U.S. patent application number 13/697871 was filed with the patent office on 2013-04-11 for method for producing steam generator tubes.
The applicant listed for this patent is Jan Bruckner, Martin Effert, Joachim Franke, Lars Klemm. Invention is credited to Jan Bruckner, Martin Effert, Joachim Franke, Lars Klemm.
Application Number | 20130087106 13/697871 |
Document ID | / |
Family ID | 43536619 |
Filed Date | 2013-04-11 |
United States Patent
Application |
20130087106 |
Kind Code |
A1 |
Bruckner; Jan ; et
al. |
April 11, 2013 |
METHOD FOR PRODUCING STEAM GENERATOR TUBES
Abstract
A method for producing steam generator tubes is provided. The
method is intended to allow a technically particularly simple
production process and at the same time allow particularly high
flexibility with regards to the materials that may be used to
achieve a particularly high efficiency of a steam generator. For
this purpose, an insert is fixed in slots of a former shaft, the
former shaft with the insert is introduced into a steam generator
tube, the fixing of the insert on the former shaft is released and
the former shaft is removed again from the steam generator
tube.
Inventors: |
Bruckner; Jan; (Uttenreuth,
DE) ; Effert; Martin; (Erlangen, DE) ; Franke;
Joachim; (Nurnberg, DE) ; Klemm; Lars;
(Erlangen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bruckner; Jan
Effert; Martin
Franke; Joachim
Klemm; Lars |
Uttenreuth
Erlangen
Nurnberg
Erlangen |
|
DE
DE
DE
DE |
|
|
Family ID: |
43536619 |
Appl. No.: |
13/697871 |
Filed: |
May 9, 2011 |
PCT Filed: |
May 9, 2011 |
PCT NO: |
PCT/EP2011/057426 |
371 Date: |
November 14, 2012 |
Current U.S.
Class: |
122/235.14 ;
72/137; 72/370.13 |
Current CPC
Class: |
F22B 37/18 20130101;
B21F 3/06 20130101; F22B 37/103 20130101; B21C 37/26 20130101; F22B
37/10 20130101 |
Class at
Publication: |
122/235.14 ;
72/370.13; 72/137 |
International
Class: |
F22B 37/18 20060101
F22B037/18; B21F 3/06 20060101 B21F003/06; B21C 37/26 20060101
B21C037/26 |
Foreign Application Data
Date |
Code |
Application Number |
May 31, 2010 |
EP |
10164426.8 |
Claims
1-8. (canceled)
9. A method for producing steam generator tubes, comprising: fixing
an insert in a plurality of grooves of a former shaft; introducing
the former shaft with the insert into a steam generator tube;
releasing the fixing of the insert to the former shaft; and
removing the former shaft again from the steam generator tube.
10. The method as claimed in claim 9, wherein the insert is fixed
to the former shaft with a pretension.
11. The method as claimed in claim 9, wherein the plurality of
grooves are introduced in a helical shape into the former
shaft.
12. The method as claimed in claim 11, wherein the former shaft is
rotated out of the steam generator tube.
13. The method as claimed in claim 9, wherein the plurality of
grooves are implemented as conical.
14. The method as claimed in claim 9, wherein the insert comprises
a plurality of wires.
15. A steam generator tube, comprising: a steam generator tube
produced by means of the method as claimed in claim 9.
16. A steam generator, comprising: a steam generator tube as
claimed in claim 15.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the US National Stage of International
Application No. PCT/EP2011/057426, filed May 9, 2011 and claims the
benefit thereof. The International Application claims the benefits
of European Patent Office application No. 10164426.8 EP filed May
31, 2010. All of the applications are incorporated by reference
herein in their entirety.
FIELD OF INVENTION
[0002] The invention relates to a method for producing steam
generator tubes.
BACKGROUND OF INVENTION
[0003] A steam generator is a closed, heated vessel or a pressure
pipe or tube system which serves the purpose of producing steam at
high pressure and high temperature for heating and operational
purposes (e.g. for the operation of a steam turbine). With
particularly high steam capacities and pressures, such as, for
example, during energy production in power stations, water-tube
boilers are used in which the flow medium, usually water, is
located in steam generator tubes. Water-tube boilers are also used
in applications involving the combustion of solids, since the
combustion chamber in which the heat generation takes place through
combustion of the respective raw material can be configured at will
by the arrangement of tube walls.
[0004] A steam generator of said type designed in the manner of a
water-tube boiler accordingly comprises a combustion chamber, the
encompassing wall of which is formed at least partially by tube
walls, i.e. steam generator tubes which are welded so as to be
gas-tight. On the flow medium side, these steam generator tubes, as
evaporation heating surfaces, initially form an evaporator into
which unevaporated medium is introduced and evaporated. The
evaporator is in this case usually arranged in the hottest area of
the combustion chamber. Arranged downstream of this, on the flow
medium side, where appropriate, is a device for separating water
and steam, and a superheater in which the steam is heated further
above its evaporation temperature in order to attain a high degree
of efficiency in a following thermal engine such as, for example, a
steam turbine. Connected upstream of the evaporator on the flow
medium side there can be a preheater (referred to as an
economizer), which preheats the feedwater by making use of waste or
residual heat and thereby likewise increases the degree of
efficiency of the system as a whole.
[0005] For evaporator heating surfaces in steam generators, smooth
tubes or tubes with internal ribbing are used. Tubes with internal
ribbing are used when the aim is to impose a swirl on the flow of
the flow medium in the steam generator tubes, which has the effect
of imparting a higher velocity to the fluid on the inner surface of
the steam generator tubes. The use of tubes with internal ribbing
may in this case be necessary for various reasons, such as, for
example, with a low mass flow density of the evaporator under full
load. Even at high heat flow densities, the use of tubes with
internal ribbing may be necessary (in drum-type boilers, for
example): In this situation there is the risk of film boiling, i.e.
a film of steam forms on the inside of the steam generator tubes,
which, in contrast with well-mixed fluid, has a high
heat-insulating effect in the event of bubble or nucleate boiling.
The consequence of this is that, while the heat flow density
remains the same, the wall temperature may rise sharply, which can
lead to the destruction of the heating surfaces. Not least, the use
of tubes with internal ribbing can avoid flow layering (separation
of the water and steam phase) in normal load operation (such as,
for example, at minimum load in helically-tubed steam
generators).
[0006] According to the prior art, the internal ribbing of the
tubes is produced in a cold-drawing process. According to present
knowledge, tubes with internal ribbing can only be manufactured
with materials with a maximum chromium content of 5%. If the use of
tubes with internal ribbing made of alloy steels with a higher
chromium content is necessary, due, for example, to a further rise
in the steam parameters in order to raise the degree of efficiency,
then the internally ribbed tubes cannot be manufactured with the
processes available today.
SUMMARY OF INVENTION
[0007] The object underlying the invention is therefore to disclose
a method for producing steam generator tubes which allows for a
technically particularly simple manufacturing process and at the
same time permits a particularly high level of flexibility in
respect of the materials which can be used in order to achieve a
particularly high degree of efficiency of a steam generator.
[0008] This object is achieved according to the invention in that
an insert is fixed in grooves of a former shaft, the former shaft
with the insert is introduced into a steam generator tube, the
fixing of the insert on the former shaft is released, and the
former shaft is removed again from the steam generator tube.
[0009] The invention is based here on the consideration that a
particularly high level of flexibility in respect of the materials
which can be used could be achieved in that the internally ribbed
tubes are not produced in one integrated manufacturing process, but
rather that a subsequent introduction of swirl-inducing inserts
into smooth tubes should be carried out. This enables the materials
of steam generator tubes and inserts to be selected independently
of one another. A particularly simple production of the insert can
be achieved in this case with the aid of a former shaft. A negative
mold of the insert is introduced into the former shaft such that
the production of the insert can be carried out by simple integral
molding. A former shaft of said type additionally allows for
particularly easy fitting of the insert in steam generator tubes in
that the insert is fixed on the former shaft, the latter is
introduced with the integrally molded insert into the steam
generator tube, the fixing is released there, and the former shaft
is removed again from the steam generator tube.
[0010] In an advantageous embodiment of the method, the insert is
fixed to the former shaft with a pretension. As a result of such
pretension it is possible for the insert, after release of the
fixing to the former shaft, to be lifted out of the grooves of the
former shaft and therefore fixed independently in the steam
generator tube, without further manual fixing being necessary.
[0011] In a further advantageous embodiment, a number of grooves
are introduced in the manner of helix into the former shaft. A
former shaft of this type naturally produces a helical-shaped
insert, which is particularly well-suited for inducing swirl in the
flow medium.
[0012] In an additional advantageous embodiment, the former shaft
is rotated out of the steam generator tube after the release of the
fixing of insert and former shaft. This is possible due to the
symmetry of the helix, and simplifies the removal of the former
shaft from the steam generator tube provided with the insert. This
allows for an even simpler manufacturing process of an internally
ribbed steam generator tube.
[0013] Advantageously, in this arrangement, the grooves of the
former shaft are implemented in a conical design. The conical
implementation ensures easier joining and backward rotation of the
former shaft when it is removed from the steam generator tube.
[0014] In a particularly advantageous embodiment, the insert
comprises a number of wires. Specifically, as a result of the
production of the insert by means of a former shaft which comprises
a number of grooves, the insert can be manufactured in a
particularly simple manner by appropriate shaping of wires into the
grooves. This means not only a particularly economical but also a
technically simple production of an insert for a steam generator
tube.
[0015] In an advantageous embodiment, a steam generator tube
manufactured in accordance with the method described hereintofore
is used in a steam generator.
[0016] The advantages achieved with the invention consist in
particular in that through the introduction of an insert into a
steam generator tube by means of a former shaft a particularly
simple technical solution for the production and positioning of an
insert is now provided, which solution allows tubes which are
internally ribbed by means of an insert to be manufactured using
alloy steels with higher chromium content which are suited to
particularly high steam parameters and therefore a particularly
high degree of efficiency of a steam generator. The production of
the insert can therefore be achieved particularly economically,
because the former shaft can be rotated completely out of the tube
again and used for the production of the next insert. The
significant cost advantages in comparison with cold-drawn tubes
with internal ribs make the production method according to the
invention attractive even in the case of materials having less than
5% chromium.
[0017] By the use of a former element in the form of grooves on a
former shaft, the insert has low tolerances in respect of its
geometry in the assembled state. As a result of assembly with the
former shaft, moreover, no cross-braces or similar ancillary
devices are needed in order to ensure the desired geometry of the
swirl insert in the assembled state. Swirl inserts can be produced
with the aid of a former shaft in commercially available lengths
(e.g. 12 m).
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The invention is explained in greater detail with reference
to a drawing, in which:
[0019] FIG. 1 shows a former shaft for carrying out the method
according to the invention,
[0020] FIG. 2 shows a magnified view of the former shaft in
section,
[0021] FIG. 3 shows a flow diagram of the method according to the
invention, and
[0022] FIG. 4 is a schematic diagram of a once-through steam
generator in a tower design format.
[0023] Like parts are labeled with the same reference numerals in
all the figures.
DETAILED DESCRIPTION OF INVENTION
[0024] FIG. 1 shows a former shaft 1 which is provided in a main
area 2 with grooves 4 running around the shaft in helical fashion.
In this case the grooves 4 are arranged in the form of a threefold
helix around the cylindrical body of the former shaft 1. Depending
on the desired profile of the insert which is to be produced, the
grooves 4 can also be embodied as a helix having almost any desired
number. Depending on the requirement, the desired grooves 4 can be
produced individually (number, pitch, dimensions) by means of a
metal-cutting machining process. The length of the main area 2 of
the former shaft 1 is slightly greater than the smooth tube into
which the insert is intended to be introduced. The main area 2 of
the former shaft 1 is followed in the axial direction by a
connection area 6 which is not provided with grooves 4 and which
serves to handle the former shaft 1 during the method according to
the invention.
[0025] FIG. 2 shows the former shaft 1 in section, in a magnified
representation. The profile of the grooves 4 incorporated into the
former shaft 1 can be identified at the cut face 8. The grooves 4
have a conical profile. Such a profile allows for a simpler joining
and backward rotation of the former shaft 1 during the
manufacturing process of the insert (not shown in greater detail)
for a steam generator tube.
[0026] FIG. 3 shows a schematic diagram depicting the individual
steps of the production process according to the invention. In step
A, one or more wires are inserted into the former shaft 1,
according to the number of grooves 4 which are to be introduced
into it. This results in the production of the one-pitch or
multi-pitch swirl insert. In step B, the wire or wires is/are fixed
to the former shaft 1 under pretension. In step C, the former shaft
1 is introduced into a steam generator tube which is smooth on the
inside, and the insert is in this way positioned in the steam
generator tube.
[0027] In step D, the fixing of the insert formed of wires on the
former shaft 1 is released. As a result of the preceding fixing
with pretension in step B, the release of the fixing leads to a
lifting of the insert out of the grooves 4. In step E, the former
shaft 1 is rotated out of the steam generator tube in the manner of
a screw, along the helical-shaped grooves 4. This is assisted by
the conical shape of the grooves 4. As a result of the release of
the fixing and by the reverse rotation of the former shaft 1, the
insert is released from the former shaft 1, and, assisted by the
internal stress, comes into firm contact with the inner wall of the
steam generator tube. The former shaft 1 is rotated completely out
of the tube, and can be used in step F for the production of the
next insert.
[0028] The once-through steam generator 10 according to FIG. 4 is
implemented in a tower design format and as a two-pass steam
generator. It has an encompassing wall 12 which, at the lower end
of the first gas pass formed by it, transitions into a
funnel-shaped base 14. The encompassing wall 12 is formed in a
lower area, or evaporator area, from evaporation tubes 16, and in
an upper area, or superheater area, from superheater tubes 16'. The
evaporator tubes 16 and superheater tubes 16' are joined to one
another, for example welded, in a gas-tight manner on their
longitudinal sides. The base 14 comprises a discharge aperture 18
for ash (not shown in greater detail).
[0029] The evaporator tubes 16 of the encompassing wall 12, through
which a flow medium, in particular water or a water-steam mixture,
flows from bottom to top, are connected at their inlet ends to an
inlet manifold 20. On the outlet side the evaporator tubes 16 are
connected by means of a water separation system (not shown in
greater detail) to the superheater tubes 16' which follow
downstream on the flow medium side.
[0030] The evaporator tubes 16 of the encompassing wall 12 form an
evaporation heating surface 22 in the section of the gas pass
located between the inlet manifold 20 and the water separation
system. This is followed by a reheater or superheater heating
surface 24 formed from the superheater tubes 16'. In addition,
arranged in the second gas pass 26, through which the hot gases
flow downward, and in the transverse pass 28, connecting it on the
hot gas side to the first gas pass, are further heating surfaces
30, only represented schematically, such as an economizer and
convective superheater heating surfaces.
[0031] Mounted in the lower area of the encompassing wall 12 are a
number of burners for a fossil fuel, in each case in an aperture 32
of the encompassing wall 12. Four apertures 32 are visible in FIG.
1. At an aperture 32 of this kind the evaporator tubes 16 of the
encompassing wall 12 are curved so as to circumvent the respective
aperture 32, and run on the outside of the vertical gas pass. These
apertures can, for example, also be provided for air nozzles.
[0032] As a result of the use of steam generator tubes with
internal ribbing in the steam generator 10, produced according to
the described method, it is possible to make use also of steels
having a chromium content of more than 5% for their manufacture.
Such steam generator tubes are suitable for particularly high steam
parameters, and so enable a particularly high degree of efficiency
of a steam generator to be achieved.
* * * * *