Measuring and testing – With fluid pressure – Clamp – plug – or sealing feature
Reexamination Certificate
2002-10-09
2003-08-05
Raevis, Raves (Department: 2856)
Measuring and testing
With fluid pressure
Clamp, plug, or sealing feature
C073S049500, C073S04050R, C073S865800, C138S089000, C138S090000
Reexamination Certificate
active
06601437
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a tool for testing or isolating a section of any tubing, pipe, flange, fitting, or combination of the same.
BACKGROUND TO THE INVENTION
In industrial applications such as oil or gas refineries, offshore drilling and production platforms, pulp and paper plants, power utilities, pipelines, coiled tubing, oil and gas wells, marine facilities, or any other industry or plant involving piping, the integrity of welds and of flanges or fittings often needs to be tested. In the oil and gas industry, for example, tight environmental and operating regulations exist on emissions from a weld or joint. Further, with thousands of welds in each plant, it is in the industry's interest to minimize the amount of fluid lost in each weld. Testing tools are therefore required to test the integrity and permeability of each weld. Fittings must also be tested after welding to test and confirm structural strength.
Furthermore, in these industries it is often necessary to isolate a section of pipe for various reasons. In maintenance applications, safety dictates that when work is being performed on a section of pipe connected to a system, the portion of the pipe being worked on should be isolated from the rest of the system in order to prevent accidental harm to an operator through fluid discharge in the pipe. Also, when TIG welding or welding stainless steel piping, the oxygen level around the weld should be minimized, necessitating a means of isolating the section around a weld in order to introduce a purge gas. Another application is a positive purge with an inert gas through the tool to a vent point.
These problems are well known, and tools for solving these problems exist in the prior art. For example, U.S. Pat. No. 5,844,127 to Berube et al. teaches a tool to isolate a section of pipe or to test the internal integrity of the pipe. The tool uses two o-rings spaced at a certain distance apart and a method of introducing pressure between the o-rings.
The problem with this design of tool is that o-rings do not provide a good seal. In order for the tool to be able to be inserted into a pipe, the tool's diameter must necessarily be less than the inner diameter of the pipe. The difference is made up by using flexible o-rings. The problem is that because the o-rings are flexible, high pressures will cause the o-rings to extrude into the gap between the tool and the pipe wall, diminishing the effectiveness of the seal. This will cause a slow drop in test pressures even though there may be no leak. The test pressure must then be topped up which will negate a true hydro test in accordance with ASME standards B31.1 and 31.3. After the test pressure is released, the extruded seals may remain wedged in the tool/pipeline gap necessitating that the operator disassemble the tool inside the pipeline for piece by piece removal.
Canadian Patent No. 1,312,557 to Dufort teaches an alternate method whereby a membrane is forced into the pipe wall, creating a seal. However, this tool again has a gap between the tool and the pipe wall, and the membrane will again be distorted under high pressure, negating the effectiveness of the seal.
Other sealing methods in the prior art including using “torquing” methods to set a seal or metal grip in place. This however results in the introduction of “hoop stress” to the inside or outside of the pipe, distorting the pipe and creating a future weak spot. The use of metal grips also creates problems because the inner surface of the pipe is damaged by the torqued connections, potentially creating future crevice corrosion problems. Also when metals are in contact the potential always exists for galvanic corrosion to occur. The longer the metals are in contact, the more severe this problem becomes.
Besides sealing deficiencies, the prior art also fails to teach a tool that is able adaptable to the various configurations required in industry. Tools such as '557 to Dufort are solely for testing weld integrity, and do not provide an isolation tool. Patent no. '127 to Berube discusses both isolation and testing, but does not discuss an adaptation of the tool to aid in low oxygen welding. The lack of these capabilities means that other tools must be used, increasing the costs of maintaining and testing pipes.
SUMMARY
The present invention overcomes the deficiencies of the prior art by creating a sealing means which cannot be extruded under operational pressures. It further provides a tool whose configuration can easily be modified in order to accommodate a number of scenarios, making the tool more versatile by allowing the tool to have multiple purposes.
The present invention uses a novel sealing method in which a seal is compressed into a rigid cavity, preventing the creep problems associated with prior art tools. Because there is no creep, a better seal is formed, allowing tests to be conducted with higher precision results. The lack of creep also makes removing the tool much easier, since the tool will not become jammed within the pipe. This saves the operator time since the tool will not have to be disassembled in situ. The configuration of the seal further allows both low and high pressure sealing, enabling a better seal to be made in either situation. Also, the seal includes a number of ridges along its outer pipe-contacting surface, allowing the seal to accommodate imperfections on the inside wall of the pipe, such as pits or scratches, or to cut through any films or wax buildup on the inside wall of the pipe. All of these improvements create a better seal.
The seal in the present invention is also non-damaging to the pipe. The tool therefore does not cause scratching, galvanic conductance, or torquing stresses. This is a significant improvement over the prior art since the tool does not weaken the integrity of the pipe being tested.
The present invention uses the above novel seal in a number of ways, making the present invention versatile. The tool can be configured to test welds by introducing water at high pressure under the weld and monitoring whether the weld can withstand the pressure. The tool can also be used to test a flange by isolating the flange and again introducing water at high pressure, thus determining whether the flange is properly welded to the pipe.
The tool can further be used to test for leaks in a weld by isolating the section under the weld and introducing helium. By creating a shroud around the outside of the weld and by using a helium testing tool an operator can determine whether or not any leaks exist within the weld.
The tool can further be used as a welding aid. In welds involving certain types of metals it is important to minimize the oxygen level at the weld. The present tool can be used to isolate the down-pipe section of the pipe being welded to facilitate the introduction of inert gas that can be used to create the proper environment for this type of weld.
The unique seal and the versatility of the various configurations of the present invention results in a significant improvement over the prior art.
According to the present invention then, there is provided apparatus for testing or isolating a section of pipe, comprising a cylindrical mandrel for insertion into a section of pipe, said mandrel including at least one portion of progressively increasing diameter; at least one seal member disposed concentrically around said mandrel and actuatable in response to applied fluid pressure to move along said at least one portion, causing said seal member to radially expand into sealing contact with an inner surface of said pipe.
According to another aspect of the present invention, there is also provided a resilient seal member for sealing against the inner surface of a tubular member to contain fluid pressure, said seal member comprising a first portion normally smaller in outer diameter than the inner diameter of said tubular member and being radially expandable into sealing contact with said inner wall, and a second portion normally biased into slidable contact with said inner surface.
Acc
Cygan Michael
Donner Irah H.
Hale and Dorr LLP
Raevis Raves
United Testing Corp.
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