Note: Descriptions are shown in the official language in which they were submitted.
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: This invention is concerned with a method of attach-
ment of an end-piece to a tubular element and is more
. especially applicable to the attachmen-t of a metallic end-
piece to a tubular filter of ceramic material.
- In order to carry out the attachment of a tubular
filter element and especially an element of ceramic material
to a filter support of any predetermined type, it is an
advantage to provide the filter with an end-piece which is
preferably metallic and which can subsequently be readily
secured by welding, brazing or tube-expanding in the filter
: support. This operation gives rise to difficulties, however,
since the joint formed between the tubular filter 2nd the
end-piece must on the one hand be mechanically sound and on
the other hand ensure suitable leak-tightness at the level of
;- the joint. In particular, it is absolutely necessary to
ensure that this joint does not have any flaws such as cracks
or open porosities which would be liable to modify the
overall permeability of the filter employed.
The method in accordance with the present invention
make~ i~ possible to connect a tubular element and especially
.: a ~lbular filter to an end~piece by means of a joint having
high mechanical strength, a very high degree o~ leak~tiyhtness
and excellent corrosion resi.stance, especially with respect
to ~luorine derivativesO This methol is therefore of great
value for securlng to a support a composite tubu~ar filter
element o~ ceramic material and of small thickness, a filter
o~ this type being intended to be employed in particular ior
the separation of uranium isotopes by gaseous ~i~fusion and
~or the separation of hydrocarbons in the petrochemical
.30 industryD
To this end, the method under consideration
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essentially consists in depositing a layer of a ceramic
product at the end portion of the tubular element by spray-
coating in the hot state and in bonding the metallic end-
piece to said end portion by spraying a ceramic or metallic
substance in the hot state.
; In order to obtain perf~ct leak-tightness at the
- level of the joint formed between the filter and the end-
piece, the entire end portion of the filter must be coated
with a compact, homogeneous and impermeable lay0r of ceramic
material. In other words, the internal end portion, the
external end portion and the end face of the filter must be
coated with the ceramic layer. Deposition of said layer of
ceramic product and bonding of the end~piece can be carriea
out in one or a number of steps. Pre~erably, the determina
tion of the number of operations of deposition and/or of
bonding is selected as a function of :
- the fragility of the filtert which must not be
subjected to any thermal shock or be liable as a con~equence
:.,
;~ to undergo impair~ent of its mechanical or permeametric
- 20 characteristics~
- the nature and thickness of the spray~coatings for
- deposition and/or bonding which determine the spraying means
to be adopted~ the angle and the spraying distance a~d the
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,- gaseous mixture~ to be employed,
- the permeametric characteristics of the filter and
end-piece assemblies obtained which must not be lower in
- value than the characteristics of uncoated filters.
;~ In orler to carry out the spraying of the ceramic
prod1ct and of the c~ramic or metallic bonding substancer :Lt
,30 ~ is possible for example to adopt a plasma-spray torch or a
flame-spray torch~ The ceramic product employed at the time
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of deposition on the filter can be the same as the ceramic
substance employed for bonding the metallic end-pieceO Simi-
larly, the spraying means employed can be the same or the
formation of the deposit and for the bonding operation.
Finally and in accordance with an important feature, both the
filter and the filter and end-piece assembly are subjected
to a movement of rotation during the spraying of the layer of
ceramic product and during the bonding of the end-piece.
Among the ceramic products and the ceramic substances
employea, it is possible in particular to choose from alumina~
zirconia, manganese dioxide, titanium oxide, calcium fluoride,
magnesium oxide, the mixed oxides such as A1203, MgO, the
aluminates of metals selected from magnesium, nickel, cobalt
and chromium. As can readily be understood, these products
and substances are selected as a function of the end products
to be obtained.
A number of different examples relating to the
practical application of the method of attachment o~ a tubular
-~ end-piece in aGcordance with the invention are described
hereinafter without an~ limitation ~einy implied, reference
being made to the accompanying diagrammatic figures, in which :
- Fig. 1 illustrates the practical application oE
the first step of the method i
Fig. 2 is a sectional view of one end of a composite
tubular filter coated with a layer of ceramic product ,
- Fig. 3 illustrates the practical application of the
second step of the method ;
` - Fig~ 4 is a sectional view of the end-piece which
is se~ured to the composite tubular filter.
The components illustrated in the drawings are
limited solely to those which are necessary in order to gain
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'- a clear understanding of the invention and are designated by
the same reference numerals in each figure.
~ Fig. 1 shows a macroporous cylindrical tube l which
'' is formed of ceramic material and the internal sur~ace of which
is lined with a microporous lay~r 2, said tube being open at
the end on which it is desired to fix a tubular end piece.
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Fig. 1 also illustrates the tube 1 which is fitted internally
in the vicinity of said open end with a removable shield 3
preferably formed of flexible material such as rubber, and
r 10 externally with a screen 5 through which the tubular element
passes. Said shield and said screen prevent a ceramic product
which is sprayed onto the end of th~ tube 1 by means of spray~
torches 6`from being depositel over an exce~si~e area o~ the
tube 1 and of the microporous layer 2 of this latter.
In Fig. 2, the -tube 1 provided with the microporous
layer 2 is illustrated in the form in which it is obtained
after spraying of the ceramic product. Said product thus
orms a surface coating~ the external portion of which is shown
at 7, the internal portion at 4 and the end face at 8~
In Fign 3, the metallic end-piece 9 to be secured to
the tube 1 is placed against the end portion of th~ ~ube 1 and
of the layer 2 to which the coatings 4~ 7 and 8 h~ve p~eviou~
ly be~n applied a~ de~cribed in the foregoin~. rrorches 6'
whlch are identical with or di~ferent from the torche~ 6
then spray a ceramic or'metallic substance onto the assembly
thus ~ormed, with'the'result that the components of the
assen~ly are thus bonded' together.
Finally, 'it is apparent that the tube 1 as illus~
trated in FigO 4 is bonded to the metallic en~ piece ~ by
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` 30" means o~ the layer 10 of sprayed substance obtained in
~' accordance wlth -the'me~hod'descr'ibed in the foregoing.
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; A few explanatory details in regard to the practical
application of the method according to the invention will be
given below by way of example.
~ n alumina coating 0.3 mm in thickness is sprayed in
900 passes by means of flame spray torches on a tubular
~ilter of ceramic material 20 mm in diameter and 500 mm in
length which rotates about its own axis at a speed of 3.3
revolutions per second. The alumina spray-coating passes are
; separated by stationary periods each lasting 1 second during
which the filter is allowed to cOOlr A metallic end-piece is
then fitted in position against said filter. Rotational
i motion is resumed and an alumina coating 0.6 mm in thickness
is then again deposited by spraying in 1800 passes by means
of the same ~lame-spray guns~ In this second step, a
stationary period o~ 1 second duration is also observed between
each spray-coating pass. The assembly thus ob~ained is
strictly leak-tight under an internal pressure o~ 2 bar and
has a tensile strength which is highe~ than 900 newton. 5ince
the cerami~-ceramic bond thus formed is homogeneous, it does
not apply any binding stress and can be employed to useful
purpose in installations in which temperatures ar~ liable to
rise to approxlmately 600C whereas an aluminum-aluminum bond
cannot be employed at temperatures above 200C.
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