WO1995027170A1

WO1995027170A1 - Device and method of fixing a supporting ring to a pipe

Info

Publication number: WO1995027170A1
Application number: PCT/SE1995/000355
Authority: WO
Inventors: Per Johan Ehnemark; Peter Schaub
Original assignee: Abb Tekniska Röntgencentralen Ab
Priority date: 1994-04-05
Filing date: 1995-04-03
Publication date: 1995-10-12
Also published as: SE9401140D0; SE502775C2; SE9401140L

Abstract

A device for fixing a divisible supporting ring (2) to a pipe (1) comprises hollow expansion members (51, 52, 53, 54) arranged between the pipe and the supporting ring. The supporting ring, which in fixed position surrounds the pipe, supports a track (3), preferably a track for a manipulator (4) for inspection equipment for a nuclear power plant. The expansion members may be caused to expand by filling them with a pressure medium and be pressurized, thus fixing the supporting ring to the pipe by frictional forces.

Description

Device and method of fixina a supportina rina to a pipe
TECHNICAL FIELD
The present invention relates to a device for fixing a divisible supporting ring, which supporting ring supports a track, preferably a track for a manipulator for inspection equipment for a nuclear fuel plant, to a pipe, which supporting ring in fixed position surrounds the pipe, and to a method of fixing a supporting ring to a pipe.

BACKGROUND ART
Pipes in nuclear power plants, for example steam pipes, are inspected at certain intervals with respect to any defects such as cracks, corrosion, etc. The inspection equipment, which may comprise, for example, a video camera, X-ray equipment, or ultrasonic probes, is moved by a manipulator over the surface of the pipe. The manipulator runs along a track, often in the form of a rail, which is arranged on a supporting ring which is applied around the pipe so as to form a circular track, surrounding the pipe, for the manipulator.

The supporting ring with the track normally consists of two semicircular parts, which are applied around the pipe and locked to each other so as to form a closed track for the manipulator. The supporting ring surrounds the pipe and is fixed thereto by frictional force. The pipes normally exhibit certain tolerances in diameter, typically their diameter may lie, for example, within the interval 770-810 mm. In order for the supporting ring to achieve the desired frictional force and, in addition, be used for pipes with different diameters, it comprises a number of mechanical springs acting on the pipe in a radial direction, thus achieving the desired frictional force.

One problem with the above-described supporting ring is to achieve a sufficient frictional force against the pipe, so that the supporting ring with the manipulator can be supported and fixed to the pipe. The frictional force is in direct proportion to the spring force, which is determined by the spring rate apd the change in length of the springs. However,
; w a great spring force means that great forces must be utilized F for closing the supporting ring around the pipe. Less spring a
t force produces less friction, which entails a stable assembly where the supporting ring, because of weight displacement of the manipulator, may change its position. Different distances between the pipe and the supporting ring also provide different frictional forces.

One and the same supporting ring with a constant diameter may, therefore, be used only for a small number of pipe dimensions.

A further problem with the described supporting ring is to centre it concentrically with the pipe and to direct it coaxially with the pipe. The radially acting springs strive to give the supporting ring a location concentric with the pipe, but the centring forces are small and cannot overcome the frictional forces between the pipe and the supporting ring.

The supporting ring must, therefore, be adjusted into a concentric location, and in the majority of cases also be fixed to the pipe by wedges when the frictional force is not sufficient.

A drawback with the mechanical springs is that the supporting ring is heavy. For inspection of a whole pipe length, the supporting ring must be moved along the pipe. This entails a repeated number of operations comprising detachment of the supporting ring, movement to a new inspection surface at the pipe, and attachment and orientation of the supporting ring around the pipe in the new position. The handling of the supporting ring as well as springs and wedges in these t situations constitutes a complicated and time-consuming procedure which must be carried out in situ in a region with * an often high radioactive radiation intensity and an ensuing high exposure for operators and equipment.

SUMMARY OF THE INVENTION
The invention aims to provide an improved and simplified attachment device for a supporting ring of the kind described in the introductory part of the description, which makes possible a fast and simple handling of the ring when it is to be fixed to, and detached from, the pipe which is to be inspected.

What characterizes a device according to the invention will become clear from the appended claims.

Advantageous improvements of the invention will become clear from the following description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in greater detail with reference to the accompanying drawing, wherein
Figure 1 shows a pipe selected for inspection, on which a
supporting ring is mounted with a device according to
the invention,
Figure 2 shows a cross section along the line II-II shown in
Figure 1, and
Figure 3 shows a cross section along the line III-III shown in
Figure 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figure 1-shows a pipe 1 selected for inspection, for example a steam pipe for a nuclear power plant, on which a supporting ring 2 is mounted. The pipe 1 may be oriented in an arbitrary direction. The supporting ring 2 supports a circular track in the form of a rail 3 with a T-shaped cross section. Along the track a manipulator 4 may run. The manipulator supports inspection equipment 41, for example a video camera, X-ray equipment, or ultrasonic probes, for inspection of the pipe for possible defects.

Figure 2 shows a cross section of the pipe 1 with the supporting ring 2, which consists of two semicircular parts 21 and 22 interconnected by hinges and locking means. In the space between the pipe 1 and the supporting ring 2, four elongated expansion members 51,52,53,54, tangentially oriented with the supporting ring, are arranged and distributed two at each part 21 and 22, respectively. Each one of the expansion members consists of a hollow, reinforced rubber hose which is closed at its ends. Via valves (not shown in the figures) the rubber hoses may be filled and pressurized with a pressure medium, such as gas or hydraulic fluid, which causes them to expand. The expansion proceeds until the expansion members are in contact with both the pipe and the supporting ring.

After this, the increased pressurization achieves a tangentially extended radial force, which fixes the supporting ring 2 around the pipe 1. All the expansion members are connected to the same pressure medium. One condition for the above-mentioned attachment is that the distance between the pipe and the supporting ring does not exceed the diameter of the pressurized reinforced rubber hose.

Since the expansion members 51,52,53,54 are in the form of hoses which are closed at their ends, and which in each cross section have a constant circumference which is independent of the pressure, and which are oriented in a direction tangential to the supporting ring, a self-centring effect is achieved upon pressurization. When filling with pressure medium, such a hose strives to assume a shape between the pipe and the supporting ring, which shows a constant cross section along the whole hose. Thus, if the supporting ring is asymmetrically mounted around the pipe when the hoses start to be filled, internal forces will be created inside the hoses. These forces will strive to conduct pressure medium to that end of the hose which has the smallest cross-section area.

As viewed from the outside of the hose, therefore, forces arise between the supporting ring and the pipe which strive to centre the supporting ring around the pipe. These forces are in direct proportion to the pressure in the hose and attain equilibrium only when the centring has been achieved. Since the hoses are arranged along two substantially parallel planes and bring about a centring force in each one of these planes, an orientation of the supporting ring in a direction axial to the supporting ring is also achieved.

The supporting ring may be provided with attachments (not shown in the figure), in which pull ropes may be fixed, whereby the supporting ring may be moved along the pipe by remote control. The supporting ring is applied around the pipe and the expansion members are filled, whereby the supporting ring is locked and centred around the pipe. The manipulator with the inspection equipment is started and inspection is carried out. After a partial inspection has been carried out, the expansion members are evacuated whereby the locking ceases. The supporting ring is moved along the pipe by means of the pull rope to a new inspection surface, whereafter the expansion members are pressurized and the supporting ring is locked and centred again. Inspection of a whole pipe section may in this way be carried out by means of remote control by personnel at a radiation-protected location.

The device is also suited to retain other equipment as well, such as grinding equipment, since a high pressure in the expansion members may provide very great expansive forces between the pipe and the supporting ring. The expansion members may also advantageously be applied to fix and centre inspection equipment which is moved inside a pipe. In this case, the expansion members are placed outside a supporting ring with rails on the inside, intended to be moved inside a pipe.

Claims

CLAIMS 1. A device for fixing a divisible supporting ring (2), which supporting ring supports a track (3), preferably a track for a manipulator (4) for inspection equipment for a nuclear power plant, to a pipe (1), wherein the supporting ring (2) in fixed position surrounds the pipe (1) and comprises hollow expansion members (51,52,53,54) between the pipe (1) and the supporting ring (2), characterized in that the expansion members comprise tangentially oriented, elongated hoses of, for example, reinforced rubber, which are closed at their ends and have a circumference which in each cross section is constant and independent of pressure.

2. A device according to claim 1, characterized in that the expansion members (51,52,53,54) are arranged in at least two mutually substantially parallel planes.

3. A method of attachment of a divisible supporting ring (2) to a pipe, which supporting ring supports a track (3), preferably a track for a manipulator (4) for inspection equipment for a nuclear power plant, wherein the supporting ring is caused to surround the pipe, characterized in that between the pipe and the supporting ring, elongated expansion members (51,52,53,54), which have a constant circumference independent of pressure, are arranged in a tangential direction in two parallel planes and are caused to expand by being filled with a pressure medium and pressurized, whereby the supporting ring is centred around the pipe and aligned coaxially with the pipe by a pressure equalization in the expansion members, and whereby frictional forces arise which fix the supporting ring to the pipe.