GB2171339A

GB2171339A - Method for joining at least one pipe to a pipe flange or pipe plate

Info

Publication number: GB2171339A
Application number: GB08601916A
Authority: GB
Inventors: Johannes Jacobus Broodman
Original assignee: JOGEMA HOLDING; Jogema Holding BV
Current assignee: JOGEMA HOLDING; Jogema Holding BV
Priority date: 1985-02-21
Filing date: 1986-01-27
Publication date: 1986-08-28
Also published as: NL186404C; DE3605494A1; NL186404B; GB2171339B; DE3605494C2; GB8601916D0; NL8500492A

Abstract

Method for joining at least one pipe 2 to a pipe flange 8, or plate, in which the pipe is in a bore which has a conical widening 6. The pipe is slid into said bore until the pipe end is situated over a certain distance beyond the start of the conical widening. Hereafter a plug 3 is pressed into said pipe end, and said pipe end, said flange or plate and said plug are welded together, filling said conical widening with weld material. After this welding the plug is drilled out. <IMAGE>

Description

SPECIFICATION Method for joining at least one pipe to a pipe flange or pipe plate The invention relates to the joining of at least one pipe to a pipe flange or pipe plate, preferably, however, the joining of several pipes to a pipe flange or pipe plate and in particular the case in which at least three pipes are joined to a flange with a relatively small distance between the pipes and in which by preference a flat machined upper surface, of the flange or plate, facing the pipes is required and the inner diameter of the pipe to be joined is equal or virtually equal to the diameter of the drilled hole in the flange or plate on the entrance side.

Applications of joints of this type with three pipes situated at a small mutual distance on a plate are known, for example for connecting flanges on ultracentrifuges where three joints are necessary from a pipe system to the centrifuges.

Although the welding of pipes to flanges or pipe plates with sufficient distance between the pipes does not in principle present any problem, a welding technology difficulty arises if aluminium is used as the construction material.

With a relatively large distance between the pipes the solution has until now been found in a special preliminary machining of the flanges or plates by means of a nose-shaped groove and the welding of the pipe ends to the nose end by means of plasma alternating-current welding as is shown in the attached Figure 1.

With too small a mutual distance of the pipes a groove-type preliminary machining of this type is, however, no longer possible. The said preliminary working is also often undesirable because packings for the sealing of the mutual openings in the flange and the equipment to be connected can no longer be fitted.

To overcome these difficulties, more especially in the case where the mutual distance of the pipes is very small, a method has been developed in which several pipes are extruded simultaneously from one block. Although when viewed purely technically this method offers a good solution, here too a limit is placed on the actual minimum distance between the pipes.

Other solutions for the joining of pipes located close to each other consist of the machining of wrought pieces in a manner such that on the reverse of the flange pipe pieces are formed which are suitable for welding on pipes of the same type. See the attached Figure 2.

Here too there is, however, a question of an expensive workpiece, while as a result of the welded joint a weakening of the pipes nevertheless still occurs. In view of the still small distance between the pipes the welding-on is moreover no simple matter and this welding procedure has to take place automatically.

The above problems are now solved by the method according to the invention which is characterised by: the making of a drilled hole in the flange or plate in which the pipe is a slide fit and of a conical widening in an extremity of the drilled hole; the sliding of the pipe into the drilled hole from the extremity situated opposite the conical widening until the pipe end is situated preferably over a distance at least equal to the wall thickness of the pipe beyond the conical widening; the fitting of a plug in the extremity of the pipe which is situated in the drilled hole, which plug consists of the same material as the pipe and the flange or plate; the welding of the pipe end to the flange or plate, the space bounded by the wall of the conical widening, the extremity of the pipe and of the plug being filled with welding material; the drilling out of the plug.

The invention will now be explained in more detail by reference to the attached drawings.

Figure 3 shows a section of a pipe plate before the welding; Figure 4 shows the section after the joint has been made; Figure 5 shows a section of a flange with a modified preliminary machining of the flange; Figure 6 shows a similar section to the preceding figures with a specially constructed plug; Figure 7 and 8 show sections of a flange with a post-treatment tool.

In Figure 3 a flange 8 is shown provided with two drilled holes 5, no pipe yet having been placed in the righthand drilled hole, while a pipe 2 with a plug 3 therein is fitted on the left.

Although in Figure 3 only two drilled holes are shown the invention is of course not limited thereto.

In general, as mentioned above, three pipes will be welded close to each other on the flange.

After a drilled hole 5 has been made, the extremity opposite the side in which the pipe is slid is preliminarily machined in a manner such that a conically widened section 6 is produced which begins from a certain height within the drilled hole 5.

This height and the slope of the conical section are determined by the mutual pitch of the drilled holes, in which connection the bevel must at least satisfy the requirements with respect to accessibility for the welding and the quality of the welded joint is guaranteed.

After the making of the drilled hole 5 and the conical widening 6 the pipe 2 is fitted in the drilled hole from the side of the flange situated opposite until the extremity of the pipe is preferably situated at least over a distance equal to the wall thickness of the pipe beyond the point in the drilled hole where the weld preliminary machining 6 starts. A plug 3 of the same material as the pipe or the flange is then fitted in the pipe 2. The said plug 3 is slid into the pipe 2 in a manner such that the top edge of the plug is virtually flush with the top edge of the pipe. The plug 3 may be provided in its end near the conical widening 6with a conical bevel 10 running towards its extremity with the result that together with the conical preliminary machining 6, a circular welding groove 11 is produced into which the extremity of the pipe 2 debouches.The bevel 10 of the plug starts at least over a distance equal to the wall thickness of the pipe higher in the drilled hole than the conical bevel in the flange. Thus Y > d, where d is the wall thickness of pipe 2.

The extremity of the pipe 2 is then welded both to the wall of the conical widening 6 and the conically narrowed extremity of the plug 3, the circular groove 11 being filled with welding material.

After the welding the plug 3 is finally removed, for example drilled out, and the flange face is machined.

The final result is shown in Figure 4.

The conical widening 6 can also be constructed in a different manner, for example by first forming a flat annular surface 12 which extends around the extremity of the inserted pipe 2, beyond which the conical surface itself begins. As a result of this a larger bonding length between the weld 4 and the pipe 2 is obtained. See Figure 5.

By providing the plug 3 with a drilled hole 7 as is shown in Figure 6, an automatic welding machine can be placed thereon in a simple manner, as a result of which the welding process can take place still more accurately and rapidly.

If the user, with a view to fitting packings on the flange surface 8, desires a structure of the welded section which is equivalent to that of the original flange material, the structure of the weld can be refined by deformation of the flange or the section at the point of the weld and the weld itself, either accompanied or not accompanied by a heat treatment in which recrystallisation occurs.

A tool 9 by means of which the top side of the flange can be deformed at the point of the weld in the above-mentioned manner is shown in Figure 7.

Figure 8 shows a possible final state.

A further advantage of the said method is that any irregularities - such as porosity in the weld, are completely eliminated and a very smooth internal surface is obtained at the point of the die 9 in the drilled hole.

The quality of the bonding of the pipe to the flange beneath the welding zone is also promoted thereby.

It is obvious that the flange construction is preferably retained in a counter-die during the foregoing procedure and that the temperature of the construction is held at a level such that adequate recrystallisation is obtained. The degree of deformation necessary and the recrystallisation temperature are determined by the type of material.

Preferably the pipe 2 closely fits into the hole 5 and the plug 3 closely fits into the end of pipe 2, so that the heat conduction through the slits between hole 5 and pipe 2 and between pipe 2 and plug 3 is maximum and the welding heat is conducted quickly away from the welding zone. In connection herewith the plug 3 is preferably solid to take up as much welding heat as possible.

Claims

1. Method for joining at least one pipe to a pipe flange or pipe plate, characterised by: the making of a drilled hole in the flange or plate in which the pipe is a slide fit and of a conical widening in an extremity of the drilled hole; the sliding of the pipe into the drilled hole from the extremity situated opposite the conical widening until the pipe end is situated preferably over a distance at least equal to the wall thickness of the pipe beyond the conical widening; the fitting of a plug in the extremity of the pipe which is situated in the drilled hole, which plug consists of the same material as the pipe and the flange or plate; the welding of the pipe end to the flange or plate, the space bounded by the wall of the conical widening, the extremity of the pipe and of the plug being filled with welding material; the drilling out of the plug.

2. Method according to Claim 1, characterised in that the plug which in its extremity is situated near the conical widening of the drilled hole is narrowed conically towards its extremity, the bevel being situated during the fitting of the plug preferably at a distance approximately equal to the wall thickness above the bevel in the flange.

3. Method according to Claim 1 or 2, characterised in that the conical widening begins from a flat annular surface extending around the pipe.

4. Method according to one of Claims 1 to 3 incl., characterised in that the plug is provided with a drilled hole in its free extremity for supporting a welding tool.

5. Method according to one of Claims 1 to 4, characterised in that the welded section of the joint between the pipe and the flange or plate is deformed by means of a suitable tool by partially pressing in in order to make the structure of the weld identical to that of the original flange or plate material.

6. Method according to Claim 5, characterised in that the weld is simultaneously subjected to a recrystallising heat treatment.

7. Method according to one of the preceding claims, characterised in that the flange or plate is retained during the welding procedure in a counterdie.

8. Method according to one of the preceding claims, characterised in that each of the parts to be welded is held during the welding procedure at a heat level such that adequate recrystallisation occurs.

9. Method according to one of the preceding claims, characterised in that the pipe closely fits into the drilled hole and that the plug closely fits into the pipe end.

10. Method according to one of the preceding claims, characterised in that the plug is solid and is pressed into said pipe end.

11. Method for joining at least one pipe to a pipe flange or pipe plate substantially as herein described with reference to Figures 3 to 8.