Claims:WE CLAIM:
1. An apparatus for induction pressure welding of butt joints in pipes of thermal power plants comprising of top assembly placed on bottom assembly, wherein each said assembly includes metallic casing accommodating metallic conductor provided with cooling water inlet and outlet together with purging gas tubes assembly.

2. An apparatus for induction pressure welding of butt joints in pipes of thermal power plants as claimed in claim 1, wherein the bottom aluminum chamber body is having a wider opening slot to suit the bottom copper conductor left and right assemblies.

3. An apparatus for induction pressure welding of butt joints in pipes of thermal power plants as claimed in any of the preceding claims, wherein the top copper conductor includes cooling water circulation with slot passage formed by means of atleast two holes at the top so as to connect the inlet and outlet of cooling water pipes respectively, in which a step is provided at the bottom of the top copper conductor on either side for perfect seating with bottom copper conductor.

4. An apparatus for induction pressure welding of butt joints in pipes of thermal power plants as claimed in any of the preceding claims, wherein said copper conductor bottom left and right assemblies comprising of copper bodies left and right, thin silver foil and copper body is in which the copper sheet provided with slot passage for cooling water inlet and outlet with the holes at the ends of the slot for inlet entry and outlet exit, and a step is placed at the top to seat with top copper conductor.

5. An apparatus for induction pressure welding of butt joints in pipes of thermal power plants as claimed in any of the preceding claims, wherein a plurality of positioner rings are provided so as to hold the pipes with annular gap around the top and bottom copper conductor.

6. An apparatus for induction pressure welding of butt joints in pipes of thermal power plants as claimed in any of the preceding claims, wherein the purging gas tube assembly comprises main line including a tube and connected to the at least two tubes for effective purging by means of a header at one end.

7. An apparatus for induction pressure welding of butt joints in pipes of thermal power plants as claimed in any of the preceding claims, comprising of clamp fixed on the outer peripheral of the bottom aluminium chamber by means of screw.
8. An apparatus for induction pressure welding of butt joints in pipes of thermal power plants as claimed in any of the preceding claims, wherein laminated foils with opening are provided to place the top/bottom copper conductor assembly inside the top/bottom aluminium chamber casing.

9. An apparatus for induction pressure welding of butt joints in pipes of thermal power plants as claimed in any of the preceding claims, wherein a coating of iron powder, silica and binder mix is placed in the gap between the copper assemblies and aluminium chamber assemblies.
, Description:An apparatus for induction pressure welding of butt joints in pipes of thermal power plants
FIELD OF INVENTION
[001] The Present invention generally relates to pipe to pipe joining process and device without slag inclusion during welding. The present invention is particularly relates to an apparatus for induction pressure welding of butt joints in pipes used in the economizers of thermal power plants.

BACKGROUND OF THE INVENTION

[002] High pressure, high temperature steam generation used for thermal power generation normally consisting super heaters, re- heaters, evaporators and economizers etc. Normally all the equipment are made up of multiple tubes and pipes and it is common practice to join the end of the metal pipes first by root Tungsten Inert Gas (TIG) welding and subsequently Shielded Manual Arc Welding (SMAW) process is carried out to avoid the slag inclusion thus forming sound weld metal deposition inside the components. Hence, Induction pressure welding is essential to avoid the two stages and process of welding. There is no ready reference device available for induction pressure welding of non-standard pipes used in the economizer coils of high pressure stream generation.

[003] Hence, it is required to devise an apparatus for induction pressure welding of butt joints in pipes of thermal power plants, for which the present invention has been introduced.

PRIOR ART:

[004] Now, reference may be made to US 33 89 238 directing to apparatus and method for welding submerged pipes by induction Heating.

[005] This invention pertains to the art of induction heating and more particularly to an apparatus and method for welding submerged pipes by induction heating.

[006] Here, a porous sleeve is wrapped around the joint formed by the ends of the pipe. A nonporous sleeve is then utilized to surround the porous sleeve being coterminous therewith. An inductor surrounds the nonporous sleeve and is supplied with heating current. Pressure applying means are utilized to effect the pressure weld.

[007] Further, said apparatus comprising a porous sleeve surrounding said abutting ends, and covering the joint between said ends, a nonporous, sleeve-like member surrounding said porous sleeve and

[008] conterminous therewith, means for clamping said nonporous sleeve against said porous sleeve to hold said porous sleeve firmly against said abutting ends, an inductor means surrounding said non-porous sleeve radially opposite said joint between said ends for heating said ends adjacent said joint to a pressure welding temperature and means for forcing said ends together to produce a pressure weld.

[009] From the above, it has been observed that the heating process is circumferential through a single piece, whereas the present invention is made into two halves. Moreover, the method of insulation is also different and simple and sturdy in the present invention.

OBJECTS OF THE INVENTION

[0010] An object of the present invention is to provide an apparatus for induction pressure welding of butt joints in pipes of thermal power plants.

[0011] Another object of the present invention is to provide an apparatus for induction pressure welding of butt joints in pipes of thermal power plants which is efficient.

[0012] Yet another object of the present invention is to provide an apparatus for induction pressure welding of butt joints in pipes of thermal power plants which is used for the pressure welding of non-standard pipes employed in the economizer coils of high pressure steam generation.

SUMMARY OF THE INVENTION

[0013] The invention relates to development of a device suitable for welding pipe to pipe joint using conventional induction pressure welding.

[0014] According to the invention, the whole device is divided into two parts namely top assembly and bottom assembly. The top assembly consisting of Aluminium casing and copper conductor with provision for cooling water inlet and outlet and purging gas inlet connection. The bottom assembly consisting of Aluminium casing with Copper conductor left and right assembly with cooling water inlet and outlet connection. The copper conductor assemblies of top and bottom are sprayed with powdered coating for insulation purpose between copper conductor and Aluminium casing. They are fixed with laminated rectangular thin sheets to place the Copper conductor assemblies inside the respective Aluminium casings. Cooling water circulation is provided by means of slots made in the both the Copper conductors with holes at the bottom for inlet and outlet connections.

They are sealed by brazing by means of placing silver foil and Copper sheet to avoid leakage. The purging gas connections are made through connectors provided at the end of the tubes and other ends are projected and placed to the welding zone inside the top and bottom assemblies. Inside packing is made by filling the gap using Iron powder, Silica & binder between the Copper conductors and Aluminium casing for rigidity. The bottom assembly is connected to the bus bar terminals through the holes provided in the bottom Copper assemblies left and right. The top Copper assembly connected to the frame of the cooling water circuit through the holes provided in the top Copper conductor Assembly. Four numbers of positioner rings are provided to hold the pipes which are to be welded. The diameter formed by the top and bottom Copper conductor assemblies are so chosen that required annular gap is maintained between the outer diameter of the pipes to be welded and the inner diameter of the positioned top and bottom Copper conductor assemblies for the fusion during welding. The purging air header is clamped in the Aluminium casing through fastener. The positioner rings in plural are provided with springs for flexibility for pipes setting and one number is tightened rigidly through screw for guiding the pipe. This device is suitable for welding pipes used in thermal power generators.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0015] Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings of the exemplary embodiments and wherein:

Figure 1shows: The top A and Bottom B subassemblies for induction pressure welding.
Figure 2 shows: The Aluminium chamber body with holes, slots and step.
Figure 3 shows: The bottom Aluminium chamber body with purging gas assembly, positioner rings and bottom copper conductor left and right assemblies.
Figure 4 shows: The top Aluminium chamber body with purging gas assembly, positioner rings and top copper conductor assembly.
Figure 5 shows: Slots and holes provided on the bottom Copper conductor left and right.
Figure 5a shows: The slots and holes provided on the top Copper Conductor.
Figure 6 shows: The silver bracing details with copper sheet to seal the inlet and outlet cooling water circuit.
Figure 7 shows: The ceramic coating details with lamination sheets on top and bottom Copper conductors left and right assemblies.
Figure 8 shows: The details of positioner rings
Figure 9 shows: Details of laminated insulation sheets
Figure 10 shows: Details of bottom purging gas assembly
Figure 10a shows: The details of top purging gas assembly
Figure 11 shows: The top A assembly and bottom B assembly with
work piece in position to weld
Figure 12 shows: The clamp and screw used fixing the gas purging assembly over the Aluminium chamber body top and bottom.

DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE PRESENT INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS

The present invention imparts teaching regarding an apparatus for induction pressure welding of butt joints in pipes of thermal power plants comprising of top and bottom chamber assembly.

Description of the top Aluminium chamber assembly (A):

[0016] The top Aluminium chamber of assembly comprising of the following components:

(1) Top Aluminium Chamber body (Fig 2)

[0017] The Aluminium chamber body is having atleast two holes (a) at the top for the interconnection of the copper conductor (top) by means of atleast two hylum pins (10) and atleast two holes at the bottom (b) for fine setting of the copper conductor (top) so that the copper conductor (top) can be placed exactly at the centre of said Aluminium chamber body. Top slot(c) is provided to insert the copper conductor top (05). Atleast two positioner holes (d) at the top and counter boring located at the inside of the chamber (not shown) so that the positioner ring (11) can be placed with spring (not shown) and in turn the positioner ring can be tightened by screw. On either side of the Aluminium chamber body, internal curved slots (e) are positioned to accommodate the positioner rings (11). The purpose of the positioner rings is to hold the work piece (pipes) with annular gap (h1) around the copper conductor (top) and copper conductor bottom. On the outer peripheral of the chamber, atleast two through holes (f) are provided to insert the upper purging gas tubes assembly and atleast one additional hole (g) with tapping to clamp the purging gas tube assembly (07).

(2) Copper conductor top (Figure 5a):

[0018] Cooling water circulation with slot passage is formed by means of atleast two holes at the top (08 and 09) so as to connect the inlet and outlet of cooling water pipes respectively. A further step (s1) is provided at the bottom of the copper conductor (top) on either side for perfect seating with bottom copper conductor. Boring is made to accommodate the pipe outer diameter to be welded plus the annular gap (h1) after matching the copper conductor top and bottom.

(3) Positioner rings (Fig. 8):

[0019] A plurality of positioner rings (11) is placed inside the slots of the Aluminium chamber bodies (01 and 02) and held by positioner screws internally with springs placed in the counter bore of the respective Aluminium chamber bodies and another one number of positioner ring (11) without spring tightened using Screw and Nut (28) firmly with the bottom Aluminium Chamber (01) for initial setting. By this means the required annular gap is maintained circumferentially between the outside diameter of the pipes (20 and 21) which are to be welded to accommodate the fused up step weld metal thickness all around without obstruction.

(4) Upper purging gas tube assembly (Fig.10a):

[0020] The main line includes a tube (22) bend with right angle and connected to the at least two tubes (24 and 25) for effective purging purpose by means of a small header (23) at one end. At the other end, a nut (07) is provided to connect the inlet of the purging system.

(5) Clamp ( Figure12):

[0021] The clamp (26) is fixed on the outer peripheral of the bottom aluminium chamber (01) by means of screw (27). This is used to strongly hold the purging gas assembly.

(4) Laminated rectangular opening foils (Figure 9):

[0022] These laminated foils with opening (14) are used to place the topcopper conductor assembly inside the top Aluminium chamber casing (02).
II. Description of the bottom chamber assembly (B):

(1) Bottom Aluminium Chamber Body:

[0023] The bottom aluminium chamber body is similar to top chamber body except, 1. The opening slot(c) is more widened to suit the bottom copper conductor left and right assemblies (03 and 04). 2. One of the slot made without counter boring and through drill so that one of the positioner rings (11) is tightened with screw and nut (28) rigidly. On the outer peripheral of the bottom Aluminium chamber, two through holes (f) are provided to insert the bottom purging gas tubes assembly (06) and one additional hole (g) with tapping (as done in the top chamber) to clamp the bottom purging gas tube assembly (06).

(2) Copper conductor bottom left and right assemblies (Figure 5):

[0024] The copper conductor bottom assembly comprising of copper bodies left and right (03 and 04), thin silver foil (18) and copper sheet (16). The copper body is provided with slot passage for cooling water inlet and outlet with the holes at the ends of the slot for inlet entry and outlet exit (29 and 30). A further step is placed at the top (S2) to seat with top copper conductor (05). The inlet and outlet passage is first covered with thin silver foil sheet (18) and copper sheet (16) is placed above the thin silver foil and finally silver brazing is carried out. The purpose of the brazing is to have leak free inlet and outlet of the cooling water passage. Multitude of holes (31) are provided at the bottom of the left and right of bottom copper conductor assemblies without interrupting the cooling water inlet and outlet passage. These holes are used to connect the bus bar of the induction welding machine. Spray coating (12) is made on the top portion of the assemblies to insulate the copper assemblies from Aluminium chamber casing.

(3) Bottom purging gas assembly (Fig. 10):

[0025] This is similar to the top purging gas assembly, but differs with bending radius of tube (24 and 25) to suit to the bottom profile of the Aluminium chamber packing top surface.

(4) Clamp (Figure 12):

[0026] The clamp (26) is fixed on the outer peripheral of the bottom aluminium chamber (01) by means of screw (27). This is used to strongly hold the purging gas assembly.

(5) Laminated recangular opening foils (Figure 9):

[0027] These laminated foils (15) are used to place with the opening bottom copper conductor assemblies (03 and 04) inside the bottom Aluminium chamber casing (01).

Common item used in the both top (A) and bottom (B) assemblies.
Iron powder, silica and Binder:

[0028] Iron powder, silica, and binder is proportionately mixed and filled in the gap in-between the copper assemblies and Aluminium chamber assemblies for rigid stability. This is carried out for both top and bottom. Now the two A and B assemblies are ready for the conventional induction welding process as detailed below:

[0029] The assemblies A and B are matched. B is clamped in the bus bar through holes 31 to the welding machine where’s as A is connected to the arm through hole 13. The pipes (20 and 21) which are to be welded are inserted into the Aluminium casing and rests on the positioner rings. Both tubes (20 and 21) edge prepared ends touch each other and rests on the plurality of the positioner rings satisfying the two conditions viz., annular gap and concentric centre to the copper conductor assemblies. The positive and negative terminals are connected to the holes (31) provided at the bottom copper conductor assemblies and purging gas is connected through connectors (06 and 07). The cooling water circulation for the top assembly A is governed through holes (08) and (09) and fixed through hole (13) with the equipment whereas the bottom assembly B is governed through holes (29) and (30). Now the machine is switched on to finish the welding process.

[0030] It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims:-