CA1152876A

CA1152876A - Bladder type hydraulic expander

Info

Publication number: CA1152876A
Application number: CA000390195A
Authority: CA
Inventors: John A. Aikin; David A. Scott
Original assignee: Atomic Energy of Canada Ltd AECL
Current assignee: Atomic Energy of Canada Ltd AECL
Priority date: 1981-11-17
Filing date: 1981-11-17
Publication date: 1983-08-30

Abstract

TITLE
BLADDER TYPE HYDRAULIC EXPANDER

INVENTORS
J.A. Aikin D.A. Scott ABSTRACT OF THE DISCLOSURE

A tube expanding device which makes use of very high fluid pressure to expand the tube while isolating the fluid from the tube. The tube expander comprises a two piece mandrel having sealing rings adjacent each end and a tubular bladder which slides over the mandrel in sealing engagement with the sealing rings. The bladder is retained in position on the mandrel by shoulders adjacent the sealing rings. Fluid to expand the bladder is supplied through an inlet in the mandrel which connects with a radial passage.

Description

This invention relates to tube expanding devices and, more particularly, to a hydraulic tube expander.
In large steam generators it is desirable to expand the tubes against the walls of the bores in the tube supporting sheets prior to welding.
It is known to use hydraulic tube expanders for such purposes and one of thé principal advantages of hydraulically expanded joints between tubes and tube sheets is the relatively low residual stresses produced. However, the requirement that no contaminants, particularly water or oil used by the expander, contact the area to be seal welded, could not be met by existing hydraulic expanders~
In order to overcome the problem of contamination of the area to be welded, it was proposed to provide a bladder to retain the hydraulic fluids.
It is therefore an object Qf this invention to provide a - bladder-type hydraulic tube expander which isolates the working fluid.A further object of this invention is the provision of a bladder-type tube expander which is re-usable.
A further ob~ect of the invention is the provision of a tube expander capable of withstanding the high fluid pressures required.
Accordingly, the present invention provides a tube expanding device for swaging a tube against a bore in a tubesheet through the use of very high fluid pressure said expander comprising a ~andrel; a tubular bladder adapted to slide over said mandrel so as to have its ends engage said mandrel, and grooves in said mandrel, each said groove receiving an 0-ring adapted to be in sealing engagement with an adjacent portion of said bladder which extends over each said 0-ring, whereby said bladder isolates said fluid from said tube~
In the accompanying drawing which illustrates a preferred embodiment of the lnvention, Figure 1 is a sectional side elevational view of the bladder type hydraulic tube expander of this invention.

A

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~2--Figure 2 is a partly sectional side elevational view of the hydraulic tube expander of this invention in operative engagement with a tube expanded against a tube sheet.
Referring now in detail to the drawing in which a bladder-type hydraulic tube expander is shown generally at 10. The tube expander includes a body or mandrel 12 machined from high strength stainless steel.
The main portion 14 of the mandrel 12 has a threaded end 16 of reduced diameter which is received in a threaded bore 18 in an end por-tion 20 of the mandrel 12. Both the main portion 14 aand the end portion20 of the mandrel have annular grooves 22 and 24, respectively, to receive the 0-ring type sealing rings 26. The design of these annular grooves is critical. It has been found that the dimensions should be such as to give the sealing ring an initial squee~e of 20-25% when the tube expander is assembled. The inside and outside radii of the groove should be 0.02 inches which is 3 or 4 times greater than that of conven-tional designs, and the dimensions of the sealing ring groove should be no greater than those for conventional non-rolling seals. The larger radii reduce stress concentration and cutting of the sealing ring. The circular 0-rings 26 which should have a shore hardness of 90 or more are made of Buna M or natural rubber, to withstand operating pressures up to 40,000 psi.
An inlet port 30 in the main portion of the mandrel 12 adapted to be colmected to a source of high pressure fluid (not shown) communi-cates with a radial supply passage 32.
Prior to assembly of the mandrel 10, the portions 14 and 20 areinserted into a bladder 36 which is in the form o~ a cylindrical tube.
Shoulders 38 and 40 on the mandrel portions 14 and 20, respectively, retain the bladder 36 in place and the selaing rings 26 provide a seal between the bladder 36 and the mandrel 12. The bladder is made of a high yield strength plastic ccapable of returning to its original shape to permit withdrawal of the hydraulic expander 10 from the tube 44. It has been found that suitable materials for the bladder 36 are a superpoly-amide or nylon sold under the trademark Ertalon 66SA or polyamides sold under the trademarks Dalron and Jaytron. Ertalon 66SA is a trademark of 28'7~

Firma Robert Tavernier, Belgium; and Jaytron is a trademark owned by Johnson Industrial Products, Toronto, Canada.
The asse~bled bladder-type hydraulic expander shown in figure 2 is in place in a tube 44 supported by a tube sheet 46 as it would appear after the tube 44 has been expanded against the tube sheet 46.
Fluid under very high pressure entering through the passages 30 and 32 causes the bladder 36 to expand against the tube wall 44. Unlike the existing 0-ring type hydraulic, the working fluid i~ isolated from the tube 44 by the bladder 12 and is effectively retained by the two 0-rings 26.

Claims

CLAIMS:

1. A tube expanding device for swaging a tube against a bore in a tubesheet through the use of very high fluid pressure said expander comprising a mandrel, a tubular bladder adapted to slide over said mandrel so as to have its ends engage said mandrel, and grooves in said mandrel, each said groove receiving an O-ring adapted to be in sealing engagement with an adjacent portion of said bladder which extends over each said O-ring, whereby said bladder isolates said fluid from said tube.

2. A tube expanding device for swaging a tube against a bore of a plate through the use of very high fluid pressure, said expander comprising a mandrel having a removable end portion; a tubular bladder adapted to slide over said mandrel so as to have its ends engage shoulders on said mandrel and said end portion, grooves in said mandrel and said end portion adjacent said shoulders, each said groove receiving an O-ring adapted to be in sealing engagement with an adjacent portion of said tubular bladder which extends over each said O-ring, and inlet means for supplying fluid under pressure between said mandrel and said bladder.

3. A tube expanding device as claimed in claim 2 wherein said yield strength plastic capable of returning to its original shape after being subjected to said fluid pressure.