Measuring device arrangement

Abstract

Measuring device arrangement comprising a measuring device, a capillary connecting line and a connection adapter, wherein the capillary connecting line is fixed in the connection adapter and can be connected to a fluid-carrying process device, and wherein the connection adapter has an end face with a substantially circular cross-sectional area which can be fixed in a recess of the measuring device or a recess of the process device, wherein the adapter (4a) and the recess (6) have a section (12, 14) with a continuously increasing cross-sectional area, and wherein the section (12, 14) with a continuously increasing cross-sectional area has a conical outer surface on the adapter (4a) and on the recess (6), characterized in thatthat the diameter (S) of the cross-sectional area of ​​the end face (7) of the adapter (4a) is smaller than a cross-sectional area (D) of a fluid-connecting bore (9) of the recess (6) and wherein the cone angle of the recess (6) is substantially 30° and that the cone angle of the adapter (4a) is between 25° and 29°, and wherein the distance W between an outer wall of the capillary connecting line (2) and a wall surface of the bore (9) in the recess (6) is more than 1.5 mm and less than 8.0 mm..

Description

[0001] The invention relates to a measuring device arrangement comprising a measuring device, a capillary connecting line, and a connection adapter, wherein the capillary connecting line is fixed in the connection adapter and can be connected to a fluid-carrying process device, and wherein the connection adapter has an end face with a substantially circular cross-sectional area that can be fixed in a recess of the measuring device or a recess of the process device, wherein the adapter and the recess have a section with a continuously increasing cross-sectional area, and wherein the section with a continuously increasing cross-sectional area has a conical outer surface on the adapter and on the recess. STATE OF THE ART

[0002] The measuring device typically includes a pressure gauge in which pressure applied to a measuring element causes a deflection of the measuring element, which can be evaluated and displayed or transmitted as a measurement signal to an external evaluation device.

[0003] To prevent the ingress and accumulation of process residues, the measuring device is typically separated from the process equipment via a capillary connection line. This results in a connectable measuring device assembly consisting of a capillary connection line and a measuring device, whereby the capillary connection line can be sealed with a membrane and filled with a separate transmission medium, e.g., oil, for pressure transmission to the measuring device. Such a device is disclosed, for example, in German patent application DE 2 531 787 A1, in which the metal membrane is welded on.

[0004] This is of interest, for example, to the food industry, as the processes there often contain or process components that cannot be reliably removed from a dead-end connection of a measuring device that is not separated by a membrane when the system is cleaned, and which contaminate subsequent processes and productions.

[0005] The capillary connecting line is required to mount the measuring device at a location suitable for reading or maintenance. Furthermore, the capillary connection allows for cooling or temperature differential between the process equipment and the measuring device along its length, as the process being measured often operates at a higher temperature than is advantageous or permissible for the operation of the measuring device.

[0006] Since every temperature change causes the transmission medium in the capillary tube or measuring device to expand, resulting in an error with respect to the pressure being measured, the inner diameter of such a capillary tube is chosen to be as small as possible. Therefore, capillary tubes with the smallest possible inner diameter and thus a small filling volume are usually used, so that the aforementioned potential influence of errors on the measuring device is minimized.

[0007] The wall thickness, or the outer diameter, of the capillary connecting line depends on the maximum pressure in the intended measuring range and can be several times the inner diameter.

[0008] Such a capillary connecting line typically has at least one adapter attached to one end, which allows the capillary connecting line to be detachably connected to a corresponding recess in either the process equipment or the measuring device. For example, US patent application US 5,595,406 A describes a measuring device arrangement in which the measuring device arrangement can be fixed in the recess by means of a spring mechanism acting upon it with a spring force. German patent application DE 103 49 008 A1 discloses a measuring device arrangement that is screwed into the recess. A direct connection of the capillary connecting line to both the process equipment and the measuring device would be disadvantageous, since without an adapter the measuring device would have to be permanently connected to the process equipment on a regular basis, and quick replacement would be difficult or impossible.Furthermore, a direct connection of the capillary tube to the process equipment and / or the measuring device would require the capillary tube to be either screwed or welded directly onto the system due to the pressure conditions typically expected. However, this is difficult because a capillary tube with a small diameter is hard to grip reliably: welding can weaken the wall thickness, posing a risk of kinking and breakage; conversely, the tube is difficult to grip without tools to apply sealing forces and effectively direct them against a sealing surface.

[0009] Therefore, adapters are used, which are attached to at least one end of the capillary connecting line, to permanently create a detachable, pressure-tight connection and to simplify handling. Such a measuring device arrangement is disclosed in US 6,926,313 B1, US 2008 / 0038152 A1, and CN 101561063 A, respectively.

[0010] The adapter can be screwed onto the pipe, for which a thread is first cut onto the outside of the capillary connecting pipe. After the thread is cut, a cone is often formed directly onto the pipe end or attached using a cutting tool. The sealing force between the capillary connecting pipe and the adapter is then applied to the adapter and thus to the sealing cone via a pressure screw.

[0011] Alternatively, the adapter can also be welded onto the capillary tube as a "welding adapter." Since this connection, unlike a threaded connection, provides an extremely reliable seal, the contact surface between the capillary tube and its corresponding recess can be moved from the capillary tube itself to the welding adapter. This also offers manufacturing advantages, as the adapter can typically be produced as a turned part, and a cone can be more easily formed onto it than onto a pipe or capillary tube.

[0012] This is particularly relevant when the measuring device assembly is installed on-site at a process plant. Connecting lines and process pipes must be prepared and possibly fitted with a precise cone on-site using a special device. It is advantageous if the adapter with the cone can be supplied as a finished sealing component and only needs to be welded on-site.

[0013] A capillary connection with a welded-on adapter can also be sealed directly in a recess using a second weld. This connection is either impossible or extremely difficult to remove. Furthermore, when separating the connection, chips often fall uncontrollably into the measuring device or process equipment, which can then disrupt operation.

[0014] In the following, the invention is presented with an adapter welded onto the capillary connecting line, and the adapter is hereinafter also referred to as a welding adapter, whereby the invention is not limited to this in accordance with the preceding explanations. TASK OF INVENTION

[0015] The object of the invention is to provide a cost-effective solution for a separable, high-pressure-tight connection between a process unit, which typically has a recess for attaching a capillary connecting line and is oriented towards a manufacturing or processing process, and a measuring device. Furthermore, a measuring device arrangement is to be provided that, in addition to allowing the measuring device arrangement to be separated from the process unit, enables the replacement of individual components of the measuring device arrangement, and allows for the restoration of a reliable and high-pressure-tight hydraulic connection between the measuring device and the process unit. SUMMARY OF THE INVENTION

[0016] According to the invention, the diameter of the cross-sectional area of ​​the end face of the adapter is smaller than a cross-sectional area of ​​a fluid-connecting bore of the recess, wherein the cone angle of the recess is substantially 30°, and wherein the cone angle of the adapter is between 25° and 29°, and wherein the distance W between an outer wall of the capillary connecting line and a wall surface of the bore in the recess is more than 1.5 mm and less than 8.0 mm, so that the adapter pressed into the recess has a substantially annular contact area with the recess.

[0017] This approach proposes a simple and cost-effective design for the adapter and the corresponding recess, enabling the adapter to be reliably pressed into the recess with a tight seal. The contact area between the adapter and the recess is not flat, but rather annular, running along an edge. This edge is formed either by the transition from the adapter's end face to a widening lateral surface, or by the transition from the typically conical recess to an opening or bore that leads into a process line containing the medium being measured.

[0018] In the case of a clamping cone connection deemed advantageous, the adapter and the recess are designed relative to each other such that increased surface pressure in the contact area of ​​the seal is achieved by the adapter's cone angle being slightly smaller than the recess's cone angle. When the screw is tightened, the weld adapter is pressed into the recess, creating a concentrated, annular surface pressure along the edge of an opening or bore in the recess. The edge formed by the transition from the recess to the opening or bore is pressed into the conical section of the adapter, plastically deforming the adapter's outer surface along an annular contact area. This results in maximum, rigid sealing with low axial contact pressure.

[0019] If the end face of the adapter is larger than the diameter of the recess in the area of ​​the opening or bore, the end face of the adapter is pressed laterally into the cylindrical surface of the recess, and the maximum sealing pressure occurs along a circumferential edge that laterally limits the end face of the adapter.

[0020] A slight plastic deformation or compression in the contact area has not proven to be a disadvantage; instead, it results in a well-defined ring-shaped sealing surface.

[0021] However, with this combination it has been found that if certain dimensions are adhered to, a particularly high and reliable sealing effect can be achieved, which results from the pairing of certain diameters or from the design of certain distances.

[0022] It is intended that the respective angles of inclination of the increasing cross-sectional area at the adapter and at the recess differ, at least in the contact area. The angle of inclination for a point on the surface is defined as the angle of a tangent axially connected to the surface at that point relative to the axial center axis of the capillary tube or the adapter, which is typically rotationally symmetrical. In the case of a conical surface, the angle of inclination corresponds to the cone angle of the surface.

[0023] It is also possible, and advantageous with regard to various requirements, for the section with a continuously increasing cross-sectional area at the adapter and / or at the recess to have a radially symmetrical surface that is concave or convex in the axial direction. In this way, when the adapter is pressed into the recess, the force component directed radially towards the capillary connection can be influenced and predetermined depending on the respective diameter of the annular contact area.

[0024] However, since high temperatures are required for welding and the resulting unavoidable temperature stress on the adapter can also lead to distortions on surfaces or, in particular, sealing surfaces, it is provided that the capillary connecting line is fixed in a bore in the adapter and is attached to the adapter by welding in a tapered mounting area at a distance from the contact area.

[0025] The capillary connection is, for example, implemented at a front nose section, which is sufficiently spatially separated from the sections with the widening cross-sectional areas to prevent any adverse effects on the sealing surfaces in the contact area due to heating during welding. In particular, cross-sectional changes of any kind, whether caused by unilateral heating of a component or heat transfer through a component, impede the overall heating rate of the component. With proper design and dimensioning of the cross-sectional change, welding on the same component, in this case the welding adapter, can minimize critical temperature increases. Therefore, it is advantageous to design the weld nose in a stepped manner or at least with a non-continuous change in shape, offset from the contact area.

[0026] The capillary connecting line is preferably attached to the adapter by means of frontal or end-face welding, since the welding result can be easily assessed visually even before a leak test, and the welding is easily accessible and therefore easy to carry out.

[0027] A distance of preferably 2 to 6 mm between an outer wall of the capillary connecting tube and an outer wall of the adapter surrounding the capillary connecting tube is considered particularly advantageous.

[0028] Under these conditions, the measuring device arrangement is very reliable and remains leak-proof even under high pressures and temperatures over the long term, and exhibits the smallest possible temperature / volume error, since the seal is designed to be inflexible even against sudden pressure peaks.

[0029] It is also conceivable to apply this pressure-tight connection by means of an adapter only on one side of the capillary connecting line, and to weld the other side directly with a welding adapter according to the prior art, or to attach the connection according to the invention by means of a connecting piece at a point of interruption in the capillary connecting line.

[0030] The adapter does not need to be plate-shaped or rotationally symmetrical. Here, "adapter" can also refer to any other form of process or pipe connection, or to a part of a process plant, pipe, or upstream measuring system setup that can be used as a measuring access point and to which a measuring device can be connected via a capillary tube.

[0031] In this context, a capillary tube is a fluid-conducting tube with a relatively small inner diameter. Depending on the design, the outer diameter can be 8 mm or more. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The following section provides a more detailed explanation of some exemplary embodiments of the inventive concept, which are illustrated in the drawing. It shows: Fig. 1 a schematic representation of the measuring device arrangement, Fig. 2 a schematic sectional view of a seal according to the invention in a transition area between a capillary connecting line provided with an adapter and a recess adapted thereto in the process device and Fig. 3a to 3d each show a sectional view of different designs of an adapter.

[0033] Fig. Figure 1 shows a measuring device arrangement on a process unit 1 with a capillary connecting line 2, which connects a measuring device 3 to the process unit 1 via two adapters 4a and 4b in a pressure-transmitting manner. The adapter 4a associated with the process unit 1 is separated from a process medium located in the process unit 1 and to be measured by a membrane 5.

[0034] In Fig. Figure 2 shows a schematic sectional view of a seal according to the invention in a transition area between the capillary connecting line 2 provided with the adapter 4a and a recess 6 adapted to it in the process device 1.

[0035] The capillary connecting line 2 is welded from an end face 7 into a hollow cylindrical weld nose 8 and thereby secured in the adapter 4a. This weld nose 8 projects without contact into a bore 9, which supplies the process medium guided in the process unit 1 to the recess 6 and to the capillary connecting line 2, which is tightly fixed therein via the adapter 4a. The diameter S of the cross-sectional area of ​​the weld nose 8 is significantly smaller than the diameter D of the bore 9.

[0036] The adapter 4a is pressed into the recess 6 by means of a fastening screw 10 and sealed, so that a sufficiently fluid-tight connection is established between the capillary connecting line 2 and a pressure feedthrough 11 on the part of the process device 1.

[0037] The adapter 4a has a section 12 at a distance from the end face 7 with a widening cross-sectional area, the outer surface of which is formed by a conical lateral surface 13.

[0038] The recess 6 also has a section 14 directed towards the adapter 4a with a cross-sectional area that also widens, the outer surface of which is also formed by a conical lateral surface 15.

[0039] When the fastening screw 10 is tightened and the adapter 4a is pressed into the recess 6, the adapter 4a comes into sealing contact with an opening edge 16 of the bore 9 at the transition to the outer surface 15 of the recess 6 in the contact area of ​​the outer surface 13. Further tightening of the fastening screw 10 generates a high, ring-shaped surface pressure in this contact area.

[0040] A distance W exists between an outer wall of the capillary connecting tube 2 and a wall surface of the bore 9 in the recess 6. This distance is greater than 1.5 mm and less than 8.0 mm, or preferably greater than 2 mm and less than 6 mm. The diameter of the bore 9, in the area of ​​the opening edge 16, defines the dimensions of the annular contact area and its distance from the capillary connecting tube 2. A minimum distance of 1.5 mm or 2 mm ensures that the capillary connecting tube 2 is not subjected to excessive mechanical stress when the adapter 4a is pressed into place and could potentially be damaged. At the same time, sufficient clearance is provided to allow for easy yet reliable sealing of the connection between the adapter 4a and the recess 6.

[0041] A particularly high sealing effect is promoted by the fact that the outer surface 13 of the adapter 4a has a smaller cone angle and is therefore more pointed than the outer surface 15 of the recess 6.

[0042] In the Fig. Figures 3a to 3d show various embodiments or shapes of the adapter 4a as examples. In all cases, the distance between an outer wall of the capillary connecting tube and an outer wall of the adapter surrounding the capillary connecting tube is more than 1.5 mm, or preferably more than 2 mm, and less than 8.0 mm, or preferably less than 6 mm.

[0043] In Fig. 3a indicates that adapter 4a is shown in accordance with the in Fig. In the embodiment shown in section 12, a conical outer surface 13 is present. However, a weld nose 8 is missing. The capillary connecting line 2 is welded to the adapter 4a in the area of ​​the end face 7.

[0044] Fig. Figure 3b shows a concave profile of the outer surface 13 of the adapter 4a as well as a similarly conical shape of the weld nose 8.

[0045] In Fig. 3c the adapter 4a has a convex lateral surface 13.

[0046] In Fig. In section 3d, adapter 4a, like recess 7, has a conical lateral surface 13 or 15. The cone angle B of the recess is approximately 30°, while the cone angle A of adapter 4a is approximately 25°.

[0047] The invention is not limited to the preceding detailed embodiments and can be modified to the extent described above.

Claims

[1] Measuring device arrangement comprising a measuring device, a capillary connecting line and a connection adapter, wherein the capillary connecting line is fixed in the connection adapter and can be connected to a fluid-carrying process device, and wherein the connection adapter has an end face with a substantially circular cross-sectional area which can be fixed in a recess of the measuring device or a recess of the process device, wherein the adapter (4a) and the recess (6) have a section (12, 14) with a continuously increasing cross-sectional area, and wherein the section (12, 14) with a continuously increasing cross-sectional area has a conical outer surface on the adapter (4a) and on the recess (6), characterized by, that the diameter (S) of the cross-sectional area of ​​the end face (7) of the adapter (4a) is smaller than a cross-sectional area (D) of a fluid-connecting bore (9) of the recess (6) and wherein the cone angle of the recess (6) is substantially 30° and that the cone angle of the adapter (4a) is between 25° and 29°, and wherein the distance W between an outer wall of the capillary connecting line (2) and a wall surface of the bore (9) in the recess (6) is more than 1.5 mm and less than 8.0 mm. [2] Measuring device arrangement according to claim 1, characterized by , that the section (12, 14) with a continuously increasing cross-sectional area at the adapter (4a) and / or at the recess (6) has a radially symmetrical lateral surface curved in the axial direction concave or convex. [3] Measuring device arrangement according to one of the preceding claims, characterized by, that the capillary connecting line (2) is fixed in a bore (9) in the adapter (4a) and is attached to the adapter (4a) by welding in a tapered fastening area at a distance from the contact area. [4] Measuring device arrangement according to claim 3, characterized by , that the capillary connecting line (2) is attached by means of frontal or end-face welding. [5] Measuring device arrangement according to one of the preceding claims, characterized by , that the distance W between an outer wall of the capillary connecting line (2) and a wall surface of the bore (9) in the recess (6) is more than 2 mm and less than 6 mm. [6] Measuring device arrangement according to one of the preceding claims, characterized by, that the capillary connecting line (2) has a membrane (5) on the process side and the capillary connecting line (2) is filled with an oil or other transmission fluid which differs from the process medium to be measured.

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