Note: Descriptions are shown in the official language in which they were submitted.
Scarification
Multi-Flame Burner and Method for Heating a Work lee
The invention relates to a multi-flame burner with burner heads and
accompanying
connection pipes, which are set up to generate at least one burner flame
directed along
a respective flame axis when supplied with a fuel, as wail as to a method for
preheating
a workplace, in particular a pipe or large-diameter pipe, with a corresponding
multi-
flame burner.
Prior Art
Workplaces must be preheated In a very wide range of material handling and
manufacturing processes. The present invention here draws reference first and
foremost to preheating in welding operations. However, the invention can
basically also
be used in other methods In which Introducing heat by means of flames Is
desired.
In known welding processes, the workpieces to be welded are preheated for
various
reasons. The primary danger associated with a lack of preheating Iles In the
so-called
hydrogen embrittlement in the heat affected zone. In addition, transformable
steels
there tend to exhibit an increased hardness at elevated cooling rates of the
kind
encountered without preheating. This yields an Increased tendency toward cold
clack
formation In the joining region of the workplace. For example, these
disadvantages
become even greater while welding pipes with an increasing pipe diameter. For
this
reason, preparing large-diameter pipes via preheating for a subsequent welding
operation represents a preferred application for the present invention.
The achievable hardness, and hence the danger of cold cracks, here essentially
depends on the thickness of the workplace to be machined, two- or three-
dimensional
heat dissipation, present alloy elements and their contents, the respective
heat
introduced In the welding operation and/or the component temperature. The
tatter can
be influenced by preheating. Preheating reduces the cooling rate of the seam
region.
and Improves hydrogen effusion. In addition, It has a favorable effect on the
residual
welding stress state of the welded joint.
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The necessary preheating temperature can be respectively ascertained, and the
heat
to be introduced and/or the use of respective preheating device can be
determined
based hereupon. In particular the basic tenacity of the material, its wall
thickness, the
seam shape, the used welding technique and welding speed are to be considered
when determining the preheating temperature.
Preheating is basically required at processing temperatures of under 5 C and
when
specific thickness limits are exceeded (especially for high-strength steels).
For
example, the preheating temperature measures 80 to 200 C.
As a rule, workplaces are preheated prior to welding preferably using multi-
ffame
burners, which for masons explained in greater detail below are operated with
acetylene and oxygen-containing fuel mixtures or acetylene and compressed air-
containing fuel mixtures, for example. Preheating takes place to prepare a
region
/5 proximate to the welded seam on the workplace (e.g., pipe or large-
diameter pipe) for
Introducing a welded seam in this preheated region, which is hence
already,wann at
the start of the welding process (warm here means at least warmer than the
ambient
air).
In 'particular when preheating large-diameter pipes, concentrated heat must be
Introduced into the region close to the welded seam, without melting the
workplace
surface and leaving behind residual moisture from the exhaust gas of the
flame.
However, the large amount of hot exhaust gases that arises given a
concentrated
Introduction of heat places a burden on the burner itself, depending on burner
configuration. This can end up thermally damaging the used burner heads. This
applies
in particular given improper operation and adjustment. Appropriate safety
precautions
are expensive.
In this conjunction, pipes with a diameter ranging from 1 to 12 meters are
designated
as large-diameter pipes.
Therefore, the need exists for improved ways of heating workplaces, in
particular pipes
and large-diameter pipes, which do not exhibit these disadvantages and can be
safely
operated.
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Disclosure of the Invention
Against this backdrop, the invention proposes a multi-Rama burner with burner
heads
and accompanying connection pipes, which are set up to generate at least one
burner
flame directed along a respective flame axis when supplied with a fuel, as
well as a
method for preheating a workplace, in particular a pipe or large-diameter
pipe, with the
use of a corresponding multi-flame burner having the features described below.
Ma consequence, the set object is achieved by offsetting at feast half of the
connection pipe, so that the flame axes of respectively adjacent burner heads
am
Inclined relative to each other.
While the Invention is described primarily with regard to preheating pipes or
large-
diameter pipes, it Is not limited thereto, since it was found that the present
invention
can be used to special advantage for preheating Individual components or
component
groups even in large container construction In general
The multi-flame burner Is preferably configured in such a way that all
connection pipes
are offset In design.
It is especially preferred that the multi-flame burner be configured in such a
way that
' the offset connection pipes exhibit an offset angle of 30 to 60 ,
preferably of approx.
45 .
It Is particularly advantageous for the mufti-flame burner to be characterized
by the fact
that the connection pipes be pivoted with a respective connection nozzle by
way of a
screw joint, wherein the respective other end of the connection nozzles is
secured to a
shared feed line, and can be supplied with the fuel through the shared feed
line.
In an advantageous further development of the Invention, the burner heads are
provided in at least two groups (A and B) of burner heads, wherein the burner
heads of
at least one first group (A) am each =angled alternately to the burner heads
of at least
one other group (B), and the flame axes of the burner heads of at least the
first group
are inclined relative to the flame axes of the burner heads clot least the one
other
group.
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The burner heads within each group are best arranged In the same direction or
parallel
to each other.
It can also be advantageous to provide the burner heads in at least two
groups,
wherein the burner heads of the at least two groups each are alternately
arranged, and
the flame axes of the burner heads in at least one or each group each deviate
in
relation to the flame axes of at least one or each other group. For example,
the flame
axes within each group can be arranged In parallel. This makes serial
production
especially easy.
In an advantageous further development of the invention, the burner heads each
exhibit flame axes, which 13113 axially and/or radially inclined in relation
to a
perpendicular on a center line of the feed line, preferably respectively
adjacent burner
heads Inclined by an angle of 5 to 45 relative to each other.
A corresponding multi-flame burner is preferably configured in such a way that
the
flame axes of the adjacent burner heads are each skewed In relation to each
other. For
example, they can be InclIned axially or radially to the perpendicular on the
center line
by an angle of 5 to 45 . Among other factors, the respectively selected angles
also
depend on the requirements of the respective heating process. A tighter angle
Is
required in particular given the necessity of extensive local heating. Larger
angles are
possible if the goal Is to discharge the generated exhaust gases in an
especially
effective manner.
The multi-flame burner best exhibits a gas supply device set up to supply the
multi-
flame burner with at least one gaseous fuel, wherein the gas supply device Is
preferably set up to supply the multi-flame burner with an acetylene-
containing fuel
mixture, especially preferably an acetylene-(compressed) air-mixture or an
acetylene-
oxygen mixture, as the at least one gaseous fuel.
Advantageously provided is at least one gas supply device set up to supply the
multi-
flame burner with at least one gaseous fuel. The latter is preferably
controllable In
design, so that the respectively introduced thermal output can be controlled
and/or the
provision of respectively adjusted gas mixtures ensures an especially
advantageous
adaptation to the material to be welded.
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In a Wither advantageous embodiment, a multi-flame burner according to the
invention
exhibits at least 4,6 or 8 burner heads. The burner heads are preferably
spaced apart
to 15 cm from each other. Corresponding distances depend on the homogeneity of
the heating to be achieved ancUor the permissible temperature of the burner
heads.
5
In another preferred embodiment, the burner heads exhibit burner nozzles,
wherein the
burner nozzles of the respectively adjacent burner heads are offset by Ito 10
cm
relative to a shared center fine between the burner nozzles. As also explained
In
greater detail below in conjunction with the figures, the origins of the
respective flames
are here spaced a defined distance apart from each other, thereby further
reducing the
Influence of the burner heads on each other.
It was found that an especially advantageous length for the totality of the
burner head
and connection pipe ranges from 8 to 25 cm for numerous applications.
An advantageous further development of the present invention provides that the
multi-
flame burner exhibit a feed line configured ass bent shaft, wherein the bent
shaft Is
preferably made essentially out of stainless steel.
The feed line, which can also be referred to as a shaft or expressed
differently once
again as a pipeline, Is best made out a metallic material for supplying the
fuel. A bent
configuration makes It adjustable to the shape of the workplace to be
preheated, e.g.,
to the cunfature of a large-diameter pipe to be preheated, which is very
advantageous
In terms of the present Invention. From a production standpoint, stainless
steel Is
especially suitable as the metallic material for such a bent configuration.
As mentioned, the burner heads with the flame axes Inclined In relation to
each other
are advantageously each alternately secured to a shared feed line and can be
supplied
by way of the latter in a corresponding multi-flame burner. The feed line here
simultaneously functions as a fuel distributor and fastening device for the
burner heads.
For example, a corresponding feed line can be bent, and thereby adjusted to
the shape
of a workplece to be heated. During the manufacture of a mufti-flame burner
according
to the invention, the feed fine is advantageously deformed In such a way as to
essentially reproduce the corresponding shape of the workplace. In other
words, for
example. It Is best that a circular segment have the same midpoint as a Verge-
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=
diameter) pipe to be preheated and a bend adjusted based on the larger radius
(pipe
radius plus radial distance between the pipe and feed line). In addition,
other shapes
may also be advantageous and In keeping with the Invention.
The adjustabillty of the mufti-flame burner to the shape of the workplace to
be
preheated, In particular to the diameter of the pipe to be preheated, is an
essential
advantage to the present invention In relation to prior art.
In terms of the method, the set object is achieved by a method for preheating
a
workplace, in particular a pipe or large-diameter pipe, in which a multi-flame
burner is
used, and burner flames generated by the multi-flame burner are directed at
the
workpiece. The method according to the Invention benefits from the advantages
specified above and below, to which express reference can thus be made.
/5 Additional Advantages of the Invention
The burner heads are alternately interleaved relative to each other according
to the
Invention, so that the respectively created llamas point away from each other.
As a
result, the hot exhaust gases generated by the flames cannot damage each
other.
Corresponding burner heads are usually attached to a shared feed line in the
form of a
pipeline. The latter can be straight or bent as desired, and exhibits a
central ands that is
also straight or bent, depending on the configuration of the feed One. The
alignment of
flame axes is here advantageously such that the latter are inclined axially
(i.e.,
longitudinally relative to the feed line) and/or radially (Le., transversely
relative to the
latter) in relation to a respective perpendicular on the central axis at the
attachment
site. The inclination of adjacent burner heads is here preferably opposite in
at least one
of these directions. This can mean that the burner heads are radially
alternately
Inclined clockwise and counterclockwise In relation to the axis of the feed
line.
As a consequence, one essential aspect of the present invention involves an
arrangement or alignment of the burner heads, and hence the flame and exhaust
gas
direction, that deviates from prior art. The exhaust gas is guided by
Inclining the
= burners in such a way that their primary flames hit a region near the
welded seam In
line with their function, but the exhaust stream does not heat the adjacent
burner(s). As
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=
explained below, preferably defined angular positions of the burners relative
to each
other are possible and must be maintained for this purpose. The latter
advantageously
arise from offsetting the connection pipes, and potentially from how the
connection
pipes are aligned at the rotatable screw joint.
As a consequence, the invention makes it possible to introduce a maximum
thermal
output onto a small space. In particular onto a large-diameter pipe that
itself rotates.
Despite a more concentrated Introduction of heat by comparison to devices in
prior art,
the danger of burners heating is minimized, even given an incorrect operation.
This
results in lower downtimes and less need for repairs, which makes
corresponding
. methods economically advantageous. The measures proposed by the invention
yield a
significantly reduced burner weight in relation to the thermal output to be
introduced.
=
The overall achievable lower burner costs and more effective utilization of a
corresponding burner lead to economic advantages in comparison to known
devices, in
particular in the construction of large containers.
As already mentioned, a corresponding multi-flame burner can advantageously be
supplied with an acetylene mixture, in particular an acetylene/oxygen mixture,
maidng ft
possible to also we the advantages for known acetylene processes with the
burner
according to the Invention. As known, the especially hot, concentrated
acetylene/oxygen flame yields a rapid temperature rise on the workplace
surface, and
causes heat to accumulate inside the workplace at high temperature gradients,
so that
a large amount of heat can be locally introduced. However,
acetylene/compressed air
flames and/or acetylene/suction air burners can, also be used, for example.
Acetylene/compressed air flames are soft and gentle, yet Intensive and
efficient They
can be very well controlled over the entire area of potential acetylene/air
mixture
formation, and are largely immune from re-ignition. This yields advantages
relating to
Industrial safety. However, the achievable lower surface temperature results
In a
thorough heating of the workplace. Even lower temperature gradients can be
achieved
with the mentioned suction air burners, which operate according to the Bunsen
principle.
The described multi-flame burners as a whole advantageously exhibit 4,6 or 8
burner
heads. As a consequence, this yields advantages by comparison to previously
known
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three-headed preheating burners, since a larger area of a workplace can be
heated at
any one time. For example, the arrangement according to the invention makes it
possible to attach eight or more burner heads to a distribution pipe,
specifically the
already mentioned feed line, without the latter overheating themselves or each
other
impermissibly. As mentioned, a larger thermal output can as a result be
introduced
over a small space. in particular over a rotating large-diameter pipe. The
number of
usable burner heads is not confined to four or eight rather, burners with 10,
12, 14, 18,
18 or 20 burners or a higher number of burners can also be manufactured.
It Is especially advantageous If the respective burner heads arranged adjacent
to each
other each exhibit diverging flame axes, and thus generate diverging burner
flames. As
mentioned, this causes the exhaust gas streams of corresponding burner flames
to
point away from each other, and no reciprocal overheating takes place.
The invention will be explained in greater detail with reference to the
attached
drawings, which show a preferred embodiment of the invention.
Brief Description of the Drawings
Fig. 1 shows a burner head, which can be used for a mult-fiame burner
according to
an embodiment of the invention.
Fig. 2 shows a schematic, side view of a multi-flame burner according to an
embodiment of the invention.
Fig. 3 shows a schematic, longitudinal view of a multi-flame burner according
to an
embodiment of the invention.
Elements corresponding to one another on the figures bear identical reference
numbers. Repeated explanations an be avoided for the sake of clarity.
Embodiments of the Invention
Fig. 1 shows a schematic view of a bumer head 1 exhibiting a nozzle ring 12
that can
3.5 have any desired number of preferably concentrically arranged
nozzles, through which
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fuel can escape. igniting the fuel produces a burner flame 13. which runs
along a flame
axis 14. The burner head 1 can be attached to a feed line by way of an offset
connection pipe 4 along with a screw joint 15 and connection nozzle 16. For
example,
the connection nozzle 16 Is welded to the feed line.
Fig. 2 shows a schematic, side view of a multi-flame burner according to an
especially
preferred embodiment of the invention, which is marked 10 Meta The multi-lame
burner 10 encompasses a total of eight burner heads 1, each with respectively
accompanying, offset connection pipes 4. not all of which are provided with
reference
numbers. The burner heads 1 are here combined into groups of burner heads A
and B.
A first group of burner heads A Is here arranged in such a way that the
respective
nozzle units or the nozzles provided there can yield burner flames with flame
axes
essentially arranged In the same direction. The same holds true for the burner
heads hi
group B. However, the flame axes 14 in group A and the flame axes 14 in glow B
are
/5 Inclined or skewed relative to each other given the inclined position of
the burner heads
1, so that respectively produced exhaust gases and/or the generated waste heat
will
not damage adjacent burner heads 1.
The screw joints 15 described above and the connection nozzles 16 are used to
secure
the burner heads 1 to a feed line 2, for example one that Is bent, and hence
can be
adjusted to the shape of a workplace to be machined. The feed line can be
coupled
with a supply line 3, which can exhibit other devices, such as a manometer and
regulator. In particular, such a supply line can exhibit a mixing unit 31,
with which an
acetylene/oxygen mixture and/or an acetylene/air mixture can be generated.
In another, simplified configuration of the invention, it can also be
advantageous for
specific, less demanding applications to do without the screw joint 15, and
hence the
ability of the offset connection pipe to rotate. In this case, the connection
nozzle 18 can
be lengthened and offset in design, thereby combining the connection nozzle 16
and
connection pipe 4 into a single component
Fig. 3 shows a longitudinal view of a multi-flame burner according to an
especially
preferred embodiment of the invention, which is also marked 10. As evident,
the
respective burner heads 1 are slanted relative to each other, so that the
arising flames
13 point away from each other. The feed ihm 2 can be bent or straight In
design.
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Refebince List
1 Burner head
A, B Group
Multi-flame burner
12 Nozzle ring
10 13. Burner flame
14 Flame axis
16 Screw joint
16 Connection nozzle
2 Connection line, shaft
= 3 Supply line
4 Offset connection pipe
20.
31 Mixing unit
=
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