Claims:WE CLAIM

1. The process of connecting the two Hemi spherical Dished End (HSDE) without inside welding and welding from only one side comprising the steps of:
Edge Preparation with proposed style such that the inside welding of the connecting sphere is eliminated;
Root Welding by Tungsten Inert Gas Welding (6);
2 or 3 Passes of Shielded Metal Arc Welding (7); and
Semi-Automated Submerged Arc Welding to complete the welding (8).

2. The process as claimed in claim 1, wherein the process takes less than 2 days.
, Description:FIELD OF THE INVENTION

[001] The present invention, in general, relates to Connecting sphere of High Pressure High Temperature Steam Generator Manufacturing. The present invention, in particular, relates to the design development in Edge Preparation for welding two Hemi spherical Dished Ends.

BACKGROUND OF THE INVENTION

[002] High Pressure High Temperature Steam Generator consists of a component Connecting Sphere. Connecting Sphere is made of two Hemi spherical Dished End (HSDE) joined by Circular Seam Welding and three nozzles. High Pressure High Temperature Steam Generator is Once Through Super Critical Boiler working at high pressure and temperature parameters.

[003] The connecting sphere acts as connecting link between Separator storage tank and Water Storage Down-comer which in turn connects to Mixing System. The Spherical structure is considered to avoid Backflow due to Eddy flow, which is circular in nature.. The connecting sphere, weighing around 3000 Kg to 3500 Kg, is made of two Hemi spherical Dished End (HSDE) joined by Circular Seam Welding and three nozzles out of which two on top placed at 45 deg apart for connection to storage tank and one vertically downwards for connecting to Water Storage Down-comer.

[004] The two Hemi spherical Dished Ends (HSDE) is of low alloy specification with Outside Diameter (OD) ranging from 810 mm to 875 mm and thickness ranging from 63.5 mm to 95 mm joined by Circular Seam Welding and three nozzles, two on top with OD ranging from 368.3 to 419.2 mm and thickness ranging from 56.35 to 71.4 mm placed at 45 deg apart for connection to storage tank and the third with OD 520.7 to 571.8 mm and thickness from 71.35 to 86.4mm vertically downwards for connecting to mixing system.

[005] The sequence involved in the Cirseam Butt Joint are two HSDE to be Edge Prepared, followed by Circular Seam Welding on inside, grinding on the inside and then welding on outside first manually for two or three passes and finally by Semi-Automated Submerged Arc Welding (SAW). The inside and outside welding is required because of the Edge Preparation Style to ensure full penetration welding. The inside welding is to be performed by the operator manually by inserting the welding torch through the hole of the bottom nozzle of ID 350 to 400 mm which is very difficult for the operator to access and the process is Time Consuming. The probability of defect is more due to accessibility and course correction is also difficult. An alternative Edge Preparation style is required to avoid internal welding and at the same time to ensure full penetration Welding.

[006] Accordingly, Fig 1 shows the connecting sphere model with two HSDE and 3 Nozzles. Section A-A of Fig 1 represents the Edge Preparation and welding of two HSDE item (1) and item no (2).

[007] Fig 2 shows the cross-section A-A with prior art Edge Preparation Style and Cirseam Butt Joint. The HSDEs item no (1) and item no (2) first to be Edge Prepared as per the style shown, followed by Circular Seam Welding on inside (3), grinding on the outside and then Welding on outside (4) first manually for two or three passes and finally by Semi-Automated Submerged Arc Welding (SAW). This process takes 4 days to complete.

OBJECTS OF THE INVENTION

[008] Therefore, the object of the invention is to develop a new style of edge preparation for HSDE to establish full penetration welding by eliminating the inside welding of connecting sphere. The further object of the invention is to propose a welding process on one side only and thereby reduce the overall cycle time.

SUMMARY OF THE INVENTION

[009] The edge preparation of HSDE are proposed to eliminate inside welding, such that the probability of defect in inside welding is more due to poor welding accessibility and course correction is also difficult. Also, the cycle time for completion of welding can be reduced, of Connecting Sphere and at to enable full penetration of the weld. The Proposed Edge Preparation Style envisage for root welding by Tungsten Inert Gas Welding (TIG), followed by Shielded Metal Arc Welding (SMAW) and then Semi-Automated Submerged Arc Welding (SAW). Internal grinding is not required if Root Welding is done by TIG and also it ensures full penetration welding.
[0010] Non-Destructive Examination (NDE) and Hydro test were conducted for Cirseam butt joint and reports certified the Proposed Edge preparation Style met the intended Statutory and design requirements of Connecting Sphere.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0011] Fig 1: Connecting Sphere Model
[0012] Fig 2: Prior Art Edge Preparation Style
[0013] Fig 3: Proposed Edge Preparation Style
[0014] Fig 4: Detailed Welding Process of Proposed Edge Preparation Style

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

[0015] It should be appreciated by those skilled in the art that any block diagrams herein represent conceptual views of illustrative systems embodying the principles of the present subject matter. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudo code, and the like represent various processes which may be substantially represented in computer readable medium and executed by a computer or processor, whether or not such computer or processor is explicitly shown.

[0016] In the present disclosure, the word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

[0017] While the present disclosure is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described in detail below. It should be understood, however that it is not intended to limit the present disclosure to the particular forms disclosed, but on the contrary, the present disclosure is to cover all modifications, equivalents, and alternative falling within the spirit and the scope of the present disclosure.
[0018] The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, device or method that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or device or method. In other words, one or more elements in a system or apparatus proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or apparatus.

[0019] In the following detailed description of the embodiments of the disclosure, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.

[0020] The present invention will be described in detail below with reference to an embodiment as shown in the drawing.

[0021] According to the present invention referring to Fig 3 shows the proposed Edge Preparation Style and Cirseam Butt Joint. The HSDEs item no (1) and item no (2) first to be Edge Prepared as per the proposed style and welded as shown in item no (5) with root welding by Tungsten Inert Gas Welding (TIG), followed by Shielded Metal Arc Welding (SMAW) for 2 or 3 passes and then Semi-Automated Submerged Arc Welding (SAW). Edge preparation is a design for making groove at end of pipes for welding to achieve better fusion and weld strength. Passes are the layers in welding process. 2 or 3 passes of SMAW after TIG to be done for further movement and loading on SAW Machines.

[0022] The edge preparation style of HSDE are Proposed in such a way that inside welding of the connecting sphere is eliminated.

[0023] The process of connecting the two HSDE without inside welding and welding from only one side as shown in Fig 4 comprising the steps of:
[0024] Edge Preparation with proposed style
[0025] Root Welding by Tungsten Inert Gas Welding (6)
[0026] 2 or 3 Passes of Shielded Metal Arc Welding (7)
[0027] Semi-Automated Submerged Arc Welding to complete the welding (8)

[0028] Because of this proposed Edge Preparation Time, cycle time of manufacturing Connecting Sphere is drastically reduced.

[0029] With the proposed method, the inside welding is eliminated and thereby the accessibility issue is avoided and probability of defect is reduced. The proposed welding sequence with TIG, SMAW and SAW ensured full penetration welding. NDE and Hydro test were conducted and reports certified the Proposed Edge preparation Style met the intended Statutory and design requirements of Connecting Sphere.

[0030] The total time required for completing the process is only 2 days. The cycle time is reduced to half because of the proposed method and also eliminated the difficulty in inside welding.

[0031] The invention has been described in an illustrative manner, and it is to be understood that the terminology that has been used is intended to be in the nature of words of description rather than of limitation. Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the specification, the reference numerals are merely for convenience, and are not to be in any way limiting, the invention may be practiced otherwise than is specifically described.