Background of the Invention It is conventional for pipes, tubes and the like to be tested for leaks. Such a practice involves sealing the pipe at locations adjacent the open end of the pipe and pressurizing the pipe, or a portion thereof, with a fluid such as gas, including air or nitrogen, or a liquid such as a hydraulic fluid.

One common test involves testing the weld formed between an end of the pipe and a flange. A prior art flange test plug 10 with a disk-shaped seal 12 is illustrated in FIGs. 1 and 2. The purpose of the flange test plug 10 is to enable a hydraulic pressure and leak test to be performed on a weld 14 between the weld-neck flange 16 and the pipe 18 without the necessity of filling and pressurizing the entire piping system. To this end, the flange test plug 10 is inserted into the weld-neck flange 16 so that test plug 10 seals the open end of the flange 16 and locates the disk-shaped seal 12 on an opposite side of the weld 14. See FIG. 1. The test plug 10 has tightening means 20 which can axially compress the disk-shaped seal 12 until the seal 12 is squeezed radially outward to seal against the inner diameter 22 of the pipe 18. See FIG. 2.

Fluid is admitted to the space within the pipe 18 between the flange 16 and the seal 12 and pressurized to conduct the test. After the test, the fluid is depressurized, the seal 12 is uncompressed as illustrated in FIG. 1, and the test plug 10 is withdrawn from the open end of the flange 16.

A problem experienced with the above-described, prior art flange test plug 10 is that, in order to install and remove the test plug 10, the uncompressed seal 12 must have a sufficiently small diameter to fit past any projection 14a of the weld 14. A typical weld 14 often extends inwardly about 0.2 inches or more depending upon the welder and the welding practice. Thus, since known flange test plugs are limited to passing a weld projection 14a of about 0.1 inches or less, conventional methods of installing the plugs 10 include grinding away the weld projections 14a so that the portion of the flange test plug 10 including the seal 12 can be inserted past the weld 14.

A further, more difficult, problem is presented by a pipe (not shown) which has a weld-neck flange (not shown) with a smaller opening than the inner diameter of the pipe. For example, a 24 inch 1500 class flange may be welded to a pipe having an inner diameter of about 7/8 inch larger than the diameter of the flange. Thus, in order to insert the seal of the flange test plug by the weld, the uncompressed seal must be at least 1.0 inch smaller in diameter then the inner diameter of the pipe, and the seal must be capable of expanding diametrically about more than 1.0 inch to seal against the pipe. Furthermore, the unsupported, expanded seal must be capable of maintaining a tight seal under high test pressures which tend to further deform the seal, and after the pipe is depressurized, must be capable of retracting to its original diameter so that it can be withdrawn through the smaller diameter weld-neck flange opening. The applicant is not aware of any prior art flange test plugs capable of meeting the above stated requirements.

Another well known type of prior art test plug is the hydrostatic test plug 30 illustrated in FIGs. 3-5. The hydrostatic test plug 30 is used to seal the open end 32 of a pipe 34 to enable a pressure test to be run on an entire piping system. The hydrostatic test plug 30 has a disk-shaped seal 36 which is capable of being axially compressed so that it expands diametrically into sealing engagement with the inner periphery of a pipe 34. FIG. 3 illustrates the seal 36 in an uncompressed condition, and FIG. 4 illustrates the seal 36 in a compressed condition.

Typically, the above-described, prior art hydrostatic test plug 30 is only capable of use on a specific size pipe because an outermost peripheral portion of the seal 36 which expands into engagement with the inner diameter of the pipe 34 is unsupported by the remaining parts of the plug 30 and will deform under test pressures thereby breaking the seal. Thus, expansion of the seal 36 outward from the remaining parts of the plug 30 must remain within predetermined limits.

While the above-described, prior art flange and hydrostatic test plugs may function satisfactorily under certain limited conditions, there is a need for a test plug which, when inserted into a pipe, provides a significant amount of clearance between the outermost diameter of the test plug seal and the inner diameter of the pipe and which has a seal capable of being expanded into sealing engagement with the pipe.

The seal which is expanded the full extent of the clearance should be capable of withstanding high test pressures and, when the plug is to be removed, retracting into its initial uncompressed size. More particularly, a flange test plug and method of its use should permit required portions of plugs to be inserted past weld projections without requiring grinding away of the weld projections, and a hydrostatic test plug and method of its use should permit the seals of plugs to be expanded significantly so that a single test plug can be used for a range of pipe sizes.

Objects of the Invention With the foregoing in mind, a primary object of the present invention is to provide an inner diameter test plug assembly which is for use in creating a fluid-tight seal within the inner periphery of a pipe and which provides significant clearance between its uncompressed seal outer diameter and the inner diameter of the pipe.

Another object of the present invention is to provide a novel inner diameter test plug having a seal which is capable of significant outward radial expansion and which can withstand high test pressures when expanded so that the fluid-tight seal is maintained throughout pipe/weld testing procedures.

A further object of the present invention is to provide a novel test plug having a seal which can fully retract into its initial uncompressed shape after being installed and used to test a pipe/weld.

A still further object of the present invention is to provide a unique test plug which can create an effective seal for a wide range of pipe inner diameters.

Yet another object is to provide a unique method of sealing a pipe with a test plug which enables large clearances to exist between the uncompressed seal and the inner diameter of the pipe and which is capable of use in high pressure testing conditions.

Summary of the Invention More specifically, the present invention provides an inner diameter pipe plug for creating a fluid-tight seal along an inner periphery of a pipe. The plug has an annular compressible seal having an outermost diameter in an uncompressed condition of at least about 0.2 inches less than the inner periphery pipe diameter so that the seal in an uncompressed condition provides a plug seal-to-pipe clearance of at least about 0.2 inches. The annular seal is made of a material having a durometer of at least 80, is capable of expanding outwardly and radially into sealing engagement with the inner periphery of the pipe, and is capable of maintaining a fluid-tight seal for test pressures up to at least about 5,000 psi.

Brief Description of the Drawings The foregoing and other objects, features and advantages of the present invention should become apparent from the following description when taken in conjunction with the accompanying drawings, in which : FIG. 1 is a cross-sectional view of a prior art flange test plug having a seal which is in an uncompressed condition ; FIG. 2 is a cross-sectional view of the flange test plug of FIG. 1 after the seal has been compressed and engages the pipe;

FIG. 3 is a cross-sectional view of prior art hydrostatic test plug having a seal which is in an uncompressed condition; FIG. 4 is a cross-sectional view of the hydrostatic test plug of FIG. 3 after the seal has been compressed and engages the pipe ; FIG. 5 is a cross-sectional view of the prior art hydrostatic test plug illustrated in FIG. 4 along the line 5--5 ; FIG. 6 is a cross-sectional view of a first embodiment of a flange test plug according to the present intention, the seal of the plug being illustrated in an uncompressed condition; FIG. 7 is a cross-sectional view of the flange test plug illustrated in FIG. 6 after the seal has been compressed and engages the pipe; FIG. 8 is a cross-sectional view of an alternate embodiment of a flange test plug according to the present invention, the seal of the plug being illustrated in an uncompressed condition; FIG. 9 is a cross-sectional view of the flange test plug illustrated in FIG. 8 after the seal has been compressed and engages the pipe ; FIG. 10 is a partial cross-sectional view of another embodiment of a flange test plug according to the present invention, the seal of the plug being illustrated in an uncompressed condition; FIG. 11 is a partial cross-sectional view of the flange test plug illustrated in FIG. 10 after the seal has been compressed and engages the pipe ; FIG. 12 is an elevation view of one of the compression plates, or hubs, of the flange test plug illustrated in FIG. 10 ; and FIG. 13 is a graph comparing the torque required to outwardly expand a seal between a pair of the tapered compression plates illustrated in FIG. 10 versus a pair of flat compression plates.

Detailed Description of the Preferred Embodiment The novel features of the inner diameter test plug of the present invention can be utilized in many different types of test plugs, for example, flange test plugs and

hydrostatic test plugs, as will be discussed in detail below. However, all permit relatively large plug-to-pipe clearances, and all utilize a high durometer seal which is capable of withstanding high test pressures even when significantly compressed and expanded. For purposes of the present application, a high test pressure includes pressures in a range of about 2,500 to 5,000 psi, and a high durometer seal is one that has a durometer of at least about 80. While the test plugs of the present invention are capable of withstanding the above recited pressures, they can also be utilized during low pressure testing at pressures well below the stated range.

One embodiment of an inner diameter test plug according to the present invention is illustrated in FIGs. 6 and 7. The flange test plug 40 is used to enable a hydraulic pressure and leak test to be performed on a weld 44 between the weld-neck flange 46 and the pipe 48 without the necessity of filling and pressurizing the entire piping system. To this end, the flange test plug 40 has a front wall 50 for confronting and creating a seal with the open end 46a of the weld-neck flange 46. A tubular flange weldment 52 extends from the test plug front wall 50 to an inner annular compression plate, or washer, 54. An annular, lubricated, high durometer seal 42 is positioned between the inner annular compression plate 54 and a rear compression plate, or washer, 56. A second tubular flange weldment 58 extends from the rear compression plate 56 through the annular seal 42 for preventing the annular seal 42 from deforming in an inward radial direction when compressed. A set of threaded shafts 60 extend from the test plug front wall 50 to the rear compression plate 56 and are used in conjunction with compression nuts 62 to compress, or decompress, the annular seal 42. Thus, when the test plug 40 is inserted into the pipe 48, the annular seal 42 can be compressed and expanded to form a seal against the inner diameter of the pipe 48 at a location on the opposite side of the weld 44 so that the weld 44 can be tested. See FIG. 7.

As previously stated, the weld 44 is formed with an inward projection 44a which provides a narrower diameter than the inner diameter of the pipe 48. Thus, the weld projection 44a restricts entrance to test plug seals which do not provide a large enough clearance between the inner diameter of the pipe and the outermost diameter

of the test plug seal. In addition, a test plug which fits past the weld projection 44a must have a seal capable of significant expansion. The expanded seal must be capable of withstanding high test pressures despite having a large expanded portion which is unsupported by the remaining parts of the test plug sized appropriately to fit past the weld projection 44a.

The flange test plug 40 illustrated in FIGs. 6 and 7 is designed to provide sufficient clearance to fit past weld projections and to provide the capability of creating a seal with a pipe having an inner diameter as much as about 1.0 inch larger than the uncompressed seal 42. The primary reasons for the test plug's enhanced capability is the shape and durometer of the seal 42 and the lubrication used on the seal surfaces confronting the compression plates 54 and 56.

The flange test plug 40 has a seal 42 which is provided with an annular shape instead of the prior art disk shape. The cross-sectional area normal to the pipe axis of the annular seal 42 is much smaller than the cross-sectional area of a disk-shaped seal.

For reasons stated below, this permits use of high durometer seals which are required for utilizing high test pressures. A high durometer disk-shape seal requires too much clamping/compression force to cause the seal to expand into sealing engagement with the pipe, and an expanded, unsupported low durometer seal is unable to withstand high test pressures.

The elastic materials used to manufacture seals have a characteristic durometer which is a property similar to hardness and rigidity. An external force more readily deforms a lower durometer material then a higher durometer material ; therefore, less compressive force is required to expand a lower durometer seal into engagement with a pipe inner diameter. However, when the pipe is pressurized, a high durometer seal is capable of maintaining the integrity of the seal at pressures much greater than that at which the low durometer seal fails. This is particularly true in the test plugs of the present invention, since the large initial plug-to-pipe clearance requires a large expanded, unsupported portion of the seal which is acted upon by the high test pressure. Thus, a low durometer seal will deform and leak under the required expansion/pressure.

Another disadvantage of low durometer seals is that, even if the unsupported area of the seal is small, the low durometer seal is more readily squeezed into the space between the outer diameter of the plug compression plates, or washers, and the inner diameter of the pipe. The unwanted extrusion of the seal in this space can result in a permanent jam after the pipe is depressurized. The jamming prevents ready removal of the test plug from the pipe and can cause permanent damage to the seal.

For these reasons, the test plugs of the present invention utilize a high durometer seal with an annular shape.

When used on pipes having inner diameters greater than eight inches, preferably the surfaces of the high durometer seal 42 of the present invention are lubricated to enable greater radial expansion for a given compressive force. To this end, when the compression nuts 62 are tightened, the dimension of the seal 42 parallel to the pipe axis is reduced due to the compressive forces exerted between the inner annular compression plate 54 and the rear compression plate 56. Since the second tubular flange weldment 58 prevents the annular seal 42 from extruding in an inward radial direction, the seal 42 extrudes radially outward. The percentage radial outward expansion of the seal 42 is proportional to the percentage reduction of the axial dimension, and the change in the axial dimension is proportional to the compressive force and the axial dimension. The change in axial dimension is inversely proportional to the area over which the compression force is applied, a shape factor, and a modulus of elasticity of the seal material. Modulus of elasticity is a property closely related to durometer; because, both relate to the ease or difficulty of deformation of the seal.

The shape factor is determined by the proportions between the surfaces unrestrained versus the surfaces to which compressive force is applied. Thus, the more easily the seal 42 is able to overcome friction against the surfaces over which the compressive forces are applied, the lower the effective shape factor. Therefore, lubricants applied to the surfaces of the seal 42 confronting the compression plates, 54 and 56, will reduce the compressive force required to obtain a given radial expansion.

The thickness of the seal 42 in a direction parallel to the pipe axis also has an effect on the ability of a seal to handle a large pressure drop, particularly when the seal

has a large unsupported dimension. Increasing the seal thickness increases the pressure that the seal 42 can resist without leaking. For purposes of example, the test plug 40 preferable has a high durometer seal having a thickness in the range of about 0.5 to 3 inches; however, the thickness of the seal could be further increased, as needed.

Another embodiment of an inner diameter test plug according to the present invention is the flange test plug 140 illustrated in FIGs. 10 and 11. The flange test plug 140 is also used to enable a hydraulic pressure and leak test to be performed on a weld between a weld-neck flange and the pipe without the necessity of filling and pressurizing an entire piping system. However, the flange test plug 140 is particularly suited for use on pipes having relatively smaller inner diameters, for instance, inner diameters of between 4 inches and 8 inches. Such pipe inner diameters typically utilize relatively small, economical, shaft diameter sizes which do not provide a sufficient amount of tightening torque to exert 1000 psi compressive force on the full cross sectional area of the seal. In addition, such pipe inner diameters require the use of unlubricated seals to eliminate unwanted extrusion of the expanded seal between the inner diameter of the pipe and the outer diameter of the components of the test plug.

Similar to the previously discussed flange test plug 40, the test plug 140 has a front wall 150 for confronting and creating a seal with an open end of the weld-neck flange. A tubular flange weldment 152 extends from the test plug front wall 150 to an inner compression plate, or hub, 154 and through an annular seal 142 to a rear compression plate, or hub, 156. Thus, the annular high durometer seal 142 is positioned between the compression hubs, 154 and 156, which when compressed causes the seal 142 to radially expand outward to form a seal with the inner diameter of the pipe. See FIG. 11. A threaded shaft 160 extends from the test plug front wall 150 to a compression nut 162 to compress, or decompress, the annular seal 142.

As best illustrated in FIGs. 10-12, one unique aspect of the test plug 140 is the use of a pair of identical compression hubs 154 and 156 which have tapered seal confronting surfaces, 154a and 156a, recessed from innermost beads 154b and 156b.

The surfaces, 154a and 156a, can have any degree of taper; however, preferably the taper is about 45°. The purpose of the tapered surfaces, 154a and 156a, is to effect outward expansion of the seal in a manner which requires a relatively low amount of installation torque. This is particularly important since lubrication is preferably not used. The purpose of recessing the tapered surfaces, 154a and 156a, with the beads, 154b and 156b, is to prevent unwanted lateral extrusion of the seal. For some pipe inner diameter sizes which do not tend to experience unwanted extrusion, for instance, 4 inch diameter sizes, the beads, 154b and 156b, can be eliminated so that the tapered surfaces confronting the seal are not recessed.

Testing has revealed that the tapered surfaces 154a and 156a effect greater outward radial expansion of an annular seal with less tightening torque as compared with compression hubs having flat seal confronting surfaces. For example, the graph provided in FIG. 13 illustrates the amount of torque required to expand an annular seal which has an outer diameter, under a no-torque condition, of about 7.2 inches.

The graph indicates that when the annular seal is applied with 100, 300 and 500 ft-lbs <BR> <BR> of torque, it is expanded to about 7. 3,7. 8 and 8.3 inches, respectively, when tapered hubs are used, and only about 7.25, 7.55 and 7.9 inches, respectively, when flat hubs are used. Thus, the tapered hubs reduce the amount of tightening torque required to expand the seal 142 into fluid-tight engagement with the inner diameter of the pipe.

Another advantage of utilizing tapered hubs 154 and 156 is that the unlubricated seal 142 was found to extrude less between the pipe and the hubs as compared to when flat hubs are utilized. It is believed that the tapered surfaces of the hubs 154 and 156 effect a reduction of friction between the hubs and the seal 142.

Thus, the tapered surfaces provide a friction reducing function similar to lubrication, however, without the unwanted extrusion.

Another alternate embodiment of an inner diameter test plug according to the present invention is the flange test plug 70 illustrated in FIGs. 8 and 9. The flange test plug 70 is also used to enable a hydraulic pressure and leak test to be performed on a weld between a weld-neck flange and the pipe without the necessity of filling and pressurizing an entire piping system. To this end, the flange test plug 70 has a front

wall 80 for confronting and creating a seal with an open end of the weld-neck flange.

A tubular flange weldment 82 extends from the test plug front wall 80 to an inner annular compression plate, or washer, 84 and through an annular seal 72. The annular, lubricated, high durometer seal 72 is positioned between the inner annular compression plate 84 and an intermediate cone-shaped washer 86. A set of threaded shafts 90 extend from the test plug front wall 80 to a rear compression plate 94 and are used in conjunction with compression nuts 92 to compress, or decompress, the annular seal 72.

One unique aspect of the test plug 70 is the use of a plurality of segmented support members 96 for at least partially supporting a radially extruded portion of a compressed seal 72. To this end, the support members 96 have an inclined surface 98 which confronts an inclined surface 88 of the intermediate cone-shaped washer 86.

The segmented support members 96 are urged into engagement with the cone-shaped washer 86 by an annular spring 78 and the rear compression plate 94. In an uncompressed state, the support members 96 are positioned as illustrated in FIG. 8 to provide maximum plug-to-pipe clearance. Each threaded shaft 90 carries a spring 76 extending between the rear plate 94 and an inwardly extending flange 74 connected to the cone-shaped washer 86 in order to force an uncompressed test plug into the as illustrated uncompressed condition. However, in a compressed condition as illustrated in FIG. 9, the rear compression plate and the cone-shaped washer 86 are displaced toward one another and cause the support members 96 to slide up the inclined surface 88 of the cone-washer 86 so that the support members 96 are located adjacent to the inner diameter of the pipe and the seal 72.

In operation, when the test plug 70 is inserted into a pipe and the compression nuts 92 are tightened, the gap between the cone-shaped washer 86 and the rear plate 94 is reduced and completely closed as illustrated in FIG. 9. This causes the support members 96 to slide upward and outward along the inclined surface 88 of the cone- shaped washer 86 to locate the support members near the seal 72 and close to the inner diameter of the pipe. Further tightening of the compression nuts 92 causes the cone-shaped washer 86 to advance toward the inner annular compression plate 84.

The advancement of the washer 86 compresses the seal 72 and expands it radially into sealing engagement with the inner diameter of the pipe. When pressure is admitted to test the weld, the seal 72 deflects toward and contacts the closely located support member segments 96 which support the expanded seal 72 and prevent further bending of the seal 72 as the test pressure is increased. After the test is concluded, pressure is removed; tension in the bolts is relaxed; and the seal 72 and support members 96 retract into their original uncompressed position as illustrated in FIG. 8 to permit removal of the test plug 70 from the narrow weld/pipe opening.

Other unillustrated test plugs are also contemplated utilizing the unique concepts of the present invention. For example, the prior art hydrostatic test plug illustrated in FIGs. 3-5 can be modified to utilize an annular-shaped, lubricated, high durometer seal. In addition, the test plug could be further modified to use retractable, segmented support members capable of supporting the expanded portion of the seal adjacent the pipe inner diameter. Thus, the hydrostatic test plug modified according to the present invention could provide significant initial plug-to-pipe clearances and form a seal which is capable of withstanding high test pressures. Such a single modified hydrostatic test plug is capable of use with various pipes including a wide range of inner diameters.

A method of using any or all of the above described test plugs is also contemplated by the present invention. The first step is to insert a test plug into the open end a pipe such that the test plug provides significant plug-to-pipe clearance, where required. Preferably, the plug-to-pipe clearance is at least about 0.2 to 1.0 inches ; however, the clearance could be increased, as needed. The test plug should be provided with an annular shaped seal made from a high durometer material.

Depending on the size of the inner diameter of the pipe, the surfaces of the seal confronted by compression washers may, or may not, be lubricated with a lubricant, such as grease. Preferably, the high durometer material is urethane which has the additional advantage of providing good recovery from a compressed to an uncompressed condition.

The test plug is then tightened to compress the seal and expand the seal into sealing engagement with the inner diameter of the pipe. The inner diameter of the pipe can be between about 3 to 42 inches, or larger. The seal must be expanded to the extent of the above referenced plug-to-pipe clearance; thus, the seal must be expanded radially outward at least about 0. 2 to 1.0 inches, or more, as required.

Test pressure up to 5,000 psi is then applied to the portion of the pipe being tested. After the testing is complete, the pressure is removed, and the seal is retracted to its initial uncompressed shape so that the test plug can be removed from the pipe.

An additional method step could include providing the test plug with retractable, segmented support members capable of supporting the expanded seal adjacent the pipe inner diameter. Such a method would also include inserting the test plug into the open end of a pipe when the support members are in a retracted position, and thereafter, expanding the support members to a position adjacent the seal and the inner diameter of the pipe. After testing is complete, the support members are retracted to permit ready removal of the test plug from the pipe.

In view of the foregoing, it should be apparent that the present invention now provides an inner diameter test plug providing significant plug-to-pipe clearances during insertion and removal of the test plug and significant expansion of the seal into sealing engagement with the inner diameter of the pipe. The seal created is capable of withstanding high test pressures and capable of being applied on pipes having a range of inner diameters.

While a preferred embodiment of the present invention has been described in detail, various modifications, alterations, and changes may be made without departing from the spirit and scope of the present invention as defined in the appended claims.