A plug for sealing pipes in heat exchangers

Abstract

This utility model pertains to heat engineering. A blanking plug for sealing pipes in heat exchangers consists of a cylindrical body with an eccentric washer installed at one end. The other end of the body contains a blind threaded hole and a conical recess, in which a conical sleeve is installed coaxially with the body. The threaded hole extends to the middle of the sleeve's length on the side of its cylindrical section. A screw connects the sleeve to the plug body, the end of which is threaded along a section corresponding to the length of the unthreaded section in the conical sleeve's bore. The diameters and thread parameters on all structural elements of the blanking plug are identical. The technical result consists of optimizing and increasing the reliability of the repair process for failed heat exchanger pipes by reducing the time required for installing and removing the blanking plugs installed in them to ensure a tight seal.1 z.p. f-ly, 3 il.

Description

[0001] The utility model relates to heat engineering, in particular, to the technology of repairing heat exchangers.

[0002] During long-term operation of tubular heat exchangers, defects may appear in their tube bundles, which will make further operation of the devices impossible.

[0003] The most common of these include depressurization of pipe connections with tube sheets and damage to the integrity of the pipes (the appearance of through cracks and fistulas in the pipe walls).

[0004] These defects may be caused by:

[0005] fluctuations in temperature and pressure of coolants, leading to the appearance of alternating stresses in pipes, causing fatigue failure of pipes;

[0006] high speeds of coolants, causing vibrations of the tube bundle and leading to abrasion of the tube walls at the edges of the openings of the intermediate partitions;

[0007] corrosive aggressiveness of some coolants (acids, alkalis, sea water, wet steam, etc.), leading to thinning of the pipe walls and the formation of cracks under the influence of coolant pressure.

[0008] The tightness of the connections between tubes and tube sheets is usually restored either by additional flaring of the tubes or by welding.

[0009] As for the integrity of the pipes, it's virtually impossible to restore. Defective pipes must be replaced with new ones. The pipe replacement process is quite lengthy, labor-intensive, and expensive, requiring the machine to be shut down and taken out of service.

[0010] However, it is possible to restore the unit's functionality without replacing the pipes. To do this, the defective pipes must be plugged—sealed at their ends—to prevent mixing of the two coolants: inside the pipes and in the intertube space.

[0011] Pipe sealing is carried out using special plugs installed at the ends of damaged pipes to form a sealed connection.

[0012] The main requirement for plugs is their reliability, i.e. the ability to ensure the tightness of connections during the operation of heat exchange equipment for a specified period of time.

[0013] Another important requirement for plugs is the requirement for ease of installation and removal (when partially or completely replacing pipes with new ones in the heat exchanger).

[0014] These requirements are largely met by plugs, which are conical pins with a smooth side surface, usually made of the same material as the pipe material.

[0015] Conical plugs are installed into pipes using a press-impact method and are quick and easy to install. These plugs reliably seal the ends of damaged pipes with internal diameters from 8 to 76 mm at relatively low coolant pressures (up to 1 MPa).

[0016] However, removing such plugs (as opposed to installing them) takes significantly more time. In cases where the end of the plug protrudes above the tube sheet by approximately half its length, it can usually be removed from the end of the pipe by "prying" it out, i.e., lightly striking the protruding end with a hammer in opposite directions. If the plug is "driven" deeper into the pipe, then a hole is drilled in the end of the plug, a thread is cut in it, a pin from a slide hammer is screwed into the plug, and the pin is driven out toward you.

[0017] Sometimes, to seal pipes in devices operating at higher pressures, conical plugs are welded to the ends of the pipes after their installation, ensuring reliable sealing of pipes in devices with coolant pressures of up to 50 MPa.

[0018] Welded plugs are installed fairly quickly, but their removal is always time-consuming and labor-intensive. Before removing the plug from the pipe using a slide hammer (as with non-welded plugs), the weld must first be removed (usually with a grinder). This, firstly, poses the risk of damaging the tube sheet; secondly, if a large number of damaged pipes are involved, the time required to remove the weld increases significantly.

[0019] The above mentioned disadvantages of conical plugs have led to the development of new plugs with a more complex design, capable of providing reliable sealing of pipe ends in devices with coolant pressures exceeding 50 MPa without the use of welding.

[0020] Such plugs include TORQ N' SEAL screw plugs, developed by the American company JNT Technical Services, taken as a prototype, such a plug consists of a plug body, a conical sleeve, a screw and an eccentric washer.

[0021] During installation, the plug is installed at the end of the defective pipe, then a torque wrench with a hexagonal tip is used to screw the screw into the plug body, moving the conical sleeve inside the body and thereby expanding the walls of the body in the radial direction, and thus creating a hermetic seal.

[0022] The entire process of installing the plug into the pipe, including preparing the surface of its walls, takes no more than 5-7 minutes.

[0023] Removing the plug from the pipe takes considerably longer. After unscrewing the screw, you first need to remove the conical bushing from the housing. To do this, you need to cut a thread in the bushing hole for the pin of a slide hammer. Only then can you remove the plug body from the pipe using the same slide hammer, but with a pin of a different thread size than the one in the conical bushing.

[0024] The disadvantage of this design is that threading the tapered sleeve is often difficult, as it depends on the location of the damaged tube, which may be located in a hard-to-reach spot: in the outer row of the tube sheet close to the wall of the apparatus body; or in the tube of an air cooler, where it can only be accessed through a plug hole in the chamber, etc. This circumstance significantly lengthens the process of removing the plugs, especially if there are a large number of plugged tubes.

[0025] SPbGMTU has developed a new design of screw plug, the use of which reduces unproductive time spent during repairs of heat exchangers.

[0026] The technical result of the proposed design of the plug-plug is the optimization and increase in the reliability of the repair process of failed heat exchanger tubes by reducing the time of installation and dismantling of the plug-plugs installed in them to ensure tightness.

[0027] To achieve the specified result, a thread with the same parameters as the thread in the plug body and on the screw is made in the axial hole of the conical sleeve, a structural element of the plug-plug, through which the screw passes when installing the latter in the defective pipe.

[0028] The technical design solution for the proposed plug is presented at:

[0029] Fig. 1 - plug assembly;

[0030] Fig. 2 - detailing of the plug;

[0031] Fig. 3 - plug, prototype.

[0032] At the end of the defective pipe 1 of the heat exchanger (Fig. 1), a plug body 2 is placed with an eccentric washer 3 at one end and a blind hole 4 with a thread and a recess 5 at the other, in which a conical sleeve 6 is installed with a thread in the internal axial hole, through which a screw 7 is screwed into the body 2, made with a thread at the end and with a threadless part 8 up to the head of the screw (Fig. 1, 2).

[0033] Installing the eccentric washer 3 on the front end of the plug housing 2 prevents the plug housing from rotating at the initial moment of installation (before the radial expansion of the plug housing) when screwing screw 7 into the housing.

[0034] In the proposed design of the plug, also in order to prevent the conical sleeve 6 from rotating together with the screw when the screw is screwed into the plug body, a threaded section is made in the axial hole of the sleeve up to its middle on the side of its cylindrical part of the body (Fig. 2), and a threaded section on the screw is made at its end in a section corresponding to the length of the threadless part in the conical part of the sleeve body (Fig. 2).

[0035] Installation of the plug-plug of the proposed design during repair work is carried out in the same way as the installation of the plug in the pipes in the prototype (Fig. 3): during installation, the plug is installed at the end of the defective pipe, then a screw is screwed into the plug body using a torque wrench with a hexagonal tip, moving the conical sleeve inside the body, thereby increasing the impact in the radial direction on the walls of the plug-plug body, expanding them, and thus creating a hermetic seal, plugging the defective pipe.

[0036] When dismantling the plug of the proposed design, a slide hammer is used: after unscrewing the screw with a stud, first remove the sleeve from the plug body, and then remove the body itself from the pipe with a slide hammer, while the dismantling time is significantly reduced due to the use of a stud and the execution of threads with the same parameters on all elements of the proposed plug design.

[0037] Thus, when carrying out repair work on defective pipes of heat exchangers to seal them, before installing the plug, threads are cut in its elements in accordance with the proposed design of the plug, which ensures a reduction in time and labor costs without reducing the quality of sealing (plugging) of pipes during repair of heat exchangers.

Claims

1. A plug for sealing pipes in heat exchangers, consisting of a cylindrical body, at one end of which an eccentric washer is installed, and at the other end of the body a blind threaded hole and a conical recess are made, in which a conical sleeve is installed coaxially with the body with a thread in the axial hole, made up to the middle of the length of the sleeve from the side of its cylindrical section, and a screw connecting the sleeve to the body of the plug, at the end of which a thread is made on a section along the length corresponding to the length of the threadless section in the hole of the conical sleeve, wherein the diameters and parameters of the thread on all elements of the plug structure are made identical.

2. A plug according to paragraph 1, characterized in that the unthreaded section of the screw is made with a diameter smaller than the internal diameter of the thread in the axial hole of the conical sleeve.

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