DE102010060981B3 - Pipe flange used in e.g. chemical plant, has screws that are inserted into through-holes of plastic flange portions, to connect flange portions with counter-element under force application of sealing ring - Google Patents

Abstract

The flange has sealing ring (3) which is arranged between plastic flange portions (2a,2b) and counter-element. The screws (4) are inserted into through-holes (5) of plastic flange portions to connect flange with counter-element under force application of sealing ring. A supporting surface (10) of flange portions is provided facing seal surface (1) of supporting ring (9). The plastic flange and counter-element are drawn with respect supporting ring, so as to seal plastic flange portions.

Description

The invention relates to a pipe flange with an annular sealing surface having a plastic flange, a counter-element, a sealing ring assembly between the plastic flange and the counter element and with screws which are inserted into through holes of the plastic flange and connect the plastic flange with the counter element under application of force to the sealing ring assembly. The invention further provides a pipe flange connection with a metal flange having an annular sealing surface, a plastic ring provided for insulation purposes, which is placed on the metal flange on a side opposite the sealing surface, a counter element, a sealing ring arrangement between the metal flange and the counter element and with screws. which are inserted into through holes of the metal flange and the plastic ring and connect the metal flange and the plastic ring arranged thereon by applying force to the sealing ring assembly with the counter element. In both versions, plastic is provided on the opposite side of the annular sealing surface of the flange, where the screws are supported with their heads or mother.

In chemical and petrochemical process plants, flanges made of plastic are used in areas with corrosive media. Suitable materials are, for example, reactive resin molding materials or thermoplastics such as polypropylene, polyethylene and polyvinylidene fluoride. The known flange connections are adapted in their geometry to the steel flanges, for example according to DIN of the nominal pressure level PN10 or according to the standard ASME the nominal pressure levels Class 150 and 300.

In contrast to steel, plastic flanges can only tolerate low surface pressures. Another problem is that plastics relax over a long period of time, ie, are flowable to some extent, and so do not permanently transfer the stress from the flange blade rotation. Against this background, soft seals, usually elastomers or polytetrafluoroethylene are used as a sealing material in the known plastic flange connections, the assembly is carried out at very low torques. In the case of commercially available screws and the torques recommended for plastic flanges, the screws are stressed only between 10% and 20% of their yield strength. The term yield strength in the context of the invention refers to the typical 0.2% yield strength R _p0.2 . The 0.2% proof stress is the mechanical stress at which the residual strain related to the initial length of the specimen is exactly 0.2% after relief. At higher loads of the object under consideration, in practice, either pronounced plastic deformation usually occurs Deformations or to a break.

Since a certain relaxation is observed in plastic flanges, the already low surface pressure decreases even further at the beginning, so that a secure seal is no longer guaranteed even with the described soft seals. Furthermore, the train on the screws then so low that they can solve themselves without an additional backup in vibration or the like. Another problem is that already comparable small tilting moments in soft seals can sometimes lead to a no longer sufficient surface pressure or overpressing of the seal on parts of their circumference.

To compensate for the setting behavior, the screws are tightened in the known, in their shape derived from steel flanges plastic flanges before leakage occurs. If the tightening occurs during the operation of the system, there is an increased risk for the fitter. In contrast, a shutdown of the system is associated with significant operating restrictions. The frequent operation of the screws when tightening also increases the risk of incorrect operation. If, for example, the low torques usually provided for plastic flanges are not accidentally adhered to, overpressing of the seal and thus a leak can occur even during the drawing, so that there is an immediate increased risk of accidents.

The disadvantages and limitations described also apply to metal flanges, which are covered with a plastic ring for insulation purposes.

In addition to the standard flanges derived plastic flanges and special flanges for connecting plastic pipes are known. So is out of the EP 1 914 465 A1 a special flange known in which pieces of plastic pipe only have a Vorschweißbund. The flanges of a tensile material then act on the Vorschweißbunde and pull them together. The disadvantage is that these special flanges are not readily compatible with other types of flanges, the screws between the flanges are also stretched freely. A direct support of the flanges against each other in the area of the screws is not provided. The introduction of force into the collar and in the seal is in need of improvement.

Against this background, the invention has the object, a pipe flange specify with a plastic flange or provided with a plastic ring for insulation purposes, which is characterized by increased reliability and comparatively low testing and maintenance costs.

Based on the above-described pipe flange connection, the object is achieved in that the sealing ring assembly has an annular portion and a laterally adjoining support ring, wherein the flange and the counter-element are pulled onto the support ring on block, whereby the seal by means of the sealing portion in the force shunt , Furthermore, it is provided that between the heads or nuts of the screws and the plastic flange or the plastic ring provided for insulation for power distribution, a metallic intermediate piece is arranged, which connects at least two through holes.

While low torque must always be maintained in generic plastic flanges having through holes for prior art screws, the present invention teaches a combination of features that permits high torques.

First, the invention is based on flanges, on the one hand have provided for abutment with the sealing ring assembly sealing surface and on the other hand through holes for the screws. This results in a simple, one-piece design of the flange can be derived based on the dimensions and distribution of the through holes of conventional standard metal flanges. The fact that both the sealing surface and the through holes are formed in a one-piece flange, resulting in a large area, which can be used for the support of the flange and the counter-element, usually a further flange.

In addition, a metallic intermediate piece is provided for Kraftvereilung, which is arranged below the heads or nut of the screws and at least two adjacent through holes interconnects. This dimensionally stable metallic intermediate piece ensures that the forces exerted by the screw heads or nuts are distributed over the largest possible range. It is thus avoided that the heads or nuts seize by the lower stability of the plastic and the relaxation of the plastic in the material of the plastic flange or provided for insulation plastic ring. The exercisable with the screws on the flange connection force can thus be significantly increased.

The design of the sealing ring assembly is adapted to an increased surface pressure. Thus, a support ring is provided, on which the flange and the counter element are pulled to block. The inventive combination of the generic flange with through holes, the metallic intermediate piece for distributing the force exerted by the screw force on a maximum surface and the arrangement of the sealing portion of the sealing ring assembly in the force shunt can now very high for plastic flanges or metal flanges with a plastic ring for insulation purposes Surface pressures and a higher load on the screws can be realized.

Since the force exerted by the screw heads or nut is distributed over an enlarged area, overall a reduced setting behavior can be observed. Furthermore, in the context of the invention, increased surface pressures can be set, so that even with a certain setting of the seal arrangement, there is still a surface pressure which is sufficient for a secure seal. Another advantage is that the pipe flange connection is overall very stable and not susceptible to tilting moments. The risk of overpressing is eliminated or at least significantly reduced by the inventive design with the intermediate piece and the arrangement of the sealing portion in the force deficit. Retightening the screws, if this is still necessary in the context of the invention, can thus be done with a significantly lower risk to people and the environment.

The counter element can be in the context of the invention, a further flange, in particular a plastic flange but also a metal flange with or without a plastic ring for isolation purposes. In addition, the counter element can also be a blind flange or a flange connection of a device. If the mating element is also a plastic flange or a metal flange with a plastic ring provided for insulation purposes, this further flange is expediently designed as described above, wherein therefore also a metallic intermediate piece for force distribution is arranged there. In particular, in the connection of two similar flanges a symmetrical or substantially symmetrical structure is appropriate.

In the context of the invention, a functional, wide interpretation of the term screw is required. As a screw in the context of the invention, for example, a nut provided with two bolts or a arranged on the counter-element stud bolts are referred to. Conveniently, the screws are standard screws Metal. Since in the context of the invention increased torques and an increased surface pressure compared to conventional plastic flanges is achieved, there is also a greater burden on the tightened screws. While according to the prior art the load is usually between 10 and 20% with respect to the 0.2% proof stress in standard screws, the load of the tightened screws according to a preferred embodiment of the invention is at least 40%, preferably at least 60% of the 0, 2% proof strength R _p02 . For the majority of applications, the load should be at least 50%, for example 70% of the 0.2% proof stress. It has been found in practice that at a higher utilization of the screws, the risk of an automatic loosening is significantly reduced. On the other hand, to ensure sufficient reserves against overloading, the value of 70% of the 0.2% proof stress is particularly suitable.

The intermediate piece connects in the context of the invention at least two through holes and thus distributes the force exerted by the screws on the area between these through holes. The intermediate piece is expediently designed as a continuous or segmented metal ring in the context of the invention. An optimum force distribution is achieved with a metal ring, which also utilizes the entire available width of the flange below the screws. The intermediate piece should also be selected so that it does not deform significantly under the action of the force exerted by the screws to actually ensure a full surface as possible loading of the underlying plastic flange or the underlying intended for isolation plastic ring. The thickness of the intermediate piece is to be selected depending on the flange diameter and thereby provided tightening torques of the screws. For a majority of the flange dimensions, the thickness of the metallic intermediate piece is at least 10 mm, for example 15 mm. As a material, stainless steel is particularly suitable.

According to the invention, the sealing ring arrangement has a support ring and an annular sealing section adjoining laterally thereon. Before mounting the sealing ring assembly, the annular sealing portion usually has a greater thickness than the adjoining support ring, so that then pulled during assembly of the flange and the counter element on the support ring on block, whereby the sealing portion is compressed accordingly. For the sealing portion of the usual sealing materials such as graphite, elastomeric plastic or PTFE are suitable.

According to the invention, the flange and the counter element can be pulled onto the support ring with a large surface pressure. The reduced in comparison surface pressure of the sealing portion in the force shunt results essentially from the excess of the sealing portion relative to the support ring and the compressibility of the sealing material. Depending on the requirements, the geometry of the sealing ring arrangement can thus be set precisely. If the total surface pressure due to a setting behavior of the pipe flange connection is reduced to a certain extent, this initially only impacts in the region of the support ring, wherein the surface pressure prevailing on the sealing section and thus the sealing effect remain unaffected. Also, the screws, if this is required in the context of the invention, be tightened readily, because then the re-increased surface pressure is absorbed by the support ring.

The support ring may in principle be formed from a fiber material, plastic or metal, which material must have a higher strength than the sealing portion, so that the counter element and the flange can be pulled onto block. If the support ring still has a certain flexibility in the context of the invention, the surface pressure at the sealing section can also be changed to a certain extent. However, the support ring is suitably equipped by a suitable choice of material and dimensions so that at usual and slightly increased torques of the screws overpressing of the sealing portion is reliably avoided. In particular, it can be provided that even with a complete utilization of the screw (100% of 0.2% proof stress) overpressing is avoided. If the tightening torque is improper, the screws will crack before the gasket is over-pressed. When assembling or retightening the screws, such an error is noticed immediately, without there being a loss of tightness and thus possibly a serious accident.

The sealing portion and the support ring can basically kept ready as separate elements. However, an embodiment in which the sealing ring arrangement is formed by a continuous two-component sealing ring is preferred. In the context of such a configuration results in a simplified handling of only one part, which must be arranged between the flange and the counter element. Furthermore, the support ring can also extend with a section of reduced thickness in the region of the sealing portion and serve there as a carrier for the sealing material.

Also preferred is an embodiment in which the support ring has through holes through which the screws are guided. In the context of such an embodiment, the support ring also extends directly in the region of the screws, so that there is a complete support of the forces exerted by the screws forces possible. A not exactly defined Flanschblattrotation, ie an inclination of the flanges due to the forces exerted by the screws tensile forces can be avoided or at least reduced to a predetermined level. Also, a precise calculation of the pipe flange connection is facilitated, with different tightening torques and the change of the material for the plastic flange or provided for insulation plastic ring effect less. With a force support over the support ring in the region of the through holes and a reduction of the flange thickness can be considered, whereby a significant material savings can be achieved. The increase in flange blade rotation otherwise to be expected with a reduction in the flange thickness is prevented by the direct support over the support ring in the region of the screws.

Since the sealing portion is arranged in the force shunt in the context of the invention, based on the entire contact surface of sealing ring assembly and plastic or metal flange, a comparatively large average surface pressure of for example 20 N / mm ^{2 can be} adjusted. This average surface pressure results from an increased surface pressure on the support ring and a reduced surface pressure to a suitable extent at the sealing portion.

Contrary to the design of conventional standard flanges, which have a step between the sealing surface and the region of the through holes, in the context of the present invention a planar transition is preferred in order to be able to pull the flange and the counter element, usually a further flange, against the support ring , If, nevertheless, a step is provided, the thickness of the support ring can be increased accordingly, in order then to be able to set a defined surface pressure on the sealing section in the block position. According to a particularly preferred embodiment, the plastic or metal flange on the side of its sealing surface from its inner edge to its outer edge is flat or at least substantially flat.

If, according to a previously described variant of the invention, the pipe flange connection has a metal flange with a plastic ring provided for insulation purposes, further measures for insulation are also expedient. For example, the shaft of the screws is provided with an insulating sleeve to avoid a short circuit over the screw shaft. Furthermore, the sealing ring arrangement itself must also be formed from an insulating material in order to avoid direct electrical contact via the sealing ring arrangement.

The invention will be explained in the following with reference to a drawing showing only one exemplary embodiment. Show it:

1 a pipe flange connection with two plastic flanges,

2a to 2c alternative embodiments of sealing ring arrangements of the pipe flange connection,

3 a pipe flange connection with two metal flanges and arranged on these metal flanges for isolation plastic rings.

1 shows a pipe flange with two an annular sealing surface 1 having plastic flanges 2a . 2 B , In the context of the invention can also only a plastic flange 2a or 2 B be provided, which is then connected to a different counter-element, such as a different flange, a blind flange or a housing connection.

Between the two plastic flanges 2a . 2 B is a sealing ring arrangement 3 intended. The two plastic flanges 2a . 2 B are under load of the sealing ring assembly 3 through a variety of screws 4 connected through through holes 5 the plastic flanges 2a . 2 B are guided.

Under screws 4 be in the context of the invention screws with a head and a nut, the threaded bolt shown in the embodiment 6 with nuts 7 or understood with a mother cooperating studs.

According to the invention, the sealing ring arrangement 3 an annular sealing portion 8th and a support ring 9 on. In addition, on a support surface 10 the plastic flanges 2a . 2 B that of the respective sealing surface 1 opposite, a metallic spacer 11 for the distribution of the nuts 7 over a conventional washer 12 applied force provided. The metallic intermediate piece 11 connects at least two circumferentially consecutive through holes 5 and is designed according to a preferred embodiment as a ring, preferably as an unsegmented ring In order to achieve a uniform force distribution, the intermediate piece extends 11 also over the entire or at least substantially the entire width of the support surface 10 ,

Through the intermediate piece 11 can with the screws 4 very large forces are exerted without the plastic material of the plastic flanges 2a . 2 B locally overloaded in the area of the screws. Strong influences by relaxing, ie a certain flow of the plastic flanges 2a . 2 B can be avoided.

To be able to absorb an increased surface pressure, the two plastic flanges 2a . 2 B on the support ring 9 pulled on block, so that then according to a previously precisely set excess of the sealing portion 8th a predetermined compression of the sealing portion 8th and thus there is a defined surface pressure in the sealed area. When the plastic flanges 2a . 2 B After mounting to a certain extent set, this initially only affects the on the support ring 9 acting forces and not on the relevant for the sealing sealing portion 8th out. Due to the block position on the support ring 9 is also an over-pressing of the sealing section 8th safely avoided, so that during assembly readily high torques, as they are common with conventional metal flanges, can be provided.

Due to the areal distribution of forces, the plastic flanges have 2a . 2 B a significantly reduced tendency to relax. In addition, the tightening torques can be chosen so large that even with a certain drop in the surface pressure over time for a secure seal on the sealing portion 8th required values are not fallen below. Finally, a tightening of the screws 4 easily possible, because then through the support ring 9 the risk of overpressing the sealing portion is excluded or at least significantly reduced.

If between the two plastic flanges 2a . 2 B By external forces acts a tilting moment, this can also be done by the support ring 9 be taken, so that overall results in a comparatively rigid flange, which contributes to a further increase in reliability.

The screws 4 are in the context of the invention suitably selected and mounted so that the load of the tightened screws at least 40%, preferably at least 50%, more preferably at least 60% of the 0.2% proof strength R _p0.2 corresponds. For example, a value of 70% of the 0.2% proof stress is suitable, so that then there are still sufficient safety reserves against tearing of the screws 4 is present. According to a further preferred embodiment, the support ring is in the embodiment 9 with through holes 5 ' provided, so that the support ring also directly in the field of screws 4 extends. Tilting or at least excessive tilting of the plastic flanges 2a . 2 B , which is also referred to as Flanschblattrotation, can be avoided.

The 2a to 2c show alternative embodiments of sealing ring assemblies 3 . 3 ' . 3 '' which can be used in the context of the invention.

2a shows the in 1 illustrated sealing ring assembly with an outer support ring 9 and a subsequent thereto sealing section 8th , wherein the support ring, as well as the 1 it can be seen, through holes 5 ' At least before first use of the seal is the thickness of the sealing portion 8th bigger than the thickness of the support ring 9 , The sealing section 9 may be formed from conventional sealing materials, for example elastomer, PTFE or graphite. If the sealing section 8th has elastic properties, this can spring back when loosening the flange and then again has a greater thickness than the support ring 9 on. According to the 2a becomes the sealing ring arrangement 3 formed by a coherent Zweistoffdichtring.

The 2 B shows an alternative embodiment of the sealing ring assembly 3 ' , where the support ring 9 ' and the sealing section 8th' be kept as separate parts. The support ring can through holes as previously described 5 ' or as in the embodiment of 2 B represented, be formed without through holes with a correspondingly reduced width.

Another possible embodiment is in the 2c shown. This sealing ring arrangement 3 '' includes an outer support ring 9 '' which is preferably made of steel or stainless steel and may for example have a thickness of 1.5 mm. Inside then closes one from the material of the support ring 9 formed corrugated ring section 13 on, which together with double-sided sealant pads 14 the sealing section 8th'' forms.

3 shows a pipe flange connection, wherein the two metal flanges 22a . 22b isolated from each other. First, this is a sealing ring arrangement 3 provided, which is carried out as previously, but wherein the support ring 9 is formed of an insulating material. To the screws 4 around is an insulating sleeve 23 arranged. To make an electrical connection via the screws 4 To avoid is also on the support surfaces 10 the metal flanges 22a . 22b to make an isolation. For this purpose are on both flanges 22a . 22b Plastic rings 24 hung up, with through holes 5 '' for the screws 4 are provided.

Basically, in such an insulated pipe flange connection with two metal flanges 22a . 22b the same problems previously encountered in connection with plastic flanges 2a . 2 B are described. So to avoid that the plastic rings 24 locally overloaded, here is the intermediate piece described above 11 intended. The two plastic rings 24 can like the intermediate piece 11 be segmented either continuously or around the circumference, including the plastic rings 24 in a segmented shape with a segment at least two adjacent through holes 5 connect. As related to the 1 also described here, the sealing ring assembly is braced so that the metal flanges 22a . 22b on block on the insulating support ring 9 issue. Also, the further embodiment of in 3 Flange connection shown corresponds to the previously described embodiment according to the 1 ,

Claims (9)

Pipe flange connection with an annular sealing surface ( 1 ) having plastic flange ( 2a . 2 B ), with a counter element, with a sealing ring arrangement ( 3 ) between the plastic flange ( 2a . 2 B ) and the counter element and with screws ( 4 ) in through holes ( 5 ) of the plastic flange ( 2a . 2 B ) and the plastic flange ( 2a . 2 B ) under application of force to the sealing ring arrangement ( 3 ) connect to the counter element, characterized in that the sealing ring arrangement ( 3 ) an annular sealing portion ( 8th ) and a laterally adjoining support ring ( 9 ), wherein the plastic flange ( 2a . 2 B ) and the counter element on the support ring ( 9 ) are pulled to block, whereby the sealing by means of the sealing portion ( 8th ) takes place in the force shunt, and that on a support surface ( 10 ) of the plastic flange ( 2a . 2 B ), the sealing surface ( 1 ), for power distribution, a metallic intermediate piece ( 11 ), which has at least two through holes ( 5 ), is in a bad mood. Pipe flange connection with an annular sealing surface ( 1 ) having metal flange ( 22a . 22b ), with a plastic ring intended for insulation ( 24 ), which at one of the sealing surface ( 1 ) on the opposite side of the metal flange ( 22a . 22b ) is placed, with a counter element, with a sealing ring arrangement ( 3 ) between the metal flange ( 22a . 22b ) and the counter element and with screws ( 4 ) in through holes ( 5 . 5 '' ) of the metal flange ( 22a . 22b ) and the plastic ring ( 24 ) and the metal flange ( 22a . 22b ) and the plastic ring ( 24 ) under application of force to the sealing ring arrangement ( 3 ) connect to the counter element, characterized in that the sealing ring arrangement ( 3 ) an annular sealing portion ( 8th ) and a laterally adjoining support ring ( 9 ), wherein the metal flange ( 22a . 22b ) and the counter element on the support ring ( 9 ) are pulled to block, whereby the sealing by means of the sealing portion ( 8th ) takes place in the force shunt, and that at the metal flange ( 22a . 22b ) opposite side of the plastic ring ( 24 ) for distributing a metal intermediate piece ( 11 ), which has at least two through holes ( 5 . 5 '' ), is in a bad mood. Pipe flange connection according to claim 1 or 2, characterized in that the intermediate piece ( 11 ) is a metal ring. Pipe flange connection according to one of claims 1 to 3, characterized in that the load of the tightened screws ( 4 ) corresponds to at least 40%, preferably at least 60% of the 0.2% proof strength R _p0.2 . Pipe flange connection according to one of claims 1 to 4, characterized in that the support ring ( 9 ) Through holes ( 5 ' ) through which the screws ( 4 ) are guided. Pipe flange connection according to one of claims 1 to 5, characterized in that the sealing ring arrangement ( 3 ) is a two-fluid seal. Pipe flange connection according to one of claims 1 to 6, characterized in that based on the entire contact surface of sealing ring arrangement ( 3 ) and plastic or metal flange ( 2a . 2 B . 22a . 22b ) the average surface pressure is at least 20 N / mm ² . Pipe flange connection according to one of claims 1 to 7, characterized in that on the plastic or metal flange ( 2a . 2 B . 22a . 22b ) the sealing surface ( 1 ), at which the sealing section ( 8th ) of the sealing ring arrangement ( 3 ), just in the flange area merges, in which the through holes ( 5 ) are arranged. Pipe flange connection according to claim 8, characterized in that the plastic or metal flange ( 2a . 2 B . 22a . 22b ) on the side of its sealing surface ( 1 ) is even from its inner edge to its outer edge.

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