Measuring and testing – Probe or probe mounting
Reexamination Certificate
2000-12-19
2003-03-18
Larkin, Daniel S. (Department: 2856)
Measuring and testing
Probe or probe mounting
C356S241100
Reexamination Certificate
active
06532840
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a robotic inspection system for in situ inspection of gas turbine cannular combustion components for the purpose of evaluating the condition of the components.
Maintenance costs and equipment availability are two of the most important concerns of a gas turbine operator. Proper maintenance is required to minimize equipment downtime and provide long-term reliable operation. Maintenance inspections of gas turbines are broadly classified as standby, running and disassembly. Disassembly inspections are generally categorized into three types: combustion inspection, hot gas path inspection and major inspection. All three types of inspections require shutdown and disassembly of the turbine to varying degrees to enable inspection and replacement of aged and worn components. The combustion inspection includes evaluation of several components of the combustion system including the transition piece. The transition piece is a thin-walled duct used to conduct high-temperature combustion gases from the combustion chamber to the annular turbine nozzle passage. The transition piece and other combustion components are generally inspected for foreign objects, abnormal wear, cracking, thermal barrier coating TBC condition, oxidation/corrosion/erosion, hot spots/burning, missing hardware and clearance limits. Components which fall outside established threshold limits are replaced to maintain optimum operating conditions for the entire system. If not rectified, these conditions could lead to reduced machine efficiency and damage to the turbine that may result in unplanned outages and significant repair costs.
Removal and installation of transition pieces is the most time-intensive operation of the combustion inspection. This operation contributes most significantly to the combustion inspection outage duration and corresponds directly to time lost producing power. To remove transition pieces, all upstream components must be removed, i.e., fuel nozzles, water injectors and various other hardware. Each transition piece is then dismounted and removed one by one in sequence through two access openings in the turbine casing. It will be appreciated that for certain gas turbines, there can be as many as fourteen transition pieces requiring removal.
To date, recommended practice has been to remove the transition pieces and other combustion components to facilitate inspection and refurbishment. Inspection has consisted primarily of visual methods consisting of the unaided eye with auxiliary lighting. Visual methods in known problem areas have been enhanced with the use of liquid red dye penetrant to improve visibility of small hairline cracking. These inspections have typically been performed offline of the combustion inspection process. Such prior inspection practices have many disadvantages, including the time required for disassembly and installation, the lack of direct retrievable defect data for engineering evaluation and historical comparison and complete reliance on human factors. Accordingly, there is a need for more efficient methods to inspect the transition pieces of the gas turbine combustion systems to minimize outage times while providing an accurate assessment of the condition of each transition piece.
BRIEF SUMMARY OF THE INVENTION
In accordance with a preferred embodiment of the present invention, there is provided a robotic inspection system for gas turbine combustion components comprised of three robotic manipulators with miniature cameras and lighting for inspecting various parts of the transition piece of each combustor in situ. The manipulators are driven remotely using a combination of automated and manual motion control to position the inspection heads, e.g., video cameras, lighting and/or measuring devices, to various locations about and in the combustor enabling a detailed visual inspection of its transition piece and flow sleeve without disassembly and removal of these components from the turbine. The robotic inspection system hereof is thus intended for use during a gas turbine maintenance outage.
Particularly, the robotic inspection system hereof includes three tools, i.e., an exterior manipulator, an interior manipulator and an annulus manipulator. It will be appreciated that the transition piece includes an outer impingement sleeve, typically perforated, and an interior transition piece body defining generally an annulus therebetween. The forward ends of the transition piece body and impingement sleeve are generally circular in configuration with top and bottom sides being flattened progressively toward the first-stage nozzle. The exterior manipulator is deployed for inspection of the external surfaces of the impingement sleeve and has seven distinct motions. The exterior manipulator includes a segmented arcuate rail movably mounted on a carriage disposed within the casing of the turbine, the carriage being supported externally of the casing by a mast. When all of the arcuate rail segments are connected end-to-end to one another, the rail extends in excess of 90° such that an inspection head forming part of a robotic inspection subassembly carried on an end segment can inspect top, bottom and side surfaces and along the entire length of each impingement sleeve in a quadrant of the annularly arranged combustors.
The robotic inspection subassembly on the end segment mounts a generally axially extending rail on which is mounted an upper arm. The rail is movable in a circumferential direction with the arcuate segments as the latter are displaced circumferentially along the carriage to locations radially outwardly of the impingement sleeves and within the interior surface of the casing. The upper arm is pivotable relative to the rail about a first axis to extend between adjacent impingement sleeves and carries at its distal end a pivotally mounted forearm. The upper arm is also rotatable about its long axis such that when the forearm is extended, the inspection head carried at the distal end of the forearm can be located between and radially inwardly of an impingement sleeve for inspection of its radial inner surface. The inspection head is rotatable about pan and tilt axes relative to the forearm and includes a vision module, e.g., one or more cameras and a lighting system. With this arrangement, the inspection head can be located to inspect the entire peripheral surface of each impingement sleeve of the cannular combustion system. A video micrometer external to the tool may be used in conjunction with the vision module to effect measurements.
The interior manipulator is mounted to the aft combustion casing for inspecting the interior surface of the transition piece body. The interior manipulator includes an elongated arm carried in a spherical bearing in a mount secured to the casing flange. The interior end of the arm carries an inspection head similar to that of the exterior manipulator. The arm projects through the mount exteriorly of the casing and is pivoted by two linear actuators coupled between the mount and the arm to locate the inspection head adjacent the interior surface of the transition piece body. The arm also carries concentric inner and outer tubes. Actuation of an electric motor carried by the outer tube extends and retracts the inner tube carrying the inspection head. The inner tube carries pan and tilt motors such that the inspection head can be rotated about pan and tilt axes for visual inspection of the interior surfaces of the transition piece body.
The annulus manipulator includes a manually positioned inspection head for inspecting the side seam welds along the exterior surface of the transition piece body in the annulus between the transition piece body and the impingement sleeve. The annulus manipulator includes a support structure for supporting a pair of spaced guide plates each having a pair of contoured surfaces, e.g., grooves in opposition to one another. The grooves generally correspond to the contours of the side seam welds of the transition piece body. A middle carriage plate carries s
Aslam Sami
Bentzel Kathleen Lynne
Bousquet Michael John
Hatley Kenneth John
Hatley Richard Michael
General Electric Company
Larkin Daniel S.
Nixon & Vanderhye
Rogers David
LandOfFree
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