Resin coating layer and life-extension method for piping

Abstract

A resin coating layer according to the present invention is formed by curing a thermo-setting resin composition on an inner wall of a heat transfer tube. Forming the resin coating layer allows the heat transfer tube to be easily repaired without involving a cutting process of the heat transfer tube.

Claims

1. A life-extension method of a heat transfer tube, comprising: filling a viscous liquid thermo-setting resin into the heat transfer tube; and forming a resin coating layer on an inner wall of the heat transfer tube by simultaneously heating the entire outer peripheral surface of the heat transfer tube to cause a temperature difference in the thermo-setting resin filled-up inside the heat transfer tube so that temperature is higher at the inner wall side thereof than at a center portion thereof while simultaneously removing uncured thermo-setting resin composition in a viscosity state inside of the heat transfer tube by introducing gas or air into the heat transfer tube, thereby simultaneously curing the thermo-setting resin composition on the entire inner wall side of the heat transfer tube.

2. The life-extension method of the heat transfer tube according to claim 1, wherein the thermos-setting resin composition includes a phenol resin, an urea resin, a melamine resin, an epoxy resin or a polyurethane resin.

3. The life-extension method of the heat transfer tube according to claim 1, wherein the heat transfer tube is used for feeding corrosive liquid, corrosive gas, high-temperature water, low-temperature water.

4. The life-extension method of the heat transfer tube according to claim 1, wherein the heat transfer tube is a heat exchanger selected from any one of a fin-tube heat exchanger, an air-cooled heat exchanger, a direct contact heat exchanger, a spiral heat exchanger, a plate heat exchanger, a double-pipe heat exchanger, a shell-and-tube heat exchanger, a spiral tube heat exchanger, a spiral plate heat exchanger, a tank coil heat exchanger, a tank jacket heat exchanger, a direct contact liquid-to-liquid heat exchanger, a stationary heat exchanger, a regenerative rotary heat exchanger, a periodic flow regenerative heat exchanger, and a vortex tube.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic view illustrating a resin coating layer according to a first embodiment of the present invention.

(2) FIG. 2 is a flowchart illustrating an example of a life extension method for piping according to the first embodiment of the present invention.

(3) FIG. 3 is an explanatory view illustrating a forming process of the resin coating layer.

(4) FIG. 4 is a view illustrating a part of a heat exchanger.

(5) FIG. 5 is a flowchart illustrating an example of a life extension method for piping according to a second embodiment of the present invention.

(6) FIG. 6 is an explanatory view illustrating a forming process of the resin coating layer.

(7) FIG. 7 is an explanatory view illustrating a configuration for supplying air into the heat transfer tube.

(8) FIG. 8 is an explanatory view illustrating a state where air is introduced into the heat transfer tube.

(9) FIG. 9 is a view illustrating an example of a method of removing an uncured thermo-setting resin composition.

(10) FIG. 10 is a view illustrating an example of a method of removing an uncured thermo-setting resin composition.

DESCRIPTION OF EMBODIMENTS

(11) Hereinafter, the present invention will be described with reference to the drawings. It should be noted that the present invention is not limited to the following embodiments. In addition, constituting elements in the following embodiments include elements which may be easily assumed by those skilled in the art, which are substantially the same, and which are so-called in an equivalent range. Moreover, constituent elements disclosed in the following embodiments may be appropriately combined.

First Embodiment

(12) A resin coating layer according to a first embodiment of the present invention will be described with reference to the drawings. In the present embodiment, as a piping for feeding liquid/fluid in a chemical plant or a power plant, a heat transfer tube provided in a heat exchanger is used. FIG. 1 is a schematic view illustrating the resin coating layer according to the first embodiment of the present invention. As illustrated in FIG. 1, a resin coating layer 10A according to the present embodiment is formed on an inner wall 11a of a heat transfer tube (piping) 11.

(13) The resin coating layer 10A according to the embodiment is formed by curing fine particles of a thermo-setting resin composition whose curing reaction is started at a low temperature. As the thermo-setting resin composition, a resin composition mainly containing, for example, a phenol resin, a urea resin, a melamine resin, an epoxy resin, a polyurethane resin, or the like can be used. In the present embodiment, it is preferable to use a thermo-setting resin composition mainly containing an epoxy resin because of the following reasons: it can contact a heating medium inside the heat transfer tube 11; it can stably withstand temperature changes of the heat transfer tube 11; it is easy to use and handle; and it is advantageous in cost reduction. The thermo-setting resin composition used for forming the resin coating layer 10A according to the present embodiment may be used singly or in combination of two or more. The low temperatures stated herein refer to those in a temperature range of not less than 70 C. and not more than 180, preferably not less than 120 C. and not more than 160, more preferably not less than 140 C. and not more than 155, and still more preferably about 150.

(14) Further, the thermo-setting resin composition preferably contains metal particles such as aluminum pigments. The thermo-setting resin composition containing the metal particles can suppress reduction in thermal conductivity of the heat transfer tube 11 when the heating medium is fed into the heat transfer tube 11.

(15) A film thickness of the resin coating layer 10A according to the embodiment is preferably in a range of not less than 0.1 mm and not more than 15 mm in terms of a size of an inner diameter of the heat transfer tube 11 and performance in suppressing deterioration due to the heating medium flowing in the heat transfer tube 11, more preferably not less than 0.5 mm and not more than 10 mm, and still more preferably not less than 1 mm and not more than 5 mm.

(16) Forming the resin coating layer 10A according to the embodiment on the inner wall 11a of the heat transfer tube 11 allows the heat transfer tube 11 thinned due to corrosion or the like to be easily repaired without involving a cutting process of the heat transfer tube 11.

(17) An example of a life extension method for piping according to the present embodiment that forms the thus configured resin coating layer 10A will be described using the drawings. FIG. 2 is a flowchart illustrating an example of the life extension method for piping according to the present embodiment, and FIG. 3 is an explanatory view illustrating a forming process of the resin coating layer. As illustrated in FIG. 2, the life extension method for piping according to the present embodiment includes the following processes:

(18) (a) resin fine particle sticking process (step S11) in which resin fine particles 21 obtained by charging particles of the thermo-setting resin composition are supplied into the heat transfer tube (piping) 11, and the resin fine particles 21 are stuck to the inner wall 11a of the heat transfer tube 11 by electrostatic force; and

(19) (b) resin coating layer forming process (step S12) in which the heat transfer tube 11 is heated to cure the resin fine particles 21 stuck to the inner wall 11a of the heat transfer tube 11 to thereby form the resin coating layer 10A.

(20) As illustrated in FIG. 4, a resin fine particle supply means 24 for supplying the resin fine particles 21 into the heat transfer tube 11 is provided outside a heat exchanger 23. The resin fine particles 21 are supplied from the resin fine particle supply means 24 into the heat transfer tube 11 of the heat exchanger 23. Then, as illustrated in FIG. 3, the resin fine particles 21 supplied into the heat transfer tube 11 are stuck to the inner wall 11a of the heat transfer tube 11 by electrostatic force (step S11).

(21) As described above, the resin fine particles 21 are particles obtained by charging particles of the thermo-setting resin composition. As a material for forming the resin fine particles 21, the above-mentioned thermo-setting resin composition whose curing reaction is started at a low temperature is used. As the thermo-setting resin composition, a resin composition mainly containing, for example, a phenol resin, a urea resin, a melamine resin, an epoxy resin, a polyurethane resin, or the like can be used. In the present embodiment, it is preferable to use a thermo-setting resin composition mainly containing an epoxy resin because of the following reasons: it can contact a heating medium inside the heat transfer tube 11; it can stably withstand temperature changes of the heat transfer tube 11; it is easy to use and handle; and it is advantageous in cost reduction. The thermo-setting resin composition used for forming the resin coating layer 10A according to the present embodiment may be used singly or in combination of two or more.

(22) Further, as described above, the thermo-setting resin composition preferably contains metal particles such as aluminum pigments. The thermo-setting resin composition containing the metal particles can suppress reduction in thermal conductivity of the heat transfer tube 11 when the heating medium is fed into the heat transfer tube 11.

(23) An average particle diameter of the resin fine particles 21 is preferably in a range of not less than 10 m and not more than 150 m so that the resin fine particles 21 are stably supplied into the heat transfer tube 11 and stably stuck to the entire surface of the inner wall 11a of the heat transfer tube 11, more preferably not less than 30 m and not more than 50 m, and still more preferably, not less than 35 m and not more than 45 m.

(24) The charged resin fine particles 21 are stored in the resin fine particle supply means 24. As a method of charging the fine particles of the thermo-setting resin composition, a conventionally-known electrostatic method can be used. Specifically, examples of the electrostatic methods include a method in which a high voltage (e.g., 40 KV to 90 KV) obtained by a high-voltage electrostatic generator is applied to the fine particles of the thermo-setting resin composition to charge the same.

(25) The resin fine particles 21 supplied into the heat transfer tube 11 are stuck to the inner wall 11a of the heat transfer tube 11 by electrostatic force.

(26) In the present embodiment, the resin fine particles 21 are previously charged so as to be stuck to the inner wall 11a of the heat transfer tube 11 by electrostatic force. Alternatively, however, an electrostatic device may be used to stick the resin fine particles 21 to the inner wall 11a of the heat transfer tube 11. The use of the electrostatic device allows the resin fine particles 21 to be stuck to the inner wall 11a of the heat transfer tube 11 more stably.

(27) After sticking of the resin fine particles 21 to the inner wall 11a of the heat transfer tube 11, the heat transfer tube 11 is heated to cure the resin fine particles 21 stuck to the inner wall 11a of the heat transfer tube 11 to thereby form the resin coating layer 10A (step S12). Heating the heat transfer tube 11 from outside increases a temperature of the inner wall 11a of the heat transfer tube 11, thereby curing the resin fine particles 21 stuck to the inner wall 11a of the heat transfer tube 11.

(28) Examples of a heating method for the heat transfer tube 11 includes: heating an outer peripheral surface of the heat transfer tube 11 using a heating electric wire attached to the outer peripheral surface of the heat transfer tube 11; heating the outer peripheral surface of the heat transfer tube 11 using a heater; and heating the heat transfer tube 11 using high-temperature gas (flue gas) flowing in a shell (body) of the heat exchanger 23.

(29) By curing the resin fine particles 21 stuck to the inner wall 11a of the heat transfer tube 11, adjacent resin fine particles 21 are bonded to each other to thereby form the resin coating layer 10A according to the present embodiment on the inner wall 11a of the heat transfer tube 11.

(30) Further, in the present embodiment, the number of times that the resin fine particle supply means 24 supplies the resin fine particles 21 into the heat transfer tube 11 is set to one, but the number is not limited thereto. The resin fine particle supply means 24 may supply the resin fine particles 21 into the heat transfer tube 11 plurality of times depending on a size of the inner diameter of the heat transfer tube 11, a sticking condition of the resin fine particles 21 to the inner wall 11a of the heat transfer tube 11, and the like.

(31) Thus, by using the life-extension method for piping according to the present embodiment, the resin coating layer 10A according to the present embodiment can be formed on the inner wall 11a of the heat transfer tube 11. Even if a defect, such as cracks or holes, occurs in the heat transfer tube 11 resulting from progress of corrosion at a portion of the heat transfer tube 11 where thinning or the like occurs, forming the resin coating layer 10A according to the present embodiment on the inner wall 11a of the heat transfer tube 11 allows the heat transfer tube 11 to be temporarily and easily repaired without involving a cutting process of the heat transfer tube 11. As a result, it is possible to prevent the heating medium flowing in the heat transfer tube 11 from leaking outside. Further, the resin fine particles 21 contain the metal particles, so that even when the resin coating layer 10A according to the present embodiment is formed in the heat transfer tube 11, it is possible to suppress reduction in thermal conductivity of the heat transfer tube 11 when the heating medium is fed into the heat transfer tube 11, which in turn can suppress reduction in performance of the heat exchanger 23.

Second Embodiment

(32) A resin coating layer according to a second embodiment of the present invention will be described with reference to the drawings. Like the resin coating layer 10A according to the first embodiment illustrated in FIG. 1, a resin coating layer 10B according to the present embodiment is formed on an inner wall 11a of a heat transfer tube 11.

(33) The resin coating layer 10B according to the present embodiment is formed by curing a thermo-setting resin composition whose curing reaction is started at a low temperature. As the thermo-setting resin composition, a resin composition mainly containing, for example, a phenol resin, a urea resin, a melamine resin, an epoxy resin, a polyurethane resin, or the like can be used. In the present embodiment, it is preferable to use a resin composition mainly containing an epoxy resin because of the following reasons: it can contact a heating medium inside the heat transfer tube 11; it can stably withstand temperature changes of the heat transfer tube 11; it is easy to use and handle; and it is advantageous in cost reduction. The thermo-setting resin composition used for forming the resin coating layer 10B according to the present embodiment may be used singly or in combination of two or more. The low temperatures stated herein refer to those in a temperature range of not less than 40 C. and not more than 60.

(34) Forming the resin coating layer 10B according to the embodiment on the inner wall 11a of the heat transfer tube 11 allows the heat transfer tube 11 thinned due to corrosion or the like to be easily repaired without involving a cutting process of the heat transfer tube 11.

(35) Further, the thermo-setting resin composition preferably contains metal particles such as aluminum pigments. The thermo-setting resin composition containing the metal particles can suppress reduction in thermal conductivity of the heat transfer tube 11 when the heating medium is fed into the heat transfer tube 11.

(36) An example of a life extension method for piping according to the present embodiment that forms the thus configured resin coating layer 10B will be described using the drawings. FIG. 5 is a flowchart illustrating an example of the life extension method for piping according to the present embodiment, and FIG. 6 is an explanatory view illustrating a forming process of the resin coating layer. As illustrated in FIG. 5, the life extension method for piping according to the present embodiment includes the following processes:

(37) (a) thermo-setting resin composition filling process (step S21) in which a thermo-setting resin composition 31 is supplied into the heat transfer tube 11 to fill the heat transfer tube 11 therewith; and

(38) (b) resin coating layer forming process (step S22) in which the heat transfer tube 11 is heated to cure the thermo-setting resin composition 31 on the inner wall 11a side of the heat transfer tube 11 while an uncured thermo-setting resin composition 31 on an inner side of the heat transfer tube 11 is removed to thereby form the resin coating layer 10B on the inner wall 11a of the heat transfer tube 11.

(39) As illustrated in FIG. 6, the thermo-setting resin composition 31 is supplied into the heat transfer tube 11 of a heat exchanger 23 to fill the heat transfer tube 11 therewith (step S21).

(40) As illustrated in FIG. 7, a thermo-setting resin composition supply means 32 for supplying the thermo-setting resin composition 31 into the heat transfer tube 11 is provided outside the heat exchanger 23. The thermo-setting resin composition 31 is supplied from the thermo-setting resin composition supply means 32 into the heat transfer tube 11 of the heat exchanger 23.

(41) As described above, as a material for forming the thermo-setting resin composition 31, the thermo-setting resin composition whose curing reaction is started at a low temperature is used. As the thermo-setting resin composition, a resin composition mainly including, for example, a phenol resin, a urea resin, a melamine resin, an epoxy resin, a polyurethane resin, or the like can be used. In the present embodiment, it is preferable to use a resin composition mainly including an epoxy resin because of the following reasons: it can contact a heating medium inside the heat transfer tube 11; it can stably withstand temperature changes of the heat transfer tube 11; it is easy to use and handle; and it is advantageous in cost reduction. The thermo-setting resin composition used for forming the resin coating layer 10B according to the present embodiment may be used singly or in combination of two or more.

(42) Further, as described above, the thermo-setting resin composition 31 preferably contains the metal particles such as aluminum pigments. The thermo-setting resin composition containing the metal particles can suppress reduction in thermal conductivity of the heat transfer tube 11 when the heating medium is fed into the heat transfer tube 11.

(43) When the thermo-setting resin composition 31 is supplied into the heat transfer tube 11, a solution containing the thermo-setting resin composition 31 may be supplied considering a viscosity of the thermo-setting resin composition 31.

(44) After the heat transfer tube 11 is filled with the thermo-setting resin composition 31, the heat transfer tube 11 is heated from outside to cure the thermo-setting resin composition 31 on the inner wall 11a side of the heat transfer tube 11 while the uncured thermo-setting resin composition 31 on the inner side of the heat transfer tube 11 is removed (step S22).

(45) As described in the previous embodiment, examples of a heating method for the heat transfer tube 11 includes: heating an outer peripheral surface of the heat transfer tube 11 using a heating electric wire attached to the outer peripheral surface of the heat transfer tube 11; heating the outer peripheral surface of the heat transfer tube 11 using a heater; and heating the heat transfer tube 11 using high-temperature gas (flue gas) flowing in a shell (body) of the heat exchanger 23.

(46) Further, when the heat transfer tube 11 is heated from outside, a heating temperature, a heating time, and the like are controlled considering the diameter size of the heat transfer tube 11 and the like. This causes a temperature difference in the thermo-setting resin composition 31 inside the heat transfer tube 11, thereby allowing a difference in progress of the curing reaction of the thermo-setting resin composition 31 in the heat transfer tube 11 to be made. As a result, it is possible to adjust a thickness of the thermo-setting resin composition 31 to be cured in the heat transfer tube 11.

(47) Further, as illustrated in FIG. 7, an air supply means 33 is provided outside the heat exchanger 23. The air supply means 33 introduces air 34 into the heat transfer tube 11 to extract the uncured thermo-setting resin composition 31 on the inner side of the heat transfer tube 11. The heat transfer tube 11 is heated from outside, so that the heat is transferred from the inner wall 11a side of the heat transfer tube 11. Accordingly, the temperature is higher at the inner wall 11a side of the heat transfer tube 11 than at a center portion thereof. Thus, the thermo-setting resin composition 31 in the vicinity of the inner wall 11a of the heat transfer tube 11 is cured faster than the thermo-setting resin composition 31 existing around the center of the heat transfer tube. Further, the uncured thermo-setting resin composition 31 is in a high viscosity state, while the cured thermo-setting resin composition 31 is low in viscosity and stuck to the inner wall 11a of the heat transfer tube 11. Thus, as illustrated in FIG. 8, by introducing the air 34 into the heat transfer tube 11, it is possible to remove only the uncured thermo-setting resin composition 31 on the inner side of the heat transfer tube 11 while curing the thermo-setting resin composition 31 on the inner wall 11a side of the heat transfer tube 11.

(48) As a result, a hollow resin film can be formed in the heat transfer tube 11, whereby the resin coating layer 10B according to the present embodiment is formed only at the inner wall 11a side of the heat transfer tube 11.

(49) Further, in the present embodiment, the air 34 is introduced from the air supply means 33 provided outside the heat exchanger 23 into the heat transfer tube 11, but what is introduced is not limited thereto. An inert gas such as nitrogen (N.sub.2) gas or argon (Ar) gas may be introduced.

(50) Further, in the present embodiment, the air supply means 33 is used as a means for removing only the uncured thermo-setting resin composition 31 on the inner side of the heat transfer tube 11, but the means is not limited thereto. FIGS. 9 and 10 are views each illustrating an example of a method of removing the uncured thermo-setting resin composition. As illustrated in FIG. 9, a spherical body 35 is introduced to supply the air 34 into the heat transfer tube 11, thereby allowing removal of only the uncured thermo-setting resin composition 31 on the inner side of the heat transfer tube 11 while curing the uncured thermo-setting resin composition 31 in the heat transfer tube 11.

(51) Further, as illustrated in FIG. 10, by fitting a pushing member 37 having a diameter smaller than the inner diameter of the heat transfer tube 11 to a leading end of a cable 36 and introducing the pushing member 37 into the heat transfer tube 11, only the uncured thermo-setting resin composition 31 on the inner side of the heat transfer tube 11 can be removed.

(52) Further, in the present embodiment, the number of times that the thermo-setting resin composition supply means 32 supplies the thermo-setting resin composition 31 into the heat transfer tube 11 is set to one, but the number is not limited thereto. The thermo-setting resin composition supply means 32 may supply the thermo-setting resin composition 31 into the heat transfer tube 11 plurality of times depending on the size of the inner diameter of the heat transfer tube 11, a film thickness of the resin coating layer 10B formed on the inner wall 11a of the heat transfer tube 11, and the like.

(53) Further, in the present embodiment, the number of times that the air supply means 33 supplies the air 34 into the heat transfer tube 11 is set to one, but the number is not limited thereto. The air supply means 33 may supply the air 34 into the heat transfer tube 11 plurality of times depending on the size of the inner diameter of the heat transfer tube 11 and the like, a film thickness of the resin coating layer 10B formed by the thermo-setting resin composition 31 supplied into the heat transfer tube 11 at the first time, and the like.

(54) Thus, by using the life-extension method for piping according to the present embodiment in which the difference in the temperature transferred to inside of the heat transfer tube 11 when the heat transfer tube 11 is heated from outside is utilized, only the uncured thermo-setting resin composition 31 can be removed from the heat transfer tube 11. Accordingly, the resin coating layer 10B according to the present embodiment can be formed only on the inner wall 11a side of the heat transfer tube 11. Thus, even if a defect such as cracks or holes occurs in the heat transfer tube 11 resulting from progress of corrosion at a portion of the heat transfer tube 11 where thinning or the like occurs, forming the resin coating layer 10B according to the present embodiment on the inner wall 11a of the heat transfer tube 11 allows the heat transfer tube 11 to be temporarily and easily repaired without involving a cutting process of the heat transfer tube 11. As a result, it is possible to prevent the heating medium flowing in the heat transfer tube 11 from leaking outside. Further, the resin coating layer 10B according to the present embodiment is cured by being heated from outside the heat transfer tube 11, so that a one-liquid type thermo-setting resin composition can be used to form the resin coating layer 10B. Thus, as compared to a case where a two-liquid type thermo-setting resin composition is used to form the resin coating layer 10B, a cured state, such as a film thickness, of the thermo-setting resin composition 31 can be easily adjusted. Further, the thermo-setting resin composition 31 contains the metal particles, so that even when the resin coating layer 10B according to the present embodiment is formed in the heat transfer tube 11, it is possible to suppress reduction in thermal conductivity of the heat transfer tube 11 when the heating medium is fed into the heat transfer tube 11, which in turn can suppress reduction in performance of the heat exchanger 23.

(55) Although the present invention is applied to the heat transfer tube 11 provided in a fin-tube heat exchanger in the above embodiments, but the application is not limited thereto. The invention may be applied to heat exchangers of other types, such as a gas-to-liquid air-cooled heat exchanger and a direct contact heat exchanger. Further, the application of the resin coating layer 10A according to the present embodiment is not limited to a gas-to-liquid heat exchanger, but the resin coating layer 10A may be useful in a liquid-to-liquid heat exchanger or a gas-to-gas heat exchanger. Examples of the liquid-to-liquid heat exchanger include a spiral heat exchanger, a plate heat exchanger, a double-pipe heat exchanger, a shell-and-tube heat exchanger (multi-pipe cylindrical heat exchanger), a spiral tube heat exchanger, a spiral plate heat exchanger, a tank coil heat exchanger, a tank jacket heat exchanger, and a direct contact liquid-to-liquid heat exchanger. Examples of the gas-to-gas heat exchanger include a stationary heat exchanger, a regenerative rotary heat exchanger, a periodic flow regenerative heat exchanger, and a vortex tube.

(56) Further, in the embodiments, the present invention is applied to the heat transfer tube provided in the heat exchanger, but the application is not limited thereto. For example, piping to be used in the present invention is not limited in particular as long as it can feed liquid/gas in a chemical plant, a power plant, or the like. Thus, for example, the present invention can also be applied to a repairing work of piping for corrosive liquid, piping for corrosive gas, piping for high-temperature water, piping for low-temperature water, or the like.

REFERENCE SIGNS LIST

(57) 10A, 10B RESIN COATING LAYER 11 HEAT TRANSFER TUBE 21 RESIN FINE PARTICLE 23 HEAT EXCHANGER 24 RESIN FINE PARTICLE SUPPLY MEANS 31 THERMO-SETTING RESIN COMPOSITION 32 THERMO-SETTING RESIN COMPOSITION SUPPLY MEANS 33 AIR SUPPLY MEANS 34 AIR 35 SPHERICAL BODY 36 CABLE 37 PUSHING MEMBER