Patent Application
20100119986
The present invention generally relates to a multiple hearth furnace (MHF).
Multiple hearth furnaces (MHFs) have been used now for about one century for heating or roasting many types of material. They comprise a plurality of hearth chambers arranged one on top of the other. Each of these hearth chambers comprises a circular hearth having alternately a central material drop hole or a plurality of peripheral material drop holes therein. A vertical rotary shaft extends centrally through all these superposed hearth chambers and has in each of them a rabble arm fixing node. Rabble arms are connected in a cantilever fashion to such a rabble fixing node (normally there are two to four rabble arms per hearth chamber). Each rabble arm comprises a plurality of rabble teeth extending downwards into the material on the hearth. When the vertical rotary shaft is rotated, the rabble arms plough material on the hearth with their rabble teeth either towards the central drop hole or towards the peripheral drop holes in the hearth. Thus, material charged into the uppermost hearth chamber is caused to move slowly downwards through all successive hearth chambers, being pushed by the rotating rabble arms over the successive hearths alternately from the periphery to the center (on a hearth with a central material drop hole) and from the center to the periphery (on a hearth with peripheral material drop holes). Arrived in the lowermost hearth chamber, the roasted or heated material leaves the MHF through a furnace discharging opening.
It will be appreciated that the vertical rotary shaft and the rabble arms are not only subjected to severe mechanical stresses, but they also have to withstand high temperatures and very corrosive atmospheres. Consequently, it is particularly important to warrant that structural rigidity of these elements is not affected by overheating, and that high temperature corrosion (in particular accelerated chloride corrosion due to overheating) as well as low temperature corrosion (in particular corrosion due to acid condensation as a direct consequence of overcooling) are reliably avoided. Furthermore, non-uniform temperature distributions may result in mechanical stresses causing deformations or even mechanical ruin of the shaft or the rabble arms.
In documents describing very early multiple hearth furnaces it is sometimes mentioned that rabble arms may either be water or gas cooled. Nevertheless, operating hearth furnaces exclusively include—as far as applicants know—gas cooled rabble arms. Indeed, if there is a leakage in a water cooled rabble arm, the whole furnace has to be shut down in order to find and repair the leakage, whereas a leakage in a gas cooled rabble arm does not necessarily require a direct intervention. However, gas cooled MHFs have serious drawbacks too. For example, a gas cooling circuit is not always capable of warranting a precise control of surface temperature. It follows that some surfaces of the vertical rotary shaft or the rabble arms or may be overheated or overcooled, which leads to the drawbacks mentioned above.
In most MHFs, the vertical rotary shaft as well as the rabble arms are tubular structures that are cooled by a gaseous cooling fluid, generally pressurized ambient air. (For the sake of simplicity, the gaseous cooling fluid will be called herein “cooling gas”, even if it may be a mixture of several gases, such as e.g. air). The vertical rotary shaft includes a cooling gas distribution channel for supplying the cooling gas to the rabble arms. From this cooling gas distribution channel, the cooling gas is channeled through the connection between the rabble arm and the rabble arm fixing node into the tubular structure of the rabble arm. As the cooling system of the rabble arm is normally a closed system, the cooling gas returning from the rabble arm must be channeled through the connection between the rabble arm and the rabble arm fixing node into an exhaust gas channel in the vertical rotary shaft.
In the last hundred years, there have been described various embodiments of such gas-cooled vertical rotary shafts and cantilever rabble arms for a MHF. For example:
U.S. Pat. No. 1,468,216 discloses a vertical hollow shaft of a MHF, in which a central partition wall separates a cooling gas distribution duct from an exhaust duct, each of them having a semicircular cross-section. In each hearth chamber, a cooling gas flow is branched off from the cooling gas flow in the cooling gas distribution duct to be rerouted through a rabble arm cooling system and to be thereafter evacuated into the exhaust duct. It follows that in the cooling gas distribution duct the flow rate and, consequently, the velocity of the gas strongly diminish from the bottom to the top and in the exhaust duct strongly they strongly increase from the bottom to the top. This results in a very un-uniform cooling of the vertical rotary shaft as well in a lengthwise as in a circumferential direction.
U.S. Pat. No. 3,419,254 discloses a double-shell gas-cooled vertical rotary shaft. The central space within the interior shell constitutes an intake duct and the annular space between the outer shell and the inner shell an exhaust duct. While this system warrants a more uniform cooling of the vertical rotary shaft in a circumferential direction of the shaft, cooling in the lengthwise direction of the shaft is still very uniform.
U.S. Pat. No. 2,332,387 also discloses a double-shell gas-cooled vertical rotary shaft. In this shaft, the annular space between the outer shell and the inner shell constitutes an intake duct and the central space within the interior shell an exhaust duct. The outer shell is—except at the rabble arm supports—of substantially the same diameter from the bottom to the top. In order to have a more uniform cooling gas flow within both ducts, U.S. Pat. No. 2,332,387 teaches to increase the diameter of the interior shell from the bottom to the top. A first disadvantage of this system is that the cooling gas strongly heats up from the bottom to the top of the annular intake duct, which results in a poorer cooling of the shaft and the rabble arms in the upper hearth chambers. A further disadvantage of this system is that the geometry of the shaft must be different in each hearth chamber, which makes its manufacturing of course more expensive.
The invention provides a MHF with a more uniform gas cooling of the shaft and the rabble arms.
More particularly, the present invention proposes a multiple hearth furnace comprising, in a manner known per se: a plurality of hearth chambers arranged one on top of the other; a hollow vertical rotary shaft extending centrally through the hearth chambers and including an outer shell; in each of the hearth chambers, at least one rabble arm secured to the shaft; a gas cooling system for the shaft and the rabble arms including, within the outer shell, an annular main distribution channel for supplying a cooling gas to the rabble arms and a central exhaust channel for evacuating the cooling gas leaving the rabble arms; and a connecting means for connecting the rabble arms to the shaft including cooling gas supply means in direct communication with the annular main distribution channel and cooling gas return means in direct communication with the central exhaust channel. In accordance with the present invention, the gas cooling system further comprises an annular main supply channel surrounding the annular main distribution channel and being outwardly delimited by the outer shell. A cooling gas inlet is connected to the annular main supply channel. A cooling gas passage between the annular main supply channel and the annular main distribution channel is spaced from the cooling gas inlet, so that cooling gas supplied to the cooling gas inlet has to flow through the annular main supply channel through several hearth chambers before it flows through the cooling gas passage into the annular main distribution channel. It will be appreciated that with such a system, the whole main supply flow of cooling gas is first used to provide an efficient and uniform cooling of the outer shell of the vertical rotary shaft in several hearth chambers. The constant, high flow rate in the annular main supply channel warrants a relatively small temperature increase of the cooling gas between the cooling gas inlet and the cooling gas passage in the annular main distribution channel. In this inner annular distribution channel, the flow of the cooling gas—which now diminishes from hearth chamber to hearth chamber—is relatively well protected against additional warming up, so that the rabble arms in all superposed hearth chambers are supplied with a cooling gas at substantially the same temperature. All this results in a very efficient and uniform cooling of the shaft and the rabble arms.
The gas cooling system can e.g. comprise a single cooling gas inlet connected either to the lower or to the upper end of the vertical rotary shaft, i.e. the cooling gas supplied to the cooling gas inlet has to flow through the annular main supply channel through all hearth chambers before it flows through the cooling gas passage into the annular main distribution channel. However, in a preferred embodiment, the gas cooling system further comprises partition means partitioning the annular main supply channel and the annular main distribution channel in a lower half and an upper half. A lower cooling gas inlet is then connected to the lower half of the annular main supply channel at the lower end of the shaft, and an upper cooling gas inlet is connected to the upper half of the annular main supply channel at the upper end of the shaft. A lower cooling gas passage is arranged between the lower half of the annular main supply channel and the lower half of the annular main distribution channel and located near the partition means, so that cooling gas supplied to the lower cooling gas inlet has to flow upwards though the lower half of the annular main supply channel up to the partition means before it can flow through the lower cooling gas passage into the lower half of the annular main distribution channel. An upper cooling gas passage is arranged between the upper half of the annular main supply channel and the upper half of the annular main distribution channel and located near the partition means, so that cooling gas supplied to the upper cooling gas inlet has to flow downwards though the upper half of the annular main supply channel down to the partition means before it can flow through the second cooling gas passage into the upper half of the annular main distribution channel. It will be appreciated that this system results in a further improvement of the cooling system of the shaft and the rabble arms. With this split system, it is e.g. easier to equilibrate gas supply for the rabble arms in the superposed hearth chambers.
A preferred embodiment of the outer shell comprises: shaft support tubes and cast rabble arm fixing nodes interconnecting the shaft support tubes, wherein at least one rabble is fixed to each of the rabble arm fixing nodes. In this shaft, the rabble arm fixing node and the shaft support tubes are advantageously welded together. The shaft support tubes are advantageously made of thick walled stainless steel tubes and are dimensioned as structural load carrying members between the rabble arm fixing nodes. It will be appreciated that such a shaft can be easily manufactured at relatively low costs using standardized elements. It provides however a strong, long-lasting support structure that has a very good resistance with regard to temperature and corrosive agents in the hearth chambers.
A preferred embodiment of a rabble arm fixing nodes advantageously comprises a ring-shaped cast body made of refractory steel. It will be appreciated that such a rabble arm fixing node is a particularly compact, strong and reliable connection means for connecting the rabble arm to the vertical rotary shaft.
A preferred embodiment of a rabble arm rabble arm includes a tubular structure for circulating therethrough a cooling gas and plug body connected to the tubular structure of the rabble arm received in a socket on the vertical rotary shaft. It will be appreciated that such a plug body, which can be manufactured without necessitating complicated casting moulds, is a particularly compact, strong and reliable connection means for connecting the rabble arm to the vertical rotary shaft.
A further preferred embodiment of a rabble arm fixing nodes comprises a ring-shaped cast body including: at least one socket for receiving therein the plug body of the rabble arm. A central passage forms the central exhaust channel for the cooling gas within the rabble arm fixing node. First secondary passages are arranged in a first ring section of the cast body, so as to provide gas passages for cooling gas flowing through the annular main distribution channel. Second secondary passages are arranged in a second ring section of the cast body, so as to provide gas passages for cooling gas flowing through the annular main supply channel. The cooling gas supply means is arranged in the cast body so as to interconnect the annular internal supply channel for the cooling gas with at least one gas outlet opening within the socket and advantageously comprises at least one oblique bore extending through the ring-shaped cast body from the second ring section into a lateral surface delimiting the socket. The cooling gas return means is arranged in the cast body so as to interconnect the central passage with at least one gas inlet opening within the socket and advantageously comprises a through hole in axial extension of the socket. This embodiment of an arm fixing node combines a low pressure drop cooling gas distribution in the shaft and a solid fixing of the rabble arm on the shaft with a very compact and cost saving design. With its integrated gas passages, it substantially contributes to the fact that the vertical rotary shaft, which includes three co-axial cooling channels therein, can be manufactured using a very small number of standardized elements. It also essentially contributes to warranting a strong, long-lasting shaft support structure with a very good resistance with regard to temperature and corrosive agents in the hearth chambers.
In a preferred embodiment, a section of the shaft extending between two adjacent hearth chambers comprises: a shaft support tube arranged between two arm fixing nodes to form the outer shell of the section of the shaft, the shaft support tube delimiting the annular main supply channel to the outside; an intermediate gas guiding jacket arranged within the shaft support tube so as to delimit the annular main supply channel to the inside and the annular main distribution channel to the outside; and an inner gas guiding jacket arranged within the intermediate gas guiding jacket so as to delimit the annular main distribution channel to the inside and the central exhaust channel to the outside. In this preferred embodiment, the intermediate gas guiding jacket advantageously comprises: a first tube section with a first end fixed to the first fixing node and a free second end; a second tube section with a first end fixed to the second fixing node and a free second end; a sealing means providing a sealed connection between the free second end of the first tube section and the free second end of the second tube section, while tolerating relative movement in the axial direction of both free second ends. Similarly, the inner gas guiding jacket advantageously comprises: a first tube section with a first end fixed to the first fixing node and a free second end; a second tube section with a first end fixed to the second fixing node and a free second end; a sealing means providing a sealed connection between the free second end of the first tube section and the free second end of the second tube section, while tolerating relative movement in the axial direction of both free second ends. The sealing means advantageously comprises a sealing sleeve fixed to the free second end of one of the first or second tube sections and engaging in a sealed manner the free second end of the other tube section. It will be appreciated that such a shaft section can be easily manufactured at relatively low costs using standardized elements.
The rotary hollow shaft further advantageously comprises: an outer thermal insulation on its outer shell, the outer thermal insulation including an inner refractory layer of micro porous material, an intermediate refractory layer of insulating castable material and an outer refractory layer of dense castable material.
A preferred embodiment of a rabble arm advantageously comprises: an plug body for fixing the rabble arm to the rotary hollow shaft; an arm support tube fixed to the plug body; and a gas guiding tube arranged inside the arm support tube and cooperating with the latter to define between them a small annular gap for channeling the cooling gas from the shaft to the free end of the rabble arm, wherein the interior section of the gas guiding tube forms a return channel for the cooling gas from the free end of the rabble arm to the shaft. In this embodiment, the plug body is advantageously a solid cast body including at least one cooling gas supply channel and at least one cooling gas return channel. The at least one cooling gas supply channel and the at least one cooling gas return channel are then advantageously provided as bores in the solid cast body.
Such a rabble arm further advantageously comprises: an arm supporting tube; a micro porous thermal insulation layer arranged on the arm supporting tube; and a metallic protecting jacket covering the micro porous thermal insulation. In a preferred embodiment, metallic rabble teeth fixed to the metallic protecting jacket by welding, wherein anti-rotation means are arranged between the arm supporting tube and the metallic protecting jacket.
Further details and advantages of the present invention will be apparent from the following detailed description of a preferred but not limiting embodiment with reference to the attached drawings, wherein:
The MHF as shown in
Reference number 20 identifies a vertical rotary hollow shaft coaxially arranged with the central axis 21 of the furnace 10. This shaft 20 passes through all hearth chambers 12, wherein a hearth without central material drop hole 18—such as e.g. hearth 142 in FIG. 1—has a central shaft passage opening 22 to allow the shaft 20 to freely extend therethrough. In a hearth with a central material drop hole 18—such as e.g. hearth 141 in FIG. 1—the shaft 20 extends through the central material drop hole 18. It will be noted in this context that the central material drop hole 18 has a much bigger diameter than the shaft 20, so that the central material drop hole 18 is indeed an annular opening around the shaft 20.
Both ends of the shaft 20 comprise a shaft end with a journal rotatably supported in a bearing (not shown in
Now follows a brief description of material flow through the MHF 10. In order to heat or roast material within the MHF 10, this material is discharged from a conveying system (not shown) through a furnace charging openings 32 into the uppermost hearth chamber 121 of the MHF. In this chamber 121 material falls onto the hearth 141, which has a central material drop hole 18. As the shaft 20 is continuously rotated, the four of rabble arms 26 in the hearth chamber 121 push the material with their rabble teeth 30 over the hearth 141 towards and into its central material drop hole 18. Through the latter material falls onto the hearth 142 of the next hearth chamber 122. Here, the rabble arms 26 push the material with their rabble teeth 30 over the hearth 142 towards and into its peripheral material drop holes 16. Through the latter, material falls onto the next hearth (not shown in
As known in the art, both the shaft 20 and the rabble arms 26 have internal channels through which is circulated a gaseous cooling fluid, usually pressurized air, which will be called hereinafter for the sake of simplicity “cooling gas”. The object of this gas cooling is to protect the shaft 20 and the rabble arms 26 against damage due to the elevated temperatures in the hearth chambers 12. Indeed, in the hearth chambers 12 ambient temperature may be as high as 1000° C.
The flow diagram of
Reference number 42 in
The shaft 20 includes three concentric cooling gas channels within an outer shell 50. The outermost channel is an annular main cooling gas supply channel 52 in direct contact with the outer shell 50 of the shaft 20. This annular main supply channel 52 surrounds an annular main distribution channel 54, which finally surrounds a central exhaust channel 56.
It will be noted that between hearth chambers 124 and 125, i.e. approximately in the middle of the shaft 20, a partition means, as e.g. a partition flange 58, partitions the annular main supply channel 52 and the annular main distribution channel 54 in a lower half and an upper half. This partitioning does however not affect the central exhaust channel 56, which extends from the lowermost hearth chamber 128 through all hearth chambers 128 to 121 to the top of the shaft 20. If it is necessary hereinafter to make a distinction between the lower and upper half of the annular main supply channel 52, respectively between the lower and upper half of the annular main distribution channel 52, the lower half will be identified with the superscript (′) and the upper half with the superscript (″)
The lower cooling gas inlet 44′ is directly connected to the lower half 52′ of the annular main supply channel 52. The cooling gas supplied to the lower cooling gas inlet 44′ consequently enters beneath the lowermost hearth chamber 128 into the lower annular main supply channel 52′ and is then channeled through the latter up to the partition flange 58 between hearth chambers 125 and 124, wherein the flow rate of the cooling gas remains unchanged over the whole length of the lower annular main supply channel 52′. This constant flow rate of cooling gas over the whole length of the lower annular main supply channel 52′ warrants that the outer shell 50 of the shaft 20 is efficiently cooled in the four lower hearth chambers 128 . . . 125.
Just below the partition flange 58, there is a lower cooling gas passage 60′ between the lower annular main supply channel 52′ and the lower annular main distribution channel 54′. Through this lower cooling gas passage 60′, the cooling gas enters into the lower annular main distribution channel 54′. Via at least one cooling gas supply channel 625 . . . 628 in its rabble arm fixing node 285 . . . 288 each rabble arm cooling system 26′5 . . . 26′8 in the lower half of the MHF 10 is in direct communication with the lower annular main distribution channel 54′. Via at least one cooling gas exhaust channel 645 . . . 648 in its rabble arm fixing node 285 . . . 288, each rabble arm cooling system 26′5 . . . 26′8 in the lower half of the MHF 10 is also in direct communication with the central exhaust channel 56. Consequently, in the rabble arm fixing node 285, a secondary cooling gas flow is branched off from the main cooling gas flow in the lower main distribution channel 54′ and rerouted through the rabble arm cooling system 26′5 to be thereafter directly evacuated into the central exhaust channel 56. In the rabble arm fixing node 286, another part of the gas flow in the annular main distribution channel 54′ passes through the rabble arm cooling system 26′6 and is thereafter also evacuated into the central exhaust channel 56. Finally, in the last rabble arm fixing node 288, all the remaining gas flow in the lower main distribution channel 54′ passes through the rabble arm cooling system 26′8 and is thereafter evacuated into the central exhaust channel 56.
The flow system in the upper half of the shaft 20 is very similar to the flow system described above. The upper cooling gas inlet 44″ is directly connected to the upper half 52″ of the annular main supply channel 52. The cooling gas supplied to the upper cooling gas inlet 44″ consequently enters into the upper annular main supply channel 52″ above the uppermost hearth chamber 121 and is then channeled through the latter down to the partition flange 58 between hearth chambers 124 and 125, wherein the flow rate of the cooling gas remains unchanged over the whole length of the upper annular main supply channel 52″. This constant flow rate of cooling gas over the whole length of the upper annular main supply channel 52′ warrants that the outer shell 50 of the shaft 20 is efficiently cooled in the four upper hearth chambers 121 . . . 124.
Just above the partition flange 58, there is an upper cooling gas passage 60″ between the upper main supply channel 52″ and the upper annular main distribution channel 54″. Through this upper cooling gas passage 60″, the cooling gas enters into the upper main distribution channel 54″. The connection of each rabble arm cooling system 26′4 . . . 26′1 in the upper half of the furnace 10 to the upper main distribution channel 54″ and the central exhaust channel 56 is as described above for rabble arm cooling systems 26′4 . . . 26′1 in the lower half. Consequently, in the rabble arm fixing node 284, a secondary cooling gas flow is branched off from the main cooling gas flow in the upper main distribution channel 54″ and rerouted through the rabble arm cooling system 26′4 to be thereafter directly evacuated into the central exhaust channel 56. In the rabble arm fixing node 283 another part of the gas flow in the upper main distribution channel 54″ passes through the rabble arm cooling system 26′3 and is thereafter also evacuated into the central exhaust channel 56. Finally, in the uppermost rabble arm fixing node 281 all the remaining gas flow in the upper main distribution channel 54″ passes through the rabble arm cooling system 26′1 and is thereafter evacuated into the central exhaust channel 56. From the central exhaust channel 56 the exhaust gas stream is then either directly evacuated into the atmosphere or evacuated by means of a rotary connection into a pipe for a controlled evacuation of the gas (not shown).
The outer shell 50 of the shaft consists mainly of intermediate support tubes 68 interconnected by the rabble arm fixing node 28. Such a rabble arm fixing node 28 comprises a ring-shaped cast body 70 made of refractory steel. The intermediate support tubes 68 are made of thick walled stainless steel tubes and are dimensioned as structural load carrying members between successive rabble arm fixing nodes 28. The intermediate support tubes 68 interconnected by massive rabble arm fixing nodes 28 constitute the load bearing structure of the shaft 20, which supports the rabble arms 26 and allows to absorb important torques when the rabble arms 26 are pushing the material over the hearths 14. It will further be noted that—in contrast to prior art shafts—the outer shell 50 described herein is advantageously a welded structure, the ends of the intermediate support tubes 68 are welded to the rabble arm fixing nodes 28, instead of being flanged thereon.
As explained above, the section of the shaft extending between adjacent hearth chambers 124 and 125 (i.e. the central shaft section) is rather particular because it comprises the partitioning flange 58, as well as the cooling passages 60′, 60″ between the annular main supply channel 52 and the annular main distribution channel 54. Before describing this particular central shaft section, a “normal” shaft section will now be described, also with reference to
As can be seen in
To complete thermal protection of the shaft 20, the latter is advantageously recovered with a thermal insulation (not shown). Such an insulation of the shaft 20 is advantageously a multilayer insulation including e.g. an inner refractory layer of micro-porous material, a thicker intermediate refractory layer of insulating castable material and an even thicker outer refractory layer of dense castable material.
A preferred embodiment of a rabble arm fixing node 28 is now describe with reference to
Considering now more particularly
When securing a new rabble arm 26 to the shaft 20, the plug body 110 of the rabble arm 26 has to be introduced into the socket 100 of the rabble arm fixing nod 110. During this introduction movement, the outer concave conical seat surface 114 first guides the plug body 110 into axial alignment with the cylindrical guiding surface 116. Thereafter both cylindrical guiding surfaces 116 and 116′ cooperate with one another for axially guiding the plug body 110 into its final seat position in the socket 100. It will be appreciated that axial guidance provided by the two cylindrical guiding surfaces 116 and 116′ considerably reduces the risk of damaging the plug body 110 or the socket 100 during the final coupling operation.
The rabble arm 26 further comprises an arm support tube 120 welded with one end to a shoulder surface 122 on the rear side of the plug body 110. This arm support tube 120 has to withstand the forces and torques acting on the rabble arm. It advantageously consists of a thick walled stainless steel tube extending over the whole length of the rabble arm 26. A gas guiding tube 124 is arranged inside the arm support tube 122 and cooperates with the latter to define between them a small annular cooling gap 126 for channeling the cooling gas to the free end of the rabble arm 26. The interior section of the gas guiding tube 124 forms a central return channel 128 through which the cooling gas flows back from the free end of the rabble arm 26 to the plug body 110.
It will be noted that one end of the gas guiding tube 124 is welded to a cylindrical extension 130 on the rear side of the plug body 110. The diameter of this cylindrical extension is smaller than the internal diameter of the arm support tube 120, so that an annular chamber 131 remains between the cylindrical extension 130 and the arm support tube 120 surrounding the cylindrical extension 130. This annular chamber 131 is in direct communication with the small annular cooling gap 126 between the gas guiding tube 124 and the arm support tube 122.
As already explained above, the plug body 110 is a solid cast body comprising several bores that will now be described. In
Referring now to
When one of the rabble arms 26 is dismounted, the clamping bolt 150 is extracted with rabble arm 26, i.e. it remains in the plug body 110 of the rabble arm 26. In order to be able to extract the hammer head 154 through the through hole 104 in the bottom of the socket 100, this through hole has the form of a key hole having a form corresponding roughly to the cross-section of the hammer head 154. It follows that by rotating the hammer head 154 by 90° about the central axis of the bolt shank 152, the hammer head 154 can be brought from the “hooked position” shown in FIG. 6”, into an “unhooked position”, in which it can be axially extracted through the keyhole 104 into the socket 100. Similarly, when a new rabble arm 26 is mounted, the hammer head 154 is first in a position in which it can axially pass through the key hole 104. Once the plug body 110 is seated in its socket 100, the hammer head 154, which is now located on the other side of key hole 104, can be brought into the “hooked position” shown in
The clamping device shown in
After removing the blind flange 188 and the thermally insulating plug 190, one has access to the coupling heads 174, 176 of the actuation tube 170 and the positioning tube 172. The actuation tube 170 is used to tighten the threaded sleeve 160. The positioning tube 172 mainly serves as an indicator of the position the hammer head 154 has with regard to the key-hole 104. Its coupling head 176 is therefore provided with an adequate positioning mark. It will be noted that the positioning tube 172 may also be used for fixing the clamping bolt 150 while loosening the threaded sleeve 160 by means of the actuation tube 170. Finally, the coupling head 174 of the actuation tube 170 may also have marks thereon, which in combination with the marks on the coupling head 176 of the positioning tube allow to check whether a sufficient tightening torque has been applied to the clamping device. It remains to be noted that the blind flange 188 may be removed during operation of the cooling system without a substantial gas leakages. Indeed, the threaded sleeve 160 seals the rear end of the actuation tube 170 and the front end of the actuation tube is sealed within the central through-hole 178 in the end-cup 180.
The aforementioned metallic protecting jacket 186, which is seen on
| Number | Date | Country | Kind |
|---|---|---|---|
| 91311 | Feb 2007 | LU | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP08/51171 | 1/31/2008 | WO | 00 | 8/13/2009 |
