CA2155271C

CA2155271C - Tube extractor

Info

Publication number: CA2155271C
Application number: CA 2155271
Authority: CA
Inventors: Thomas Waring
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1995-05-26
Filing date: 1995-08-02
Publication date: 2000-03-07
Anticipated expiration: 2015-08-02
Also published as: CA2155271A1

Abstract

A tube extractor includes a hardened 360 expandable cone which is expandable inside the end of a tube. A
cylindrical stand off spaced from the expandable cone can be moved with respect to the expandable cone by rotating and extractor nut to extract the tube.

Description

. . ~ 215~~~~.

TUBE EXTRACTOR
BACKGROUND OF THE INVEN~ON
1. FIELD OF THE INVENTION
The present invention relates in general to tools for use in and around nuclear pressure vessels or s' pressure vessels, and in particular to a new and useful tube extractor for removing tubes from a nuclear vessel, moderator or generator tube sheet.

2 . DESCRIPTION OF THE RELATED ART
Current methods for removing tubes which have been tack expanded into a tube sheet of a nuclear pressure vessels or pressure vessels, normally result in extensive damage to the tube or the total loss of the tube.
In one method, the inside diameter (I.D.) of the tube is threaded using a suitably sized fine thread tap to a depth of about 1/2~~. A threaded mandrel is threaded into the tube and a draw bolt is used to extract the tube from the tube sheet.
According to a second method, the tack expanded portion of the tube is machined, leaving a very thin wall inside the tube sheet. This relieves the compression of the tube in the tube sheet, enabling the tube to be _ . 215571 removed.
Still a third method involves driving a tube back through the tube sheet using a suitable drift. This method is totally unacceptable, however, because of the potential risk of damaging the tube sheet.
SUMMARY OF THE INVENTION y 1 The invention is a hardened 360° barb shaped expandable cone mounted on a threaded draw bolt. The cone expands to grip the inside diameter (I.D.) of the tube very near the end of the tube. After use the mandrel of the cone leaves a very slight ring-shaped indentation which is fused when the tube is seal welded upon reuse.
There are several advantages to the invention over other currently used methods.
The invention does very little damage to the tube end which makes the tube reusable. This is important when new tubes are being installed and it becomes necessary to relocate a tube for whatever reason. The invention is also extremely portable, weighing less than 1 lb., requires no machinery to install and may be used in very confined spaces. It is very simple by design, making it cheap to produce or giving it the potential to be produced very quickly so as not to hold up production in an emergency situation. It is very quick to use, requiring only a minute to remove a tube.
Any of the current methods in use typically damage the tube significantly, require prior machining of the tube end and require a minimum of 10 to 15 minutes per tube end.
Accordingly, another object of the present invention is to provide a tube extractor which is simple in design, rugged in construction and economical to manufacture.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure.
For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawing and descriptive matter in which a preferred embodiment of the invention is illustrated.
BRIEF DESCRIPTION OF THE DRAWI~~G
The single figure in the drawing is a perspective view of the tube extractor of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the drawing in particular, the invention embodied therein comprises a tube extractor, generally designated 10 having an end 12 for insertion into a tube, and an opposite end 14 which extends from the end of the tube during use.
An expandable cone 8 is hardened to resist wear and to allow it to grip the I.D, of the tube. Due to its ~~n°
gripping feature, it can be positioned very close to the end of the tube without fear of ripping out during the extraction process. Depending on how tight the tube is, the mandrel 8a of the cone 8 may be placed only 1/16" into the front of the tube end. The cylindrical mandrel leaves a very slight ring-shaped indention very close to the tube end which would be fused when the tube is seal welded, if the tube was required to be reused with no reduction.
In use, the expandable cone 8 is positioned with its sharp cone shaped section 8b just inside of the tube. An expansion cone 7 is advanced by turning an expansion nut 6 with a suitable wrench, into the expandable cone 8. On initial contact of the cone with the tube I . D. , a further 1/4 to ~ turn is all that is required to grip the tube. A
cylindrical stand off 4 is engaged against the tube sheet using a knurled extractor nut 3. A view port 5 may be positioned at any convenient orientation such that the tube may be viewed during the extraction process.
To extract the tube, one tightens the extractor nut 3 using a suitable wrench. A second wrench may be used on a jamb nut 1 if the assembly rotates during the extraction process. Cone 8 is slotted at 8c and made of hardened metal, but expands as cone 7 is forced into the hollow open end of cone 8. A retention nut 9 on the draw bolt at an end of the expandable cone 8 is provided.
The tube extractor 10 is extremely small and compact and requires no prior machining of the tube in order to make it work. It can be used in small inaccessible areas such as the plenum of a steam generator at the tube sheet conveniently.
It is light and portable enabling it to be carried into confined areas without risk of damage to surrounding finished surfaces, as may be the case if heavy, awkward machinery were to be used.
In the event a tube needs to be cut prior to extraction, a device such as that described in U.S. Patent No. 5,077,456 may be employed to cut the tube.
While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

Claims

1. A tube extractor for removing a tube from a steam generator tube sheet, the tubes having an open end and an inside diameter, comprising:
an expandable cone having a hollow open end with an outside sharp coned shaped section for engaging the inside diameter of a tube near the open end of the tube;
an expansion cone positioned in the sharp coned shaped section of the expandable cone;
an expansion nut rotatable to advance the expansion cone into the expandable cone for expanding the expandable cone;
a cylindrical stand off connected to and spaced from the expandable cone for engaging against the tube sheet when the expandable cone is in the end of the tube;
an extractor nut for moving the stand off with respect to the expandable cone for extracting the tube from the tube sheet; and a draw bolt for carrying the extractor nut, the stand off, the expansion nut, the expansion cone and the expandable cone.

2. A tube extractor according to claim l, wherein the expandable cone comprises a cylindrical mandrel and a conical portion connected to cylindrical mandrel.

3. A tube extractor according to claim 2, wherein the expandable cone is slotted and is made of hardened metal.

4. A tube extractor according to claim 3, including a jamb nut connected to an end of the draw bolt and spaced from the extractor nut.

5. A tube extractor accordingly to claim 1, wherein the cylindrical stand off includes a view window for viewing the end of the tube into which the expandable cone is extended.

6. A tube extractor according to claim 5, including a retention nut on the draw bolt at an end of the expandable cone which is remote from the expansion cone.