WO1997037206A1

WO1997037206A1 - Weld testing assembly

Info

Publication number: WO1997037206A1
Application number: PCT/CA1997/000213
Authority: WO
Inventors: Guy Berube; Glenn Carson
Original assignee: Guy Berube; Glenn Carson
Priority date: 1996-04-02
Filing date: 1997-04-02
Publication date: 1997-10-09
Also published as: AU2147097A; CA2223247A1

Abstract

The invention provides an assembly for hydrostatic testing of welds between components, such as but not limited to welds which connect components such as nozzles (2) or patches (40) to a pressure vessel (1). A sealing body (8) is secured against one of the components to define a sealed space (25) adjacent to the weld (5) to be tested. The body is secured by at least one tie rod (9), positioned to pull the body against the component by tightening of a nut (12). Pressure testing can then be carried out by introducing pressurized fluid into the sealed space and applying appropriate monitoring techniques to check for leakage.

Description

WELD TESTING ASSEMBLY

TECHNICAL FIELD

This invention relates to the testing of welds, and particularly but not necessarily only hydrostatic testing of welds for nozzles, studs, flanges, patches, etc. on or connected to pressure tanks or vessels.

The testing of weld integrity on nozzles or other components welded to pressure vessels traditionally involves the whole vessel having to be filled with a pressurizing fluid medium. This usually means that a large volume of fluid is required, and, if the fluid is not used in the actual operation of the system of which the vessel is a part, purging of the equipment has to be performed both before and after weld testing.

DISCLOSURE OF INVENTION

It is an object of the invention to provide a weld testing assembly which can be arranged to create a sealed space adjacent to a weld, for example a weld securing a component such as a nozzle or patch to a pressure vessel, in such a way that pressurizing fluid is only required for a relatively small volume directly adjacent the weld to be tested. In the case of pressure vessels and the like, this eliminates the necessity for filling the entire pressure vessel with the pressurizing fluid.

The invention comprises a sealing assembly secured to the welded components so as to define a sealed space adjacent the weld to be tested. The sealing assembly is secured against the vessel by suitable means such as at least one tie rod, so as to maintain a seal during the pressure test. The weld is then tested by introducing a pressurizing fluid into the relatively small sealed space.

Further features of the invention will be described or will become apparent in the course of the following detailed description.

BRIEF DESCRIPTION OF DRAWINGS

In order that the invention may be more clearly understood, the preferred embodiment thereof will now be described in detail by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a cross-sectional view of one embodiment of a weld testing assembly for a nozzle extending from a pressure vessel;

Fig. 2 is a cross-sectional view of an alternative weld testing assembly for a nozzle; Fig. 3 is a cross-sectional view of another alternative weld testing assembly for a nozzle;

Fig. 4 is a cross-sectional view of a more complex weld testing assembly for a nozzle, useful for large welds;

Fig. 5 is a cross-sectional view of a weld testing assembly for a spigot extending from a pressure vessel;

Fig. 6 is a cross-sectional view of a weld testing assembly for a patch in the wall of a pressure vessel;

Fig. 7 is a cross-sectional view of an alternative embodiment of a weld testing assembly for a patch; and Fig. 8 is a cross-sectional view of another alternative embodiment of a weld testing assembly for a patch.

BEST MODE FOR CARRYING OUT THE INVENTION

Fig. 1 shows a weld testing assembly configured to test a weld 5 which holds a nozzle 2 in a hole in the wall of a pressure vessel 1. A flange 3 is mounted on the nozzle 2 via a flange weld 4. The weld testing assembly is secured against the inner wall of the vessel, to define a sealed area 25. The assembly has an external blind 6, which matches the form and shape of the flange 3. The blind can be mounted on the flange using any appropriate fastening means, such as nuts and bolts, through corresponding holes in the flange and the blind. There is at least one hole 20 in the blind 6, and normally several such holes, each such holes accommodating a threaded tie rod 9. The tie rod 9 connects the blind 6 to a body 8, which is situated inside the pressure vessel 1 and which has walls 16 which seal against the wall of the pressure vessel, outside the nozzle weld 5. The seal is achieved by any suitable means, such as by using a rubber O-ring 14, held in place by a groove 23 at the end of the walls 16. A lead seal could be used as one alternative. Each tie rod 9 passes through a hole 21 in the body and is threaded into a nut 10. Each nut 10 is sealed to the body by a seal weld 19.

The tie rods 9 pull the body 8 towards the blind 6, via tightening of the nuts 12, to create the sealed area 25. Preferably, a packing box 11 is used to provide an effective seal where the tie rods extend through the blind, the packing box being mounted on the tie rod 9 on the outside of the blind 6. In the preferred embodiments, an O-ring 27, preferably accommodated in suitable grooves in the packing box and the blind, provides a seal between the packing box assembly and the blind. When the nut 12 is tightened, it creates a seal to define the sealed area 25, but it also produces a longitudinally-oriented mechanical stress in the nozzle weld 5. Accordingly, the weld's ability to withstand the mechanical stress in addition to the hydrostatic pressure created by the pressurizing fluid during the test provides the operator with additional confidence in the integrity of the weld, because it will have to withstand more stress than it will experience during normal operational use. Clearly, alternative tightening and sealing arrangements could be used, and the use of such alternatives is within the scope of this invention.

In the embodiment shown in Fig. 1 , the body 8 is generally cup-shaped, having a disc 17 to which the wall 16 is via a body weld 18. The disc has one hole 21 for each tie rod 9. The weld testing assembly also has vent and filler pipes 7 and 15 respectively, each communicating with the sealed area 25, for passage of pressure testing fluid into and from the sealed area. The pressurizing fluid is normally water, or conventional antifreeze if the test is carried out in cold temperatures. However, it should be understood that any number of different fluids, such as atmospheric air, nitrogen or an inert gas, may also be used. Ports to accommodate a vent and filler pipe can be situated in the blind 6 (vent and filler port 7) or in the body 8 (vent and filler port 15) or in both (as illustrated in Fig. 1. The vent and filler pipe are connected to a pressurized fluid media container and a purge fluid container via one or more valves 13, shown schematically in Fig. 1. If desired, a single port can be used for both filling and venting, although purging of the test fluid may then be less effective.

With the invention, pressurizing the sealed area 25 with fluid can thus readily be achieved, in order to test the strength and integrity of the weld using conventional monitoring means, e.g visual leak inspection, measurement of pressure drop, measurement of flow, etc.. Of course, for a secure weld, there should be no pressure drop or fluid flow once the sealed area is pressurized.

Fig. 2 shows an alternative embodiment for the weld testing assembly, where the body 8 is a one-piece hemispherical shape. A groove 23 is defined within the edge of the body to accommodate a seal 14, as in the embodiment of Fig. 1.

Fig. 3 shows another alternative embodiment of the weld testing assembly, where the body 8 is one piece which conforms to the shape of the inside of the vessel 1, in the area adjacent the weld. There is a groove 23 in the body, to hold the seal 14.

Fig. 4 shows a final alternative embodiment of the weld testing assembly configured to test a weld attaching a nozzle to a pressure vessel. This embodiment is particularly advantageous for a pressure test where the circumference of the weld to be tested is so large that three or more tie rods 9 are required to maintain the seal. This configuration provides a cost and time savings by eliminating the requirement of sealing every tie rod using a packing box. Instead, the threaded tie rods are tightened against the external blind 6 by conventional nuts to create a seal between the pressure vessel and the body 8 and between the circumferential edges of the flange 3 and the external blind. A conventional wellneck flange 30 is secured to the top of the external blind by a weld 31. A second external blind 32 is sealably connected to the wellneck flange using conventional studs (not shown) to seal the top of the test assembly. Three threaded openings are drilled in the second external blind to provide a vent port 33, a filler port 34, and a gauge port 35. During the pressure test, fluid is introduced through the filler port and passes through holes 36 drilled in the external blind 6. Fig. 5 shows an alternative embodiment of the weld testing assembly configured to test a weld 5 securing a spigot 52 to the wall of a pressure vessel. A groove 51 is machined in a cylindrical plate 50, such that the spigot fits tightly into the groove. To create a seal between the plate and the spigot, an O-ring 51 is inserted into the groove and then the plate is fitted onto the spigot. The assembly is then tightened using the tie rod, packing box, and nuts, as previously described.

Fig. 6 shows an alternative embodiment of the weld testing assembly configured to test a weld 41 securing a patch 40 to the wall of a pressure vessel. A tie rod seals the body against the inside of the pressure vessel. The body has a sealing circumference around the patch and the seal between the body and the pressure vessel is accomplished by an O-ring 23 which fits into a groove 14 in the body, as described above. To provide a second seal between the body and the opening to accommodate the tie rod, preferably a packing box 11 and a second O-ring 27 are provided. The tie rod is screwed into the first nut 10, which is welded onto the patch by an ordinary fillet weld 45. The assembly is sealed by tightening the second nut 12, as described previously.

In certain situations, it may be advantageous to pre-weld the first nut 10 to the patch in anticipation of conducting the hydrostatic test using the invention.

Fig. 7 shows an alternative embodiment of the weld testing assembly configured to test a weld securing a patch to the wall of a pressure vessel. This embodiment is required when the patch is so large that the circumference of the weld to be tested requires more than one tie rod to maintain the seal during the pressure test Fig. 8 shows an alternative embodiment of the weld testing assembly configured to test a weld securing a patch to the wall of a pressure vessel, where the assembly is sealed against the outside of the vessel.

It will be understood that the materials for the components of the weld test assembly have to be chosen according to the specific demands of the particular pressure vessel environment to be tested. In most cases, a carbon steel body will suffice. In other cases, a stainless steel body will have to be employed.

It should be appreciated that although the invention is particularly adapted to use in testing welds in pressure vessels, as described above, the invention can be readily adapted to testing any other welds, whether in pressure vessels or elsewhere.

INDUSTRIAL APPLICABILITY

The invention provides an effective and efficient means for testing the integrity of welds, particularly but not necessarily only in pressure vessels.

Claims

CLAIMS:

1. A method for testing welds between two components, characterized by the steps of: securing a sealing assembly (8) against at least one surface (1 ) of at least one of said components so as to define a sealed space (25) adjacent to the weld (5) to be tested; injecting a pressurized test fluid into said sealed space; and monitoring said sealed space for indicia of a leak of said test fluid from said sealed space.

2. A method as recited in claim 1 , where said sealing assembly is characterized by a body (8) which is forced into engagement with said at least one surface by tightening a nut (12) on each of at least one threaded tie rod (9), where said tie rod is secured relative to said components such that tightening of said nut acts to force said body towards said component.

3. A weld testing assembly, for hydrostatic pressure testing of welds between two components, said weld testing assembly characterized by: a body (8) securable against at least one surface (1 ) of at least one of said components so as to define a sealed space (25) adjacent to the weld (5) to be tested; and at least one port (7) for receiving a pressurized test fluid into said sealed space.

4. A weld testing assembly as recited in claim 3, where said body is securable against said at least one surface by tightening a nut (12) on each of at least one threaded tie rod (9), where said tie rod is secured relative to said components such that tightening of said nut acts to force said body towards said component.

5. A weld testing assembly as recited in claim 4, where said assembly is adapted to testing a weld between a nozzle (2) and a pressure vessel (1), said nozzle extending from said pressure vessel and terminating in a flange (3), said assembly having a blind (6) securable onto said flange, said body (8) being positioned within said pressure vessel, and said at least one tie rod (9) being positioned between said blind and said body to pull said blind and said body towards each other, thereby sealing said body against said pressure vessel to define said sealed space.

6. A weld testing assembly as recited in claim 4, where said assembly is adapted to testing a weld between a pressure vessel (1) and a patch (40) on the pressure vessel, said at least one tie rod (9) being secured to said patch, whereby tightening of said nut (12) pulls said body (8) towards said patch, said body extending beyond said patch such that said sealed space includes said weld.