Claims:WE CLAIM
1. An apparatus for retrieving a mandrel (103) stuck in a tube (104) of shell and tube heat exchanger (106), wherein the apparatus comprises of:
a first cylindrical rod (301) having a through hole at an angle; and
a second cylindrical rod (302) fitted into the first cylindrical rod (301) at a predetermined distance from a tip of the first cylindrical rod (301).

2. The apparatus as claimed in claim 1, wherein the second cylindrical rod (302) is loosely fitted to the first cylindrical rod (301) in the through hole at acute or right angle.

3. The apparatus as claimed in claim 1 or 2, wherein upon crossing the mandrel (103), centrifugal force is induced by rotation manually or using a rotational drive.

4. An apparatus for retrieving a mandrel (103) stuck in a tube (104) of shell and tube heat exchanger (106), wherein the apparatus comprises of:
a first cylindrical rod with blind hole (401) having a blind hole at an angle; and a shorter second cylindrical rod (402) fitted into the first cylindrical rod with blind hole (401) at a predetermined distance from a tip of the first cylindrical rod with blind hole (401).

5. The apparatus as claimed in claim 4, wherein the second cylindrical rod (302) is fitted to the first cylindrical rod with blind hole (401) by a spring (403) in the blind hole.

6. The apparatus as claimed in claim 4 or 5, wherein upon crossing the mandrel (103), a centrifugal force is induced by rotation manually or using a rotational drive element, in which an actuator is provided for engaging the shorter second cylindrical rod (402) to move in a radial or radial-axial direction by a rotational drive element, wherein the rotational drive element is a motor which is connected to the actuator to provide a centrifugal clutching force.

7. The apparatus as claimed in claims 4-6, wherein the shorter second cylindrical rod (402) slides and comes in contact with the mandrel’s thickness side upto the inner surface of the tube (104) and gets positively engaged.

8. The apparatus as claimed in claim 1-7, wherein the shorter second cylindrical rod (402) is smaller than the first cylindrical rod with blind hole (401).

9. The apparatus as claimed in claims 1-8, wherein the predetermined distance is determined by maximum shear strength of the shorter second cylindrical rod (402).

10. The apparatus as claimed in claims 1-9, wherein the predetermined angle is = 90°.

Dated this 23rd day of January 2021

SOMA RANI MISHRA
IN/PA-1159
OF L. S. DAVAR & CO.
APPLICANT’S AGENT
, Description:AN APPARATUS FOR RETRIEVING A MANDREL STUCK IN A TUBE OF A HEAT EXCHANGER

TECHNICAL FIELD
[0001] The present subject matter described herein relates to an apparatus for the retrieval of delicate, struck, guiding mandrels that form a part of the orbital, tube to tube sheet welding machine, from within the slender, small diameter tubes of shell and tube heat exchanger. More Specifically, the present invention relates to an apparatus to minimize the bending moment, induced on both the tool as well as the mount during retrieval of the delicate, thin walled guiding mandrel covering the centering shaft of the orbital tube to tube sheet welding machine.

BACKGROUND/PRIOR ART OF THE INVENTION
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Among the principles of heat exchanger design, shell and tube heat exchanger is an efficient and compact arrangement. The prominent importance associated with shell and tube design is the separated existence of tube and shell side fluid and is obtained by welding tube with tube sheets. The productivity is increased by automation of the welding between tube and tube sheet by introducing an orbital tube to tube sheet welding machine. This machine is provided with a centering shaft for aligning the machine along with the axis of the tube. Based on the tube’s inner diameter to be welded with tube sheet, standardized guiding mandrels will be wrapped over the centering shaft of the welding machine for the sole purpose of centering.
[0004] After completion of welding the tube with the tube sheet, the welding machine is pulled which does the intended operation of retrieval of the guiding mandrel out of the tube. For welding slender tubes, and to suit the space between the centering shaft and the to be welded slender tube, delicate, thin mandrels are used. At cases, undesired, reinforcement allows the machine to be pulled out but obstructing the mandrel. In these cases, since the mandrel has a slit, it can be forced to elastically deflect by the application of force and retrieved. The general purpose, single/double contact tool, bent at right angle is used, but often fails to sustain the bending moment induced during retrieval. The axial force required to pull the mandrel reaches as high as 30 Kg and damages the mandrel at times. Hence, an arrangement capable of minimizing the bending moment and to maximize both cross sectional area, area moment of inertia and ease of pulling is designed, manufactured and tested.
[0005] In a conventional state of art, as illustrated in Fig. 1, an orbital welding machine aligned with heat exchanger is shown. The centering shaft (101) pertaining to the tube to tube sheet orbital welding machine (102), is wrapped inside the delicate guiding mandrel (103) and inserted into the tube (104) prior to the welding between tube (104) and tube sheet (105) which is comprised of a shell and tube heat exchanger (106). After welding process is completed, the orbital welding machine (102) is pulled out, with an intention to totally remove the welding machine (102) along with its accessories. In case, where the welding reinforcement is undesirably excessive (201), hindering the path of retrieval of the mandrel (103), the mandrel (103) is stuck inside the tube as shown in Fig. 2.
[0006] As per the prior art, US patent US2261564A (Method of removing stuck pipe from wells) describes the method for removing pipes that are stuck inside bore wells with diameters very high and incomparable with that of the dimensions for which the present claim is made (tubes lesser than 10mm diameter).
[0007] US patent US2832423A (Apparatus for removing stuck pipe from well bores) describes the method for removing pipes that are stuck inside bore wells with the use of levers connected through hinges and provides a better control in approach but is meant only for diameters of bore well very high and incomparable with that of the dimensions for which the present claim is made (tubes lesser than 10mm diameter).
[0008] US patent US20130220617A1 (Adjustable engagement system for tool removal) describes the method for retrieving a remote tool with a threaded connection from a remote location by including a rotational drive member that rotates an attachment having threaded portion with provisions to align it with the tool that is angularly and laterally offset with the axis of rotation of the drive member.
[0009] Though the aforementioned patents address the retrieval of a component struck inside a cylindrical bore, the size of the bore being dealt by the aforementioned methodologies could not be adopted for tubular heat exchangers, where mandrel without any provision for holding could be clutched and retrieved.
[0010] It is therby required to provide a damage-less pulling of the often struck, slender mandrel from within small diameter tubes, using an apparatus capable of minimizing the bending moment induced during application of axial force and to maximize cross sectional area, area moment of inertia and ease of pulling.

OBJECTS OF THE INVENTION
[0011] It is therefore the object of the present disclosure to overcome the aforementioned and other drawbacks in prior method/product/apparatus.
[0012] It is a primary object of the present disclosure to provide an apparatus for damage-less retrieval of the often struck, slender mandrel from within small diameter tubes of shell and tube heat exchangers, using an arrangement capable of minimizing the bending moment induced during application of axial force.
[0013] It is another object of the present disclosure to maximize cross sectional area along with area moment of inertia and ease of pulling.
[0014] It is another object of the present disclosure to provide an apparatus that remains inside the jig but ratchets out and engages with the struck mandrel at the annular area by a desired radial force.
[0015] Yet another object of the present disclosure is to minimize the induced bending moment to almost zero to achieve better efficiency.
[0016] These and other objects and advantages of the present subject matter will be apparent to a person skilled in the art after consideration of the following detailed description taken into consideration with accompanying drawings in which preferred embodiments of the present subject matter are illustrated.
[0017] These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.

SUMMARY OF THE INVENTION
[0018] One or more drawbacks of conventional systems and process are overcome, and additional advantages are provided through the apparatus/composition and a method as claimed in the present disclosure. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be part of the claimed disclosure.
[0019] Solution to one or more drawbacks of existing technology and additional advantages are provided through the present disclosure. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be a part of the claimed disclosure.
[0020] The present disclosure offers a solution in the form of an apparatus for retrieving a mandrel stuck in a tube of shell and tube heat exchanger.
[0021] The apparatus retrieves the mandrel stuck within small diameter tubes of a shell and tube heat exchanger . The apparatus is capable of minimizing the bending moment that is induced during application of axial force and to maximize cross sectional area along with area moment of inertia and ease of pulling. The apparatus comprises of a first cylindrical rod facilitating and easing the process of pulling that is inserted inside a mandrel. The first cylindrical rod is fitted inside the mandrel in a loose manner. The first cylindrical rod is provided with a blind or through hole at an angle of 90°.
[0022] A second cylindrical rod is mounted at a predetermined distance from the tip of the first cylindrical rod, which is obtained based on maximum shear strength of the cylindrical rod. The second cylindrical rod is either loosely fitted to the first cylindrical rod in a through hole variant or by an assistance of an open coil compression spring in the blind hole variant.
[0023] Upon crossing the mandrel, for the case with loose fit between rods, centrifugal force is induced by rotation either manually or using a rotational drive and for the latter case with spring in case of blind hole, the second cylindrical rod slides and comes in contact with the mandrel’s thickness side upto the inner surface of the tube and gets positively engaged.
[0024] While pulling back the first cylindrical rod, second cylindrical rod comes in contact with the stuck mandrel forming a dog (mechanical component that refrains relative movement of a mechanism or component by engaging with another component) and maintains positive contact.
[0025] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
[0026] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
[0027] It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.
[0028] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0029] The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and processes that are consistent with the subject matter as claimed herein, wherein:-
[0030] 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 present disclosure may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. In the figures, 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 or structure 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:
[0031] Fig. 1 illustrates a schematic representation of orbital welding machine aligned with the shell and tube heat exchanger of Prior art;
[0032] Fig. 2 illustrates a schematic representation of mandrel retained inside the tube due to excessive welding reinforcement according to prior art;
[0033] Fig. 3 illustrates a schematic representation of jig slid inside the mandrel, with the apparatus inserted inside the mandrel at the the time of engagement forming first embodiment in accordance with present invention.
[0034] Fig. 4 illustrates a schematic representation of apparatus that is ready to ratchet with the mandrel (first embodiment) according to the present invention.
[0035] Fig. 5 illustrates a schematic representation of second embodiment of apparatus of the present invention.
[0036] Fig. 6 illustrates schematic representation of apparatus that is ready to ratchet with the mandrel (second embodiment) of the present invention during operation.
[0037] The figures depict embodiments of the present subject matter for 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.
[0038] The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily 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 PREFERRED EMBODIMENTS OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS
[0039] While the embodiments of the disclosure are subject to various modifications and alternative forms, a specific embodiment thereof has been shown by way of example in the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure.
[0040] The terms “comprises”, “comprising”, or any other variations thereof used in the disclosure, are intended to cover a non-exclusive inclusion, such that a device, system, assembly that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such system, or assembly, or device. In other words, one or more elements in a system or device proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or device.
[0041] In a first embodiment, the present disclosure provides an apparatus to retrieve the mandrel (103) stuck within small diameter tubes (104) of a shell and tube heat exchanger (106). The apparatus is capable of minimizing the bending moment that is induced during application of axial force and to maximize cross sectional area along with area moment of inertia and ease of pulling. The apparatus comprises of a first cylindrical rod (301) that is inserted inside a mandrel (103) for facilitating and easing the process of pulling the stuck mandrel (103) from within small diameter tubes (104) of a shell and tube heat exchanger (106).
[0042] The first cylindrical rod (301) is provided with a through hole at a predetermined angle i.e. 90° as indicated in Figure 3.A second cylindrical rod (302) is inseted in the through hole of said first cylindrical rod (301) at a predetermined distance from the tip of the first cylindrical rod (301). The predetermined distance is determined based on maximum shear strength of the second cylindrical rod (302). Thus, the second cylindrical rod (302) is loosely fitted into the first cylindrical rod (301).
[0043] Upon crossing the mandrel (103), for the case with loose fit between rods (301 and 302), centrifugal force is induced by rotation either manually or using a rotational drive as illustrated in Figure 4.
[0044] In a second embodiment of the invention as best seen in Figure 5, there is provided an apparatus comprising components (401) and (402) to retrieve the mandrel (103) stuck within small diameter tubes (104) of a shell and tube heat exchanger (106). The apparatus is capable of minimizing the bending moment that is induced during application of axial force and to maximize cross sectional area along with area moment of inertia and ease of pulling. The apparatus comprises of a first cylindrical rod with blind hole (401) a open coil compression spring (403) and a shorter second cylinder (402) that fits and flushes with the surface of the first cylinder (401); that is inserted inside a mandrel (103) for facilitating and easing the process of pulling the stuck mandrel (103) from within small diameter tubes (104) of a shell and tube heat exchanger (106).
[0045] The first cylindrical rod with blind hole (401) with a blind hole at a predetermined angle i.e. 90° is flush fitted with a shorter second cylindrical rod (402) by charging a open coil compression spring (403) The predetermined distance is determined based on maximum shear strength of the shortersecond cylindrical rod (402).
[0046] The predetermined angle is = 90° for above discussed embodiment(s).
[0047] Upon crossing the mandrel (103), a force is exerted on the shorter second cylindrical rod (402), thus facilitating the positive engagement with the mandrel (103) while pulling.
[0048] For the case with spring in blind hole, the shorter second cylindrical rod (402) slides and comes in contact with the mandrel’s thickness side upto the inner surface of the tube (104) and gets positively engaged as illustrated in Figure 6.
[0049] While pulling back the first cylindrical rod with blind hole (401), shorter second cylindrical rod (402) comes in contact with the stuck mandrel forming a dog (mechanical component that refrains relative movement of a mechanism or component by engaging with another component) and maintains positive contact.
[0050] Thus, while pulling back the first cylindrical rod with blind hole (401), the shorter second cylindrical rod (402) comes in contact with the stuck mandrel (103) and forms a dog which refrains the relative movement of the apparatus with the mandrel (103) and maintains a positive contact.
[0051] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation, no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to disclosures containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. Also, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general, such construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances, where a convention analogous to “at least one of A, B, or C, etc.” is used, in general, such construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.”
[0052] It will be further appreciated that functions or structures of a plurality of components or steps may be combined into a single component or step, or the functions or structures of one-step or component may be split among plural steps or components. The present disclosure contemplates all of these combinations. Unless stated otherwise, dimensions and geometries of the various structures depicted herein are not intended to be restrictive of the disclosure, and other dimensions or geometries are possible. Also, while a feature of the present disclosure may have been described in the context of only one of the illustrated embodiments, such feature may be combined with one or more other features of other embodiments, for any given application. It will also be appreciated from the above that the fabrication of the unique structures herein and the operation thereof also constitute methods in accordance with the present disclosure. The present disclosure also encompasses intermediate and end products resulting from the practice of the methods herein. The use of “comprising” or “including” also contemplates embodiments that “consist essentially of” or “consist of” the recited feature.
[0053] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases, it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[0054] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.
[0055] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particulars claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogues to “at least one of A, B and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B”.
[0056] The above description does not provide specific details of manufacture or design of the various components. Those of skill in the art are familiar with such details, and unless departures from those techniques are set out, techniques, known, related art or later developed designs and materials should be employed. Those in the art are capable of choosing suitable manufacturing and design details.
[0057] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.
[0058] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.
[0059] While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.