CA1198692A - Double-walled tube for transporting solid material, and method of manufacturing the same - Google Patents
Double-walled tube for transporting solid material, and method of manufacturing the sameInfo
- Publication number
- CA1198692A CA1198692A CA000417155A CA417155A CA1198692A CA 1198692 A CA1198692 A CA 1198692A CA 000417155 A CA000417155 A CA 000417155A CA 417155 A CA417155 A CA 417155A CA 1198692 A CA1198692 A CA 1198692A
- Authority
- CA
- Canada
- Prior art keywords
- tube
- core tube
- casing tube
- casing
- core
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Rigid Pipes And Flexible Pipes (AREA)
Abstract
Abstract of the Disclosure A double-walled tube is produced by providing an inner core tube and an outer casing tube, wherein the outer diameter of the inner core tube is smaller than the inner diameter of the outer casing tube, with consideration of manufacturing tolerances and/or noncircularity, by such a value that insertion of the core tube into the casing tube can easily be performed because of a sufficient amount of play, and the core tube is brought into abutment under the action of repeated, successive hardening steps with a stepped radial expansion, against the inner surface of the casing tube.
Description
~ 3~2 23824-113 The present invent~on relates to a method of manufacturing a double-walled tube for transporting solid ~aterials, and also to a double~walled tube.
Double-walled tubes are used, for example, in mining under-ground operations for pneumatic transportation of small-piece min-erals which are brought in the excavated longwall face space as filling material. Moreover, the double-walled tubes are provided during hydraulic transportation of sands for use particularly in the case of excavating works. The properties of the solid mater-ial to be transported require tubes with a wear-resistant inner surface having a long service life. On the other hand, the same tubes must be designed so that they grow under the action of inner pressure loads and particularly during transportation of construction materials to the place of use under the action of rough impact loads. For satisfying both these extreme xequire-ments, for years double-walled tubes have been utilized in which a core tube is designed especially for wear loads, whereas a casing tube is designed for pressure and impact loads~ It is required that the core tube and the casing tube are fixedly connected wIth one another. In one proposal for manufacturing such double-walled tubes the co~e tube is expanded ~:n the casing tube under the act~on of cold deformation and simultaneously fixed relative to the outer surface. In another proposed method a tube is composed of a plurality of steel layers whnse heat expans~on co-efficient decreases from ins;de outwardly~ In accordance with another proposed method a glass hard ;`nner layer ~s welded with a A 11 ~1-.
hardenable tough outer layex to form a two-layer tube. Another method involves a high-hardened wear-resistant core tube over which a sheet of a tough non-hardenable metal is bent to form a slotted casing tube, and the cas;ing tube is f~nally welded along ~ts longitudinal edges. The cas~ng tu~e is shrunk on the core tube because of welding and p~ovides for the desired immo~able assembly.
Moreo~er, core tubes of slotted springy wear-resistant steels are used whose slotted edges prior to the insextion into a casing tube of a tough steel are overlapped. The slotted core tu~e is then expanded by the inner pressure and pressed against the casin~
tube, whereas finally the slot edges abut against one another.
A pressure expansion is also possible without longitudinal slots.
The expansion of ~he core tube in the cas~ng tube is carried out by a respective tool.
Finally, in accordance with another method, a slotted core tube of a hardenable tube is used whose outer diameter prior to insertion into a casing tube is greater than the inner diameter of the casing tube. The slot width and the outer dia-meter are so determined relative to one another that after the pressing-in of the core tube, because of radial compression, the return spring effect provides for firm lying of the core tube in the caslng tube with tight abutment of the slot edges. After this, hardening of the core tube takes place, and volume increase result~
ing from the hardening of the core tube no longer presses against the cas~ng tube~ In addition, there is also a possib;lity to cool the casing tube similarly, to increase the pressing force.
~2-The above discussed developments, which have taken place over several decades, make clear that the experts have not in practice been able to come to a completely satisfactory concept for manufacturing a double-walled tube with a wear-free core tube and a tough casing tube. Allproposals as a whole, regardless of whether slotted or unslotted tubes are used, deal with a core tube and a casing tube which are designed such that the outer diameter of the core tube -2a-~.
only insignificantly deviates from the inner diameter of the casing tube. Only by maintenance of these narrow tolerances do the experts see a possibility to press the core tube in the required manner against the casing tube. The ex-penditures both related to accurate manufacture of tubes and also to the devices for insertion of the tubes into one another and hardening are relatively high.
Accordingly, i~ is an object of the present invention to provide a method of manufacturing a double-walled tube for transporting solid materials, and a double-walled tube produced thereby, which avoid the disadvantages of the prior art.
More particularlyl it is an object of the present invention to provide a method of manufacturing a double-walled tube which has consider-ably lower manufacturing expenditures as compared with known methods, and both with respect to the utilized materials and the manufacturing method.
rloreover, it is also an object of the present invention to produce by this highly advantageous method a suitable double~walled pipe for solid material transport.
In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention rasides, briefly stated, in that, with consideration of manufacturing tolerances and/or non-cir~ularity duringmanufacture of the ~ube, the outer diameter of the circum-ferentially closed core tube is sufficiently smaller than the inner diameter of the casing tube and/or the inner diameter of the casing tube is sufficiently greater than the outer diameter of the core tube that the core tube with a sufficient p]ay can be easily inserted into the casing tube, and the core tube, under the action of repeatedly following hardening steps with step-like radial expansion, is brought to firm surface abutment against the inner surface of the casing tube.
The invention uses the kno~n phenomenon that during hardening of suitable carbon steels a volume increase takes place. However it has in un-predictable manner been found that this volume increase is not limited to one-time hardening. Moreover, it has been determined in a surprising manner that an already hardened tube, in the event of further repeated hardening steps, expands in a further progression and in the sense of its outer diameter con-tinuously increasing. This unexpected result leads to inventive fea~ures which are not known in the prior art, that the core tube is fixed in the casing tube unobjectionably only by hardening, and tubes can be utilized whose manufactur-ing and/or transporting requirements have great deviations in outer and inner diameter and/or noncircularity. The invention deals with the assumption that now also tubes with very high tolerances of simple quali.ty standards can be used for manufacture of double-walled tubes.
For this purpose, a core tube can be used whose outer diameter is smaller than the inner diameter of the casing tube by so much that the core tube can be inserted with sufficient play into the casing tube, or the inner diameter of the casing tube is held such that an easy problem-free insertion of the tubes is guaranteed. It is to be understood that both features can be used in combination.
Even the problem-free insertion of the core tube into the casing tube can eliminate a lot of known problems during manufacture of the double-walled tubes for the solid material transport. Further problems are eliminated in that, exclusively by a repeatedly performed hardening with stepped radial expansion, the arresting of the core tube in the casing tube takes place and simultaneously the desired wear-free condition of the core tube is attained.
In accordance with another feature of the present invention, it is ~ossible that the heating tem~eratures of the hardening steps are identical.
In dependence upon the requirements, it is also possible that the heating temperatures of the hardening steps are different from one another.
~ ~8~
A double-walled tube for transporting of solid materials in accordance with the invention has a flame-hardened core tube and a casing tube of a tough material, which are pressed against one another by hardening, wherein in accordance with the invention with consideration of manufacturing and/or trans-port requirement tolerances and/or noncirclllarity the outer diameter of the un-slotted core tube is smaller than the inner diameter of the casing tube) and under the action of repeated successive hardenings, and thereby acting step-like radial expansion of the core tube, it is brought to firm adhering surface abut-ment against the inner surface of the casing tube.
Such a tube is easy to manufacture, since core and casing tubes have relatively high tolerances, and for connection of the core tube and the casing tube as well as for manufacturing a wear-free inner surface repeatedly succes-sive hardening steps are used. In addition to drawn tube, also tube welded by longitudinal seams or spiral seams can be utili~ed. The tube diameter is in-significant so that the double tube of greater diameter can be manufactured in an economical manner. Transport-conditional noncircularity is automatically eliminated during the tube mounting.
The novel features which are considered characteristic of the present invention are set forth in particular in the appended claims. The invention it-self, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawlng.
BRIEF DESCRIPTION OF Tl~ DRAWING
Figure 1 is a view showing a vertical section of one sector of a circumferentially closed double-walled tube after insertion of both tubes into olle another, but prior to hardening; and Figure 2 is a view substantially corresponding to the view of Figure 1, but showing the tube after the hardening.
The drawings partially and schematically show a double-walled pipe 1 which serves for hydraulic or pneumatic transport of solid materials. It has an inner core tube which is identified with reference numeral 2 and composed of a hardenable carbon steel, for example C35, and an outer casing tube which is identified with reference numeral 3 and composed of a tough material, for ex-ample structural steel. At each end of the tube flanges, not shown, can be provided.
As can be seen from Figure 1, the dimensions of the core tube 2 and the casing tube 3 are selected such that, with consideration of the manu-facturing and transport-conditional tolerances and/or noncircularity, the outer diameter AK of the circumferentially closed or unslotted core tube 2 is dimen-sioned so much smaller than the inner diameter IM of the casing tube 3, that the core tube 2 can be inserted with a sufficient play Sp easily into the casing tube 3. For insertion of the core tube 2 into the casing tube 3 therefore no special steps or means are required.
After the insertion of the core tube 2 into the casing tube 3, the core tube 2 is repeatedly successively subjected to hardening steps. As a re-sult of this, the core tube 2 expands and particularly such that, after an appropriate number of hardening steps ~which depends on the play Sp between the core tube 2 and the casing tube 3), the outer surface ~ of the core tube 2 is pressed tightly against the inner surface 5 of the casing tube 3. This is shown in Figure 2. In this manner, not only the desired wear-free condition takes place Oll the inner surface 6 of the core tube 2, but also a firmly ad-hering surface abutment of the core tube 2 against the casing tube 3 is provid-ed.
It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of con-structions differing from the types described above.
While the invention has been illustrated and described as embodied in a double-walled tube, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without depart-ing in any way from the spirit of the present invention.
Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying eurrent knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.
Double-walled tubes are used, for example, in mining under-ground operations for pneumatic transportation of small-piece min-erals which are brought in the excavated longwall face space as filling material. Moreover, the double-walled tubes are provided during hydraulic transportation of sands for use particularly in the case of excavating works. The properties of the solid mater-ial to be transported require tubes with a wear-resistant inner surface having a long service life. On the other hand, the same tubes must be designed so that they grow under the action of inner pressure loads and particularly during transportation of construction materials to the place of use under the action of rough impact loads. For satisfying both these extreme xequire-ments, for years double-walled tubes have been utilized in which a core tube is designed especially for wear loads, whereas a casing tube is designed for pressure and impact loads~ It is required that the core tube and the casing tube are fixedly connected wIth one another. In one proposal for manufacturing such double-walled tubes the co~e tube is expanded ~:n the casing tube under the act~on of cold deformation and simultaneously fixed relative to the outer surface. In another proposed method a tube is composed of a plurality of steel layers whnse heat expans~on co-efficient decreases from ins;de outwardly~ In accordance with another proposed method a glass hard ;`nner layer ~s welded with a A 11 ~1-.
hardenable tough outer layex to form a two-layer tube. Another method involves a high-hardened wear-resistant core tube over which a sheet of a tough non-hardenable metal is bent to form a slotted casing tube, and the cas;ing tube is f~nally welded along ~ts longitudinal edges. The cas~ng tu~e is shrunk on the core tube because of welding and p~ovides for the desired immo~able assembly.
Moreo~er, core tubes of slotted springy wear-resistant steels are used whose slotted edges prior to the insextion into a casing tube of a tough steel are overlapped. The slotted core tu~e is then expanded by the inner pressure and pressed against the casin~
tube, whereas finally the slot edges abut against one another.
A pressure expansion is also possible without longitudinal slots.
The expansion of ~he core tube in the cas~ng tube is carried out by a respective tool.
Finally, in accordance with another method, a slotted core tube of a hardenable tube is used whose outer diameter prior to insertion into a casing tube is greater than the inner diameter of the casing tube. The slot width and the outer dia-meter are so determined relative to one another that after the pressing-in of the core tube, because of radial compression, the return spring effect provides for firm lying of the core tube in the caslng tube with tight abutment of the slot edges. After this, hardening of the core tube takes place, and volume increase result~
ing from the hardening of the core tube no longer presses against the cas~ng tube~ In addition, there is also a possib;lity to cool the casing tube similarly, to increase the pressing force.
~2-The above discussed developments, which have taken place over several decades, make clear that the experts have not in practice been able to come to a completely satisfactory concept for manufacturing a double-walled tube with a wear-free core tube and a tough casing tube. Allproposals as a whole, regardless of whether slotted or unslotted tubes are used, deal with a core tube and a casing tube which are designed such that the outer diameter of the core tube -2a-~.
only insignificantly deviates from the inner diameter of the casing tube. Only by maintenance of these narrow tolerances do the experts see a possibility to press the core tube in the required manner against the casing tube. The ex-penditures both related to accurate manufacture of tubes and also to the devices for insertion of the tubes into one another and hardening are relatively high.
Accordingly, i~ is an object of the present invention to provide a method of manufacturing a double-walled tube for transporting solid materials, and a double-walled tube produced thereby, which avoid the disadvantages of the prior art.
More particularlyl it is an object of the present invention to provide a method of manufacturing a double-walled tube which has consider-ably lower manufacturing expenditures as compared with known methods, and both with respect to the utilized materials and the manufacturing method.
rloreover, it is also an object of the present invention to produce by this highly advantageous method a suitable double~walled pipe for solid material transport.
In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention rasides, briefly stated, in that, with consideration of manufacturing tolerances and/or non-cir~ularity duringmanufacture of the ~ube, the outer diameter of the circum-ferentially closed core tube is sufficiently smaller than the inner diameter of the casing tube and/or the inner diameter of the casing tube is sufficiently greater than the outer diameter of the core tube that the core tube with a sufficient p]ay can be easily inserted into the casing tube, and the core tube, under the action of repeatedly following hardening steps with step-like radial expansion, is brought to firm surface abutment against the inner surface of the casing tube.
The invention uses the kno~n phenomenon that during hardening of suitable carbon steels a volume increase takes place. However it has in un-predictable manner been found that this volume increase is not limited to one-time hardening. Moreover, it has been determined in a surprising manner that an already hardened tube, in the event of further repeated hardening steps, expands in a further progression and in the sense of its outer diameter con-tinuously increasing. This unexpected result leads to inventive fea~ures which are not known in the prior art, that the core tube is fixed in the casing tube unobjectionably only by hardening, and tubes can be utilized whose manufactur-ing and/or transporting requirements have great deviations in outer and inner diameter and/or noncircularity. The invention deals with the assumption that now also tubes with very high tolerances of simple quali.ty standards can be used for manufacture of double-walled tubes.
For this purpose, a core tube can be used whose outer diameter is smaller than the inner diameter of the casing tube by so much that the core tube can be inserted with sufficient play into the casing tube, or the inner diameter of the casing tube is held such that an easy problem-free insertion of the tubes is guaranteed. It is to be understood that both features can be used in combination.
Even the problem-free insertion of the core tube into the casing tube can eliminate a lot of known problems during manufacture of the double-walled tubes for the solid material transport. Further problems are eliminated in that, exclusively by a repeatedly performed hardening with stepped radial expansion, the arresting of the core tube in the casing tube takes place and simultaneously the desired wear-free condition of the core tube is attained.
In accordance with another feature of the present invention, it is ~ossible that the heating tem~eratures of the hardening steps are identical.
In dependence upon the requirements, it is also possible that the heating temperatures of the hardening steps are different from one another.
~ ~8~
A double-walled tube for transporting of solid materials in accordance with the invention has a flame-hardened core tube and a casing tube of a tough material, which are pressed against one another by hardening, wherein in accordance with the invention with consideration of manufacturing and/or trans-port requirement tolerances and/or noncirclllarity the outer diameter of the un-slotted core tube is smaller than the inner diameter of the casing tube) and under the action of repeated successive hardenings, and thereby acting step-like radial expansion of the core tube, it is brought to firm adhering surface abut-ment against the inner surface of the casing tube.
Such a tube is easy to manufacture, since core and casing tubes have relatively high tolerances, and for connection of the core tube and the casing tube as well as for manufacturing a wear-free inner surface repeatedly succes-sive hardening steps are used. In addition to drawn tube, also tube welded by longitudinal seams or spiral seams can be utili~ed. The tube diameter is in-significant so that the double tube of greater diameter can be manufactured in an economical manner. Transport-conditional noncircularity is automatically eliminated during the tube mounting.
The novel features which are considered characteristic of the present invention are set forth in particular in the appended claims. The invention it-self, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawlng.
BRIEF DESCRIPTION OF Tl~ DRAWING
Figure 1 is a view showing a vertical section of one sector of a circumferentially closed double-walled tube after insertion of both tubes into olle another, but prior to hardening; and Figure 2 is a view substantially corresponding to the view of Figure 1, but showing the tube after the hardening.
The drawings partially and schematically show a double-walled pipe 1 which serves for hydraulic or pneumatic transport of solid materials. It has an inner core tube which is identified with reference numeral 2 and composed of a hardenable carbon steel, for example C35, and an outer casing tube which is identified with reference numeral 3 and composed of a tough material, for ex-ample structural steel. At each end of the tube flanges, not shown, can be provided.
As can be seen from Figure 1, the dimensions of the core tube 2 and the casing tube 3 are selected such that, with consideration of the manu-facturing and transport-conditional tolerances and/or noncircularity, the outer diameter AK of the circumferentially closed or unslotted core tube 2 is dimen-sioned so much smaller than the inner diameter IM of the casing tube 3, that the core tube 2 can be inserted with a sufficient play Sp easily into the casing tube 3. For insertion of the core tube 2 into the casing tube 3 therefore no special steps or means are required.
After the insertion of the core tube 2 into the casing tube 3, the core tube 2 is repeatedly successively subjected to hardening steps. As a re-sult of this, the core tube 2 expands and particularly such that, after an appropriate number of hardening steps ~which depends on the play Sp between the core tube 2 and the casing tube 3), the outer surface ~ of the core tube 2 is pressed tightly against the inner surface 5 of the casing tube 3. This is shown in Figure 2. In this manner, not only the desired wear-free condition takes place Oll the inner surface 6 of the core tube 2, but also a firmly ad-hering surface abutment of the core tube 2 against the casing tube 3 is provid-ed.
It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of con-structions differing from the types described above.
While the invention has been illustrated and described as embodied in a double-walled tube, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without depart-ing in any way from the spirit of the present invention.
Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying eurrent knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of manufacturing a double-walled tube for transporting solid materials comprising the steps of providing a flame-hardened circum-ferentially uninterrupted core tube member and a casing tube member of a tough material with an inner diameter of the casing tube and the outer diameter of the core tube selected such that a sufficient amount of play remains there-between; inserting the core tube into the casing tube easily because of the sufficient amount of play; and subjecting the core tube to repeatedly succes-sive hardening steps so that it radially expands and is brought to firmly adhering surface abutment against an inner surface of the casing tube.
2. A method as defined in claim 1, wherein said providing step in-cludes providing the core tube and the casing tube dimensioned such that the outer diameter of the core tube is smaller than the inner diameter of the casing tube to obtain said amount of play.
3. A method as defined in claim 1, wherein said providing step includes dimensioning the core tube and the casing tube such that the inner diameter of the casing tube is greater than the outer diameter of the core tube to obtain said play.
4. A method as defined in claim 1, wherein said hardening steps in-clude hardening the casing tube with temperatures which are equal for all said hardening steps.
5. A method as defined in claim 1, wherein said hardening steps in-cludes hardening of the core tube with temperatures which are different in said hardening steps.
6. A double-walled tube for transporting solid materials, comprising a flame hardened circumferentially uninterrupted core tube; and a casing tube of a tough material, said core tube having an outer diameter which, with considera-tion of manufacturing and/or transport-conditional tolerances and/or non-circularity, is smaller than the inner diameter of the casing tube, and the core tube is in firm adhering surface abutment against an inner surface of the casing tube as a result of repeated successive hardening steps and therefore step-like radial expansions of the core tube.
9.
9.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3148493 | 1981-12-08 | ||
| DEP3148493.0 | 1981-12-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1198692A true CA1198692A (en) | 1985-12-31 |
Family
ID=6148149
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000417155A Expired CA1198692A (en) | 1981-12-08 | 1982-12-07 | Double-walled tube for transporting solid material, and method of manufacturing the same |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1198692A (en) |
-
1982
- 1982-12-07 CA CA000417155A patent/CA1198692A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |