CA2150316C

CA2150316C - Method and apparatus for the restoration of heat exchangers and condensers

Info

Publication number: CA2150316C
Application number: CA002150316A
Authority: CA
Inventors: Thomas D. Bories
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-05-26
Filing date: 1995-05-26
Publication date: 2007-08-21
Anticipated expiration: 2015-05-26
Also published as: CA2150316A1

Abstract

A method of installing a liner in a dry parent tube of a heat exchanger includes inserting a continuous tubular liner into the parent tube, sealing one end of the continuous tubular liner and sealingly attaching the other end to a source of pressurized fluid and injecting fluid under pressure into the continuous tubular liner to hydraulically expand the tubular liner substantially into contact with the parent tube. The interior of the parent tube may be cleaned beforehand, preferably to a white metal finish. Opposed ends of the continuous tubular liner are milled to conform to the opposed ends of the parent tube, and the opposed ends of the continuous tubular liner are roller expanded into a compression fit with the parent tube. The opposed ends of the continuous tubular liner may be flared into contact with flared ends of the parent tube. An apparatus for expanding a continuous tubular liner into a compression fit with a parent tube of a heat exchanger has a first tube sealing chuck attachable to one end of the continuous tubular liner; a second tube sealing chuck attachable to the other end of the continuous tubular liner; and a pump for supplying fluid to the interior of the continuous tubular liner through one of the tube sealing chucks. The pump has a liquid inlet and a gas inlet and a switching valve to select one or both of the inlets.

Description

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TITLE OF TH8 I1iVBZiTIOlQ:
Method and Apparatus for the Restoration of Heat Exchangers and Condensers FIELD OF THE INVENTION
This invention relates to methods and apparatus for the restoration of heat exchangers and condensers.
BACKGROUND OF THE INVENTION
In the art of repairing heat exchangers and like equipment such as condensers, damaged tubes are usually taken out and replaced rather than attempting to repair them. This is evidently an expensive and time consuming process. An alternative is to repair the damaged tube in place, but the inventor is aware of no prior suggestion of how to do so.

SiJIrMARY OF THE INVENTION
The inventor has provided an elegant solution to the problem of repairing a heat exchanger or condenser that has damaged tubes that is believed to be an economical method of repairing heat exchangers or condensers. In addition, the method is applicable to the installation of a liner within a parent tube that is not necessarily extensively damaged but that the operator of the heat exchanger or condenser wishes to replace.
There is therefore provided in accordance with an aspect of the invention, a method of installing a liner in a dry parent tube of a heat exchanger to form a new interior surface of the parent tube. The method includes inserting a continuous tubular liner into the parent tube

2 such that opposed ends of the tubular liner are accessible at opposed ends of the parent tube; sealing one end of the continuous tubular liner and sealingly attaching the other end to a source of pressurized fluid; and injecting fluid under pressure into the continuous tubular liner to hydraulically expand the tubular liner substantially into contact with the parent tube. A continuous tubular liner in this context is made of a thin, corrosion resistant and strong tube.
In a further aspect of the invention, there is provided the step of, before inserting the continuous tubular liner into the parent tube, cleaning the interior of the parent tube, preferably to a white metal finish.
In a further aspect of the invention, there is provided, after installation of the continuous tubular liner, the additional step of milling the opposed ends of the continuous tubular liner to conform to the opposed ends of the parent tube, and also the method may include roller expanding the opposed ends of the continuous tubular liner into a compression fit with the ends of the parent tube.
The opposed ends of the continuous tubular liner may be flared into contact with flared ends of the parent tube.
In a further aspect of the invention, there is provided an apparatus for expanding a continuous tubular liner into a compression fit with a parent tube of a heat exchanger, in which the continuous tubular liner has opposed ends and an interior, the apparatus comprising: a first tube sealing chuck attachable to one end of the continuous tubular liner; a second tube sealing chuck attachable to the other end of the continuous tubular liner; and a pump for supplying fluid to the interior of the continuous tubular liner through one of the tube sealing chucks.

_215U316

3 In a further aspect of the invention, the pump has a liquid inlet and a gas inlet and a switching valve to select one or both of the inlets. Preferably, the first tube sealing chuck has a gas vent, and the second tuber sealing chuck has an inlet end for gas and liquid from the pump.

BRIEF DESCRIPTION OF THE DRAWINGS
There will now be described a preferred embodiment of the invention, with reference to the drawings, by way of illustration, in which like numerals denote like elements and in which:
Fig. 1 is a side view of an outlet chuck for use in the operation of the invention;
Fig. 2 is a side view of an inlet chuck for use in the operation of the invention;
Fig. 3 is a schematic showing the overall set up for carrying out the method of the invention;
Fig. 4 is a section showing the interior construction of the jaws for holding the continuous tubular liner during injection of fluid into the continuous tubular liner; and Fig. 5 is an end view of the jaws.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Referring to Figs. 1, 2 and 3, there are shown an inlet tube sealing chuck 10 for gripping one end 66 of a continuous tubular liner 60 and an outlet tube sealing chuck 12 for gripping the other end 64 of the continuous tubular liner 60. It should be appreciated that the chucks describe one manner of joining a continuous tubular liner to a conduit carrying pressurized fluid, and that in the method of installing the continuous tubular liner in a parent or damaged tube other methods could be used. The

4 embodiment shown here, though, is believed to be an invention in itself.
Referring in particular to Figs. 1 and 4, the outlet chuck 12 includes a tubular body 14 and a jaw retaining sleeve 16 that fits into the bore of the main tubular body 14. Jaw retaining sleeve 16 also has an inner bore 19 which is tapered, narrowing towards jaws 22. A
ridge 18 on jaw retaining sleeve 16 carries a seal formed of an 0-ring 28 and TeflonTm ring 32. The tubular body 14 has an inner shoulder (not shown) against which the ridge 18 abuts, preventing movement of the sleeve 16 through the tubular body 14. A set of three jaws 22 are inserted into the bore 19 of main jaw retaining sleeve 16. The jaws 22 are selected to fit around the size of continuous tubular liner 60 to be installed. Precise fit is required in order to avoid crushing the liner or leaving leaks for water to leak from. In the configuration shown in Fig. 4, the jaws are moved to the left by spring 40 and are in gripping position. As they move to the right, the grip is broken and a continuous tubular liner can be removed from the jaws.
As shown in Figs. 4 and 5, each jaw 22 covers approximately 1201 of a circle, and has a tube gripping portion 70 with sharp ridges 72 for gripping the tube. A
shoulder 74 prevents the tube being gripped from penetrating too far into the chuck. The exterior 76 of the jaws 22 is tapered, with the jaws 22 becoming wider on their outside towards the jaw retaining sleeve 16.
Collectively, the jaws 22 terminate towards the main body of the chuck in an annular shoulder or lip 78, which fits into an annular groove 80 on the inside of jaw retaining sleeve 16. Each jaw 22 is placed in the jaw retaining sleeve 16 one at a time. The taper of the jaws 22 and the taper of the bore 19 of the jaw retaining sleeve 16 means that, as the jaws 22 are forced out of the jaw retaining sleeve, as for example might occur when a tube they are gripping is pressurized from within, they tighten. The jaws must be sized for the particular size of liner to be installed. However, the main body 14 may be used with jaws

5 of different sizes.
Referring now to Fig. 1, at the end 15 of the jaw retaining sleeve 16 opposed to the jaws 22, the jaw retaining sleeve 16 is threaded and (shown at the other end of the outlet chuck 12) a vent nut 42 threads into the threaded end of jaw retaining sleeve 16 when the jaw retaining sleeve has been inserted in the body 14. 0-rings 26 and 28, with back-up Teflonlm rings 30 and 32 seal the jaw retaining sleeve 16 and ridge 18 respectively against the inside of nut 24 and the inside of tubular body 14 respectively.
Nut 24 has a threaded end 34 which threads into body 14. It should be noted that Fig. 1 is not quite to scale. End 15 of jaw retaining sleeve 16 is small enough to fit within the bore of nut 24 and pass through the nut so that nut 42 may thread into the threads of end 15 of jaw retaining sleeve 16. A spring 40 abuts against a portion of nut 42, and runs through the bore of jaw retaining sleeve 16 and presses against the jaws 22 as shown in Fig. 4. A
snap-ring 46 slips into groove 17 in end 15 of the jaw retaining sleeve 16 when assembled. An 0-ring 48 is placed between the snap-ring 46 and a release handle 50 for the snap-ring 46. Release handle 50 is a ring of stainless steel with an arm, such that movement of the arm lifts the ring away from the body 14.
The chuck is assembled as follows. Jaws 22 are slid individually into the tapered jaw retaining sleeve 16.
The body 14 is slid over the jaw retaining sleeve 16 with jaws 22 up against tapered end of the jaw retaining sleeve 16. Encasement of the ridge 18 and jaw retaining sleeve 16 _2150316

6 in the body 14 holds the jaws 22 firmly on the end of the continuous tubular liner 60. Then the nut 24 is screwed into body 14. Snap ring 46 is snapped into place in groove 17 on jaw retaining sleeve 16 with 0-ring 48 and handle 50 in place between the snap-ring 46 and nut 24. Nut 42 is screwed onto the end of the jaw retaining sleeve 34.
Pushing down on handle 50 moves the jaw retaining sleeve 16 to the left in Fig. 1, compressing spring 40 between the jaws 22 and threaded end 34 of nut 24. Compression of the spring 40, provided a suitably stiff spring is used, moves jaws 22 outward in the jaw retaining sleeve 16 and gives jaws 22 room to move in the taper of jaw retaining sleeve 16, thus allowing the jaws to receive a tube or release a tube held by the jaws. When it is desired to insert another continuous tubular liner 60 into the jaws 22, the handle 50 is again levered to slightly open the jaws 22, an end of the continuous tubular liner is inserted into the jaws 22 and the handle 50 is released.
When assembled, the sleeve 16 has a play of about 4 inch within the body 14. An opening 21 in the sleeve 16 allows fluid under pressure to leak out into the bore of body 14 where it is confined between the seals 26 and 28.
The pressure between the seals prevents the sleeve 16 from moving in relation to the body during pressurization of the liner.
The chuck 10 is identically constructed to chuck 12 only an inlet end or pipe adaptor 52 for supply of air and water into a continuous tubular liner has been substituted for the vent nut 42 (Fig. 2). Vent 44 in vent nut 42 allows air to escape, but water is blocked.
In operation, one end of a continuous tubular liner is inserted into jaws 12 as described above with the jaws 22 gripping the continuous tubular liner. By this means, the outlet chuck is attachable onto the continuous _ 2150316

7 tubular liner, and can make a sealing engagement with the chuck. Similarly, the inlet chuck is attached onto the continuous tubular liner, with the continuous tubular liner in sealing engagement with the chuck.
Referring to Fig. 3, inlet chuck 10 and outlet chuck 12 are shown in position for operation at opposed ends of a continuous tubular liner 60 that has been installed within a parent tube 62 of a heat exchanger or condenser. The liner should be made of a hard thin corrosion resistant metal such as titanium, HastalloyTm (a nickel alloy), 304 stainless steel or 316 stainless steel or other similar materials as is known in the art of inserting inserts into damaged ends of heat exchanger tubes by roller expanding, and for this purpose the jaws 22 should be made of a similarly hard material such as carbon steel. The liner must be capable of slight expansion under pressure without splitting. A preferred thickness of liner is about 0.020 inches.
Pipe adaptor 52 at the inlet end of chuck 10 is fitted onto a high pressure hose 53 from pump 54. Pump 54 is a high pressure pump up to 10,000 psi and has an air inlet 56 (with pressure for example at 90-120 lbs) and a water inlet 58 with pressure at 35 lbs. A control 61 may be used to gradually increase the pressure produced by the pump. The pump 54 supplies fluid (air and water) to the interior of the continuous tubular liner through inlet chuck 10. The fluid under pressure can force the continuous tubular liner into a compression fit with a parent tube of a heat exchanger.
A liner may be installed in a parent tube 62 of a heat exchanger (not shown) using the following method.
The method also has applicability to lining the tubes of new heat exchangers, in which case the parent tube may not even be damaged.

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8 If the parent tube is not already clean, then it must first be cleaned, using any of several known methods in the art for example hollow blasting, high pressure water, or rotating brush. The parent tubes are then dried with clean dry air to ensure that the inside of the parent tubes is dry. Next, the ends of the parent tube to a depth equal to the depth of the tubesheet may optionally be wire brushed to a white metal finish to facilitate later roller expansion of the ends of the liner. Again, the parent tube should be dried if it is not already dry.
The inside diameter of the parent tube should then be measured at several places, and a correctly sized continuous tubular liner selected. The outside diameter size of the continuous tubular liner is selected to be as close as possible to the inside diameter of the parent tube while allowing it to be inserted. This will typically be within about 0.010 inches but may be as much as 0.020 inches or more depending on the obstructions present in the parent tube. The length of the liner is slightly greater than the length of the parent tube. The continuous tubular liner is then inserted in the parent tube, with a short length of liner extending from the parent tube at opposed ends of the parent tube and thus being accessible for working on. The inlet and outlet chucks 10 and 12 are then installed on the opposed ends of the continuous tubular liner to seal one end of the continuous tubular liner with chuck 12 and to sealingly attach the other end to the fluid inlet hose 53 with chuck 10. The pump 54 is then operated to inject fluid under pressure into the continuous tubular liner and hydraulically expand the continuous tubular liner into contact with the parent tube to a metal to metal contact fit, preferably with the continuous tubular liner compressed against the parent tube. Pressure should be increased gradually at a rate of about 1000 psi each 15 . , ,, ., . . .: ...

9 seconds to avoid work hardening the liner by sharp increases and dropping of the pressure. The liner should be monitored during expansion so that the expansion of the liner outside of the parent tube is not more than about 0.070 inches to avoid overpressuring the parent tube.
The expansion of the continuous tubular liner should preferably not be so great as to expand the parent tube. The fit should preferably be within 0.0015 inches.
The ends of the continuous tubular liner are then milled to conform to the ends of the parent tube. Next, the ends of the continuous tubular liner may optionally be roller expanded into a compression fit with the parent tube, for example using roller expanders of the type described in United States patent no. 4,941,512 or as described in my co-pending Canadian patent application serial no. 2,034,343 or other methods known in the art. The continuous tubular liner may then be flared at its ends into contact with flared ends of the parent tube in accordance with known techniques. The continuous tubular liner should then be pressure tested if necessary, and inspected for leaks.
With the continuous tubular liner compressed against the parent tube, there is little room for fluids to get between the liner and parent tube so that even if the liner is not of the same material as the parent tube, a galvanic cell is not created and corrosion is inhibited.
This means that a liner may be installed that is not of the same material as the parent tube. For example, a stainless steel tube may be installed in a carbon steel parent tube.
The continuous tubular liner need not be seamless, but may be welded.
A person skilled in the art could make immaterial modifications to the invention described and claimed in this patent without departing from the essence of the invention.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of installing a liner in a dry parent tube of a heat exchanger, the method comprising the steps of:
inserting a continuous tubular liner into the parent tube such that opposed ends of the tubular liner are accessible at opposed ends of the parent tube;
milling the opposed ends of the continuous tubular liner to conform to the opposed ends of the parent tube;
sealing one end of the continuous tubular liner and sealingly attaching the other end to a source of pressurized fluid; and injecting fluid under pressure into the continuous tubular liner to hydraulically expand the tubular liner substantially into contact with the parent tube without expansion of the parent tube.

2. The method of claim 1, further comprising the step of roller expanding the opposed ends of the continuous tubular liner into a compression fit with the parent tube.

3. The method of claim 1 or 2, further comprising, before inserting the continuous tubular liner into the parent tube, cleaning the interior of the parent tube.

4. The method of claim 3 in which the parent tube is cleaned to a white metal finish.

5. The method of any one of claims 1-4, further comprising roller expanding the opposed ends of the continuous tubular liner into a compression fit with the parent tube.

6. The method of any one of claims 1-5, further comprising flaring the opposed ends of the continuous tubular liner into contact with flared ends of the parent tube.

7. The method of any one of claims 1 to 6, further comprising the step of drying the parent tube.