Title of Invention

SEAL FOR THREADED CHANNEL CLOSURE TYPE SHELL AND TUBE HEAT EXCHANGERS HAVING REMOVABLE TUBE BUNDLES

Abstract

Together with the heat exchanger, the diaphrgm 8 has to undergo multiple number of pressure/temperature cycles over a period of time and likely to get distorted. This can cause pulling of the inner edge 103 of the tongue 101 inwards, thus riding over the iner edge 104 of the groove 11 provided in shoulder of the channel. The metallic contact thus developed between the tongue 101 and inner edge 104 of the groove can obstruct transmission of load generated by tightening of the push bolts 10, thus only partly loading the gasket. This is avoided by extending the width of the tongue of the diaphragm so that the protion of the face of the tonge (towards the inner edge) rests on the face of the shoulder of the channel. This ensures controlled compression of the gasket at the same time the gasket remains supported on inner as well as outer diameters and hence properly located concentric. Further load applied on the tongue by retightening the push bolts through compression ring, can bend outer portionof the tongue slightly (without permanent deformation) towards the gasket compressing it further and thus ensuring effective gasketed joint. Minor leakage through the gasketed joint can lead to accumulation of dangerous high pressure fluid in the chamber ahead of threaded joint, as these joints become pressure tight under high pressure. This is eliminated by providing plurality of vent holes after the gasketed joint.

Full Text

FORM 2 THE PATENT ACT 1970 & The Patents Rules, 2003 PROVISIONAL / COMPLETE SPECIFICATION (See section 10 and rule 13) 1. TITLE OF THE INVENTION SEAL FOR TUBULAR HEAT EXCHANGER 2. APPLICANT (a) NAME : Larsen and Toubro Ltd. (b) NATIONALITY.: Indian Company, registered under the provisions of the Companies Act, 1956 (c) ADDRESS : L&T House, Ballard Estate, Maharashtra State, India. 3. PREAMBLE TO THE DESCRIPTION describes the PROVISIONAL The following invention. COMPLETE The following specification particularly describes the invention and the manner in which it is to be performed. 4. DESCRIPTION (Description starts from page 2) 5. CLAIMS: 2Nos 6. DATE AND SIGNATURE: Given at the end of last page of specification. 7. ABSTRACT OF THE INVENTION: On separate page Title of the invention: Seal for tubular heat exchanger. Field of the invention: This invention relates to the threaded channel closure type shell and tube heat exchangers having removable tube bundles. These heat exchangers are widely used in critical services in process industries such as Hydrocracking units, Hydrotreating units, Hydrowaxing units, Hydrofining units etc. Prior Art: The prior art is described with help of following figures. Fig. 1 shows sectional view of H-H type heat exchangers described below. Fig. 2 shows sectional view of the H-L type heat exchangers described below. Fig. 3a shows the part sectional view of the gasketed joint in the channel header. Fig. 3b shows the part sectional view of the gasketed joint in the channel header in its alternative arrangement. Threaded channel closure type heat exchangers are generally classified based on the operating pressure on the shell side and tube side. The heat exchangers having high pressure on both the shell side as well as tube side are classified as H-H type heat exchangers, while the heat exchangers having lower pressure on shell side and high pressure on tube or channel side are classified as H-L type heat exchangers. Due to these conditions, in case of H-H type heat exchangers the tubesheets themselves are subjected to lower differential pressure. Consequently, H-H type would typically have internal 2 tubesheet with an apparatus for sealing of tubesheet against shoulder of the channel. In H-L type, there being usually higher pressure on channel side and lower pressure on shell side, the tubesheets get typically exposed to high differential pressure. The tubesheets and channel covers in this case are typically of integral construction, either single piece or welded together. Tubesheets are provided with plurality of holes in which tubes 5 are fixed. The channel is provided with nozzles 6 for the tube side fluid to enter and exit the heat exchanger. The heat exchangers are preferably provided with two or more tube passes. This is achieved by provision of partitions and covers inside the channel in a known way. Both H-H and H-L type heat exchangers have channel headers 1 provided with closure consisting of a channel cover 3 and threaded lock ring 2 to retain the cover 3. The threaded lock ring 2 is screwed in the threads provided in the channel header body. A gasketed joint is provided to seal the closure. A gasket 7 is located in the groove 11, in the shoulder of the channel as shown in Fig 3a; or in an alternative arrangement, in the shoulder 12 formed in the channel as shown in the Fig. 3b. The gasket is compressed by peripheral portion i.e. tongue 101 of the diaphragm 8 which enters the groove 11 so as to compress the gasket. The diaphragm 8 is backed by a compression ring 9 at the periphery and the channel cover 3 in the central portion. The channel cover 3 is held in position by the threaded lock ring 2. 3 The push bolts/rods 10 fitted in the threaded holes at the periphery of the threaded lock ring 2 pressurize the compression ring 9 when tightened. The compression ring in turn presses the tongue of the diaphragm to seal the gasket by pressurizing it. The end thrust due to the internal pressure on diaphragm is transmitted to the outer compression ring 9 and threaded lock ring 2 and resisted by it. The push bolts/rods 10 provide incremental loading of the gasket through diaphragm for keeping the joint leak-proof. It can be seen from the above arrangement that, for obtaining the leak-proof joint the tongue 101 of the diaphragm has to enter the groove 11. Together with the heat exchanger, the diaphragm 8 has to undergo multiple number of pressure / temperature cycles over a period of time and makes it prone to distortion and deformation. This can cause the diaphragm to shrink in outer diameter thus pulling the inner edge 103 of the tongue 101 inwards, thus riding over the inner edge 104 of the groove 11 provided in shoulder of the channel, during retightening of the push bolts/rods 10. The metallic contact thus developed between the tongue 101 of the diaphragm 8 and inner edge 104 of the groove can obstruct transmission of load generated by tightening of the push bolts 10, thus only partly loading the gasket. Due to this the gasket is only superficially compressed which may cause continuous minor leaks, which not only can remain unnoticed but also can dangerously build up pressure beyond gasketed joint ahead of threaded portion of the channel header. This could lead 4 to unsafe condition for the equipment with potential risk of disastrous accidents. Considering the alternative arrangement as depicted in Fig.3b wherein a shoulder 12 is provided in place of the groove 11, it can be readily seen that, this arrangement makes the gasket 7 unconfined at its inner diameter. This can lead to uncontrolled compression of the gasket making the joint unreliable and hence unsafe. Summary of invention: The present invention 'Seal for tubular heat exchanger' endeavors to eliminate the abovementioned drawbacks of the prior art. The object of the present invention is avoiding the riding of the inner edge of the tongue of the diaphragm over the inner edge of the groove to make the joint reliable and leak proof. Another objective of the present invention is to eliminate the pressure build up ahead of the threaded joint, which can lead to disastrous accidents. This is achieved by extending the width of the tongue of the diaphragm so that the portion of the face of the tongue (towards the inner edge) rests on the face of the shoulder of the channel. In this case the tongue does not enter the groove in normal conditions. This arrangement ensures controlled compression of the gasket at the same time the gasket remains supported on inner as well as outer diameters and hence properly located concentric. Additionally when further load is applied on the tongue by retightening the push bolts through compression ring, 5 the outer portion of the tongue which overlaps the groove is free to bend slightly ( without permanent deformation) towards the gasket compressing it further and thus ensuring the gasketed joint remains effective. As there is no additional seal provided after the said gasketed joint and clearances in the threaded parts are liberal, it can be easily concluded that, no safety arrangement is required in this portion. However, when in operation, the contact surface 105 between diaphragm and channel cover; the contact surface 106 between channel cover and threaded lock ring; the contact surface 107 between male threads of thread lock ring and female threads of channel header and the contact surface 108 between threads of the push bolts and tapped holes in threaded lock ring can become nearly leak-tight and thereby, creating nearly pressure-tight chamber. Due to this even a minor leakage through the gasketed joint can lead to accumulation of dangerous high pressure fluid in the aforesaid chamber ahead of threaded joint. This is eliminated by providing plurality of vent holes after the gasketed joint. Statement of invention: Seal for tubular heat exchanger comprising groove 11 with an inner edge 404; tongue 401 of the diaphragm 13 having front face 402 extending in the radial direction and inner edge 403 parallel to the axis of the channel; the face 402 extending beyond the radial width of the groove 11 in inward direction and 6 overlapping the face of the shoulder of the channel in which the groove 11 being provided; the tongue 401 of the diaphragm 13 being thus kept away from entering the groove 11; the diaphragm having flexibility to permit deflection of the tongue, the tongue of the diaphragm being loaded from outer side by the internal compression ring 9, the said internal compression ring 9 being loaded in turn by the threaded push bolts/rods 10 being fitted in the threaded holes on periphery of the threaded lock ring 2; this load being ultimately transferred to the joint between the gasket 7 and face 402 to achieve leak-proof joint; plurality of vent holes 14 being provided after the gasketed joint and before thread lock ring so as to avoid pressure build up in case of leakage from the gasketed joint. Description of figures: The invention is now described with help of following figure. Fig. 4 shows the part section of channel showing the gasketed joint in detail. Description of invention and function: Please refer to Fig. 4. The invention 'seal for tubular heat exchanger' comprises a groove 11 in the shoulder of the channel wherein a gasket 7 is fitted. The groove 11 has an inner edge 404. Tongue 401 of the diaphragm 13 has a front face 402 extending in the radial direction and inner edge 403 parallel to the axis of the channel. The face 402 is so arranged that, it extends beyond the radial width of the groove in inward direction and overlaps the face of the shoulder of the channel, in which the 7 groove 11 is provided. The tongue 401 of the diaphragm is thus kept away from entering the groove 11 being bigger in face width than the groove itself. The tongue of the diaphragm 401 is loaded from outer side by the internal compression ring 9 which in turn is loaded by tightening of the push bolts/rods 10 fitted in the threaded holes on periphery of thread lock ring 2. This loads the joint between the gasket 7 and the face 402 of the tongue 401 to achieve leak-proof joint. Plurality of vent holes 14 is provided after the gasketed joint and before the thread lock ring 2 so as to avoid any pressure build up, in case leakage occurs from the gasketed joint. 8 We claim Dated this 18th day of April 2006 Ashwini Durve Agent for the applicant 9 1. Seal for tubular heat exchanger comprising groove 11 with an inner edge 404; tongue 401 of the diaphragm 13 having front face 402 extending in the radial direction and inner edge 403 parallel to the axis of the channel; the face 402 extending beyond the radial width of the groove 11 in inward direction and overlapping the face of the shoulder of the channel in which the groove 11 being provided; the tongue 401 of the diaphragm 13 being thus kept away from entering the groove 11; the diaphragm having flexibility to permit deflection of the tongue; the tongue of the diaphragm being loaded from outer side by the internal compression ring 9, the said internal compression ring 9 being loaded in turn by the threaded push bolts/rods 10 being fitted in the threaded holes on periphery of the threaded lock ring 2; this load being ultimately transferred to the joint between the gasket 7 and face 402 to achieve leak-proof joint; plurality of vent holes 14 being provided after the gasketed joint and. before thread lock ring so as to avoid pressure build up in case of leakage from the gasketed joint. 2. Seal for tubular heat exchanger as claimed in claim 1, as substantially described hereinbefore, with reference to the accompanying drawings. Abstract Together with the heat exchanger, the diaphragm 8 has to undergo multiple number of pressure / temperature cycles over a period of time and likely to get distorted. This can cause pulling of the inner edge 103 of the tongue 101 inwards, thus riding over the inner edge 104 of the groove 11 provided in shoulder of the channel. The metallic contact thus developed between the tongue 101 and inner edge 104 of the groove can obstruct transmission of load generated by tightening of the push bolts 10, thus only partly loading the gasket. This is avoided by extending the width of the tongue of the diaphragm so that the portion of the face of the tongue (towards the inner edge) rests on the face of the shoulder of the channel. This ensures controlled compression of the gasket at the same time the gasket remains supported on inner as well as outer diameters and hence properly located concentric. Further load applied on the tongue by retightening the push bolts through compression ring, can bend outer portion of the tongue slightly ( without permanent deformation) towards the gasket compressing it further and thus ensuring effective gasketed joint. Minor leakage through the gasketed joint can lead to accumulation of dangerous high pressure fluid in the chamber ahead of threaded joint, as these joints become pressure tight under high pressure. This is eliminated by providing plurality of vent holes after the gasketed joint.

Documents:

640-mum-2006-abstract(8-1-2008).doc

640-mum-2006-abstract(8-1-2008).pdf

640-mum-2006-abstract-1.jpg

640-mum-2006-abstract.pdf

640-mum-2006-cancelled pages(8-1-2008).pdf

640-mum-2006-claims(grantede)-(8-1-2008).doc

640-mum-2006-claims(grantede)-(8-1-2008).pdf

640-mum-2006-claims.pdf

640-mum-2006-correspondance-po.pdf

640-mum-2006-correspondance-received.pdf

640-mum-2006-correspondence(12-5-2008).pdf

640-mum-2006-correspondence(ipo)-(3-10-2008).pdf

640-mum-2006-description (complete).pdf

640-mum-2006-description (provisional).pdf

640-mum-2006-drawing(8-1-2008).pdf

640-mum-2006-form 1(8-1-2008).pdf

640-mum-2006-form 18(12-9-2006).pdf

640-mum-2006-form 2(grantede)-(8-1-2008).doc

640-mum-2006-form 2(grantede)-(8-1-2008).pdf

640-mum-2006-form 3(12-5-2008).pdf

640-mum-2006-form 3(8-1-2008).pdf

640-mum-2006-form 5(12-5-2008).pdf

640-mum-2006-form 9(26-6-2006).pdf

640-mum-2006-form-1.pdf

640-mum-2006-form-2.doc

640-mum-2006-form-2.pdf

640-mum-2006-form-3.pdf

640-mum-2006-form-5.pdf

640-mum-2006-form-9.pdf

640-mum-2006-form-pct-isa-210(24-4-2006).pdf

640-mum-2006-power of authority(24-4-2006).pdf

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