Patent Grant
7683260
The present invention relates to a swagable high-pressure connector especially suited for injecting a dielectric enhancement fluid into the interstitial void volume of an electrical power cable at elevated pressures and confining the fluid therein at a similar elevated pressure.
Swagable high-pressure connectors were previously described in United States Patent Application Publication No. US 2005/0191910. An example of a dual-housing, swagable high-pressure splice connector, assembled from two identical swagable high-pressure terminal connectors, is illustrated in
The term cable “segment,” as used herein, refers to the section of cable between two terminal connectors, while a cable “sub-segment” is defined as a physical length of uninterrupted (i.e., uncut) cable extending between the two ends thereof. Thus, a cable segment is identical with a sub-segment when no splices are present between two connectors. Otherwise, a sub-segment can exist between a terminal connector and a splice connector or between two splice connectors, and a cable segment can comprise one or more sub-segments. For the sake of efficiency, the term “cable section” will be used herein to designate either a cable segment or a cable sub-segment while the specific terms will be applied as appropriate.
Briefly stated, the method comprises filling the interstitial void volume with a dielectric property-enhancing fluid at a pressure below the elastic limit of the polymeric insulation jacket, and confining the fluid within the interstitial void volume at a residual pressure greater than about 50 psig. As used herein, the term “elastic limit” of the insulation jacket of a cable section is defined as the internal pressure in the interstitial void volume at which the outer diameter (OD) of the insulation jacket takes on a permanent set at 25° C. greater than 2% (i.e., the OD increases by a factor of 1.02 times its original value), excluding any expansion (swell) due to fluid dissolved in the cable components. This limit can, for example, be experimentally determined by pressurizing a sample of the cable section with a fluid having a solubility of less than 0.1% by weight in the conductor shield and in the insulation jacket (e.g., water), for a period of about 24 hours, after first removing any covering such as insulation shield and wire wrap. Twenty four hours after the pressure is released, the final OD is compared with the initial OD in making the above determination. For the purposes herein, it is preferred that the residual pressure is no more than about 80% of the above defined elastic limit. The residual pressure is imposed along the entire length of the section, whereby the residual pressure within the void volume promotes the transport of the dielectric property-enhancing fluid into the polymeric insulation. After the cable is filled and pressurized with the fluid, the feed is disconnected and the pressure begins to immediately decay due to diffusion transport of the fluid into the conductor shield and the insulation jacket of the cable. At room temperature, the decay to zero gage pressure typically takes several months to about a year; at 55° C. the decay to zero usually takes only a few days.
The swaging process used to form the seal between the insulation jacket and the housing of the above high-pressure connectors, described fully in the above mentioned publications, prevents “pushback” of the insulation jacket and generally satisfies the short term sealing requirement. Pushback is defined herein as the axial movement of the insulation jacket and conductor shield away from the cut end (crimped end) of the conductor of a cable section when a fluid is confined within its interstitial void volume at a high residual pressure. Absent substantial and prolonged temperature cycling, these swagable devices are probably adequate for over 80% of existing underground lateral residential distribution cables (URD). Conversely, these swagable devices are probably inadequate for over 80% of existing underground feeder distribution, sub-transmission, or transmission cables (hereinafter Feeder cables) where conductor temperature swings of over 20° C. in a 24 hour period are common and peak conductor temperatures may periodically approach the common design temperature of 90° C., in extreme cases approaching the thermal overload temperature of 130° C. A more resilient seal is desirable in order to assure reliable performance of the above high-pressure devices, particularly for use with Feeder cables.
Moreover, a durable seal is also needed because a long-term low pressure requirement remains for several years due to the dielectric enhancement fluid retained in the interstitial void volume of the cable. Potential long-term damage from leaking fluid is mitigated by the changing properties of the remaining fluid, which typically includes at least one organoalkoxysilane monomer component that hydrolyzes and oligomerizes within the cable upon reaction with adventitious water, as described in U.S. Pat. No. 4,766,011. The oligomers resulting from the hydrolysis and condensation of the organoalkoxysilane have a correspondingly higher viscosity and lower solubility in polymers than do the originally injected organoalkoxysilane monomers, and therefore do not exude from the cable as readily. However, leak-free performance is still highly desirable since there remains some chance of damage to the splice or termination from even a minor leak. Furthermore, any fluid that leaks from the connector would not be available to treat and restore the cable dielectric properties, and there may also be undesirable environmental and safety consequences of such a leak.
There is disclosed a high-pressure connector for an electrical power cable section having a central stranded conductor encased in a polymeric insulation jacket and having an interstitial void volume in the region of the stranded conductor, the high-pressure connector being suited for confining a fluid within the interstitial void volume at a residual pressure above atmospheric, but below the elastic limit of the polymeric insulation jacket, the high-pressure connector comprising:
It has been determined that, when swagable high-pressure connectors of the type shown in
Assuming all parts of the assembly are at the same temperature at any given time, the conductor is an essentially incompressible solid (e.g., a copper or aluminum stranded conductor), the insulation shield has essentially the same properties as the insulation jacket, the compressive stress in the insulation approaches zero after sufficiently long times to represent the worst possible case, and the calculated maximum diametral gap for a temperature cycle range of ΔT=90° C. is about 0.068 inches for insulation typical of 35 kV cables and conductor sizes larger than 125 mm2 (250 kcm). The calculated diametral gap is about 0.027 inches for insulation typical of 15 kV cables and conductor sizes smaller than 125 mm2 (250 kcm). This relationship is demonstrated graphically in
The initial residual gage pressure due to injection of fluid can be as high as about 1000 psig, as described in US 2005/0191910. However, this residual pressure typically decays to essentially zero after a modest time (e.g., about a year) and the remaining long-term pressure within the connector includes two components. The first component is the fluid head pressure which, for most cases, is generally close to 0 psig (pounds per square inch gage). A reasonable maximum design pressure due to fluid head which is likely to persist where typical residential rolling hills are present (e.g., a maximum 60 foot elevation change in a single sub-segment) is therefore about 30 psig. The second long-term pressure component is attributed to the vapor pressure of any residual fluid. The sum of these two pressure components should be accommodated by the connector.
The vapor pressure of a typical monomeric organoalkoxysilane employed as the dielectric enhancement fluid in cable restoration methods is less than about 1 psig at temperatures up to 90° C. and even a more volatile dielectric enhancement fluid component, such as acetophenone (represented by the dashed line in
Thus, although United States Patent Application Publication No. US 2005/0191910, hereby incorporated by reference, and Publication No. US 2005/0189130, each teaches swagable high-pressure connectors having axial restraint of the connector with respect to the cable to prevent pushback, there is no provision to prevent radial separation (i.e., the above described diametral gap) of the connector housing from the cable's insulation resulting from the substantial thermal cycling common in many Feeder cables. For the purposes herein, “substantial thermal cycling” refers to thermal cycling wherein the mode (i.e., peak) of the distribution with respect to time of ΔT, the difference between the high and low conductor temperatures, is at least about 20° C. Estimation of ΔT can be made for a given cable type and load conditions using methods well known in the art for calculating ampacity. In order to overcome leakage due to the above described (diametral) gap formation when the cable is subjected to the substantial temperature variations described above, the instant application teaches a high-pressure connector of the type illustrated in
Accordingly, the instant high-pressure connector introduces a modification of the above described design wherein the improvement comprises a means for radially securing the housing to the insulation jacket of the cable such that these two elements are mated in generalized “dovetail” fashion after the swaging operation is completed, and particularly after the cable is subjected to an electrical load and the elevated temperatures associated therewith. This generalized “dovetail” arrangement resists the radial separation of the housing from the insulation jacket when the connector and cable undergo substantial thermal cycling. As a result, the improved high-pressure connectors described herein can withstand the effects of the greatest temperature fluctuations likely to be encountered in actual cable operation and be leak-free at the above described residual pressures. This securing means can comprise an axially-projecting engagement member, which in some disclosed embodiments is referred to as an axially-projecting, circumferentially-extending spur which in some embodiments takes the form of an axially-projecting circumferential ridge disposed essentially along the inner periphery of the housing. There is thus presented a high-pressure connector for an electrical power cable section having a central stranded conductor encased in a polymeric insulation jacket and having an interstitial void volume in the region of the stranded conductor, the high-pressure connector being suited for confining a fluid within the interstitial void volume at a residual pressure above atmospheric, but below the elastic limit of the polymeric insulation jacket, the high-pressure connector comprising:
A swagable high-pressure terminal connector 110 of one type usable for injection of dielectric enhancement fluid into a cable section 10 and with which the described axially-projecting, circumferentially-extending spur can be used, is illustrated in
In a first aspect, with reference to the embodiment illustrated in
It has been observed that the polymer cold-flows into the recesses 218 under the intense compression associated with the swaging operation over the insulation jacket. Additional flow and conformation is believed to be facilitated by the rise in temperature due to electrical load when the cable is placed in service. External heating may also be provided to soften the insulation 12 and further aid the flow into the recesses 218 (e.g., a heating jacket, induction heating of the connector housing or steam heating).
Non-limiting examples of housing groove geometries contemplated herein to inhibit relative radial movement and separation of the insulation jacket and the housing are illustrated in
It should be apparent to those skilled in the art that the precise shape of the housing groove is not critical; however, it is desirable that the recess and at least one spur created are disposed essentially along the inner periphery of the housing wherein a wall of the spur adjacent to the recess has an axial component which can resist radial retraction of the polymer insulation from the housing during the cooling phase of a thermal cycle. In any of these embodiments, inwardly projecting engagement members (i.e., teeth) configured to deform and partially penetrate the insulation jacket along a periphery thereof may optionally be provided to secure the housing wall to the insulation jacket. Such teeth may be present at the inner wall of the housing within the region to be swaged over the insulation jacket (i.e., the engagement portion) and they can have triangular, square, rectangular or corrugated shapes. These optional teeth may be formed by cutting corresponding grooves in the housing wall. For example,
In one aspect of several of the embodiments discussed above, the longitudinal cross-sectional profile of the circumferential housing groove has recesses such that at least one internal axial dimension thereof (i.e., measured along the axis of the housing) is greater than the corresponding axial dimension of the groove toward the inner radius of the housing. In other words, as shown in
Xm is the maximum groove axial dimension at a radius greater than r but less then R (such as measured within and between the recesses inward of the spurs),
Xr is the groove axial dimension at radius r,
r is the inner radius of the housing, and
R is the outer radius of the housing.
It is noted that “r” may be the inner radius of the housing as illustrated in
This relationship describes the trapezoidal groove of the embodiments of
The above described housing grooves may be formed in the housing by any suitable method known in the art, such as: lathe machining, milling, investment casting, and CNC operations. While the housings have been illustrated showing only a single housing groove (such as housing groove 136 shown in
In another embodiment, the housing of a high-pressure connector having any of the above described housing groove geometries can be further modified by adding an annular elastomeric element disposed between the outer surface of the insulation jacket and the inner wall of the housing in the insulation swaging region. Due to its relatively low modulus of elasticity and rubbery nature, such an elastomeric element can reversibly expand and contract to fill the gap caused by the thermal cycling and therefore act to block a potential leak. While elastomers can also develop a permanent set, the set is much less than that of the polyethylene (PE) typically employed as the insulation. Of course, the dimensions of the housing would have to be adjusted to accommodate the annular elastomeric element. Non-limiting examples of the elastomeric element include an elastomeric O-ring or an annular cylinder which will expand as the contacted polyethylene insulation jacket recedes from creep. This enhanced sealing means can be implemented either on the circumference of the insulation jacket (such as the O-ring 134 shown in
In the embodiment of the high-pressure connector shown in
In
At this point, the swaged connector 110, and cable section 10 to which it is attached, is ready to be injected with a dielectric enhancement fluid at an elevated pressure. In a typical injection procedure, a plug pin 140, further described below, is loaded into a seal tube injector tip 160 of injection tool 139 such that it is held in place by spring collet 166, as shown in
Pressurized fluid is then introduced to the interior of connector 110 and the interstitial void volume of cable section 10 via a tube 158, seal tube inlet 154 and an annulus (not shown) formed between the seal tube injector tip 160 and the assembly of the press pin 152 and the plug pin 140. After the predetermined amount of fluid has been introduced (or a predetermined uniform pressure along the full length of the cable section has been attained, as described in detail in above cited Publication No. US 2005/0191910), a press pin actuator knob 144 is tightened (utilizing mated threads in the injection tool 139—not shown) so as to advance press pin 152 toward injection port 48, thereby pushing plug pin 140 into injection port 48 such that the nominally circular end surface of plug pin 140, located adjacent to a first chamfered end 141 of the plug pin, is essentially flush with the exterior surface of the housing 130. The first chamfered end 141 of the plug pin 140, illustrated in perspective view in
In another embodiment shown in
In this case, the cross-section of the ring 168 having the circumferentially-extending spur 176 has a single recess 171, however, the ring and spur may be formed with a second recess on the opposite side of the spur from the recess 171 illustrated in
When the swaging operation over the insulation jacket is carried out, the spur 176 penetrates the insulation jacket by deforming and indenting the insulation jacket, and the polymer thereof flows around the spur and into the recess 171. The flow is facilitated by the increased temperature due to load on the cable when the latter is placed in service. This operation results in the formation of a generalized “mortise” indentation in the polymer of the insulation jacket and provides the above-referenced generalized “dovetail” union which resists radial separation between the housing and the insulation jacket during the cooling phase of a thermal cycle.
The spur 176 is made of a stiff material with sufficient rigidity to deform and indent the insulation jacket upon application of a radially inward force thereto applied during the swaging operation while maintaining the recess 171 with sufficient size such that the polymer of the insulation jacket that is positioned therein inhibits relative radial movement and separation of the insulation jacket and the housing. The spur 176, in effect, hooks the insulation jacket. In this embodiment, the ring 168 and the spur 176 thereof are made of a ductile metal, and the housing 170 is also made of the same ductile metal. In the “ring” embodiments of the spur described above as well as the “groove” embodiments formed into the wall of the housing as illustrated in
Alternatively, the ring 168 having the axially-projecting circumferentially-extending spur 176 may be attached to the inner wall of the housing 170 by swaging at the same time as the housing 170 is swaged to the insulation jacket. Further, a shallow groove (not shown) can be formed in the inner wall of the housing 170 to accept the ring, which can then be welded or otherwise attached to the inner wall of the housing. As in the case of the housing groove described above, the shape of the spur 176 is not critical provided that the recess 171 and the spur are disposed to provide at least one wall 169 of the spur adjacent to the recess which has an axial component which can resist radial retraction of the insulation jacket from the housing during the cooling portion of a thermal cycle. Thus, the spur 176 can have a cross-sectional profile and features similar to the profile of the spurs depicted in
In a variation of the above described ring having an axially-projecting circumferentially-extending spur, the ring 168B shown in
The swagable high-pressure connectors described herein can have any of the swagable high-pressure terminal connector or splice connector configurations taught in above cited Publication No. US 2005/0191910, with the proviso that at least one axially-projecting circumferentially-extending spur is incorporated in the insulation swaging region of the housing thereof. Thus, for example, it can be a single-housing high-pressure swagable splice connector, as shown in
Housing 16 is sized so that its ID (internal diameter) is just slightly larger than the OD (outer diameter) of insulation jacket 12 and is configured to receive the end portion of both cable sections 10 therein. Housing 16, having injection ports 48 for introduction of the restoration fluid, is slid over insulation jacket 12 to either the right or the left of the exposed strand conductors 14 to allow installation of the splice crimp connector 18 and bushing 22, as described below. Bushing 22, having an ID slightly larger than the OD of splice crimp connector 18 and OD slightly smaller than the ID of housing 16, is slid onto and centered on splice crimp connector 18 such that O-ring 24, which resides in a channel in bushing 22, is directly over the central non-crimped portion thereof. Bushing 22 includes a skirt 30 at both ends thereof which is simultaneously crimped during the crimping operation that joins splice crimp connector 18 to conductor 14 (i.e., the bushing, splice crimp connector and strand conductors are crimped together in one operation). This three-piece crimping brings conductor 14, splice crimp connector 18, and bushing 22 into intimate mechanical, thermal and electrical union and contact due to the respective deformations. The crimps joining bushing skirts 30, splice crimp connector 18 and conductor 14 can be of any variety well known in the art, such as two-point, hexagonal or other suitable means that assure that the ampacity of the connection meets the relevant standards and requirements of the connector manufacturer. O-ring 24, which is compressed by the tight fit over splice crimp connector 18, makes a fluid-tight seal between bushing 22 and splice crimp connector 18.
Housing 16 is then slid over insulation jacket 12 and centered over the bushing 22 and splice crimp connector 18. A crimp is made on the exterior of the housing 16 at a position measured from the center of housing 16 to be directly over a bushing indent 28 of the bushing 22. This assures that crimping occurs directly over bushing indent 28 to electrically, thermally, and mechanically join housing 16 and the bushing 22. An O-ring 26, residing in a channel in bushing 22, is sized to make a fluid tight seal between housing 16 and bushing 22. When the high-pressure splice connector of this embodiment is to be used to inject both cable sections simultaneously (e.g., in a flow-through mode), at least O-ring 26 is omitted and, preferably, both O-rings 24 and 26 are omitted. It should be noted that the central crimp over indent 28 is only made at one or more points (i.e., not a circumferential crimp or swage, which would restrict the flow rate of fluid past the bushing) to make a mechanical, electrical and thermal connection between splice crimp connector 18 and housing 16 through the bushing 22. Alternatively, bushing 22 could itself be eliminated and housing 16 crimped (i.e., multi-point crimped) directly to splice crimp connector 18 to provide the mechanical/electrical/thermal union and contact.
After housing 16 is placed in the position shown in
At least one and preferably two injection ports 48 are employed to allow the injection of fluid at one end of each cable section and the withdrawal of water and contaminated fluid from the other, remote end of the respective cable section. Thus, each injection port may be utilized from either side (or both sides) of the splice crimp connector 20 to inject or withdraw fluid.
In the above, as well as other embodiments of the instant high-pressure splice connectors, it is preferred that the strands of the conductors 14 being joined by a crimping operation are first straightened to an orientation essentially parallel to the axis of the cable sections 10 to facilitate fluid flow into and out of the respective interstitial volume(s). Thus, in the above embodiment, the bushing/splice crimp connector combination 22/18 is first crimped to one conductor 14, such as the conductor of the left cable section 10, to be in mechanical, electrical and thermal integrity therewith. The bushing/splice crimp connector combination 22/18 is next rotated approximately 15 degrees to first straighten the original lay of the outermost layer of strands of that conductor, and then 15 more degrees, rotation being opposite to initial strand twist direction. The bushing/splice crimp connector combination 22/18 is next crimped to the conductor 14 of the right cable section 10. The bushing/splice crimp connector combination 22/18 is then rotated back (i.e., in the initial strand twist direction of the first conductor) approximately 15 degrees to straighten the lay of the outermost layer of the strands of the second conductor. Of course, the first conductor will also be rotated by this operation, thereby eliminating the counter lay of the left conductor and the original lay of the right conductor. All grease and dirt are cleaned from the straightened connectors prior to the crimping operations.
In the above embodiment, teeth 32 comprise a plurality of triangular circumferential grooves machined along the inner surface of housing 16 at each end thereof (i.e., the portions of the housing where swaging against insulation jacket 12 is to be applied). While the inside surface of the housing 16 of
In another variation of the above swagable high-pressure splice connector, illustrated in
In another embodiment of the above swagable high-pressure splice connector, illustrated in
In application, housing 62 of
In another embodiment of the above swagable high-pressure splice connector, illustrated in
Of course, those skilled in the art will recognize that any of the above swagable high-pressure splice connectors employing various sealing/securing means may be modified to provide a high-pressure terminal connector. For example, this may be accomplished by simply replacing the splice crimp connector with a termination crimp connector and forming a fluid-tight seal between the housing and the latter, the termination crimp connector also being secured to the housing. Furthermore, the termination crimp connector and the housing can be integral such that no additional seal is required between the housing and the termination crimp connector, as illustrated in
In another embodiment of a high-pressure swagable splice connector, illustrated in
In yet another embodiment, a dual-housing, swagable high-pressure splice connector, assembled from two identical swagable high-pressure terminal connectors of the type shown in
As will be apparent to those skilled in the art, the high-pressure splice connectors described herein are generally symmetrical with respect to a plane perpendicular to the cable axis and through the center of the splice crimp connector, and the assembly procedures described are generally applied to both ends of the splice. It also will be recognized that various combinations of the sealing and crimping options described herein for the different embodiments may be combined in “mix-and-match” fashion to provide the intended sealing and securing functions, although the skilled artisan will readily determine the more desirable and/or logical combinations. In general, the components of the instant connectors, except for any rubber (elastomeric) O-rings employed, are designed to withstand the anticipated pressures and temperatures and may be fabricated from a metal such as aluminum, aluminum alloy, copper, or stainless steel. Rubber washers and O-rings may be formed from any suitable elastomer compatible with the fluid(s) contemplated for injection as well as the maximum operating temperature of the connector. Preferred rubbers include fluorocarbon rubbers, ethylene-propylene rubbers, urethane rubbers and chlorinated polyolefins, the ultimate selection being a function of the solubility of, and chemical compatibility with, the fluid(s) used so as to minimize swell or degradation of any rubber component present.
Although only high-pressure terminal and splice connectors have been recited, it should be appreciated that the instant high-pressure connectors can also be used in tandem to form Y, T, or H electrical joints, described in US 2005/0191910.
It is further contemplated herein that the performance of the high-pressure connectors having any of the above described housing groove geometries can be further enhanced by adding an external seal, such as a shrink-in-place tube over the insulation jacket 12 at the housing/insulation jacket interface.
The following terminal high-pressure connectors having various housing sealing geometries with respect to the insulation jacket of a cable section were evaluated for leakage under substantial thermal cycling conditions. Each test connector employed comprised a housing having a threaded injection port 182 at one end thereof, as illustrated in cross-sectional view in
A first series of experiments was conducted in order to simulate the post injection high-pressure connector sealing performance during the phase wherein the pressure of the fluid in the cable and connector decays to a maximum head pressure of about 30 psig over a period of several days while the cable and connector are cycled from 60° C. to ambient (about 22° C.), as follows. A cable section was injected with a mixture of about 95%w of a polydimethylsiloxane fluid having a viscosity of 0.65 cS at 25° C. and about 50%w menthyl anthranilate at a pressure of 720 psig. The pump used to inject the above mixture was disconnected within minutes after this pressure was achieved throughout the test string. The test string included several I/O cable sections and high-pressure terminal connectors of different configurations in series. Leakage from the connectors was monitored throughout this test with the aid of UV light (menthyl anthranilate fluoresces bright green under UV illumination). The pressure was then allowed to decay for about 20 hours at an ambient temperature of about 22° C. The test sample assembly (a string of cable sections each with two connectors of each test geometry) was immersed in an ambient temperature, covered water bath and the temperature was increased over a period of approximately 90 minutes to about 60° C. When the water bath reached the nominal 60° C. target, heating was discontinued to allow the water to cool with the cover to the bath removed. After approximately 7 hours, the test string was removed from the water and the samples remained at ambient air temperature to the completion of the test. The pressure as a function of elapsed time from injection was recorded, as shown in
A second series of experiments was conducted in order to simulate the post injection sealing performance during the phase wherein the fluid pressure has essentially decayed to a level representing only head pressure and the vapor pressure of the dielectric enhancement fluid and wherein this pressure level remains for a prolonged period (e.g., several years). For tests 1 through 13 described below the test assembly, including the connectors and attached cables, were pressurized to 30 psig with air to simulate approximately 60 feet of vertical head, or a lesser head and some fluid vapor pressure. For tests 14 and 15 the test assembly was pressurized to 60 psig with air to simulate approximately 60 feet of vertical head and 32 psig of fluid vapor pressure. The temperature was cycled repeatedly over an approximate nominal range of ΔT=48° C. up to ΔT=80° C. That is, the test assemblies including the connectors were cycled between a low temperature of about 19° C. and a high sample temperature ranging between 67° C. and 97° C., the upper temperature being raised in an incremental or escalating sequence, as delineated below. Thus, according to this test protocol, the cable section and attached connectors were pressurized with air at 30 psig and immersed in a room temperature water bath, about 20 to 22° C. The water temperature was cycled between (escalating) high temperatures ranging from 67° C. and 97° C. (in all cases +/−1° C.) and a low temperature of tap water at 15° C. to 22° C. with a cycle time of 160 to 110 minutes, such that the system went through about 9 to 13 complete temperature cycles each day. Three typical cycles of recorded temperature versus time are shown in
Leaks were recorded, as indicated by bubbles in the water bath, and any leaking samples were removed from the experiment when both samples of a given design failed due to the thermal cycling. When only one of the duplicate samples failed, it was left in place and allowed to continue to leak or to “self-heal”. With the exception of the circumferential O-ring geometry, at least one sample of each design leaked during at least one of the disassembly and handling steps (i.e., tests 4 to 6 in Table 1). However, some samples self-healed and did not leak when subjected to subsequent tests. Thus, for example, both trapezoidal geometry sampled parts leaked after test 6, but did not leak thereafter, as indicated by the blank cells of Table 2 for tests 7 through 15. The above tests were run to failure or for the time indicated.
From Table 2 it can be seen that only the trapezoidal geometry (III) provided a fluid-tight seal under all test conditions (as indicated by the blank cells). Moreover, these samples self-healed to provide leak-free operation even after the rough handling and partial disassembly of Tests 4 through 6.
This application is a divisional of U.S. patent application Ser. No. 11/625,264 filed Jan. 19, 2007 and claims priority benefit of provisional application Ser. No. 60/761,099 filed Jan. 23, 2006, which is incorporated herein in its entirety.
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|---|---|---|---|
| 20090203265 A1 | Aug 2009 | US |
| Number | Date | Country | |
|---|---|---|---|
| 60761099 | Jan 2006 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11625264 | Jan 2007 | US |
| Child | 12426401 | US |
