Pipe joints or couplings – Repair
Reexamination Certificate
1999-07-06
2001-06-12
Wilson, Neill (Department: 3627)
Pipe joints or couplings
Repair
C285S294100, C285S412000
Reexamination Certificate
active
06244630
ABSTRACT:
BRIEF DESCRIPTION OF THE INVENTION
This invention relates generally to maintaining seals between pipe sections. More particularly, this invention relates to a technique and apparatus for non-intrusive on-line leak sealing of flange pipe joints.
BACKGROUND OF THE INVENTION
Leakage of process piping flanged joints during plant operation is a major problem and challenges maintenance and operations personnel charged with keeping plant equipment operating at peak efficiency. In many cases, leaking flanges pose safety and environmental concerns leading to plant shutdown. Numerous factors can contribute to a leaking flanged joint. These factors include: insufficient bolt loading, poor flange alignment, improper gasket selection or an improper surface finish or dimensional preparation of the gasket-sealing surface on the flange. Many new practices have been developed and employed over the years to improve the reliability of the flange joint including new gasket materials, improved bolting practices and spring type washers.
However, regardless of the training and engineering practices implemented to ensure reliable performance of flange joints, failures still occur. When bringing the system down is not financially feasible, methods for sealing the leak while the pipe remains pressurized have been effectively utilized to stop most leaks. These methods hydraulically inject viscous sealing compounds into a secondary pressure vessel while the flange joint remains under system pressure and temperature.
These hydraulic injection methods have several implementation and design engineering drawbacks. The secondary pressure vessel must undergo detailed engineering design review to ensure the structural stability. Moreover, each leak presents different problems, e.g., the size of the leak, pressure criteria and pipe sizes; thus, secondary pressure vessels are not portable from one flange to the next. Highly trained and experienced specialty contract personnel are required to evaluate the problem, to design a solution and to fabricate and install the necessary hardware. In cases where the flange gap is very small or inconsistent, these methods frequently impart physical damage to the flanges, including mechanical peening to close gaps, and drilling and tapping of holes into the flanges for injection ports. Utilization of these methods frequently lead to major refurbishment or replacement of the flanges during the subsequent shutdown, which can be difficult, time consuming and expensive. Lastly, there is the potential for the injection of sealing compounds into the process system, which can cause entire system shutdowns.
Accordingly, there is a need in the art for a non-invasive method and apparatus for sealing a leaking pressurized flange joint.
SUMMARY OF THE INVENTION
The present invention provides a method and apparatus for sealing leaks in a pressurized flanged pipe joint. The apparatus, generally speaking, uses an elongated member (preferably a two piece jacking bolt) acting against a load support structure to apply and maintain a radial load to a sealing plug located between the two flanges. The loaded sealing plug seals the leak until a more permanent repair can be made when the system is shut down. The elongated member transfers the radial load to the load support structure, which in turn transfers the radial load to another solid object. In one embodiment the load support structure is an open channel bracket having a top wall with a hole for receiving the elongated member and two sidewalls configured to fit over the outside of the pressurized flanged joint such that the elongated member is positioned over the flange gap. In this embodiment, the two side walls each have at least two holes substantially aligned across from each other with each hole configured to fit over a flange bolt, such that the radial load is transferred from the load support structure to the flange bolts.
The method according to an embodiment of the present invention places an uncompressed sealing plug between the two flange faces, applies a load to the sealing plug with an elongated member (preferably a two piece jacking bolt) to substantially seal the leak. The load is maintained by a load support structure.
The present invention provides a method and apparatus for sealing a pressurized flanged joint that is non-invasive to the process system, does not physically alter or damage the flange, uses simple re-useable parts and can be applied by a typical plant mechanic.
REFERENCES:
patent: 866395 (1907-09-01), Skinner et al.
patent: 3603616 (1971-09-01), Smith
patent: 3770301 (1973-11-01), Adams
patent: 4049296 (1977-09-01), Harrison
patent: 4927181 (1990-05-01), Ciotola
Baucom Johnny D.
Phillips Michael K.
Sullivan Michael D.
Electric Power Research Institute Inc.
Pennie & Edmonds LLP
Wilson Neill
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