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EXPERIENCE IN WELDING OF EXTRA PURE HYDROGEN FILTERS AND
CATALYTIC REACTORS DESIGN
POGREBISKY DAVID
Jerusalem
Annotation. It is considered welding experience in filters for extra pure hydrogen purification
(EPHy) producing and catalytic reactors design in the former USSR. It is shown that microplasma
welding of them has some advantages as compared with alternative welding methods and brazing. In
the majority cases such devices made of very thin palladium-based foils are more perspective than
made of thin tubes of the similar materials. In order to obtain the best quality of welded joints many
research and investigations have been made, and they permited to avoid porosity, cracks and some
other defects in welds. At the same time the another problem was solved - what constructional
materials are suitable for filtering elements (FE) and how to weld them to very thin palladium foils. In
cooperation with many organizations the Paton Welding Institute developed various original welded
FE structures that were introduced to some plants and gave positive results in their exploitation It is a
pity that due to the former USSR collapse this work has not been finished, but the obtained
experience can be used by followers of this important field in the modern technologies development.
It may permit to improve quality of chemical, metallurgical, pipe, electronic, food, pharmaceutical and
other branches of industries. Our unique results of all welded extra pure hydrogen FE and catalytic
reactors creating also opens good perspectives for hydrogen energetics and economy development,
design improved fuel elements, catalityc reactors, producing high pure hydrogen isotopes, etc.
Keywords: Hydrogen energetics, palladium, palladium alloys, welding of palladium, extra
pure hydrogen (EPHy), hydrogen filters welding, palladium membrane alloys, filtering elements (FE),
all welded FE, palladium foils welding, microplasma welding, hydrogen membrane technology
(HyMT), palladium based foils, plate FE with 0,02 - 0,07 mm Pd-foil thick, foil edge weld model, edge
weld modernization, filters for extra pure hydrogen producing, edge weld configuration, welding of
noble metals, precision welding sets, edge weld properties, weld capillary tubes, thin metals welding,
foils welding, fuel elements welding, catalytic reactors welding, optimal impulse mode, thin
constructions welding, modular-inverter welder, welding of palladium foil, defects of edge welds, weld
quality, welding .
The size and structure of this report gives possiblities to touch only the main these
problems questions, whose part was not in general considered before. Anybody, who wants
to know more about this material and its author, can look through the site
www.actualweld.com, and we shall save its references numeration here, using the same
corresponding marking, but with the additional signs "R", as compared with new references
to these report.
After the former USSR collapse many interesting and perspective elaborations,
especially that were began with the former United Republics participation, fell into decay. It
is a pity, but elaborations in the field of extra pure hydrogen filters welding, this hydrogen
usage in many important purposes, which were successfully started and improved many
years ago, have been stopped. The level of fulfilled and planning works was such high, that
the special the USSR Comission of Extra Pure Hydrogen (EPHy), consisting nearly 30
members, was organized. It included representatives of specialists of the various branches:
welding, thermotechnics, metallurgy, chemistry, electronics. All together a lot of scientists,
engineers, designers, managers, production workers and technicians of many institutes,
plants and other organizatios worked under the given problem, but the chief of the
mentioned above comission - Yushchenko K. (Ukraine Academician now) as well as this
comission secretary (the author of this report) worked at the Paton Welding Institute, where
Yushchenko K. works still now as the vice-director. After these works stopping we have not
this comission now, but have to underline that much later of this comission start the National
Hydrogen Association was organized and began as catalyst for the hydrogen economy and
technologies development in the USA [1]. It is a good example for Russia and other
countries which want to improve their life and technologies.
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The first Soviet apparatuses for extra pure hydrogen producing were brazed from
palladium based tubes with diameter 2,5 mm and wall thick 0,1 0,12mm. As a filler material
were used alloys at the base of silver, and the quality of brazed joints was very low. Many
organizations began to search other ways of such apparatuses creating. As the best way it
was choosed the project of palladium foils usage - instead of tubes - and using welding as
a method of foils joining. Among alternative welding methods the microplasma method
looks more attractive, and the Paton Welding Institute began to work in this direction being
in cooperation with: The State Institute of Nitrogen Production, The Novomoskovsk
Chemical Complex Plant, The Sverdlovsk (now Ekaterinburg Plant of Color Metals
Treatment, The State Institute of Rare Metals, The State Institute of Glass Fibres and Glass
Plastics (now SUPERMETAL), Institute of Metallurgical Thermo Technique, Polytechnic
Institute (now University) of Sverdlovsk (Ekaterinburg), The Krasnoiarsk Plant of Color
Metals,The Institute of Vacuum Technique and others.
Here we have to mention the scientists, engineers and specialists that helped us to
receive some interesting results, sometimes unique, in all welded hydrogen filters and
filtering elements design and producing, as well as in important research and investigations:
K.Khrenov, A.Rodina, A.Krygjnenko, G.Leskov, L.Mironov, V.Lebedev,A.Rossoshinsky,
V.Gvozdecky, D.Shnaider, D.Dudko, P.Geld, E.Rytvin, I.Kirnos, N.Timofeev, A.Tolchinsky,
V.Skliarevich, U.Baichtok,V. Makedonsky, V.Komkov, N.Kaliniuk, O.Smiyan, V.Vasiliev,
E.Serduk, A.Gulak, N.Slotincev, A.Furmanov, N.Doronicheva, D.Tykochinsky, U.Popovcev,
G.Kagan, L.Boltai, B.Graiver, A.Ivonin, G.Kylikov, E.Cherepenin, S.Dzubenko, E.Gusev, M.
Sosna, L. Potapenko, V.Goloskokv, V.Golttsov, V.Griaznov, A.Mischenko, N.Soldatenkov,
N.Roshan, A.Pinsker, S.Kykyi, C.Kyrymchina, U.Ushkov, U. Tatarinov, S.Grinblat, V.
Nasonov and other.
There are a lot of welding problems that we solved during our fruitful work.
We developed the model of edge weld joint formation (Fig.1), and it was shown that
usually radius of such weld has to be more than metal thickness on 25-75% [5R]. It was
also considered such weld formations in conditions of gaps between edges [20R26R]
(Fig.1d).
Fig. 1. Weld model of edge foil joint (1 - edges to be welded, 2 - fixing and cooling device, 3
- welding arc, g -gap):
a) liquid metal redistristribution in the weld while ideal edges assembling; b) view of a weld;
c) pronounced scaled structure formation; d) the principle of edges metal assembling while
gaps beetween them
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There were studied some peculiarities of thin materials welding -without a filler
material usage, especially in pulse mode, when each weld is a family of many-many the socalled identical points-spots, produced by consecutive carrying out of welding current
pulces.
Possibilities of welding with large gaps have been proved and realized, There are
created the principles of correspondence equipment building which permit to make edge (or
flanged butt) welds when gaps up to 200% of material thickness and edges displacementsis
nearly 300%. The minimal d raising of edges - under heat deflection and fixing rigging - has
to at the range of 3-4 and 5-7 material thick (for continious and pulse mode accordingly). In
case of large errors sometimes may be equal up to 12-14 thicknesses of material, but we
have to use a special equipment developped with our participation. It gave real possibility to
make edge welded joint of foils devided by mesh gasket (Fig.2.)
Fig.2. Edge welded joint of foils devided by mesh gasket
Our experiments permits to choose the best shielding gas for palladum foils welding
- Ar +4-6% H2 and to understand that impulse mode much better than continious one (Fig.
3). We see that the latter regime give not good structure of weld - with big dendrite grains
and porosity (Fig.4.)
Fig.3. Palladium base foil (0,1 mm thick) welded in continuous (left) and pulse (right)
modes
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Fig.4. Further comparison of palladium foils welds made in continuous and pulse modes
(top - horizontal cross section made in the plate that is perpendicular to the edges; left down
- welds made with different gaps between edges)
We can avoid porosity of joins, if to weld with step s equal nearly 45 % of a single
welded spot (welfing pool) l length, but sometimes there are cracks in foils welds.
Configuration and location of cracks could be classificated as some, placed directly in weld
metal - across (or under angles up to 45 degrees) to the welding direction, and another
some that were located in the the so-called zone of foils fusing (border between base
material and weld metal actually). The first of them appeared immediately after welding or a
little bit later. We suggested, that they were mainly affected by thermal cycles of the welded
joint. So, we decided to research these cycles, using miniature thermcouples made by us
from the material that comes to hand during our work with palladium-based foils. Among
them we found some with thicknesses 0,045-0,05 mm, made of alloys Pd-10Ru and Pd40Ag, which had to give a good thermo-electric signal during experiments. After these foils
microplasma joining - by welds with minimal sizes - we cut them across to the welding line
on the strips with width nearly 0,5 mm and obtained the needed thermocouples. Their
calibration were made by melted salts of NaHSO4, K2SO4, KCl, NCl and BaCl2.
In order to understand these cracks reasons we made special thermocouples and
experiments of thermocycles measurement according to the Fig.5.
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Fig.5. Thermocouples location while research the cycles of heating and cooling of HAZ in
the temperature interval between 400 and 800 degrees: 1 - foil to be welded; 2 thermocouple; 3 - fixing and heating device; 4 - edge weld, d raising of edges - under heat
deflection and fixing rigging , Q - welding arc; Vw - direction of welding; m, n - distances
between thermocouples. In our case there were: m = 5 mm, n = 0,2 mm and d= 1,5 mm
As an object for research we use the foil 0,1 mm thick of alloy PdAgPt-15-5. The
results of our investigations are shown at the Fig.6.
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Fig. 6. HAZ thermal cycles of edge joint of the foil (PdAgPt-15-5) 0,1 mm thick while pulse
microplasma welding
Analysis of the given thermal cycles gave the conclusion - we have to weld the
appointed foil in conditions when the speed of heating in the temperature interval 400-800
degrees no more than 2000-3000 deg/s and line energy is nearly 16-24 dj/mm.
There was another problem - what materials are suitable for welding with palladium
foils. We made formulation of such materials properties demand: [18R,9 R]:
-hydrogen resistance;
-similar thermal expansion as compared with palladium alloys;
-environment stability;
-weldability with palladium alloys;
-cycles of heat treatment correspondence (if it needs afer welding fulfilment);
-thermal stability and high temperature strength (for apparatuses working at elevated
temperatures);
-low saturation by gases and absence ability to adsorb any component of a workingclass environment;
-absence of contact fusion effect with palladium alloys (also for apparatuses working
at elevated temperatures).
Using some of choosed constructional materials, it was reached a success in high
quality of welded joints with palladium foils 0,02 - 0,05 mm thick (Fig.7). The method of
fusion welding of palladium and its alloys with such materials has been worked up too
[16R].
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Fig.7. Microstructure photos of some heterogeneous welded joints of palladium foils (more
white elements) with the constructional materials (imprints while measurement of metal
hardness are visible)
With heterogeneous joints usage, made by automatic microplasma welding, some
FE have been created, and they together with some their fragments are shown at the Fig.8.
It has to be noted that the bellow type filtering element had such diameters: external - 93
mm, inner - 30, while the simplest disc FE (it is shown in the lower right corner) had the
palladium foil membrane with diameter 23 mm, but indeed such small filters have
successfully worked under about 500 degrees temperature and 300 MPa pressure in
ammonia atmosphere during a long time - at the Novomoskovsk Chemical Complex Plant.
Fig.8. FE made by automatic microplasma welding
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Some other FE stuctures and their arrangement variants are given at the Fig.9. Here
- left and right - are shown the filtering elements of bag type fixed in tube lattice. At the
center the sketch of last model of the FE flag type is given, which was protected by
European Patent [54R, 55R]. At the lower center it is shown the complect of disc FE made
of the palladium foil 002 mm thick.
Fig.9. Some other structures of FE and their arrangement variants
The collection of various FE made under our guidance in the Dneprodzerzginsk
Branch of the State Institute of the Nitrogen Industry is shown at the picture 10
Fig.10. The collection of various FE
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We have to note that FE made of palladium tubes by powder metallurgy methods all
the same demand microplasma welding. It needed for capillary tubes free ends closing. The
proposed by us cheap, safe and simple microplasma set [4] may be very suitable for these
purposes as well as for connection the bag type filtering elements with drainage tube, using
welding-braizing process with special filler materials.
Depending on the configuration, sizes and conditions of operation, each filtering
element provides an output of ten to many hundreds of liters of extra pure hydrogen per
hour. Now there are such main types of FE made of foil (Fig 11.): a) flanged type - onesided (left) and double-sided (right); b) disc type; c) bellow type; d) bag and e) flag types.
Fig.11. Classification of developed with our participation FE made of foil: a) flanged type one-sided (left) and double-sided (right); b) disc type; c) bellow type; d) bag and e) flag
types
Alike to disk filtering element may be developed catalytic reactors with hydrogenpermeable membrane wall which were proposed for the first time in the Russian A.V.
Topchiev Institute of Petroleum Syntheses and are based on tho processes that take place
in one reactor which makes quick preparation of cyclohexanone from phenol. For these
purposes the metal memrane is preferable, consisting, for example, Pd-Ru alloys. The
proposed by us (together with above mentioned institute) the new catalytic reactor structure
is shown (in the main cross section) at the Fig.12. We see that it was used the principle of
double-sided flange FE building.
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Fig.12. Catalytic reactor cross section
Below we shall show some another welded examples which illustrate good
possibilities of microplasma using for different FE structures producing (Fig.13., and Fig.
14.)
Fig.13. Two palladium foils (0,1 mm thick) welded without gaskets, but with uniform gaps
between foils ecceeding their thickness
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Fig.14. Four palladium foils (0,1 mm thick) welded without gaps
It has to be noted that during transportation (in tubes and pipe systems) the extra
pure hydrogen essentially loses its cleanliness and activity. So, when it reaches a so-called
"reacting" zone (for instance, where germanium monocrystal is growing) this hydrogen
effectivity falls perceptibly. At the same time it has been exactly established that when using
extra pure hydrogen immediately - after its producing - this hydrogen, being in so-called
"atomic" condition, acts with tremendous activity as opposed to the so-called "molecular"
condition. For example, the "atomic" extra pure hydrogen can produce very pure metals
directly from their oxides. And because of the possibility of working under heightened
temperatures, small sizes and good flexibility - to productivity - some types of the mentioned
above welded filters may be placed and used directly in the zone of super hydrogen
consumption (growing of Ge or Si monocrystals, metal oxides or ores restoration for such
companies like Intel).
That is why we suggest that it's reasonable to use a small business for compact and
complete all welded hydrogen filters producing. This business may be organized, for
example, in Moscow, Ekaterinburg, Krasnoiarsk, Jerusalem and so on. Hope that such
question may be discussed soon.
Thus we proposed some new principles of perspective filtering elements creation,
including some with palladium foils 0,02-0,07 mm thick usage. It is a pity, but they were
realized only partly. For example, the ideas of realization of edge weld modernization
haven't been enough used in practice. We did not reach visible output of modular-inverter
welders with the special shape of impulse, our experience was not transferred to welding of
fuel elemets and design of industrial catalityc reactors.
However we hope, that in the frame of works connected with hydrogen membrane
technologies (HMT) [5], after workingout and design of new filltering elements our
experience in the field of noble metals would be needed and realized in welding of new
palladium foils as ,generally, in palladium welding. There are good reasonsfor it , because
the Buykov's Russian Institute of Metallurgy worked out the perspective palladium alloys of
systems Pd-Y and Pd-In-Ru, that do not contain silver [6].
We hope that new equipment for extra pure hydrogen producing would be designed
and widely used in all branches of industry using proposed by us welds optimization and
modernization. And Russia will sell abroad, instead of tons of palladium, tens and hundreds
modern and high effective hydrogen apparatuses, catalytic reactors whose price will be
morethan incomes that will give a sale of irrevocable and unique palladium.
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REFERENCES
1. www.hydrogenassociation.org
2. The USSR invention N. 866889, Method of Thin Sheet Materials Welding.
3. European Patent Application 1 184 125 A1. Filed: 12 July 2001 - Italy RM200412, 25 July 2000 Publ: 6 Mar.2002.
4. Погребиский Д.М. Микроплазменный аппарат для сварки изделий из благородных
металлов (зубопротезирования и медико-биологических целей), Материалы 1-й
международной конференции "Производство оборудования из благородных металлов и
его применение в химической и силикатной промышленности" Берлин (Германия), 23-27
мая 2005 года, ISBN 5-93613-033-9, Москва.
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Германия, сентябрь 2006 года. М. АСМИ, 2007 с.с. 18-26.
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области водородной мембранной технологии. Материалы Второй международной
конференции - БЕРЛИН - П'М 2006. Платиновые металлы в современной индустрии
водородной энергетике и в сферах жизнеобеспечения будущего. Берлин, Германия,
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