KR19990071687A - Flexible joint - Google Patents

Abstract

The flexible joint 2 includes a first rigid wall portion 4, a second rigid wall portion 14, and a flexible wall portion 12 lying between these first and second rigid wall portions 4, 14, and these three Wall portions are disposed along this passage, defining a longitudinal passage through the joint. The sleeve 22 is fixed at one end to the first rigid wall portion 4 and extends along the passageway so as to overlap the second rigid wall portion 14. The sleeve 22 is away from the flexible wall portion 12 and can move freely with respect to the second rigid wall portion 14. According to the first aspect, an insulating material layer 24 is provided on the surface of the sleeve 22, and there is a space between the sleeve 22 and the flexible wall 12 so that the process fluid can freely occupy this space in use. . Further, according to the second aspect, the length of the portion where the sleeve 22 overlaps the second rigid wall portion 14 is measured by the sleeve 22 and the second rigid wall portion 14 when measured in the direction perpendicular to the sleeve 22. More than 5 times the distance between

Description

Flexible joint

The need for flexible joints in conduits and containers often arises in the case of the design and construction of chemical process plants. In many cases, conventional vessel and pipe equipment is too rigid for current process operating conditions, and the operation of such rigid equipment results in unacceptable rapid deterioration and failure of the process equipment. Thus, there is a need for a flexible joint that can be joined to the wall of a vessel or pipe, which has the degree of flexibility required to withstand process operating conditions. The design of flexible joints has been done for a long time. As a reference for general flexible joints used in pipe installations, see R.H. Perry and C.H. Edited by Chilton, Chemical Engineers' Handbook, Fifth Edition, pages 6-48. Typical flexible joints used in containers, pipes, etc., have first and second rigid wall portions connected by flexible wall portions. These three walls define a longitudinal passageway through which process fluid can flow and are disposed in the longitudinal direction of the passageway. In general, the flexible wall portion is in the form of a corrugated wall called "bellows" in the art.

More recently, with the development of chemical processes, there is a need to provide flexible joints that can withstand even harsher environments, such as exposure to hot fluids, corrosive and abrasive fluids. An example of a particularly harsh process environment can be found in hydrocatalytic cracking of hydrocarbons, where it is necessary to deliver a fluid containing hydrocarbon vapor and entrapped catalyst particles at high temperature. Typical process operating temperatures are around 550 ° C. in the reaction stage and about 750 ° C. in the regeneration phase. It can be seen that such high operating temperatures and the presence of abrasive elements such as cracking catalysts are very harsh conditions in the flexible part of the flexible joint. To prevent premature use of the flexible part of the flexible joint, it is necessary to make the joint a suitable resistive material such as a steel alloy and to prevent the flexible part from being directly exposed to the process fluid.

European Patent Application No. 445 352 introduces a flexible joint having a first rigid wall portion, a second rigid wall portion and a flexible wall portion at both ends welded to the rigid wall portions. These three walls define a longitudinal passage through the joint, the joint also having a sleeve member comprising a sleeve, one end of the sleeve being secured to the first rigid wall portion and the other end extending into the second rigid wall portion. The outer diameter of the sleeve is smaller than the inner diameter of the flexible wall portion and the inner diameter of the second rigid wall portion.

The conventional flexible joint also includes a box filled with a heat insulating material disposed on an outer surface of the sleeve, and a seal disposed between the free end of the sleeve and the second rigid wall portion. In a variant, a portion of the first rigid wall portion facing the passage, the inner surface of the sleeve and the inner surface of the second rigid wall portion is provided with a layer of corrosion resistant material.

The seal disposed between the free end of the sleeve and the second rigid wall portion serves to support the thermal insulation material and to prevent process fluid and debris from entering the cavity. This configuration can provide improved thermal insulation for the flexible portion of the joint. However, this is more complicated and more difficult to maintain. In addition, corrosion, embrittlement and / or relative movement between the sleeve and the second rigid wall portion results in poor seals and eventually loss of function. Debris from the seal is transferred to other parts of the plant by the process fluid, causing blockages and damage to the plant equipment.

If the seal becomes poor, hot process fluid may enter the annular space between the sleeve member and the flexible wall. The process fluid forms a stagnant layer that aids in thermal insulation. However, at the inlet of the annular region the fluid flow becomes turbulent, such that hot process fluid is in direct contact with the second rigid wall portion. This contact causes the temperature of the second rigid wall portion to rise. This does not affect the second rigid wall portion itself, but affects the weld between the flexible wall portion and the second rigid wall portion.

Accordingly, there is a need for a flexible joint that can combine its simple construction and ease of maintenance, and at the same time protect its flexible portion from the hot process fluid being handled. In particular, there is also a need for a flexible joint that can accurately control the thermal insulation of the flexible wall. Such joints are important when applied in such cases as the above-mentioned fluid catalytic cracking process, in which the flexible wall must be maintained at a temperature much lower than the temperature of the process fluid and also at a temperature higher than the dew point of the hydrocarbon being handled. If the thermal insulation is too much, the temperature of the flexible wall drops below the dew point temperature of the process fluid, resulting in condensation on the inner side of the flexible joint. This also causes the flexible wall to corrode and shorten its lifespan.

In addition, the weld between the flexible wall portion and the second rigid wall portion should also be prevented from failing.

The present invention relates to a flexible joint for use in a conduit and vessel through which a fluid flows. Specifically, it relates to a flexible joint that can be used under adverse conditions such as high temperature and can handle corrosive fluids.

1 is a cross-sectional view showing a half of a flexible joint according to a first embodiment of the first aspect of the present invention.

2 shows a sleeve portion of a flexible joint according to a second embodiment of the first aspect of the invention.

3 shows a sleeve portion of a flexible joint according to a third embodiment of the first aspect of the invention.

4 illustrates a portion of a flexible joint according to a second aspect of the present invention.

Considering this problem, the flexible joint of the present invention includes a first rigid wall portion, a second rigid wall portion, and a flexible wall portion at both ends welded to these rigid wall portions, and the three wall portions are longitudinal passages through the joint. The flexible joint further comprises a sleeve member having a sleeve, one end of which is fixed to the first rigid wall portion and the other end to the second rigid wall portion, defining a length of the passageway. The first rigid wall portion facing the passageway and the inner surface of the sleeve and the inner surface of the second rigid wall portion are provided with a layer of corrosion resistant material, the outer diameter of the sleeve member being on the inner diameter of the flexible wall portion and on the second wall portion. A second layer of thermal insulation material smaller than the inner diameter of the layer of corrosion resistant material at and disposed between the second rigid wall portion and the layer of corrosion resistant material is also provided.

Applicants have found that the use of a thermal insulation material reduces the temperature of the second rigid wall portion during normal operation such that damage to the weld is prevented and the service life of the flexible joint is increased.

Flexible joints may be used in conjunction with the walls of the vessel, more generally with conduits or pipelines. The wall portion of the flexible joint in its cross section may take any form as long as it is suitable for the cross section of the vessel or conduit in which the joint is installed. In the most common case, the cross section of the rigid wall portion is cylindrical. In general, the rigid wall portion is made of the same material as the adjacent device. Typical materials are mild steel, stainless steel and other alloyed steels, the choice of which depends on the process conditions at the time and the fluid being handled.

The flexible wall portion is arranged between the first and second rigid wall portions to absorb the relative motion between these two rigid wall portions. This relative motion is due to, for example, vibration, pressure and temperature differences in the process equipment. The flexible wall may be of any shape as appropriate. Most commonly, the flexible wall is in the form of a longitudinal waveform, commonly referred to as a "concertina" or "bellows." The magnitude and shape of this waveform is determined by the degree of flexibility and displacement required. Techniques for selecting and designing flexible walls are known in the art. The flexible wall can be made of any suitable material, including the materials mentioned in connection with the construction of the rigid wall. Thinner flexible walls are generally more resistant to stress corrosion and embrittlement failure than rigid walls. Therefore, more flexible and therefore expensive materials must be used for flexible walls. However, as an advantage of the present invention, it is possible to use common materials such as, for example, Inconel and Incoloy alloys.

The sleeve extends along the passageway in the flexible joint. One end of the sleeve is fixed to the first rigid wall portion, for which an appropriate fixing method can be used. The most suitable method of securing the sleeve to the first rigid wall portion is by welding. The sleeve extends in the passageway to overlap the second rigid wall portion. The sleeve is away from the flexible wall. The other end of the sleeve is not fixed, so that the sleeve can be moved relative to the second rigid wall portion. In general, the portion of the sleeve that overlaps the second rigid wall portion is away from the second rigid wall portion.

According to one preferred embodiment, the sleeve member is elongated from the first rigid wall portion to provide a continuous wall surface, thereby not impairing the flow of fluid through the flexible joint, ie the sleeve and the first And a portion of the 2 rigid wall portions form a substantially smooth surface passage for the flow of fluid through the joint. The distance required between the sleeve member and the flexible wall portion is such that the width of the passageway defined by the flexible wall portion is the nominal width of the flexible joint, i.e. the width of the smooth side passageway defined by the sleeve member and the portion of the first and second rigid wall portions. It is obtained by making it larger. In contrast, the suboptimal construction includes a sleeve member that extends into the passageway, such that a narrow portion exists in the fluid passageway along the joint.

The sleeve is made of a suitable material that can provide the necessary resistance to processing conditions. In general, the sleeve is made of the same material as the first and second rigid walls.

In operation, the process fluid occupies an annular space between the sleeve member and the flexible wall. The process fluid may enter the space between the free end of the sleeve member and the second rigid wall portion. The fluid in the annular space is relatively stagnant and acts as an insulating medium for the flexible wall. In order to keep the process fluid stationary in the annular space, it is preferable to position the first rigid wall portion upstream of the flexible joint when installed and used.

On the surface of the sleeve is provided a thermal insulation material. The thermal insulator may also adhere on the surface of the sleeve while making direct contact with the process fluid being handled. Preferably, this thermal insulator is provided on the surface of the sleeve facing the flexible wall. If necessary, a heat insulating material may be provided on both surfaces. The heat insulating material layer may be one or plural. In the case of using a plurality of layers, these layers may be formed of the same or different materials from each other. The number and location of the layers and the type of thermal insulation material depend on the process operating conditions the flexible joint is subjected to, the material of the flexible wall and the characteristics of the process fluid being handled. The thermal insulation material should have low thermal conductivity at high working temperatures so as to provide the insulation as required by the relatively thin layer formed thereon. This thermal insulation should contain as little ash, sulfur and chloride as possible. The thermal insulation material should be suitable for use under given process conditions, eg high temperature. It is preferable that the thermal insulation material is made of a fiber ceramic material. Suitable ceramic materials include fibers of silica, alumina, zirconia, magnesia, calcia and mixtures thereof. As suitable materials, for example, those sold under the trade names "Saffil" and "Zircar" can be used. Alternatively, the thermally insulating material but still less preferred materials are graphite and ash paper. These are also available for purchase.

According to one preferred embodiment of the invention, the layer formed of the thermal insulation material on the sleeve is covered with a protective sleeve. The protective sleeve covers almost the entire portion of the heat insulating material, thereby forming a sandwich of the sleeve and the heat insulating material. According to another preferred embodiment, the protective sleeve is not fixed to the thermal insulating material layer, thereby enabling the protective sleeve to move relative to the thermal insulating material, as a result of the relative movement between the components resulting from the thermal expansion effect, for example. Is allowed.

The flexible joint is provided with a layer of corrosion resistant material in the form of refractory oxide, which covers the surface of the sleeve adjacent the process fluid when the joint is used. Suitable refractory materials are well known in the art and commercially available. Suitable refractory materials include silica, alumina, tartannia, zirconia, calcia, magnesia and mixtures thereof. One suitable refractory material is a mixture of alumina and silica, which is sold under the trade name "CURAS 90 PF". Refractory oxides are generally used in the form of cement or tiles or blocks. The refractory oxide layer is relatively thicker than the insulating material layer. Since the refractory oxide is porous, some of the process fluid may reach the bottom. The primary purpose of refractory oxides is to protect the bottom from abrasion and corrosion. If desired, a refractory oxide layer may be provided over the insulation layer covering the sleeve surface.

The layer of thermal insulation provided on the surface of the second rigid wall portion should cover at least the portion of the surface of the second rigid wall portion that overlaps the sleeve. More preferably, the heat insulating material layer covers more of the surface of the second rigid wall portion. Any suitable material described above that can be used as the heat insulating material layer on the sleeve can be employed. In addition, one or more layers may be used, wherein these layers are made of the same or different materials. As described above for the refractory oxide formed on the surface of the sleeve, the thermal insulation layer is covered with the refractory oxide layer.

As mentioned above, the sleeve member is spaced apart from the flexible wall, thereby forming an annular space through which the process fluid can flow during operation. The process fluid in this annular space forms a reservoir of relatively stagnant fluid which serves to further insulate the flexible wall. In order for this fluid container to be able to perform its function properly as an insulator, it is important that the fluid is relatively stationary in the container. It has been found that the configuration of the free end of the sleeve member and its relationship with the second rigid wall portion have an important effect on the insulating properties of the process fluid in the annular space, in particular the length at which the sleeve member overlaps with the second rigid wall portion.

The length of the portion of the sleeve member overlapping with the second rigid wall portion is at least five times the distance from the sleeve member to the second rigid wall portion as measured in the direction perpendicular to the sleeve member.

Preferably, the length of the portion overlapping with the second rigid wall portion in the sleeve member is 100 mm or more under any condition, more preferably 200 mm or more.

It will be appreciated that the clearance between the free end of the sleeve member and the second rigid wall portion should be sufficient to accommodate any relative movement between the two components when the joint is in use. In one preferred embodiment, the sleeve member and portions of the first and second rigid wall portions form a substantially smooth faced passageway for the flow of fluid through the joint. In this case, the distance between the free end of the sleeve and the second rigid wall portion when measured along a line parallel to the longitudinal axis of the sleeve is preferably 10 mm or more, more preferably 25 mm, under any condition.

The flexible joint of the present invention can be applied to any field where a flexible joint is needed. As noted above, the flexible joints are particularly suitable for handling fluids under harsh conditions, in particular for handling corrosive fluids and / or fluids used at high temperatures. In addition, by using the refractory oxide, a flexible joint having high resistance to wear and corrosive fluid can be obtained. Such joints can be used in chemical and refining plans. As noted above, the present flexible joints are particularly useful for processes that handle fluidized solid media, such as hydrocatalytic cracking of hydrocarbons. Another particular application is the case of handling very hot gases, such as hot flue gases. With reference to the accompanying drawings will be described in more detail the present invention.

Referring to FIG. 1, a generally cylindrical flexible joint, denoted by reference numeral “2” for use in a process pipeline, includes a first rigid wall portion 4. This rigid wall portion has a narrow cylindrical outer end portion 6 and a wide cylindrical inner end portion 10 connected by a central truncated conical wall portion 8.

The flexible wall portion 12, which is generally cylindrical, extends from the first rigid wall portion 4 to the second rigid wall portion 14. The second rigid wall portion has an inner end portion, a central wall portion and an outer end portion 16, 18, 20 similar to the first rigid wall portion 4, and the direction is opposite to the first rigid wall portion. Both ends of the flexible wall are welded to the rigid walls. The first wall portion 4, the flexible wall portion 12 and the second wall portion 14 are arranged symmetrically about a single central longitudinal axis and define a passage P.

The cross section of the flexible wall 12 is in the form of a waveform, often referred to as "bellows," as is generally known in the art.

A cylindrical sleeve member 21 comprising a sleeve 22 is arranged concentrically with the wall portions 4, 12, 14, one end of which is welded (shown at a point where the outer end 6 and the central portion 8 connect with each other). Is connected to the first rigid wall portion 4). The sleeve 22 extends beyond the flexible wall 12 to overlap the inner end of the second rigid wall portion.

A layer of corrosion resistant material 26 is provided on the inner surface of the sleeve 22 and on the inner surface of a portion of the first rigid wall portion opposite the passage P. The corrosion resistant material layer 28 is also provided inside the second rigid wall portion 20.

The outer diameter of the sleeve member is smaller than the minimum inner diameter of the flexible wall portion 12 and smaller than the inner diameter of the corrosion resistant material layer 30 on the second rigid wall portion 20.

Further, there is a thermal insulation layer 30 between the inner surface of the second wall portion 20 and the corrosion resistant material layer 28.

Conventional joints associated with flexible joints, such as expansion limits, leak detection systems, weather shrouding and gas exhaust connections, have been omitted for simplicity.

In use, the flexible joint 2 of FIG. 1 is installed such that the process fluid flows from the first rigid wall portion 4 toward the second rigid wall portion 14, as indicated by arrow A. The process fluid enters the space between the sleeve 22 and the flexible wall portion 12 through the annular region between the sleeve 12 and the inner end 16 of the second rigid wall portion 14 to form a thermal insulation layer. Done.

Thermal insulation is achieved by the process fluid layer stagnating at the annular portion between the sleeve member 21 and the flexible wall portion 12. The fluid in the annular region between the sleeve member 21 and the inner end wall portion 16 of the second rigid wall portion 14 is always mixed with the process fluid in the passage P. Thus, without the heat insulating material layer 30, the temperature of the inner end wall portion 16 is raised such that the weld between the flexible wall member 12 and the second rigid wall portion 14 can be affected.

Referring to FIG. 2, it can be seen that the sleeve member 21 and the insulating material thereon are enlarged in the vicinity of the first rigid wall portion 4. As can be seen in the embodiment of FIG. 2, the sleeve member 2 has a thermal insulation layer 32 disposed on the inner side of the sleeve 22. The refractory oxide layer 26 is formed on the heat insulating material layer 32.

Referring to FIG. 3, which is similar to FIG. 2, showing a particularly preferred embodiment, the sleeve member 21 comprises a layer of thermal insulation 36 disposed on the outer surface of the sleeve 22. In addition, a cylindrical protective sleeve 38 is provided on the heat insulating material layer 36. On the inner surface of the sleeve 22 is a refractory oxide layer 26. The thermal insulation layer 36 and the protective sleeve 38 are preferably formed as close as possible to the first rigid wall portion 4 while allowing sufficient space to accommodate any relative movement between the various components. For example, space is required if the protective sleeve 38 is not rigidly bonded to the thermal insulation layer 36.

Generally, in the embodiment of FIGS. 1-3 applied to pipelines used in fluid catalytic cracking processes, the thickness of the sleeve is on the order of 10 mm. The total thickness of one or more layers of insulation is about 3-10 mm. The thickness of the refractory oxide layer is about 25 mm. When there is a protective cover, the thickness thereof is about 3 to 6 mm. It will be appreciated that the thickness of the various components will vary depending upon the application.

4 shows details (dimensions not shown) for the flexible joint according to the invention. The same reference numerals are used for the components of FIG. 4 as the components described above in connection with FIG. Thus, in FIG. 4, the sleeve member 21 extends to overlap the inner end 16 of the second rigid wall portion 14. In FIG. 4, the distance d is the distance between the outer surface of the sleeve member 21 and the inner surface of the inner end 16 provided with the layer of corrosion resistant material 28, perpendicular to the longitudinal axis of the sleeve 22. Is measured. The overlap distance? Of the sleeve member 21 in the second rigid wall portion 14, shown in FIG. 4, is at least five times the distance d. Preferably the distance l is at least 200 mm. The distance a measured from the end of the sleeve member 21 to the second rigid wall portion 14 in the direction parallel to the longitudinal axis of the sleeve 22 is 25 mm or more.

The invention is further illustrated by the following examples.

Example

The operating temperature of the flexible wall of the flexible joint according to the invention can be calculated. The flexible joint was assumed to have the general configuration shown in Fig. 1, but the insulating material layer, the protective sleeve and the refractory oxide layer shown in Fig. 3 were employed. The flexible joint is supposed to be installed in the catalyst stand-pipe of the generator of the conventional fluid catalytic cracking plant. The process fluid to be handled was to consist of a hydrocarbon gas and a trapped catalyst. In the worst case, the space between the sleeve and the flexible wall was assumed to be filled with gas without catalyst. The flexible joint has a geometry at the free end of the sleeve as seen in FIG. 4 in accordance with the requirements of the second aspect of the present invention. Details of the joint configuration, operating temperature and final temperature of the flexible wall of the joint are shown in the table below.

For comparison, similar calculations were made for flexible joints with the same configuration but without insulation. The details and results of this experiment are also presented in the table below.

<Table>

Example Comparative example Sleeve thickness (mm) 3 10 Thickness of ceramic fiber insulation layer 36 (mm) 3 none Thickness of protective sleeve (mm) 3 none Weather enclosure has exist has exist Process temperature (℃) 750 750 Maximum temperature of flexible wall (℃) 324 497

From the table, it can be seen that the temperature of the flexible wall portion of the flexible joint according to the configuration of the present invention was considerably low. This results in longer joint life and the availability of more common and economical materials available on the market.

Claims (11)

A flexible joint comprising a first rigid wall portion, a second rigid wall portion, and a flexible wall portion at both ends welded to these rigid wall portions, wherein the three wall portions define a longitudinal passage through the joint, the longitudinal direction of the passage. And wherein the flexible joint further comprises a sleeve member having a sleeve, one end of which is fixed to the first rigid wall portion and the other end to which the second rigid wall portion is fixed. A portion of the rigid wall portion facing the passageway and an inner surface of the sleeve and an inner surface of the second rigid wall portion are provided with a layer of corrosion resistant material, the outer diameter of the sleeve member being the inner diameter of the flexible wall portion and on the second wall portion. It is characterized in that a heat insulating material layer smaller than the inner diameter of the corrosion resistant material layer and disposed between the second rigid wall portion and the corrosion resistant material layer is also provided in the second rigid wall portion. Flexible joint made with gong. The flexible joint of claim 1, wherein the sleeve member and a portion of the first and second rigid wall portions form a substantially smooth faced passageway for the flow of fluid through the joint. The flexible joint of claim 1 or 2, wherein the sleeve member comprises a layer of thermal insulation material disposed between the sleeve and the corrosion resistant material layer. The flexible joint according to any one of claims 1 to 3, wherein the thermal insulation layer is disposed on a surface of the sleeve facing the flexible wall portion. 5. The flexible joint of claim 4 wherein the soft insulation layer of the sleeve member is covered with a protective sleeve. 6. The flexible joint of claim 5 wherein the protective sleeve is not coupled to the thermal insulation layer so that the protective sleeve can be moved relative to the thermal insulation material. The flexible heat insulating material according to any one of claims 1 to 6, wherein the heat insulating material is a fiber ceramic material, and is preferably a material including fibers made of silica, alumina, zirconia, magnesia, and mixtures thereof. Castle joint. 8. The flexible joint of claim 1, wherein the corrosion resistant material is a refractory oxide selected from silica, alumina, titanium, zirconia, calcia, magnesia and mixtures thereof. The length of the portion of the portion where the sleeve member overlaps the second rigid wall portion is the distance from the sleeve member to the second rigid wall portion provided with the layer of corrosion resistant material in a direction perpendicular to the sleeve. Flexible joint, characterized in that more than five times. 4. The flexible joint according to claim 3, wherein the length of the portion where the sleeve member overlaps with the second rigid wall portion is 100 mm or more, preferably 200 mm or more. The flexible joint according to any one of the preceding claims, which is used for fluid catalytic cracking, such as hydrocarbons, or handling hot flue gases.