Claims:We claim:
1. A method of eliminating of minimum 3700mm distance from bend location (11) to any one end of tube for manufacturing of economizer coils of a high pressure steam generator, the method comprising:
inspecting length of raw material tube; and
inserting a steel rod (06) inside the tube up to sleeve (07), wherein the steel rod (06) locks temporarily movement of the tube, wherein the steel rod (6) maintains minimum distance 3700mm between a collet (01) and bend location (11); and
bending the tube by bender (02) of bending machine by fixing one end of the tube with the steel rod (06).

2. The method as claimed in claim 1, wherein the bending machine comprises:
the collet (01) to hold one end of the steel tube;
the bender (02) of different radius for bending the tubes; and
a heater (03) installed near the bend location (11), wherein the heater (03) heated the tube for easy and smooth bending of the tube.

3. The method as claimed in claim 1, wherein the bending of the tube further comprises:
determining length of each circuit of the economizer tubes and number of butt joints (09) in the circuit;
bending the tube by maintaining distance of 150mm (a) to a hanger tube (08); and
bending of the tube by maintaining distance of 1000mm (b) from the bend location (11) to the bend joint (09).

4. The method as claimed in claim 1, wherein length of the steel rod (06) is about 3700mm.
5. The method as claimed in claim 1, wherein the sleeve (07) is welded on the steel rod (06) at a distance of 700mm from one end.

6. The method as claimed in claim 1, wherein thickness of the sleeve (07) is about 5mm.

7. The method as claimed in claim 1, wherein outer diameter of the steel rod (06) is 0.92 times of inner diameter of the economizer tube.

8. The method as claimed in claim 1, wherein a follower jaw (05) is provided over joining of the tube and the steel rod (06).

9. The method as claimed in claim 1, wherein the sleeve (07) is welded on the steel rod (06).
, Description:A METHOD OF ELIMINATION OF MINIMUM LENGTH REQUIRED FOR HOLDING OF ECONOMIZER TUBE FOR BENDING IN MANUFACTURING OF ECONOMIZER COILS OF A HIGH PRESSURE STEAM GENERATOR

Field of Invention
[001] The present subject matter described herein, relates to a manufacturing process of the economizer coils in the high pressure steam generators. More particularly, the present invention relates to elimination of butt joint of economizer tube to attain cycle time reduction.
Background of Invention
[002] The function of an economiser in steam generating units is to absorb heat from flue gases and add this as sensible heat to the feed water before the water enters the evaporative circuit of the boiler.
[003] Earlier the economisers were introduced mainly to recover the heat available to flue gas that leaves the boiler and provision of this additional heating surface increased the efficiency of steam generation, saving in fuel consumption, thus the name “Economisers “christened. Counter flow arrangement is normally selected so that heating surface requirement is kept minimum for the same temperature drop in the flue gas. Economiser’s coils are designed for horizontal placement which facilitate draining of the coils and favours the arrangement in second pass of boiler.
[004] An economiser’s assembly usually has multiple layers and each layer will have multiple circuit, ranging from three to four. Each circuit has unique configuration and unique length. Usually the total length of each circuit exceeds the raw material length. For example, the raw materials length purchased vary from 10000mm to 12150mm, but the length of individual circuit varies from 90000mm to11000mm. Hence, it is necessary to weld each circuit tubes in order to develop the tubes before bending. This welding is done in butt welding machines. After welding of tube by butt welding. It has to bend in bending machine. The bending machine should be capable to handling of total tube length and bend feasibility irrespective of butt joint (09) of tube locations.
[005] For economizers to make each circuit various butt joints ( 09), the welding procedure like metal inert gas (MIG), Tungsten Inert Gas (TIG), Flash Butt Welding (FBW) or Induction pressure welding (IPW) adopted for welding depending upon customer requirement, manufacturing capability, flexibility, and cost estimation. Length of each circuit is in range of 90000mm to 11000mm. So according to requirement of the customer, bending machine, and bending feasibility, total circuit length is made up to three or four parts/segments. Accordingly, three or four parts/segments are added again after bending with conventional butt joint (09) welding procedure like IPW or FBW or TIG weld. Therefore, the overall time of production is increased.
[006] According to figure 01, for bending of tube proper setting and handling is required to bend tube correctly and safely. In bending Machine, there are two jaws for handle of tubes, installed in machine. In these jaws, one is collet (01) which holds the tube at one end and another is bender (02) (which has two bending Former in same plane in opposite direction). In addition, there is one heating device (03), which heats the surface of tube to close radius bend (ratio of bend radius to Diameter of tube is 1.3) for easy and smooth bending. The minimum distance between collet (01) and bender (02) should be 1500mm; and bender (02) to heating unit (03) minimum distance should be 2200 mm. So, for any close bend Location (11) (where heating is required) and the collet (01) distance should be minimum 2200mm+1500mm = 3700mm. For example, the raw materials length purchased varies from 10000mm to 12150mm, but the length of individual circuit varies from 90000mm to11000mm. Hence, it is necessary to weld each circuit tubes in order to develop the tubes before bending. So according to requirement of customer, bending machine bending feasibility, and total circuit length are made up to three or four parts/segments. These three or four parts/segment are added again after bend with conventional butt joint (09) welding procedure like IPW OR or FBW or TIG weld. During planning of these conventional joint, for maintain 3700mm minimum distance from close bend to one end of tube, it is required to give one additional butt joint (09).

[007] So, addition of one additional joint in one part (total three or four parts so three or four joints in one circuit) give an additional cost and time consuming process. Labour requirements also are potentially increased. In this additional drawback it is very large number of defected butt joint (09) piece will produce. Operator comfort will also decrease. So that it results in more number of defective pieces with the lager extent of safety standard compromise. Terminology, technical specification will automatically increase. Grading, sampling, and control will of product will increase this will result in automatic cycle time increasing. Codes of good practicing will reduce up to lager extent. It will also increase the other additional machine movement to handle variety of tubes length.

Objects of Invention
[008] The principal object of the present invention is to provide a method of bending of economizer coil tube without giving an additional joint and elimination of minimum length of tube after bend location. The present invention eliminates requirement of one additional joint of each parts of circuit of economizer tube which reduces the joint cost and easiness in grading and sampling, and handling of tube.
[009] Another object of the present invention is to provide a method of bending of economizer tube for manufacturing of economizer coils of a high pressure steam generator which is able to facilitate easiness in loading of tubes on bending machine and bend the tubes based on assembly requirement eliminating disadvantage of tube cutting and edge preparation operations.
[0010] Yet another object of the present invention is to provide a method of bending of economizer coil tube for manufacturing of economizer coils of a high pressure steam generator which is capable of reducing cycle time of manufacturing a product and thus improves volume of production and sustainably reduces rework cost.
Summary of Invention
[0011] The present subject matter relates to a manufacturing process of the economizer coils in the high pressure steam generators. The bending machine cannot handle not less than3700mm distance from one end to any bend and accordingly the different circuit length of the economizer coils are studied and the two constrains will be taken into account. The minimum distance of 150 mm from hanger tube (08) to joint location (09). The minimum distance of 1000mm between the bend portion (11) and joint location (09). Because of these constraints one extra joint is mandatory and aging removal of the extra length tube as scrap is costly and time consuming.
[0012] A rod of length 3700mm and outer diameter is 0.92 times of inner diameter of Economizers tube with sleeve(which inner diameter equal to outer diameter of rod and thickness is 5mm)are located 700mm from any one end. Sleeve with rod are permanently welded to each other. This rod are inserted inside the tube up to 700mm By this device, the combined length of tube with rod are more than 3700mm.So, the minimum requirement of 3700mm length before any bend are now removed. Collet (01) of bending machine can hold one end of rod (06) and from collet (01), 3700mm distance heater (03) can heat the tube and bender (02) can bend the tube easily. By calculating the total length required for each coil and the supplied length of each tubes, the first part of any circuit will be made as less than 3700 and more than 1000mm irrespective of the circuit parts length. So, that for any circuit parts, the first part will be the less than3700 with help of rod (06) bending can be performed. By this method of eliminating of minimum length for bend is removed. The cycle time is reduced is one sixth of the existing method of manufacturing.
[0013] In order to further understand the characteristics and technical contents of the present subject matter, a description relating thereto will be made with reference to the accompanying drawings. However, the drawings are illustrative only but not used to limit scope of the present subject matter.
[0014]
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system or methods in accordance with embodiments of the present subject matter are now described, by way of example, and with reference to the accompanying figures, in which:
[0016] Chart-(1) Tube and bending machine arrangement setting details before bending of tube with butt joint.
[0017] Fig- (1) illustrates tube and bending machine arrangement setting details after bending of tube with constrains with butt joint as known in the art;
[0018] Fig- (2) illustrates details of rod and tube arrangement used in bending machine without butt joint, in accordance with the present subject matter;
[0019] Fig- (3) illustrates details of rod and sleeve used for adding additional length for bending, in accordance with the present subject matter;
[0020] Fig- (4) illustrates arrangements of rod with sleeve used in bending inside the economizers tube with bender and heater, in accordance with the present subject matter; and
[0021] Fig- (5) illustrates tube after bending with butt joint and with hanger tube, in accordance with the present subject matter.
[0022] The figures depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

[0023] The present subject matter relates to a manufacturing process of the economizer coils in the high pressure steam generators. The bending machine can handle minimum of 3700mm distance between bend Location (11) to any one end of tube at a time and accordingly the different circuit length of the economizer coils are studied and the two constrains will be taken into account 1. The minimum distance of 150 mm (a) from Hanger tube (08) to any joint location and 2. The minimum distance of 1000mm (b) between the bend portion and joint location. By calculating the total length required for each coil and the supplied length of each tube, the each circuit will be made as three or four parts/segments. After bending of tube, these parts are added with conventional joint like TIG, IPW, FBW etc… so after taking consideration of these two constrains listed above and maintain minimum 3700mm distance between bend Location (11) to any one end of tube with elimination of one joint .
[0024] It is therefore an object of invention to propose an improved simplified method of elimination of additional one joint of coil tube and reduction of minimum length 3700mm after bend. So that after elimination of joint and reduction of 3700mm from one end to bend Location (11) bending can be done without compromising the technical and safety standard with minimum cost.
[0025] A rod of length 3700mm and outer diameter is 0.92 times of inner diameter of Economizers tube with sleeve(which inner diameter equal to outer diameter of rod and thickness is 5mm)are located 700mm from any one end. Sleeve with rod are permanently welded to each other. This rod are inserted inside the tube up to 700mm By this device, the combined length of tube with rod are more than 3700mm.So, the minimum requirement of 3700mm length before any bend are now removed. Collet (01) of bending machine can hold one end of rod (06) and from collet (01) 3700mm heater (03) can heat the tube and bender (02) can bend the tube easily. Handling and movements of tube will easy to improve of productivity because of less number size and less number of movements. It is made simpler way to avoiding complicated movements of tubes in operations and eliminating disadvantage of prior art.
[0026] It should be noted that the description and figures merely illustrate the principles of the present subject matter. It should be appreciated by those skilled in the art that conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present subject matter. It should also be appreciated by those skilled in the art that by devising various arrangements that, although not explicitly described or shown herein, embody the principles of the present subject matter and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be for pedagogical purposes to aid the reader in understanding the principles of the present subject matter and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. The novel features which are believed to be characteristic of the present subject matter, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures.
[0027] These and other advantages of the present subject matter would be described in greater detail with reference to the following figures. It should be noted that the description merely illustrates the principles of the present subject matter. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described herein, embody the principles of the present subject matter and are included within its scope.

[0028] According to figure 02, in present method of elimination of butt joint 09 of coil and maintain 3700mm distance between bend Location 11 to any one end of tube are accomplished with the help of rod 06, which outer Diameter 0.90 to 0.98 of inner diameter of tube and length3700mm. In the figure 02, bending machine parts are arranged and there item numbers are given. The collet 01 which holds the tube at one end. There is a bender 02 on which different radius bending former can be installed to bend the tube. For very close radius of bend (Radius to Diameter of tube less than 1.3) are heating device, such as heater 03, which is supported by a beam 10 to heat the tube. All these parts are installed on machine bed 04. Further, a follower jaw 05 is provided to support to tube during bending.

[0029] According to figure 03, a solid steel rod 06 with minimum length is 3700mm and bending strength are more than economizer’s tube are to be taken. After 700mm from one end of the steel rod 06, a sleeve 07 (same material as rod (06) is welded on the steel rod 06. Further, dimensional details of the sleeve 07 and the steel rod 06 are a rod of length 3700mm and outer diameter is 0.92 times of inner diameter of Economizers tube with sleeve (which inner diameter equal to outer diameter of rod and thickness is 5mm) are located 700mm from any one end. The sleeve 07 with the steel rod 06 is permanently welded to each other.

[0030] Now, Setting of Economizers tube and the steel rod 06 as per bending machine feasibility and direction are given and shown in figure -2. After setting the economizer tube and steel rod 06, one end of tube where distance between one end and bend Location 11 is less than 3700mm as per marked (butt joint 09) drawing details and the sleeve 07 side of the steel rod 06 where distance is minimum from end of the steel rod 06 should be together and opposite direction.

[0031] According to figure 04, now, insert the steel rod 06 inside the tube up to maximum depth of 700mm as possible and it will not move further inside of tube because of sleeve 07 position and it will lock temporarily in that direction and take the collet 01 of the bending machine which hold the steel rod 06 at one end. It will maintain minimum distance between collet 01 (where the steel rod (06) one end is there) and the bend location 11 (where heating of tube are performed.) setting arrangement are shown in figure -04.

[0032] According to figure 05, the supplied raw materials length are noted down first and supplied relevant Drawings for economizer coils are studied. The length of each circuit noted down and no of butt joints 09 to make full length is so chosen in such a way that the joint location 09 will not come less than 150mm (a) to the hanger tube 08. This is to repair the welding easily in future in case any failure. Also the joint should not come 1000mm (b) from the bend location 11 to the bent joint 09. This distance is maintained to avoid the joint failure during bending if the joint falls in the jaw portion of the bending machine.

[0033] By the above arrangement, operator bends the economizer’s tube and after completion of bending, the steel rod (06) is removed by pull in opposite direction of the economizer’s tube. By this process there is no need of maintaining minimum 3700mm distance in economizers tube, after bending or to give minimum one additional joint to maintain this 3700mm length.

[0034] By above process, it can be done in any one circuit of any part and similar fashion it can be done for other circuits. By elimination of minimum distance requirement of 3700mm and minimum one joint additional joint are removed in the length of each parts of circuit. Now 3 to 8 parts/segments in each circuit are sufficient to make circuit length. Each parts of each circuit length will be less than 3700mm and more than 1000mm and bending can be done very easily without any making additional joint.

[0035] From the present method, bending feasibility, distance between bend location 11 and the collet (01) should be minimum Length 3700mm can be achieved by adding some length either permanently or temporary. With a temporary insert of dummy piece of steel rod 06 (outer diameter 0.90 -0.98 of economizers tube to than internal bore of tube) inside economizers tube. After bending of tube Dummy temporary rod 06 can be pulled and used for other parts of circuit to bend.

[0036] Advantages of the present invention:

[0037] Benefits of this is especially advantageous (1) when new products, changes to old products or upgrades are required. Producing large quantities of a product often is more cost effective.

[0038] (2) Reductions in time and cost per product are amplified by the flexibility of these systems.

[0039] (3) Labour requirements also are potentially reduced because a smaller number of workers can produce batches of products.

[0040] (4) In this additional benefit is very less number of defected piece will Produce.

[0041] (5) Operator comfort will also increase. So that it will result in more number of defect free piece with the lager extent of safety standard followed.

[0042] (6) Terminology, technical specification will automatically reduce. Grading, sampling and control of product will reduce that will result in automatic cycle time reduction. Codes of good practicing will improve up to lager extent.

[0043] (7) It will also reduce the Machine movement to handle variety of tubes length.

[0044] (8) Another Object of invention is to propose an improved bend so that it can be manufactured easily from the available material to bend in simplified way, which is capable to operate in standard length.
[0045] Although embodiments for the present subject matter have been described in language specific to structural features, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features and methods are disclosed as embodiments for the present subject matter. Numerous modifications and adaptations of the system/component of the present invention will be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the scope of the present subject matter.