WO2007059790A1

WO2007059790A1 - Method of welding a tube end to the outer wall of a support with a reduced inner side of the tube end; arrangement, produced according to this method; ultrasonic flow meter

Info

Publication number: WO2007059790A1
Application number: PCT/EP2005/012643
Authority: WO
Inventors: Morten Storgaard Nielsen
Original assignee: Siemens Aktiengesellschaft
Priority date: 2005-11-25
Filing date: 2005-11-25
Publication date: 2007-05-31

Abstract

The invention relates to a method of welding a tube end to the outer wall of a support, in particular to the outer wall of a measuring tube (5) of an ultrasonic flow meter, an arrangement produced by the method, and an ultrasonic flow meter. The axis of a tube connection piece (3) is inclined relative to the perpendicular to the support surface. In a region (13) in which an acute angle is enclosed between the outer side of the tube (3) and the support surface, the end face (15) of the tube end is reduced by material being removed from the inner side of the tube (3). After that, the joint location between tube (3) and support (5) is welded by applying a fillet weld (17) from outside. This has the advantage that the welded joint (17) is simpler to produce and that the relevant regulations are observed at the same time.

Description

description

METHOD FOR WELDING A TUBE WITH THE OUTER WALL OF A CARRIER WITH A REDUCED INSIDE PIPE; ARRANGEMENT MADE ACCORDING TO THIS PROCEDURE; ULTRASOUND FLOWMETER

The invention relates to a method for welding a pipe end to the outer wall of a carrier, in particular to the outer wall of a measuring tube of a Ultraschalldurchfluss- measuring device, according to the preamble of claim 1, an arrangement produced by the method, according to the preamble of claim 2 and an ultrasonic flow device according to the preamble of claim 3.

An ultrasonic flowmeter is known for example from DE 103 28 662 Al. A flowing medium whose flow volume is to be measured is passed through a measuring tube, on the tube wall axially offset from each other ultrasonic transducers are mounted. These are operated alternately as transmit and receive transducers. For flow measurement, an ultrasonic signal is sent upstream and downstream. From the time difference between the transit time of the upstream signal and the transit time of the downstream signal, the volume flow of the medium can be calculated.

In an ultrasonic flowmeter that works on the Doppler principle, already sufficient to attach an ultrasonic transducer to the measuring tube wall, which serves both as a transmitter and as a receiver of an ultrasonic signal.

For mounting ultrasonic transducers on the measuring tube, various possibilities are known. In the clamp-on technique, the ultrasonic transducers are pressed against the outer wall of the measuring tube and thus radiate the ultrasonic signal through the wall into the flowing medium. Better signal ^¬ properties can be achieved in embodiments, in which the ultrasonic transducer is in direct contact with the medium. For this purpose, for example, an ultrasonic transducer is installed in an opening of the pipe wall or a pipe socket is welded to the outside of the pipe wall, which receives the ultrasonic transducer. The attachment of a pipe socket has the advantage that the measuring arrangement is associated with a lower production cost. If the pipe socket is fastened to the outside wall of the measuring pipe by means of a welded connection, this welded joint must be designed in accordance with the standard EN 13445-3: 2002 for unburnt pressure vessels. For welding neck, ie only on the outside of the wall welded nozzle, this standard stipulates that the face of the nozzle to reduce mechanical stresses in the Schweißverbin- düng before welding by reducing the pipe wall thickness in the end area is reduced. For a nozzle with a wall thickness of, for example, 5 mm, the wall thickness should be no more than one millimeter directly at the end face of the pipe end. This is achieved by providing a conical taper at an angle of, for example, 45 ° at the end of the pipe. However, if the pipe socket is to be welded to the outer wall of the carrier or measuring tube such that the tube axis of the nozzle is inclined relative to the vertical on the support surface, the problem arises that it in the area in which between the outside of the tube and the Carrier surface is enclosed an acute angle, it is difficult to get to the weld groove with a welding torch, even if the reduction of the pipe wall thickness was made in an optimized manner.

The invention has for its object to provide a method for welding a pipe end to the outer wall of a carrier, an assembly, which is produced by the method, and an ultrasonic flow meter, with which even a secure, pressure-resistant welded joint is ensured when the tube axis is inclined relative to the vertical on the support surface. To solve this problem, the new method for welding a pipe end to the outer wall of a carrier of the type mentioned in the features indicated in the characterizing part of claim 1 features. In the claims 2 and 3, an arrangement, which is produced by the method, and an ultrasonic flowmeter are described.

The invention has the advantage that the welding groove is also easily accessible to a welding torch in the region in which an acute angle is enclosed between the outside of the tube and the carrier surface. As a result, a secure welding into the area, in which the pipe end touches down on the support surface allows. Gaps between the pipe end and the

Support surface and thus the possibility of crevice corrosion during long-term use, especially in the use of stainless steel are largely avoided. In addition, due to the good accessibility for the welding torch, the welding process is accelerated and thus reduces the manufacturing cost of the welded joint. The pressure-skill of the welded connection is improved, since the radius of the fillet weld is increased in the area of acute angles and thus centers of mechanical stress are weakened.

When using the new method of attaching a pipe stub to a measuring tube of an ultrasonic flowmeter, in addition to improving the weld joint, it is possible to attach the pipe stub to the measuring tube with a greater inclination. This allows the arrangement to radiate sound signals at an acute angle in the measuring tube, which advantageously the length of the sound path in the flowing medium can be increased. This achieves an improvement in the measurement accuracy of the ultrasonic flowmeter. This is all the more effective if, in order to reduce the influence of the flow profile in the measuring tube on the measurement result of the pipe socket is mounted offset from the pipe center, so that the sound signal is guided laterally past the axis of the measuring tube. Namely, such an offset further reduces the value of the smallest angle included between the outside of the pipe socket and the carrier surface. A production of the welded joint in a conventional manner would therefore further complicated.

With reference to the drawings, in which an embodiment of the invention is shown, the invention and refinements and advantages are explained in more detail below.

Show it:

1 shows a schematic diagram of an ultrasonic flowmeter and

Figure 2 is a welded joint.

FIG. 1 shows an example of an ultrasonic flowmeter with two ultrasonic transducers 1 and 2, which are each held in a pipe socket 3 or 4, which in turn are fastened to the outer wall of a measuring tube 5 by a welded connection. For measuring the volume flow rate of a medium which flows through the interior of the measuring tube 5 according to an arrow 6, sends at a time of the

Ultrasonic transducer 1, an ultrasonic signal according to an arrow 7, which is received by the ultrasonic transducer 2. In a device 8 for controlling the ultrasonic transducers 1 and 2 and for evaluating the received signal, the transit time of the upstream signal is measured and stored. At another time, the ultrasonic transducer 2 sends in the reverse direction according to an arrow 9, an ultrasonic signal downstream, which is received by the ultrasonic transducer 1. Again, the duration is measured in the device 8. Based on the maturities and taking into account the geometric data of the measuring tube 5 and possibly the medium temperature of the volume flow of the medium is calculated by the measuring tube 5 and, for example, over a fieldbus 10 to a parent, not shown for clarity lead station for further processing in an automation system reported.

In a preferred embodiment, the axis 11 of the pipe socket 3 and the axis 12 of the measuring tube 5 form an angle α of 40 °. That is, the tube axis 11 of the pipe socket 3 is inclined relative to the vertical on the support surface, namely the outer wall of the measuring tube 5, by 50 °. The result is that in an area 13 between the outside of the pipe socket 3 and the support surface an acute angle is included, which corresponds to the angle α. In contrast, an obtuse angle forms in an opposite region 14. The end of the pipe socket 3 is welded in the entire peripheral region with the outer wall of the measuring tube 5.

As an alternative to the exemplary embodiment shown with two ultrasonic transducers on a measuring tube, in a so-called multi-path application, a plurality of pairs of ultrasonic transducers can be provided, which correspondingly form a plurality of sound signal paths. For example, it is possible for an ultrasound pair to generate a sound path that travels in the plane of the drawing in front of the axis 12 of the measuring tube 5, while another pair of transducers is located behind it in the plane of the drawing and forms a sound path that travels behind the axis 12. With such a transducer arrangement, measurement errors caused by the airfoil or by a swirl in the flow can be largely eliminated. Due to the resulting offset of the pipe socket relative to the center of the measuring tube 5, the indicated effect of a tapering of the angle between the outside of the pipe socket and the support surface is additionally enhanced.

As materials for measuring tube 5 and / or pipe socket 3, for example, iron or steel in various designs, in particular stainless steel suitable. The welding Connection between the pipe stub 3 and 4 and the measuring tube 5 can be made with different methods depending on the application. For example, gas metal arc welding (MIG / MAG) or tungsten inert gas welding (TIG) can be considered. A common wall thickness of the pipe socket 3 and 4 is 5 mm with a diameter of about 35 mm. The diameter of the measuring tube 5 is usually between 100 and 4000 mm. With the new type of welded connection even diameters up to 25 mm can be made possible.

Figure 2 shows the connection of the pipe socket 3 with the measuring tube 5. The same parts are provided with the same reference numerals. The end face 15 of the end of the pipe socket 3 is reduced to avoid mechanical stresses in the welded joint before welding by reducing the pipe wall thickness in the end. This reduction takes place in a region 13 in which between the outside of the pipe socket 3 and the support surface, that is the outer wall of the measuring tube 5, an acute angle is included, in that material is removed from the inside of the pipe socket 3. In this case, an inner edge 16 is formed. In another region 14, in which an obtuse angle is created between the outside of the pipe socket 3 and the carrier surface, material is removed from the outside, for example by a chip-removing process, to reduce the front surface. Around the joint around a fillet weld 17 is then placed with a welding torch. In this illustration it is clear that remain virtually no gaps between the parts by the selected type of connection between pipe socket 3 and measuring tube 5, that the welded joint can be produced by simple means and that the relevant regulations are met.

Claims

claims

A method for welding a pipe end to the outer wall of a carrier, in particular to the outer wall of a measuring tube (5) of an ultrasonic flowmeter, wherein the tube axis (11) relative to the vertical on the support surface is inclined and wherein the end face (15) of the pipe end to avoid mechanical stresses in the welded joint before welding is reduced by reducing the pipe wall thickness in the end region, characterized in that the end face (15) of the pipe end in a region (13) in which between the outside of the tube (3) and the support surface a sharpener Angle (oc) is enclosed, is reduced by removing material from the inside of the tube (3), and then that the tube end is welded to the carrier from the tube outside.

2. Arrangement, produced by the method according to claim 1, with a carrier, in particular a measuring tube (5) of a UIt- raschalldurchflussmessgeräts, and with a tube (3) whose end is welded to the outer wall of the carrier (5), wherein the Pipe axis (11) relative to the vertical on the support surface is inclined and wherein the end face (15) of the pipe end to avoid mechanical stresses in the Schweißver connection before welding is reduced by reducing the pipe wall thickness in the end region, characterized in that the end face (15 ) of the tube end in a region (13) in which between the outside of the tube (3) and the support surface an acute angle (α) is included, is reduced by that from the inside of the tube (3) material is removed, and that the tube end is welded to the carrier from the tube outside.

3. Ultrasonic flowmeter with a medium-flow through measuring tube (5), with at least one transmitting / receiving transducer

(1, 2), which is held by a pipe socket (3, 4), which in turn is attached to the outer wall of the measuring tube (5) as a carrier, so that a substantially along the axis (11) of the pipe socket (3, 4) extending ultrasonic signal is sendable or receivable, and with a device (8) for controlling the transducer and evaluation of Empfangssig- signal, characterized in that the pipe socket (3, 4) by a welded connection is attached to the support (5), wherein the tube axis (11) relative to the vertical on the support surface is inclined and wherein the end face (15) of the pipe end to avoid mechanical stresses in the welded joint before welding is reduced by reducing the pipe wall thickness in the end in that the end face (15) of the pipe end is made smaller in a region (13) in which an acute angle (a) is enclosed between the outside of the pipe (3) and the support surface by reducing it from the inside of the pipe (3 ) Material is removed, and that the pipe end is welded to the carrier from the outside of the tube.