AU652093B2

AU652093B2 - Tube plug

Info

Publication number: AU652093B2
Application number: AU35206/93A
Authority: AU
Inventors: John McComas; Donald Joseph Want
Original assignee: WE Smith Engineering Pty Ltd
Current assignee: WE Smith Engineering Pty Ltd
Priority date: 1992-03-12
Filing date: 1993-03-12
Publication date: 1994-08-11
Anticipated expiration: 2013-03-12
Also published as: AU3520693A

Description

1 I- 65209' pOOO11 Regulation 3.2

AUSTRALIA

Patents Act, 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Original 1 ii I src TO BE COMPLETED BY THE APPLICANT NAME OF APPLICANT: t t

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ACTUAL INVENTORS: ADDRESS FOR SERVICE: W.E. SMITH ENGINEERING PTY.

LI MITED (ACN 000 053 207) DONALD JOSEPH WANT and JOHN MCCOMAS Peter Maxwell Associates Blaxland House, Suite 10, 5 Ross Street, NORTH PARRAMATTA NSW 2151 ,i I re Irrrri I r INVENTION TITLE: DETAILS OF ASSOCIATED PROVISIONAL APPLICATION NO: TUBE PLUG PL 1328 12TH MARCH, 1992 The following statement is a full description of this invention, including the best method of performing it know to me:- -1- -2- 44 U. *4n br The present invention relates to tube plugs and, in particular, to means for plugging or sealing failed tubes in shell and tube-type heat exchangers. The tube plugs of the invention can be adapted to a variety of heat exchange equipment throughout the petro-chemical and power generation industries.

In tube-type heat exchangers, a first fluid flows through the tubes or tubeholes of the heat exchanger while a second fluid surrounds the outside of the tubes or tubeholes such that heat exchange occurs between the two fluids.

Degradation of a tube or tubehole may lead to an impending leak and further degradation of the tube or tubehole will lead to a leak which allows the two fluids to mingle. When this happens it is sometimes necessary to plug the degraded tube or tubehole so that the fluid does not flow through the tube or tubehole, thereby preventing leakage from or into that tube or tubehole.

There have been many problems over the years in achieving reliable plugging or sealing of failed tubes or tubeholes in shell and tube-type heat exchangers. This has caused loss of production and significant downtime of plants with such leakages. For instance, with feedwater heaters in power stations, serious problems affecting heater performance and lifetime can result from leaking tube plugs.

In high pressure feedwater heaters the main traditional method for plugging leaking or failed tubes or tubeholes involved sealing through welding. However, due to the nonideal weld. .j environment, including lack of cleanliness, i -3i inability to pre-heat, accessibility problems and the like it is very difficult to achieve a reliable welded seal.

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Explosion-plugging has also been employed in the past with varying success.

The types of plugs that have been used in the past all have had varying success, the type of plug used successfully in one type of exchanger, cannot be applied to another due to different process ciemistry, pressures, temperatures, corrosion aspects and the like. Since heat exchanger downtime directly affects the efficiency of the plant in which it is installed and plant shutdowns are sometimes required to plug leaking tubes or tubeholes, it would therefore be advantageous to have a tube plug which can be easily and quickly installed and which will not fail causing further problems and downtime.

.It is an object of the present invention to overcome or substantially ameliorate the disadvantages of the prior art by providing a simple, reliable, non-welded tube plug that can be installed relatively quickly even when environmental conditions are not ideal.

According to the invention, there is provided a tube plug for sealing a heat exchanger tube or tubehole, the tube plug comprising:a stationary member adapted to be located fixedly inside the tube or tubehole, an annular sealing member adapted to be positioned within the tube or tubehole so as to bear against the stationary member, said sealing member being adapted upon i -I -L ~-LI -4axial compression to expand outwardly against the tube wall, a compressing member adapted to be located within the tube or tubehole with the sealing member being positioned between the stationary member and the compressing member, and, aO 00 means for urging the compressing member against the sealing member so as to compress the sealing member between the stationary member and the compressing member so that the sealing member expands outwardly against the tube wall to provide a seal, the compressing member including a guide portion that slidably engages a reference portion of the stationary member so that the compressing member is guided whilst being urged against the sealing member.

Preferably, the guide portion is a male cylindrical mo-'ber that slidably engages in a matching female reference portion of the stationary member.

Alternatively, the guide portion may be a female annular member that slidably engages around a matching male reference portion of the stationary member.

It is preferred that the guide portion be formed integrally with the compressing member. The guide portion may, however, comprise a separable part of the compressing member when not in use but is fixedly or inseparably engaged to the compressing member when in use in the tube or tubehole.

The urging means may be a fastener screw that engages a suitably threaded cavity in the compressing member so that I when the fastener screw is screwed, it urges the compressing i member into the tube or tubehole and against the sealing member.

In another form, the urging means may be a fastener nut that engages a suitably threaded stud that serves as the guide portion so that when the fastener nut is screwed, it urges the compressing member toward the tube opening and against the sealing member.

In order that the invention may be readily understood and put into practical effect, reference will be made to the accompanying drawings, in which:j Fig. 1 is an axial section view of a tube plug according to a first embodiment of the invention located in a counterbored and tapped heat exchanger tube or tubehole of a typical power station heat exchanger, Fig. 2 is an axial section view of a tube plug according to a second embodiment of the invention located in a tapped heat exchanger tube or tubehole, S, Fig. 3 is an axial section, view of a tube plug according to a third embodiment of the invention located in a tapped heat exchanger tube or tubehole, and Fig. 4 is an axial section view of a tube plug according to a fourth embodiment of the invention located in a tapped heat exchanger tube or tubehole.

I -6- The tube plug 11 shown in Fig. 1 is located in a tube or tubehole 12 of a heat exchanger 13 (only partly shown).

'i The tube or tubehole 12 has been counterbored in the region j 14 to produce a shoulder 15 which has a radial width typically of at least 0.2 mm and to produce an adequate wall surface finish so as to ensure optimal sealing performance of the seal. The tube has also been tapped in the region 16.

Located in the counterbored region 14 is a female collar 17 which serves as a stationary member. The female collar 17 bears against the shoulder 15. Also located in the j counterbored region 14 is a male plug 18 which serves as a compressing member, and an annular seal 19.

i 'i The seal 19 consists of a ring of suitable material, such as graphite, which has been preformed and pre-compressed to achieve a close-fit tolerance within the tube 12 and around the male plug 18.

The male plug 18 has an integrally foirmed cylindrical guide portion 20 of smaller diameter than the main portion of the plug 18 that passes slidably through and bears against the inner surface of the bore of the seal 19 and passes i partly through the cavity 21 of the collar 17.

A fastener screw 24, which, in this instance, is a socket set screw operable by a separate and removable set screw tool, serves as a means for urging or forcing axially the male plug 18 against the annular seal 19 so as to cause compression and outward expansion of the seal 19 against the wall of the tube or tubehole 12. In so doing, the guide i

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S-7portion 20 5lides through the female cavity 21 of the collar 17 and enables the male plug 18 to locate centrally or align with the female collar 17, with the result that substantially equal outward expansion forces are experienced throughout the circumference of the seal 19.

The shoulder 15 produces a loading reaction surface for the female collar 17 to bear against as axial forces are applied to the seal 19 by the tightening of the fastener screw 24 against the male plug 18.

The seal 19 performs its function by being axially compressed to achieve a positive seal on all faces. The initial radial clearances are taken-up due to the ductile S properties of the seal 19 which enables it to distort and seal the resulting contact areas. The other parts of the plug assembly 11 enable this axial loading to occur and to ensure that no seal movement occurs during operation of the concerned exchanger.

The seal 19 is required to seal with respect to potential leakage from either ide (shellside or tubeside) of the assembly 11. As such the design conditions of both sides must be considered when deciding the seal characteristics.

The relationship of the outside to inside diameters and of length of the seal 19 is determined by the size of the tube concerned, materials, pressures and temperatures. The length varies considerably and is determined by pressures, temperatures, seal material and condition of the tube surface to which a seal is applied. Typical size ranges would be: C '9 r Outside diameter/Inside diameter Ratio: 2:1 to 1.03:1 for one-inch nominal diameter tubes and low pressures and temperatures:outside diameter 25.2mm inside diameter 19.2mm (thus 25.2:19.2 1.31:1) Length can be from 25mm to 1mm.

The male plug diameters should be such that the larger diameter of the main portion fits closely in the counterborcd tube while the smaller diameter of the guide portion 20 fits closely inside the seal's inside diameter. The length of the oo male plug 18 is determined by the length of the seal 19 and 0 the required strength to withstand both the axial force from the fastener screw 24 and the worst case design conditions of the exchanger. The guide portion of the male plug 18 should S ce be chamfered, radiused or tapered to locate centrally within the female collar 17 when the plug assembly is fitted together.

oooo The female collar 17 has fine-toleranced outside and o inside diameters for optimum seal performance. The 0 tolerances are relative to the tube inside diameter and guide portion diameter. The length of the female collar 17 is determined by strength considerations.

The length of the fastener screw 24 is determined by strength considerations and is usually at least as long as its diameter.

Although not shown, the tube plug 11 may be assembled -9such that a suitably modified male plug and female collar are t fitted within the tube or tubehole 12 in reverse order to that shown in Fig. 1. With such an arrangement, the male plug (which now serves as the stationary member) is inserted i first with its large diameter end bearing against the shoulder 15 and with its smaller diameter guide portion (now serving as the reference portion) pointing towards the tube opening and having the annular seal located around the smaller diameter portion. The female collar (which now serves as the compressing member) is then urged into the tube by use of a fastener or other urging means so that its annular cavity walls (which now serves as the guide portion) fits over the male plug smaller diameter portion and compresses the seal to the desired degree for axial expansion against the tube wall.

The tube plug 30 shown in Fig. 2 is engaged in a tube or tubehole 31 that has not been counterbored as in the tube or tubehole 12 of Fig. 1 but has been tapped by threading 38 near the tube opening.

Located in the tube or tubehole 31 furthest from the tube opening is a compressing collar 32 having an annular wall portion 33 with a female cavity 34 located therewithin.

The cavity 34 is threaded and screwably receives a suitably threaded stud 35, a portion of which emerges from the tube opening. The compressing collar 32 and the attached stud are therefore able, when not impeded, to move in unison into and out of the tube or tubehole 31. Surrounding the stud 35 within the tube 31 is an annular seal 36 and a hollow set screw 37 which serves as the stationary member by screwably engaging the threading 38 near the tube opening.

The stud 35 serves as the guide portion of the compressing collar 32 as it passes snugly through or engages slidably the bore of the hollow set screw 37. In this embodiment, the bore of the hollow set screw 37 serves as the reference portion of the stationary member.

In order to urge the compressing collar 32 against the seal 36, a fastener nut 41, threadably attached to the stud 1 4 35 and abutting against the hollow set screw 37, is tightened against the set screw 37. Whilst tightening the fastener nut C i 41, the stud 35 is held rotationally stationary by means of a screwdriver tip (not shown) engaging a slot 39 of the stud As the fastener nut 41 is tightened, the stud 35 is caused to slide outwardly of the tube or tubehole 31 bringing with it the compressing collar 32. The leading annular face of the compressing collar 32 urges against one side of the seal 36, with movement of the seal 36 being resisted by the set screw 37 bearing against the other side of the seal 36.

T- The set screw 37 produces a loading reaction surface for the seal 36 to bear against as axial forces are applied to the seal 36 by the compressing collar 32.

The seal 36 is caused to be compressed and outwardly r-panded against the wall of the tube or tubehole 31.

Because the stud 35 is located centrally with the set screw 37, substantially equal outward expansion forces are 3mm r~m~ -11experienced throughout the circumference of the seal 36, effectively sealing the contact surfaces of the tube or tubehole 31.

The tube plug 45 shown in Fig. 3 differs from the assembly 30 shown in Fig. 2 only in that the compressing collar and stud pieces of assembly 30 are now integrally formed in the one piece compressing member 46.

The compressing member 46 has a smaller diameter threaded stud portion 47 and a larger diameter tube surface bearing portion 48 that serves the same role as the annular wall portion 33 of the compressing collar 32 shown in Fig. 2.

As the fastener nut 50 is tightened onto the stud portion 47, 6 0 the leading annular face 49 of the tube surface bearing portion 48 is caused to urge against one side of the seal 51, with movement of the seal 51 being resisted by the stationary set screw 52 bearing against the other side of the seal 51.

SS In the same way that sealing was produced with the assembly of Fig. 2, the tightening of the fastener nut 50 eventually 0o causes the seal 51 to be compressed and outwardly expanded with substantially equal outward expansion forces so that it 4 44 seals the contact surfaces of the tube.

o o The tube plug 55 shown in Fig. 4 differs from the assembly 30 shown in Fig. 2 only in that the stud and fastener nut pieces of assembly 30 are replaced by a single piece bolt 56, the integrally formed stud portion 57 of which has an inside left-handed thread 58. Tightening of the bolt I 56 against the hollow set screw 59 by rotation of the fastener portion 60 of the bolt 56 causes the compressing -12collar 61 to be pulled towards the tube opening thereby, in a manner similar to that described for the assemblies of Figs.

2 and 3, causing the seal 62 to be compressed and outwardly expanded into sealing relationship with the contact surfaces of the tube.

In each of the aforementioned embodiments of the invention, each component of the tube plug except for the seal, will be fabricated of metal alloys suitable for the process chemicals and temperatures present.

Various modifications may be made in details of design o: and construction without departing from the scope or ambit of the invention.

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Claims

1. A tube plug for sealing a heat exchanger tube or tubehole, the tube plug comprising:- a stationary member adapted to be located fixedly inside the tube or tubehole, an annular sealing member adapted to be positioned within the tube or tubehole so as to bear against the first stationary member, said sealing member being adapted upon axial compression to expand outwardly against the tube wall, a compressing member adapted to be located within the tube or tubehole with the sealing member being positioned between the stationary member and the compressing member, and, means for urging the compressing member against the sealing member so as to compress the sealing member between the stationary member and the compressing member so that the sealing member expands outwardly against the tube wall to provide a seal, the compressing member including a guide portion that slidably engages a reference portion of the stationary member so that the compressing member is guided whilst being urged against the sealing member.

2. The tube plug of claim 1 wherein the guide portion is a male cylindrical member that slidably engages in a matching female reference portion of the stationary member.

3. The tube plug of claim 1 wherein the guide portion is a female annular member that slidably engages around a matching i male reference portion of the stationary member. -14-

4. The tube plug of any one of claims 1 to 3 wherein the guide portion is formed integrally with the compressing member.

The tube plug of any one of claims 1 to 3 wherein the guide portion comprises a separable part of the compressing member when not in use but is fixedly or inseparably engaged to the compressing member when in use in the tube or tubehole.

6. The tube plug of any one of claims 1 to 5 wherein the urging means is a fastener screw that engages a suitably threaded cavity in the compressing member so that when the fastener screw is screwed, it urges the compressing member into the tube or tubehole and against the sealing member.

7. The tube plug of any one of claims 1 to 3 wherein the urging means is a fastener nut that engages a suitably threaded stud that serves as the guide portion so that when the fastener nut is screwed, it urges the compressing member toward the tube opening and against the sealing member.

8. A tube plug substantially as hereinbefore described with reference to any one of the drawings. ri Dated this 12th day of March, 1993. W.E. SMITH ENGINEERING PTY. LIMITED Patent Attorneys for the Applicant: "ETER MAXWELL ASSOCIATES 93 1 024 ABSTRACT A tube plug (11) for sealing a heat exchanger tube or tubehole (12) has a stationary member (17) which is located fixedly inside the tube or tubehole There is an annular sealing member (19) that is positioned so as to bear against the stationary member (17) and which is adapted, so that upon axial compression thereof, it radially expands against the tube wall. A compressing member (18) is positioned such that the sealing member (19) is between the stationary member (17) and the compressing member (18). There is an urging means (21) that urges the compressing ou o o"o member (18) against the sealing member (19) so as to compress o «c i 0 0 o^oc the sealing member between the stationary member and the o00o 0 a compressing member so that the sealing member expands 000 0 o outwardly against the tube wall to provide a seal. The compressing member (18) includes a guide portion (20) that S°o°o slidably engages a reference portion of the stationary member 0 0 °o so that the compressing member is guided whilst being urged o o against the sealing member. 0 00 0 0 0000 00 0 o0 o oooo 0 00