JPS60194295A - Multitubular heat exchanger - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a shell-and-tube heat exchanger.

A shell-and-tube heat exchanger has a shell with at least one tube sheet, and the open-ended tubes are welded to this tube sheet. In use, a first fluid flows through the tube and a second fluid flows through the shell to effect heat transfer between the fluids. When a leak occurs in a pipe, it is common practice to plug the pipe and make it redundant, but when making a large number of pipes redundant,
Since heat exchangers lose efficiency, it is clearly advantageous to repair defective tubes in a heat exchanger instead of plugging the tubes.

British Patent No. 2,052.559 consists of inserting a tubular sleeve into the defective tube of a shell-and-tube heat exchanger and sealingly joining the end region of the sleeve to the tube and tubesheet to bridge the defect. A method of repairing defective tubes in a shell-and-tube heat exchanger is disclosed. Although such a repair is acceptable under normal operating conditions, it is questionable under extreme temperature conditions because of the stiffness of the sleeve, which causes loads on the end joints to exceed safe amounts.

According to the present invention, a method for repairing a defective tube of a shell-and-tube heat exchanger includes inserting a tubular sleeve into the defective tube and sealingly coupling the end region of the sleeve to the tube to bridge the defect. In the method, the tubular sleeve has one of the following characteristics: axial deflection and being mechanically keyed to the tube at a location adjacent said joint in the end region of the sleeve.
or a combination thereof.

Axial deflection is imparted by corrugating the sleeve circumferentially at multiple locations along its length.

Mechanical keying may be accomplished by pressing or expanding the material of the sleeve into tight engagement with the tube or tubesheet, with or without grooves.

The connection between the sleeve and the tube may be an explosion weld at both ends, or an explosion weld at one end and a brazed connection at the other end.

Typically, when sub-excessive temperatures occur, the rigid sleeve will contract, causing the end joint to become severely distorted. However, given an axial deflection, the sleeve can contract axially to relieve the load on the end joint by t, and the joint retains its integrity.

If circumferential corrugations are employed, the corrugations will flex and act like a Perot to provide the necessary axial movement. The sleeve design concentrates the shrinkage strain at temperatures below the extreme (or the expansion strain at temperatures above the excessive) into specific thin areas that can weaken or create failure points. Care must be taken not to let this happen. A constant wall thickness should be maintained throughout the sleeve.

If a mechanical keying is employed without axial deflection of the sleeve, the keying should be designed to absorb axial contraction/expansion loads to reduce the load on the end joints. It has become.

The combination of axial deflection and mechanical keying increases reliability of repair part integrity in the face of temperature extremes.

The present invention relates to a shell-and-tube heat exchanger when repaired by the method as described above.

The method of repairing tubes of a shell-and-tube heat exchanger according to the invention will be explained by way of example with reference to the accompanying drawings, which are fragmentary cross-sectional views.

The drawing shows a tube plate 1 and tubes 2 of a shell-and-tube heat exchanger, the heat exchanger for transferring heat between liquid metal flowing in the shell and water flowing in the tubes. be. There are a number of tubes 2, each of which is sealed to the tubesheet by welding. During use, some of the welds between the tubes and the tubesheet become bad, and in order to avoid plugging the tubes and making them redundant, each tube with defective welds 4 is fitted with a tube. A sleeve 3 is inserted, which is hermetically connected to the tube at one end region and to the tube sheet at the other end region, thereby bridging the defective weld.

The sleeve 3 has a number of circumferential corrugations, which act like bellows and can expand axially if excessive temperatures occur.

The lower end region of the sleeve 3 shown in the drawing is connected to the tube by high temperature brazing, and the upper end region to the tube sheet by explosive welding. Two lands 5 are formed in the lower end region of the sleeve, the outer diameter of which is such that there is a suitable clearance for the lands to be inserted freely into the tube. In the middle of the land there are two grooves 6 for accommodating waxed bamboo material, l) the waxed bamboo material is generally engaged in the grooves like a circular clip prior to inserting the sleeve into the tube. Formed into a toroid shape. Also, before inserting the sleeve into the pipe, both the inner wall of the pipe and the tube hole in the tube plate are cleaned, and after inserting the sleeve, the lower end is expanded radially outward by roll swaging to completely remove the land. in contact with the wall, thereby creating a capillary gap for the molten brazed bamboo material between the sleeve and the tube. Of course, the swaging tool is inserted from above the tubesheet.

The brazing head for making the connections has a high frequency induction heating coil positioned within the bore of the sleeve in the desired brazing area. After brazing, another heating coil of longer length is used to temper the joint. The brazing instrument may have a feedback mechanism, using millimeter signals from the sensing device to automatically control the brazing cycle. The sensing device is a thermocouple, but it is also possible to use fiber optics to measure temperature changes, a light guide directed downwards, a supply tube provided to guide the conductor, and a cover gas tube for the brazing operation. Appropriate sensing devices may be developed.

The upper end of the sleeve is explosively welded to the tubesheet at 7 by detonating gunpowder disposed within the sleeve and violently expanding the sleeve radially into abutment with the tube holes in the tubesheet, thereby causing the sleeve to is metallographically bonded to the tube sheet.

In another method, the inner walls of the tube and the tube holes in the tubesheet are cleaned by galvanic or electrochemical techniques prior to bonding. Electrolytic erosion technology is a technique that removes material from the bonding surfaces of tubes and tubesheets by short-lived, repetitive electrical sparks between electrodes inserted into holes in the tubes and tubesheets and the bonding surfaces of the tubes and tubesheets.

Yet another method uses spur welding in place of brazed joints. In this way, there is no need to provide a groove for the waxed bamboo material.

As an alternative to or in addition to imparting axial deflection to the sleeve, the sleeve may be mechanically keyed to the tubesheet and tube just inside the joined joint 8.9. In these positions, keying may be accomplished by, for example, pressing the sleeve into small grooves cut into the tube plate and/or tube wall, or alternatively by very tight contact expansion applied from within the sleeve. It is done by force. If the expansion method is used to create the required braze joint fit gap,
This often creates the keying by a bulge in the tube and three 1 just above the brazing area.

[Brief explanation of drawings]

The accompanying drawings are fragmentary cross-sectional views showing the relationship between the tubes, tube sheets, and sleeves of the shell-and-tube heat exchanger according to the present invention. 1...tube plate, 2...tube, 3...sleeve.

Claims (1)

[Scope of Claims] (1) A tubular heat exchanger in which a tubular sleeve is inserted into a defective tube of the shell-and-tube heat exchanger, and the end region of the sleeve is sealingly coupled to the tube to bridge the defect. In the method of repairing a defective tube, the tubular sleeve (3) is mechanically keyed to the tube (2) at a location adjacent to the following special order, namely the axial deflection, and the joint in the end region of the sleeve (3). 1. A method for repairing defective tubes in a shell-and-tube heat exchanger, characterized by having one or a combination of both. (The deflection in the 4-axis direction is determined by the length J of the sleeve (3).
A method based on the first term of the range of 1% tolerance given by adding corrugations in the circumferential direction at multiple positions along Ic. (3) Mechanical keying is achieved by press-fitting or expanding the material of the sleeve (3) into the tube (2) with or without grooves.
or the method according to claim 1 or 2, carried out by tightly engaging the tube plate (1). (4) The connection between the sleeve (3) and the tube (2) is at both ends. The method according to any one of claims 1 to 3, wherein both ends may be explosive welded, or one end may be explosive welded and the other end may be joined by brazing. . (5) A shell-and-tube heat exchanger repaired by the method according to any one of claims 1 to 4.