1. Field of the Invention
The invention relates to inspection port systems that facilitate internal inspection of gas turbine engines. More particularly, the invention relates to a standardized gas turbine inspection port system with port and port plug that are utilized throughout the engine. Preferably the each inspection location on the gas turbine that utilizes the standardized inspection port system has identical component dimensions and are oriented along common axial and radial positions (e.g., 6 o'clock and/or 12 o'clock radial orientation) to facilitate internal inspection of all corresponding blade/vanes that share a common row about the entire turbine casing circumference.
2. Description of the Prior Art
Industrial gas turbine engines are often equipped with inspection port systems that facilitate inspection instrument access to turbine internal components from the exterior of the turbine casing. U.S. Pat. No. 3,936,217, the entire contents of which is incorporated by reference herein, shows a typical inspection port system with a cylindrical inspection port, mating port plug that seals the inspection port, and external flanged port member projection outside the turbine casing (also referred to as a stub tube tube). The port plug and cylindrical inspection port have mating complimentary interlocking lug pins and J slots that function as a securing mechanism to retain the plug with the port. Another known plug/port securing mechanism are mating male and female threads.
Port plugs are inserted into the gas turbine inspection port system by advancing the elongated plug into the turbine casing through the stub tube. Thereafter the plug tip is inserted into the relatively narrow diameter inspection port tube along a narrow alignment path, which is analogous to threading a needle, while taking care not to drop the plug into the turbine casing.
Individual inspection port system access locations and dimensions on a gas turbine engine vary among engine designs. For example, different inspection rows within a gas turbine compressor or combustor section often have different length dimensions between the gas turbine casing inspection hole and the stub tube flange, as well as different port diameters. Often the flange dimension and configuration for each respective stub tube will vary on the same turbine and radial position about the case circumference will also vary from one row to another or among different turbine models. Lack of uniformity raises inspection service challenges. For example, an inspection tool suitable for one inspection row may be too large in diameter or length for a different inspection port system access point in the same or in a different inspection row. Length variances between a stub tube flange and gas turbine casing inspection hole often requires a service technician to configure inspection instruments differently from row to row so that instrument insertion distance can be correlated with instrument orientation within the turbine casing. Different stub tube flange configurations and/or dimensions requires different instrument anchoring or other securement methods relative to the turbine casing or perhaps use of adapter flanges.
Thus, a need exists in the art for a standardized gas turbine engine inspection port system that enhances engine inspection and maintenance by providing preferably identically dimensioned access paths and external anchoring flanges for inspection tool and other service tool insertion into the gas turbine engine, with system ports arrayed along common aligned locations in a plurality of turbine blade/vane rows.
An additional need exists for an inspection port plug and plug installation/removal service method that facilitates easy plug insertion and alignment into an inspection port system inspection port body, with reliable sealing of the gas turbine casing inspection hole.
Another need exists for an inspection port plug and plug installation/removal service method that reduces likelihood of inadvertently dropping a port plug into the gas turbine casing during removal or installation.
Accordingly, a suggested object of the invention is to enhance engine inspection and maintenance by providing a standardized gas turbine engine inspection port system with preferably identically dimensioned access paths and external anchoring flanges for inspection tool and other service tool insertion into the gas turbine engine, with system ports arrayed along common aligned locations in a plurality of turbine blade/vane rows.
An additional suggested object of the invention is to facilitate easier port plug insertion and alignment into an inspection port system inspection port body, with reliable sealing of the gas turbine casing inspection hole, than presently know inspection port systems.
Another suggested object of the invention is to reduce likelihood of inadvertently dropping a port plug into the gas turbine casing during removal or installation.
These and other objects are achieved in one or more embodiments of the invention by a standardized port inspection system that is incorporated in plural locations within a gas turbine engine casing, to facilitate internal engine inspection. Inspection port system components that are incorporated in the inspection system, including for example inspection port bodies, port plugs, stub pipes and inspection flanges, preferably have identical internal diameter, stub flange dimensions and axial length from the gas turbine casing inspection seat to the stub flange for standardized mounting of inspection instruments at different locations about the turbine. The access inspection ports of the port inspection system are preferably axially and radially aligned along the turbine casing (e.g., at the 6 o'clock, 12 o'clock or both radial positions) for establishing a common reference position along all turbine blade/vane rows. The inspection system port plug incorporates a magnetically attractive pole piece constructed of material having a magnetic permeability greater than the remainder of the plug for concentration or redirection of an attractive magnetic field circuit generated by an inspection port plug service tool during plug insertion or retrieval. Magnetic attraction to a service tool facilitates port plug insertion and retrieval from the inspection port along precisely maneuvering paths and reduces likelihood of inadvertent dropping of a port plug into the gas turbine casing during plug maneuvering.
Embodiments of the invention feature a gas turbine inspection port plug apparatus for insertion into a mating gas turbine inspection port of a turbine inspection port system that is coupled to a gas turbine engine casing. The port plug has an elongated plug shaft, constructed of a material having a first magnetic permeability, for insertion into a mating gas turbine inspection port. The port plug also has a plug seating surface on a distal end of the plug shaft, for sealing engagement with a mating inspection opening seat defined by a gas turbine engine casing upon insertion of the plug shaft into a gas turbine inspection port. There is a plug cap on a proximal end of the plug shaft. Preferably the port plug also has a plug securing mechanism, for retention engagement with a complementary gas turbine inspection port securing mechanism when the plug is inserted into an inspection port. A magnetically attractive pole piece constructed of material having a second magnetic permeability greater than the first magnetic permeability is oriented in proximity to the plug shaft proximal end, for concentration or redirection of an attractive magnetic field circuit generated by an inspection port plug service tool during plug insertion or retrieval. For example the pole piece may be coupled to a proximal end of the cap opposite to its connection to the plug shaft proximal end. The pole piece may be constructed of a magnetic lamina stack and may be shaped to direct the service tool generated magnetic field. The plug securing mechanism may comprise threads configured for complimentary mating engagement with threads formed in the inspection port, including interrupted thread patterns that facilitate retention by push and twist motion. The plug securing mechanism alternatively may comprise lugs or lug-receiving slots formed in the plug for twist-lock engagement with corresponding mating lugs or slots formed in a complimentary gas turbine inspection port securing mechanism; and a biasing element coupled to the plug for axially biasing the plug securing mechanism relative to a complimentary gas turbine inspection port securing mechanism, such as a spring-biased J-lock retention mechanism. Any known form of plug/inspection port retention mechanisms may be utilized in connection with the inspection port plugs of the invention.
Other embodiments of the invention feature a method for servicing an inspection port plug adapted for sealing an inspection port of a gas turbine engine inspection port system in a gas turbine engine having a turbine casing enclosing plural axially spaced rows of vanes and blades that are oriented radially about a turbine shaft and an axially aligned inspection opening defined by the turbine casing, having an inspection opening seat. In the gas turbine an inspection port is affixed to the turbine casing in general axial alignment with the inspection opening seat. The inspection port has a generally cylindrical port body, a funnel on a proximal end of the port body, and a gas turbine inspection port securing mechanism. The turbine port inspection system has an inspection port plug that includes an elongated plug shaft, constructed of a material having a first magnetic permeability, for insertion into the gas turbine inspection port. The port plug has a plug seating surface on a distal end of the plug shaft, for sealing engagement with the mating inspection opening seat defined by a gas turbine engine casing upon insertion of the plug shaft into the inspection port. The port plug has a plug cap on a proximal end of the plug shaft and a plug securing mechanism, for retention engagement with the complementary gas turbine inspection port securing mechanism when the plug is inserted therein. A magnetically attractive pole piece constructed of material having a second magnetic permeability greater than the first magnetic permeability, is oriented in proximity to the plug shaft proximal end, for concentration or redirection of an attractive magnetic field circuit generated by an inspection port plug service tool during plug insertion or retrieval. An inspection port plug service tool having a magnetic tip for generation of an attractive magnetic field circuit with the plug pole piece during plug insertion or retrieval is used during plug service.
When installing the port plug within the gas turbine in accordance with the method of the invention, the service tool magnetic tip and the pole piece are magnetically coupled, so that the inspection port plug is affixed to the service tool. Then the inspection port plug seating surface and plug are inserted into the inspection port funnel with the service tool and advanced therein to place the plug seating surface into contact with the turbine casing inspection opening seat. The respective mating plug and inspection port securing mechanisms are then engaged for retaining the port plug in the inspection port. When removing the port plug from the gas turbine, the respective mating plug and inspection port securing mechanisms are disengaged so that the port plug is separable from the inspection port then the service tool magnetic tip and the pole piece are magnetically coupled, so that the inspection port plug is affixed to the service tool. Then the port plug is removed from the inspection port and gas turbine.
Embodiments of the invention also feature a gas turbine engine with the standardized port inspection system. This invention embodiment gas turbine engine includes nested inner and outer turbine casings enclosing plural axially spaced rows of vanes and blades that are oriented radially about a turbine shaft. Plural axially aligned inspection openings are defined by the inner turbine casing, each having an inspection opening seat. A plurality of inspection ports are affixed to the inner turbine casing in general axial alignment with each respective inspection opening seat. Each inspection port has a generally cylindrical port body having a distal end for affixation to the inner casing in general axial alignment with an inspection opening seat defined by the inner casing. The respective port bodies preferably have identically dimensioned internal length and diameter. The port body proximal end facing the outer casing has a funnel. The inspection port body also has a gas turbine inspection port securing mechanism. A plurality of generally cylindrical stub tubes are affixed to and project outwardly from the outer turbine casing, each preferably having identical external flanges and inner diameters, all of which are in general axial alignment with each respective inspection opening seat and respective inspection port body. Preferably the axial length of each stub tube is chosen so that distance from its respective external flange to its corresponding respective inspection opening seat is identical or substantially identical. Each corresponding stub tube, inspection port and inspection opening seat are preferably aligned axially and radially: for example at a 6 o'clock or a 12 o'clock position or at both positions. The gas turbine has plural gas turbine inspection port plugs for insertion into a mating gas turbine inspection port. Each port plug has an elongated plug shaft, constructed of a material having a first magnetic permeability, such as Inconel® superalloy, for insertion into a mating gas turbine inspection port. A plug seating surface is formed on a distal end of the plug shaft, for sealing engagement with a mating inspection opening seat defined by a gas turbine engine casing upon insertion of the plug shaft into a corresponding gas turbine inspection port. A plug cap is formed on a proximal end of the plug shaft. The port plug has a plug securing mechanism, for retention engagement with a complementary gas turbine inspection port securing mechanism when the plug is inserted into an inspection port, and a magnetically attractive pole piece constructed of material having a second magnetic permeability greater than the first magnetic permeability, such as a ferro magnetic alloy, oriented in proximity to the plug shaft proximal end, for concentration or redirection of an attractive magnetic field circuit generated by an inspection port plug service tool during plug insertion or retrieval.
The respective objects and features of the present invention may be applied jointly or severally in any combination or sub-combination by those skilled in the art.
The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which:
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.
After considering the following description, those skilled in the art will clearly realize that the teachings of the embodiments of the invention can be readily utilized in gas turbine inspection port systems. By utilizing standardized inspection port system components that are preferably of identical or substantially identical configuration and dimensions, which also preferably are arrayed in commonly aligned axial and radial orientations about a gas turbine casing—internal turbine inspections can be performed using the same inspection equipment, equipment configuration and inspection techniques consistently from row-to-row. Common inspection system port locations from row-to-row also enhances consistent inspection of all circumferential positions within the casing. For example, inspection port alignment at the 12 o'clock or vertical radial position facilitates insertion of flexible inspection probes clockwise and/or counter-clockwise throughout the turbine casing inner circumference, for inspection of abradable surfaces or vane carriers. Similarly, insertion of a blade inspection probe at the 12 o'clock position facilitates easier inspection of all blades while the turbine is in turning gear inspection mode. The magnetically attractive port plug pole piece, in cooperation with a magnetic field generating service tool facilitates precise “thread the needle” maneuvering of the port plug into its mating funnel-necked inspection port body and subsequent firm sealing of the corresponding turbine inspection opening after cooperative mating engagement of the respective port plug and port body securing mechanisms. In embodiments of the invention the mating securing mechanisms are relatively easy to engage “push and twist-lock” J locking mechanisms or interrupted thread mechanisms. Other embodiments of securing mechanisms include mating threads on the port plug and inspection port body.
Each inspection port 40 is preferably aligned concentrically with a corresponding turbine casing inspection opening 32, inspection opening seat 34, stub pipe 50 and external flange 52. The external flange 52 provides structural support for inspection instruments 36 that are coupled thereto. As previously noted, and shown in
Other inspection port system components are shown in greater detail in
As previously described, each inspection port plug 60 seals its respective corresponding gas turbine casing inspection opening 32. Embodiments of the inspection plug 60 feature an elongated plug shaft 62 with a plug seating surface 64 on a distal end of the plug shaft, for sealing engagement with a mating inspection opening seat 34 defined by a gas turbine engine casing upon insertion of the plug shaft into a gas turbine inspection port body 42. A plug cap 66 is oriented on a proximal end of the plug shaft 62 and preferably includes one or more drive surfaces 67 for engagement with a corresponding drive surface of a plug service tool 80 mating socket 86.
The plug service tool 80 and its socket 86 facilitates installation and removal of the port plug 60 remotely from the turbine 20 exterior, through the stub pipe 50 by pushing and/or rotating the plug cap drive surfaces 67 and its securing mechanism 68 relative to its corresponding inspection port securing mechanism 46. The service tool shaft 88 has sufficient length to reach the port plug 60 and rotation is imparted on the plug by application of torque on the T handle 90. The service tool 80 also has an electromagnet 82 that is oriented within the socket 86. An electromagnetic field B is generated passing current from a current source 84 through the electromagnet 82.
In this invention the port plug 60 is selectively magnetically coupled to the plug service tool 80 electromagnet 82 for precise remote alignment and manipulation of the plug as it is inserted or withdrawn from the gas turbine 20. Magnetic coupling of the plug 60 and service tool 80 also reduces likelihood of inadvertent dropping of the plug into the turbine 20 interior. The inspection plugs 60 are generally constructed of a heat resistant metal alloy, such as an Inconel® superalloy that has a relatively low (or functionally non-existent) first magnetic permeability that is too low for sufficient direct magnetic coupling with the service tool 80. Accordingly the plug 60 has a magnetically attractive pole piece 70 that is constructed of material having a second magnetic permeability greater than that of the plug cap 66/shaft 62/plug seating surface 64 first magnetic permeability. Referring to
Although various embodiments that incorporate the teachings of the present invention have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings. The invention is not limited in its application to the exemplary embodiment details of construction and the arrangement of components set forth in the description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. For example, the port plug and inspection port body securing mechanisms mating engagement portions shown in the figures may be reversed. Other known designs of pole pieces may be substituted for the constructions and configurations shown in the figures. The port plug service tool may utilize other types of known drive surfaces other than a socket. Similarly, a permanent magnet may be substituted for the electromagnet shown in the figures. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.