Borescope assembly and method of installing borescope plugs

A borescope assembly includes a first borescope plug comprising a first perimeter geometry portion. Also included is a second borescope plug comprising a second perimeter geometry portion distinct from the first perimeter geometry portion. Further included is a first borescope hole comprising a first hole geometry portion corresponding to the first perimeter geometry portion of the first borescope plug. Yet further included is a second borescope hole comprising a second hole geometry portion corresponding to the second perimeter geometry portion of the second borescope plug.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to borescope assemblies, such as those used in turbine assemblies, as well as a method of installing borescope plugs.

Borescopes are used to visually inspect internal components of turbine assemblies, such as gas turbine engines, for example. They are typically inserted through borescope holes placed in locations of a static structure that lead to internal locations of interest. Such insertion occurs during an outage. When the turbine assembly is in operation, the borescope holes must be plugged and sealed to reduce or prevent hot gases from being emitted from the turbine which would result in overall system performance and/or safety issues. Plugging of the holes is done with a borescope plug. Typically, the borescope holes are similar in diameter, but vary in length. Similarly, the borescope plugs to be inserted into the borescope holes are similar in diameter, but vary in length. Maintenance personnel must use caution to ensure that a borescope plug of a given length is not inserted into a borescope hole with a distinct length. Incorrect insertion may create a leak path due to the fact that a short plug has a tendency to seal improperly. Additionally, incorrect insertion may impose a situation where a long borescope plug (relative to the borescope hole) is bent during insertion. This incorrect assembly condition may also result in leakages, disassembly issues, and delays during an outage.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, a borescope assembly includes a first borescope plug comprising a first perimeter geometry portion. Also included is a second borescope plug comprising a second perimeter geometry portion distinct from the first perimeter geometry portion. Further included is a first borescope hole comprising a first hole geometry portion corresponding to the first perimeter geometry portion of the first borescope plug. Yet further included is a second borescope hole comprising a second hole geometry portion corresponding to the second perimeter geometry portion of the second borescope plug.

According to another aspect of the invention, a borescope assembly for a turbine assembly includes a plurality of borescope plugs each including a main plug portion and a collar disposed along the main plug portion, wherein the collar of each of the plurality of borescope plugs comprises a perimeter geometry distinct from the perimeter geometry of the remaining collars. Also included is a plurality of borescope holes each comprising a hole geometry corresponding to the perimeter geometry of the collar of one of the plurality of borescope plugs.

According to yet another aspect of the invention, a gas turbine engine includes a compressor, a combustor assembly, a turbine, and a borescope assembly. The borescope assembly includes a first borescope plug comprising a first perimeter geometry portion. The borescope assembly also includes a second borescope plug comprising a second perimeter geometry portion distinct from the first perimeter geometry portion. The borescope assembly further includes a first borescope hole comprising a first hole geometry portion corresponding to the first perimeter geometry portion of the first borescope plug. The borescope assembly yet further includes a second borescope hole comprising a second hole geometry portion corresponding to the second perimeter geometry portion of the second borescope plug.

DETAILED DESCRIPTION OF THE INVENTION

Referring toFIG. 1, a turbine assembly, such as a gas turbine engine10constructed in accordance with an exemplary embodiment of the invention, is schematically illustrated. The gas turbine engine10includes a compressor section12and a plurality of combustor assemblies arranged in a can annular array, one of which is indicated at14. As shown, the combustor14includes an endcover assembly16that seals, and at least partially defines, a combustion section18. In one embodiment, a plurality of nozzles20-22is supported by the endcover assembly16and extends into the combustion section18. The nozzles20-22receive fuel through a common fuel inlet (not shown) and compressed air from the compressor section12. It should be appreciated that this invention is independent of the details of the combustion system, and the can annular system is referenced for purposes of discussion. The fuel and compressed air are passed into the combustion section18and ignited to form a high temperature, high pressure combustion product or air stream that is used to drive a turbine section24. The turbine section24includes a plurality of stages26-28that are surrounded by a casing32and operationally connected to the compressor section12through a compressor/turbine shaft30(also referred to as a rotor).

In operation, air flows into the compressor section12and is compressed into a high pressure gas. The high pressure gas is supplied to the combustor14and mixed with fuel, for example natural gas, fuel oil, process gas and/or synthetic gas (syngas), in the combustion section18. The fuel-air or combustible mixture ignites to form a high pressure, high temperature combustion gas stream. In any event, the combustor14channels the combustion gas stream to the turbine section24which converts thermal energy to mechanical, rotational energy.

Referring toFIG. 2, the casing32of the turbine section24is illustrated in greater detail. The casing32generally refers to a structure that surrounds and at least partially defines an internal region of the turbine section24. The casing32may be a unitary structure or may be formed of multiple segments, such as a double casing that comprises an outer casing34and an inner casing36, which are operatively coupled to each other. As shown, internal components of the turbine section24include a plurality of nozzle vanes38and rotor buckets40, for example. The internal components are surrounded by the casing32, as noted above, as well as at least one shroud42in the illustrated embodiment.

A plurality of borescope plugs44are disposed within a plurality of borescope holes46that extend through the at least one shroud42or through a nozzle outer side wall, as shown. Although shown and described as extending through the at least one shroud42, it is to be appreciated in certain embodiments, the plurality of borescope holes46extend through the casing32, or alternatively through the casing32and the at least one shroud42in combination. Regardless, it is to be understood that the plurality of borescope holes46extend through an outer structure to provide access for a borescope, or other inspection device, that may be employed to monitor internal components of the turbine section24. Although the location of the plurality of borescope holes46described herein are discussed in conjunction with the turbine section24, any portion of the gas turbine engine10may benefit from the use of the embodiments described herein. For example, the compressor section12may include the plurality of borescope holes46that require plugging during operation of the gas turbine engine10.

Each of the plurality of borescope holes46are typically of varying lengths, as they are positioned at distinct axial locations throughout the turbine section24. The plurality of borescope holes46may be of similar diameter or perimeter, however, varying diameters and perimeter are contemplated. In order to seal the plurality of borescope holes46during operation of the gas turbine engine10, the plurality of borescope plugs44are inserted into the plurality of borescope holes46. As noted above, the plurality of borescope holes46extend through the casing32and/or the at least one shroud42from a first end50to a second end52, with the second end52exposing the internal region of the turbine section24that is to be inspected. A varying number of borescope holes may be included, depending on the particular application. In the exemplary embodiment, four borescope holes and associated borescope plugs are illustrated, but more or less are contemplated. For purposes of discussion, a first borescope plug54and a second borescope plug56are specifically labeled.

Referring now toFIGS. 3-5, in conjunction withFIG. 2, the first borescope plug54and a first borescope hole58are illustrated in greater detail. The first borescope hole58extends through an outer static structure, such as the at least one shroud42and the first borescope plug54is disposed therein. In order to ensure that the proper borescope plug is being inserted into the first borescope hole58, uniquely shaped features are included in the overall assembly. Specifically, the first borescope plug54comprises a first main plug portion55that is typically cylindrical, but alternative cross-sectional geometries are contemplated. A collar60is integrally formed with, or operatively coupled to, the first main plug portion55. An outer surface62of the collar60comprises a first perimeter geometry portion64. A first insert70is integrally formed with, or operatively coupled to, a hole wall72of the first borescope hole58. The first insert70includes a cutout portion74that defines a first hole geometry portion76. The first hole geometry portion76and the first perimeter geometry portion64correspond to one another, such that it is only possible for a borescope plug having the collar60with the first perimeter geometry portion64to be inserted through the cutout portion74of the first insert70. Collars having a distinct perimeter geometry, with respect to the first hole geometry portion76of the cutout portion74, are unable to pass through the cutout portion74of the first insert70based on the mismatched geometries, thereby reducing or preventing the ability of a borescope plug other than the first borescope plug54to be inserted into the first borescope hole58. For example, the second borescope plug56(FIG. 2) is shorter than the first borescope plug54and would ineffectively seal the first borescope hole58. Therefore, the second borescope plug56comprises a second collar80with a second perimeter geometry portion82that corresponds to a second hole geometry portion84of a second borescope hole86. The distinct geometries prohibit insertion of the first borescope plug54into the second borescope hole86. Conversely, the second borescope plug56is unable to be inserted into the first borescope hole58.

Any number of contemplated geometries may be employed for the borescope plugs and the borescope holes. In one embodiment, the geometries are polygons90(FIG. 6) and can range in the number of sides that define the polygons. For example, polygons with sides ranging from three to nine, however, polygons, with more sides may be suitable. The specific geometry employed may vary. The important aspect relates to the principle that each borescope plug includes a distinct outer geometry portion that corresponds to a particular borescope hole geometry.

The distinct geometry portion of the respective borescope plugs and borescope holes refers to a portion of the borescope plugs and borescope holes that include the specific geometries. In the embodiments described above and illustrated, inserts are employed with cutout portions. The collars of the borescope plugs must pass through the cutout portions to become fully inserted into the borescope holes. The inserts and the collars may be operatively coupled to, or integrally formed with, the plurality of borescope holes46and the plurality of borescope plugs44, respectively. In alternative embodiments, the distinct geometries may be the borescope hole geometry and/or the borescope plug geometry. In other words, the plurality of borescope plugs44and/or the plurality of borescope holes46may comprise the distinct geometries necessary for proper insertion of the plugs into the holes.

In operation, each of the plurality of borescope plugs44is inserted into one of the plurality of borescope holes46. To fully insert the borescope plug into the correct borescope hole, a perimeter geometry portion of the borescope plug must fit and slide along and/or through a hole geometry portion of the borescope hole. Use of the distinct geometries reduces the likelihood that insertion of an incorrect borescope plug is inserted into one of the borescope holes, thereby advantageously providing proper sealing of the plurality of borescope holes46and avoiding damage to the plugs and/or internal components of the turbine section24.