US3782455A

US3782455A - Heat exchanger tube mounts

Info

Publication number: US3782455A
Application number: US00248842A
Authority: US
Inventors: W Wolowodiuk; J Anelli; B Dawson
Original assignee: US Atomic Energy Commission (AEC)
Current assignee: US Atomic Energy Commission (AEC)
Priority date: 1972-05-01
Filing date: 1972-05-01
Publication date: 1974-01-01
Anticipated expiration: 1991-01-01
Also published as: JPS4961743A; FR2183090B1; FR2183090A1; GB1422695A; DE2320084A1; CA964950A; SU500770A3

Abstract

A heat exchanger in which tubes are secured to a tube sheet by internal bore welding, which tubes may be moved into place in preparation for welding with comparatively little trouble. A number of segmented tube support plates are provided which allow a considerable portion of each of the tubes to be moved laterally after the end thereof has been positioned in preparation for internal bore welding to the tube sheet.

Description

United States Patent 1 1 1111 3,782,455 Wolowodiuk et al. Y 1 Jan. I, 1974 [54] HEAT EXCHANGER TUBE MOUNTS 3,527,261 9/1970 Bigler et al. 122/510 4, 4 l2l970 Cl i225 OX [75] Invemmsl Walter wdmvodiuk, New 3129231 19 7l1971 113151 21115 1 22 /51o Providence; John Anal", 3,677,339 1/1970 Pcrrin et al. 122 510 Parsippany; Bruce Edgar Dawson, Chatham, all of NJ. Primary ExaminerCharles J. Myhre [73] Asslgneez The United States of America as Assistant Examinef Theophn W Streule represented by the United States Attompy john Maier m at Atomic Energy Commission, 1 Washington, DC.

[2]] Appl. No.: 248,842

A heat exchanger in wh1ch tubes are secured to a tube sheet by internal bore welding, which tubes may be [52] US. Cl. 165/162, 122/510 moved into place in preparation for welding with [5]] lift. Ci F28b 9/00 paratively file trouble A number f segmented tube Fleld 0f Search 72, Support plates are provided allow a consider able portion of each of the tubes to be moved laterally [56] References cued after the end thereof has been positioned in prepara-- UNITED STATES PATENTS tion for internal bore welding to the tube sheet.

3,336,974 8/1967 Bernstein et al l65/l62 8 Claims, 6 Drawing Figures PATENTEU H914 3 782 455 SHEEI 2 OF 5 FIG. 2

HEAT EXCHANGER TUBE MOUNTS BACKGROUND OF THE INVENTION Most heat exchangers in which one fluid is placed in indirect heat exchange with another utilize a series of tubes to flow one fluid through, while the other fluid flows over the outside of the tubes. Tube sheets at one or both ends of the tubes are necessary to separate the fluid which flows'through the tubes before and after their journey through the tubes from the other fluid which flows over the tubes.

This separation must be maintained and requires a hermetic seal between the outside of the'tubes and the tube sheet or sheets to which the tubes are secured. The most common way'to secure the tubes to a tube sheet is to drill as many-holes through the tube sheet as there are tubes to be secured to it. Each tube is then positioned in one of the "holes so that its end is flush with one side of the tube sheet. There are a number of well known methods of. enlarging the tubes so'that their outside surfaces engage against the inside surfaces of the holes. Whether or not the tubes'are enlarged, they are usually welded to the tube sheet. The welds are effected at the ends of the tubes so that the end edge of the tube is welded to'the adjacent tube sheet surface.

There are, however,.situations where the above de- I scribed construction cannot be used. For example, in heat exchangers used in nuclear power plants, it is often necessary to weldthe tubes to the tube sheets by welds which are (effected from within .the tube sheet holes and tubes. This method of welding is often generically referred to as internal'bore welding.

In internal bore welding,'the tubes are each butt welded to tube sheets, .usually at spigots projecting from the sheets. In the case where the tubes are internal bore welded between two tube sheets, it is impossible to move the tubes coaxially into position for welding because the tubes do not pass through the sheets. This creates a construction problem in heat exchangers where tube supporting structure is positioned between the tube sheets to prevent the tubes from being moved laterally between the sheets.

Another situation in which conventional contruction techniques cannot be used without problems is where the tubes must be bent over a portion of their length to allow for thermal expansion and contraction and supported along their lengthby tube supports. It is impossible to move these tubes axially into position to be welded once the bent-portions come in contact with tube supports.

The several situations discussed above are examples where it is desirable to construct a heat exchanger by moving tubes laterally into position'to be welded to a tube sheet.

SUMMARY OF THE PRESENT INVENTION It is an object of the present invention to overcome drawbacks found in the .prior art such as those discussed above. Accordingly, a heat exchanger with at leastone tube sheet and a plurality of tubes which are supported along their length is provided with tube supports which have a number of circumferential bars which extend on each side of eachtube and which are supported by a plurality of radial support bars and which can be secured tolthe radial bars after tubeshave been moved radially into position to permanently support the tubes.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a portion of a tube and tube sheet heat exchanger employing the tube supports of the present invention;

FIG. 2 is a view in perspective showing a portion of one of the tube supports of FIG. 1;

FIG. 3 is a view, partly in section, showing how the circumferential bars of the present invention support the heat exchanger tubes;

FIG. 4 is a plan view of one of the radial support bars shown in FIG. 2;

FIG. 5 is a view, partly in section, showing how the circumferential support bars are secured to the radial bars; and

FIG. 6 is an enlarged view showing the tube supports and their securement to the tube sheet.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a portion of a heat exchanger made in accordance with the present invention. The heat exchanger designated generally as 10 has an outer shell 12 which is generally cylindrical, being tapered inward at the bottom 14 so that it is essentially closed at the bottom. The primary fluid enters at the primary inlet 16 to flow inward until it impinges against an annular shroud 18 to flow upward and over the top of the shroud l8 and then downward through a tube section 20within the shroud 18 until itis below a seal 22 which is between the shroud l8 and shell 12 at a location below the intake 16. The primary fluid then flows radially outward through openings in the shroud 18 to the space between the shroud l8 and the outer shell 12 to flow downward between them and out of the heat exchanger through the primary outlet 24. The seal 22 creates a stagnant annular layer of primary fluid above it and between the shroud 18 and the shell 12.

The tube-section 20 includes two tube sheets, specifically an upper tube sheet 30 and a lower tube sheet 32 and a plurality of tubes 34 extending between the two tube sheets. The tube sheets are annular and encircle a central conduit 36 which feeds secondary fluid downward to a lower chamber 38 which is defined by an annular perforated distribution ring 40 and an inverted dome 42 below the ring 40. The secondary fluid then flows upward through the ring 40 and then through the tube sheet 32 and the tubes 34. The tubes 34 are distributed in the annular spacebetween the central conduit 36 and the cylindrical shroud 18. After leaving the tubes 34, the secondary fluid flows through the annular upper tube sheet 30 to an upper chamber 44, where it is collected and led out of the heat exchanger 10.

The tubes 34 are supported along their length by a series of annular tube supports 51, 52, 53, 54, 55, 56, 57 and 58. These supports allow the primary fluid to flow downward through them and at the same time, support and properly space the tubes 34.

Because the primary fluid flows radially outward through the shroud 18 below the seal 22 to flow downward between the shroud l8 and shell 12, the central conduit 36, shroud l8, tube sheet 32 and tube support 58 define an annular body of stagnant primary fluid. In passing between the tube support 58 and the tube sheet 32, each of the tubes are bent. The bends allow for thermal expansion and contraction of each of the tubes .34 without tube failure. The bent portions are each situated in an area of stagnant primary fluid so that no vibration will be created by the flow of the primary fluid over the bent portions of the tubes 34.

It has already been explained why it is necessary in many heat exchangers to be able to install the tubes 34 by moving them sideways into position so that they can be welded to the

tube sheets

30 and 32. In the heat exchanger l0, it would not be possible to move the tubes 34 axially through one of the tube sheets and the tube supports toward the other of the

tube sheets

30 and 32 over the distance between the tube sheets. It would not be possible to move the bent portions through the tube supports.

lf it were attempted to move the straight portions of the tubes axially through all of the tube supports into engagement with the tube sheet 30, the tubes would have to be distorted extremely before being passed through the tube support 58. The problem is solved by designing several of the tube supports so that they can be assembled as the tubes are moved laterally inward to be engaged by those tube supports.

The tube supports 51, 52, 53 and 54, which can be referred to as solid tube supports, plates with holes drilled in them to accommodate the tubes 34 and the tie rods which will be described hereinafter. The other tube supports, namely, 55, 56, 57 and 58 which can be referred to as segmental tube supports are constructed in sections as the tubes 34 are placed in position and welded. The tubes closest to the central conduit 36 are first welded in place and the tubes immediately outward of those are welded and then the tube outward of those are welded in place. The tubes are thus progressively welded until all are in place. The segmental tube supports thus allow the tubes to be positioned while being distorted only slightly below the lower most solid support 54 so that the upper end of the tubes can be moved axially through the

supports

54, 53, 52 and 51 until the end of the tube abutts against the tube sheet 30. Thereafter, the lower portion of the tube is moved laterally inward until the lower end is positioned against the lower tube sheet 32 for welding.

A section of a segmented tube support is shown in FIG. 2. Essentially, it consists of a series of parallel curvilinear circumferential bars 60, each of which makes up a portion of one of a number of concentric circles.

The outermost circumferential bar 62 is slightly different in that it has a series of round holes through it so that it encircles the tubes which pass through the holes. The circumferential bar 64 also has a series of smaller holes 66 which allow primary fluid to pass easily through.

FIG. 3 shows two adjacent circumferential bars 60 grasping several of the tubes 34. Notice that the inner side 68 ofthe upper circumferential bar 60 does not engage against the outer side 69 of the lower bar 60 as they appear in H6. 3. Each of the circumferential bars 60 has along each side a number of spaced indentations 72 which conform to a portion of the outer surface of each of the engaged tubes 34. Since the sides of adjacent circumferential bars 60 do not touch, primary fluid passing parallel to the tubes 34 can pass downward through the circumferential bars 60.

Notice in FIG. 2 that each of the

circumferential bars

60 and 62 passes over several radial bars 70. The radial bars 70, one of which is shown by itself in FIG. 4, each have at their ends a hole 73 through which the tie rod (which will presently be described) pass. The bars 70 also have a plurality of smaller holes 74 which are used to securely fasten the

circumferential bars

60 and 62 to it.

FlG. 5 shows in cross section a bar supporting several of the circumferential bars 60. The circumferential bars 60 have holes 76, each of which is aligned with one of the holes 74 in the radial bars 70. A pin is inserted in each of the holes 74 and projects upward into one of the holes 74. The pins do not extend upward to the upper surface of the bars 60 and do not extend downward to the lower surface of the radial bars 70. The spaces above and below the pins 80 are filled with weld material 82 to secure the pins 80 in the bars 70 and the bars 60. The result, of course, is to firmly secure the circumferential bars 60 t0 the radial bars 70.

When it is desired to weld the tubes 34 in place, the radial bars 70 are secured to the central conduit 36. The tubes 34 are then positioned with inner most tubes being positioned first. They are each bent slightly at their lower portion and moved axially through the

supports

54, 53, 52 and 51 and into engagement with the tube sheet 30 where they are welded. The lower portions are then allowed to flex inward and as circumferential rows of tubes 34 are positioned, circumferential bars 60 are secured to the radial bars 70 to secure the tubes 34 in place.

The securement of the circumferential bars 60 to the radial bars 70 involves no more than aligning those bars so that the holes 74 are aligned with the holes 76. The pins 80are inserted into each of the aligned pair of

holes

74 and 76 and the weld material 82 is added.

HO. 6 shows the radial bars 70 mounted in position. Rods threaded at their ends are passed through holes 91 in the tube sheet 30 which holes lie on a circle adjacent to the conduit 36. The rod 90 is secured from downward movement by bolts 92. Vertical sleeves 94 are passed over the rods 90 until they abutt against the lower side of the tube sheet 30. Thereafter, the uppermost solid support 51 is moved upwardly into place with the rods 94 passing through holes provided therein. When the support 51 is in place, other sleeves 94 are moved upward over the rods 94 and the next lower solid support can be placed in position. The outer end of each support is held up by a temporary rigging. This procedure is followed until all of the solid supports are in place and the segmented supports are ready for positioning.

Sleeves 94 are then passed upward over the rods 90 until they abutt against the lower surface of the solid support immediately above, in this case 54. Each of the radial bars 70 has at its inner end a hole 73 which will accommodate tie rods 90 as the radial bar 70 is passed upward so that it engages the bottoms of the sleeve 94. As rows are subsequently added, the degree to which the tubes 34 must be distorted at their lower portions becomes less and less. In the preferred embodiment, the outermost circumferential bar 62 has holes 64 rather than recessions 72 in the side thereof so it cannot be moved sideways to clamp the outermost circumferential row of tubes. This is no problem because the tubes can be moved axially through the outermost circumferential bars 62 because very little flexing is necessary. Until all of the circumferential bars are in place, the radial bars 70 are supported at their outer ends by a temporary rig (not shown) until outer tie rods 98 and their associated sleeves 100 are in place. This is accomplished by aligning all of the sleeves 100 between all of the tube supports and then moving the tie rods 98 axially through the sleeves and the holes 73 at the outer ends of the radial bars 70. The rods are secured by bolts 102 from movement with respect to the tube sheets and the rigging at the outer ends of the radial bars is removed. 7

The foregoing describes but one specific embodiment of the present invention. Other embodiments being possible without exceeding the scope of the present invention as defined in the following claims.

What is claimed is:

l. A tube support for a heat exchanger having a plurality of tubes for conveying fluid in heat exchange with fluid flowing outside of said tubes comprising:

a plurality of radial bars extending outward along the radii of a circle;

a plurality of circumferential bars supported on said radial bars, said circumferential bars each being on the circumference of one of a plurality of concentric circles and each having a plurality of recessions spaced along the sides thereof so that facing recessions on adjacent circumferential bars can grasp a cooling tube between them.

2. The tube support defined in claim 1 wherein th sides of adjacent circumferential bars do not abutt to thereby provide a flow space for said fluid flowing outside of said bars.

3. The tube support defined in claim 1 wherein said radial bars have spaced recessions along the sides thereof to engage said tubes.

4. The tube support defined in claim 3 wherein said recessions on one side of each of said radial bars are at different locations along the lengths than the recessions at the other side of said bar so that said radial bars can accommodate tubes lying along one of said radii.

5. A heat exchanger having a plurality of tubes for conveying fluid in'heat exchange with fluid flowing outside of said tubes comprising:

a tube sheet;

a plurality of tube supports, each of said tube sup- 6 ports comprising:

a plurality of radial bars extending outward along the radii of a circle, the plane of said circle being generally parallel to said tube sheet;

a plurality of circumferential bars supported on said radial bars, said circumferential bars each being on the circumference of one of a plurality of circles concentric to said first defined circle, each of said circumferential bars having a plurality of recessions spaced along the sides thereof so that facing recessions on adjacent circumferential bars can grasp a cooling tube between them;

said heat exchanger further comprising:

a plurality of tie rods extending through and bolted to said tube sheet and extending through and supporting said radial bars.

6. The heat exchanger defined in claim 5 further comprising a plurality of sleeves, each of said sleeves encircling one of said tie rods, some of said sleeves being positioned between and spacing said tube supports.

7. The heat exchanger defined in claim 6 further comprising a second tube sheet, said tie rods extending through and bolted to said second tube sheet, further comprising additional sleeves encircling said tie rods and positioned between said second tube sheet and the support closest thereto.

8. The heat exchanger defined in claim 6 further comprising other tube supports, said other tube supports comprising solid plates with holes through which said tubes and said tie rods pass, said other supports being positioned between said first defined tube supports and said tube sheet, additional sleeves encircling said tie rods, some of said additional sleeves being positioned between said other tube supports, some of said additional sleeves being positioned between the other tube support closest to said tube sheet and said tube sheet.

Claims

1. A tube support for a heat exchanger having a plurality of tubes for conveying fluid in heat exchange with fluid flowing outside of said tubes comprising: a plurality of radial bars extending outward along the radii of a circle; a plurality of circumferential bars supported on said radial bars, said circumferential bars each being on the circumference of one of a plurality of concentric circles and each having a plurality of recessions spaced along the sides thereof so that facing recessions on adjacent circumferential bars can grasp a cooling tube between them.

2. The tube support defined in claim 1 wherein the sides of adjacent circumferential bars do not abutt to thereby provide a flow space for said fluid flowing outside of said bars. 3. The tube support defined in claim 1 wherein said radial bars have spaced recessions along the sides thereof to engage said tubes.

5. A heat exchanger having a plurality of tubes for conveying fluid in heat exchange with fluid flowing outside of said tubes comprising: a tube sheet; a plurality of tube supports, each of said tube supports comprising: a plurality of radial bars extending outward along the radii of a circle, the plane of said circle being generally parallel to said tube sheet; a plurality of circumferential bars supported on said radial bars, said circumferential bars each being on the circumference of one of a plurality of circles concentric to said first defined circle, each of said circumferential bars having a plurality of recessions spaced along the sides thereof so that facing recessions on adjacent circumferential bars can grasp a cooling tube between them; said heat exchanger further comprising: a plurality of tie rods extending through and bolted to said tube sheet and extending through and supporting said radial bars.