is disposed on the longitudinal axis of the reel 50, an air distributor 56 and a paint distributor 58, both mounted on the reel 50.

According to a variant, not shown in the drawings, the third motor 52 is replaced by a spring mechanism provided with an appropriate disc brake, which is able to automatically rewind the probes 30 on the reel 50.

The distributors 56 and 58 are connected upstream with the air/paint collector 54, and downstream respectively with the first 32 and the second tube 34 of each probe 30. The apparatus 10 also comprises, shown schematically in fig. 4, an air compressor 60, an air circuit 62 and a paint circuit 64, both circuits 52, 64 connected to the compressor 60. The air circuit 62 comprises a first air filter 66, able to de-humidify and de-oil a delivery unit and a service unit.

The delivery unit comprises, connected to each other, downstream of the first air filter 66, a device to regulate the air pressure 68 and an air valve 70, connected downstream to the motors 28 which feed and retract the rollers 26 and to the motor 52 of the reel 50.

The air valve 70 is connected through the air/paint collector 54 to the air distributor 56. The service unit comprises, connected downstream of the first air filter 66, a service air valve 72, connected to the motor 24 that moves the worm screw 22.

The paint circuit 64 comprises a second air filter 74, able to de-humidify and de-oil, connected to a paint pump 76 able to pick up paint from a tank, not shown here.

The paint pump 76 is for example of the low-pressure tyP^e' preferably less than about 10 bar, for example of the double membrane type.

The paint circuit 64 comprises, connected to each other and downstream of the paint pump 76, a filter 78, a paint pressure regulator 80 and a paint valve 82.

The paint valve 82 is connected by means of the air/paint collector 54 to the paint distributor 58.

The apparatus 10 also comprises a command and control unit 84, provided with a push-button panel installed on the vertical column (fig. 1) and able to command and control said valves 70, 72 and 82 both pneumatically and electrically. We shall now describe the functioning of the apparatus 10.

In a first step, the probes 30 are removed from the reel 50 through the respective pairs of rollers 26 and inserted into the pipes 12 so as to make the relative terminal elements 38 advance into the pipes 12.

The pressure of the rollers 26 on the probes 30 is regulated by means of a shock absorber 86 (fig. 1) disposed on the upper part of the coupling of the rollers 26. The speed of inlet and outlet is regulated by the command and control unit 84 by means of the motor 28 of the rollers 26.

During the entry step of the probes 30, the reel 50 rotates idly with a mechanical clutch so as to keep the probes 30 slightly under tension.

In the first step, the probes 30 are inserted into the pipes 12 until they reach the opposite end, exiting by some centimeters .

In a second step, the reel 50 is drawn by the motor 52 and the probes 3 are retracted, accompanied by the rollers 26 which work in the inverse direction with respect to the first step.

The apparatus 10 is displaced in a horizontal direction by means of the wheels 16. The probes 30 are displaced in a vertical direction by the movement of the slider 20.

During the retraction step of the probes 30, the command and control unit 84 activates the air compressor 60, regulating the air pressure and the paint pressure thereof according to the layer of paint to be deposited.

The command and control unit 84 defines the speed of return of the probes 30, for example comprised between about 0.2 m/sec and about 0.5 m/sec, acting on the motor 52 of the reel 50 (or automatically by means of the spring mechanism cited above) and on the motor 28 of the rollers 26, and commands the air valves and paint valves 70 and 82 respectively to open. The relatively low speed of movement of the probes 30 guarantees good homogeneity of the coating and prevents any dripping.

In general, the speed of return is defined according to the material to be deposited. During the retraction step of the probes 30, a coating layer is thus deposited inside the pipes 12 which functions as a protection against corrosion and rust.

Therefore, during the retraction step, the probes 30 are pulled by the rollers 26, rotated by the motor 28, and rewind on the reel 50 by means of the motor 52, or automatically by the spring mechanism cited above.

When the second step is terminated, the probes 30 can again be inserted into the already coated pipes 12, so as to repeat the second step and hence deposit another layer of coating.

Given that the apparatus 10 allows to command and control several probes 30 simultaneously, the invention allows to considerably reduce the times required for coating the pipes 12, while still guaranteeing a homogeneous coating. It is clear that modifications and/or additions of parts may be made to the apparatus 10 as described heretofore, without departing from the scope of the present invention.

It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of apparatus for the internal coating of pipes and relative method, having the characteristics as set forth in the claims and hence all coining within the scope of protection defined thereby.

Claims

1. Apparatus for the internal coating of pipes (12) in heat exchangers for boilers, condensers for cooling units or suchlike, comprising: deposition means (30) able to be inserted in said pipes (12) in order to deposit therein at least a processing substance able to achieve an internal coating layer; first feeding means (60) able to feed a gas to said deposition means (30); and second feeding means (76) able to feed said processing substance to said deposition means (30); wherein said deposition means (30) comprises mixing means (38) disposed in correspondence with a terminal portion of said deposition means (30) and able to mix together said gas and said processing substance, and wherein said terminal portion of said deposition means (30) is able to be inserted into one of said pipes (12), characterized in that said deposition means comprises at least a probe (30), and in that said mixing means (38) comprises at least a mixing chamber (46) provided inside said probe (30), in which mixing chamber (46) said gas and said processing substance are able to be mixed together.

2. Apparatus as in claim 1, characterized in that said deposition means (30) also comprises delivery means (48), able to deliver into said pipes (12) a mixture of said gas and said processing substance.

3. Apparatus as in claim 2, characterized in that said mixing means (38) also comprises guide elements able to guide said mixture of gas and processing substance towards said delivery means (48).

4. Apparatus as in claim 3, characterized in that said guide elements are disposed inside said mixing chamber

(46).

5. Apparatus as in claim 2, or 3, characterized in that said guide elements have a substantially spiral form, or similar.

6. Apparatus as in claim 2, characterized in that said delivery means (48) is able to deliver said mixture of gas and processing substance in a direction substantially orthogonal with respect to a longitudinal axis of the respective probe (30).

7. Apparatus as in any claim hereinbefore, characterized in that said first feeding means (60) is able to feed said gas at a pressure comprised between about 2 bar and about 15 bar.

8. Apparatus as in any claim hereinbefore, characterized in that said first feeding means (60) is able to feed said gas at a pressure comprised between about 5 bar and about 8 bar.

9. Apparatus as in any claim hereinbefore, characterized in that said second feeding means (76) is able to feed said processing substance at a pressure comprised between about 2 bar and about 12 bar.

10. Apparatus as in any claim hereinbefore, characterized in that said second feeding means (76) is able to feed said processing substance at a pressure comprised between about 5 bar and about 7 bar.

11. Apparatus as in any claim hereinbefore, characterized in that said deposition means comprises a plurality of probes (30), each of which is able to be progressively inserted into a corresponding pipe (12) to be coated.

12. Apparatus as in claim 11, characterized in that said deposition means also comprises guide and movement means (26, 28) able to guide and move each of said probes (30) inside said pipes (12), allowing to coat a plurality of said pipes (12) substantially simultaneously.

13. Apparatus as in claim 12, characterized in that said guide and movement means comprises a plurality of pairs of rollers (26) each of which is suitable to guide and move a corresponding probe (30) of said plurality of probes (30), making it advance or retreat in the respective pipe ( 12 ) .

14. Apparatus as in claim 12, or 13, characterized in that it comprises support means (50), rotatable along an axis of rotation, with respect to which said probes (30) are able to be wound/unwound.

15. Apparatus as in claim 14, characterized in that said support means (50) is provided, on said axis of rotation, with connection means (54) able to connect each of said probes (30) with said first feeding means (60) and with said second feeding means (74), keeping the air and said processing substance separate from each other.

16. Apparatus as in any claim hereinbefore, characterized in that it also comprises positioning means (16, 18, 20,

22, 24) able to position at least said guide and movement means (26, 28) with respect to said pipes (12) in order to dispose each of said probes (30) in correspondence with the respective pipe (12).

17. Apparatus as in claim 16, characterized in that said positioning means comprises at least a support structure (18) and a slider (20), movable vertically on said support structure (18), and able to support said guide and movement means (26, 28).

18. Apparatus as in claim 17, characterized in that said support structure (18) is movable horizontally by means of wheels (16).

19. Apparatus as in any claim hereinbefore, characterized in that it also comprises electronic command and control means (84) able to command and control at least said guide and movement means (26, 28), said first feeding means (60), said second feeding means (74), said support means (50) or said positioning means (16, 18, 20, 22, 24), in order to coat said pipes (12) internally in a substantially automatic manner.

20. Method for the internal coating of pipes (12) in heat exchangers for boilers, condensers for cooling units or suchlike, comprising a first step in which a deposition means (30) is inserted into said pipes (12), and a second step in which by means of said deposition means (30) at least a processing substance is deposited in said pipes in order to achieve an internal coating layer, characterized in that in said second step a gas is fed to said deposition means (30) and said gas and said processing substance are mixed together in a mixing chamber (46) provided in correspondence with a terminal portion of said deposition means (30) which is inserted into one of said pipes (12) in said first step.