Patent Number: 
Section: description

Referring now to the drawings generally and to to FIG. 1 in particular, the prior art tube plug (10) comprises a shell (12) and an expander member (14) The shell (12) is a substantially cylindrical member manufactured from a metal such as Inconel. Shell (12) has a conical inner surface (16) that has a larger diameter at the closed end (18) and a smaller diameter at the open end (20). The inner surface (16) is arranged such that expander member (14) is captured within the shell (12) so that movement of the expander member (14) relative to inner surface (16) causes shell (12) to expand without allowing the expander member (14) to be removed from the shell (12). The shell (12) also has a threaded bore (22) near open end (20) which has a diameter larger than the smallest diameter of inner surface (16) which allows the apparatus to be inserted through the hreaded bore (22) and into the interior of shell (12) which also has a substantially uniform wall thickness in the portion of shell (12) that is expanded by expander member (14). In addition, a plurality of lands (24) are formed on the outside surface of the shell (12) in a manner such that the height of each land (24) increases from the closed end (18) to the open end (20) while the outer surfaces of all the lands (24) is maintained at approximately the same external diameter and while the wall thickness of shell (12) remains substantially constant throughout the portion of shell (12) wherein the lands (24) are located. As shown in FIG. 2, the relative movement of expander member (14) with respect to inner surface (16) causes the shell (12) to expand until the lands (24) contact the heat exchange tube (26). As the expander member (14) is moved relative to the shell (12) the metal in the wall of shell (12) tends to flow around the expander member (14) such that inadvertent backward motion of the expander member (14) is lessened. This provides a self-locking feature. Once tube plug (10) has been expanded, the tube plug (10) is in the locked position as shown in FIG. 2. When in this locked position, a plurality of lands (24) are impressed in the wall of heat exchange tube (26). The lands (24) thereby establish a type of labyrinth seal along the inner surface of the heat exchange tube (26) which prevents fluid from flowing therethrough. Moreover, since the shell (12) has a closed end (18) there is no potential leak path through the tube plug (10). Turning next to FIGS. 3 and 4, a ribbed plug integrity testing apparatus (28) is seen to be comprised of a cup-shaped member (30) having a groove (32) at an open end (34) of the member (30) into which is fitted a circular O-ring seal (36). The member (30) is fitted over the ribbed seal plug (10) with the open end (34) of the member (30) resting against the primary face of a tube sheet (38) through which the tube (26) and plug (10) sealably extend. An anchoring rod or member (40) having an end located mandrel (42) is rotatably mounted through a seal (44) into the closed top (46) of the member (30). The mandrel (42) is flexible and is threaded to be complimentary to the internal threads of the expander member (14). Thus, ehen a speed wrench (not shown) which is connected to the anchoring rod (40) turns the attached mandrel (42) into the expander member (14), the anchoring rod is driven down against the saucer-shaped member (30) by the enlarged rod head portion (46) located above the cup-shaped member. The threading action of the mandrel (42) into the expanding member (14) thus draws the o-ring seal (36) against the tube sheet (38). Once this o-ring seal is sufficiently pressed against the tubesheet, the testing apparatus is sealed and the ribbed plug (10) can be in-situ pressure tested. The test is performed by opening a valve (48) which is normally closed and which transports a known high-pressure fluid in line (50) to the testing apparatus (28) through an aperture (52). The known pressure fluid enters the testing apparatus and is transmitted to the inside of the plug (10) above the mandrel (42) which is now in a position sealing the expander member (14). An aperture (54) located in the hollow anchoring rod (40) transmits the known pressure fluid to the bottom (56) of the plug (10) below the member (14) through an opening (58) in the mandrel (42). The pressure of the fluid in the entire plug (10) and in the testing apparatus (28) is monitored by a meter (58) located in line (50) downstream of the valve (48). The valve (48) is again closed, and if the meter indicates the pressure is stable at the known line pressure P the plug (10) is then shown free of defects. If the pressure begins to fall below the known line pressure then it is seen that the plug (10) is leaking and is faulty and must be replaced. Certain additions and modifications to the present disclosure generally and the testing apparatus in particular have been deleted herein for the sake of conciseness and readability but are considered to fall within the scope of the following claims. As an example, there are multiple variations to the design that could be made and still accomplish some or all of the goals of this invention. As described, the testing apparatus rod and mandrel threads into and pulls on the expander member of the ribbed plug. This arrangement could easily change with different types of plugs and conditions. It is possible to thread the rod directly into the head of the plug rather than using the mandrel. Likewise, the seal could be made against the head of the plug instead of on the face of the tubesheet. This would not test all the available leak paths but would check the integrity of the plug itself. Also, the testing apparatus uses the rotation of a threaded rod to apply the force necessary to create the face seal. This seal could also be accomplished by locking into the plug and hydraulically compressing the seal.