Patent Application
20140140839
The subject matter disclosed herein relates to turbine casings and, more particularly, to turbine casings with access slots and at least one service wedge configured to be removably installed in the access slots.
Gas and steam turbine engines are typically designed with casing/shell splits along the horizontal centerline of the unit. For major maintenance inspections, parts replacements, etc., the upper half casings are normally removed. The disassembly and subsequent re-assembly process is mechanically very involved along with being resource and time intensive. For example, it is necessary to attach the upper half casing to a crane and to remove fastening elements along the entire axial length of both casing/shell splits so that the crane can lift the upper half casing away from the lower half casing.
For small to medium scale inspection, maintenance, repair or replacement operations, the ability of the operator to access the interior of casings/shells is often compromised. As such, it may be necessary for the entire removal process to be conducted even for relatively minor operations if internal access to parts is required. This issue can be especially resource and time intensive particularly as compared to the scope of the relatively small scale maintenance, repair or replacement operations.
According to one aspect of the invention, a turbine casing is provided and includes first and second turbine casing shells configured to be removably coupled to one another. At least one of the first and second turbine casing shells is formed to define an access slot. At least one service wedge is configured to be removably installed in the access slot.
According to another aspect of the invention, a turbine casing is provided and includes a lower turbine casing shell, an upper turbine casing shell configured to be removably coupled to the lower turbine casing shell, the upper turbine casing shell being formed to define at least one access slot symmetrically about a centerline of the upper turbine casing shell and at least one service wedge configured to be removably installed in the at least one access slot.
According to yet another aspect of the invention, a method of accessing a turbine interior is provided. The method includes manually removably installing a service wedge with respect to a turbine casing shell formed to define an access slot in which the service wedge is sized to fit and manually accessing the turbine interior with the service wedge removed from the access slot.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
In accordance with aspects, the resources and time intensity of inspections, replacement and repair of rotating and/or stationary parts of gas or steam turbine engines can be dramatically reduced. This may be accomplished by employing at least one or more removable wedge segments as relatively small portions of the complete lower or upper casing or shell. The smaller wedge segments can be more efficiently removed than the lower or upper casing or shell during an outage thereby allowing direct operator access to blading for more complete inspections, cleaning or repair than can be achieved via a small diameter (typically 2 cm or less) borescope opening. In addition, with proper foresight the blading can be designed for replacement via the access slots formed for the wedge segments to thereby save valuable outage time, reduce lift requirements and afford more complete inspections with complete removal of the upper casings.
With reference to
In some conventional cases, it is not necessary to remove the upper turbine casing shell 12 from the lower turbine casing shell 11 in order to conduct normal inspection and repair operations. In such cases, access to the interior of the turbine casing 10 may be provided via a small (i.e., 2 cm or less) borescope opening 15 that may be formed in the upper turbine casing shell 12. During turbomachine operational modes, the borescope opening 15 is closed by a closure element that is threadably secured in the borescope opening 15. Thus, the closure element may be removed from the borescope opening 15 by rotation of the closure element about the radial dimension. As such, due to both ease of manufacture and the curvature of the turbine casing 10, the borescope opening 15 is typically circular and a diameter thereof is required to be maintained at a relatively small scale to reduce stress concentrations on the casing and so that the closure element can register with the threading. Also, the borescope opening 15 need not be larger than the small-diameter borescope itself to avoid unnecessarily reducing the structural strength of the turbine casing 10.
Since the diameter of the borescope opening 15 is small, it is generally not possible to conduct complete inspection and repair operations that require greater access to a turbomachine interior than what is provided via the borescope opening 15 (i.e., small to intermediate scale inspections and repairs) without removing the upper turbine casing shell 12 from the lower turbine casing shell. Consequently, small to intermediate scale inspections and repairs are often associated with outsized costs and turbomachine 10 downtime associated with the resource and time intensive removal process described above. Accordingly, at least one of the upper and lower turbine casing shells 12 and 11 is formed to define an access slot 20 in which the service wedge 30 is sized to fit. The service wedge 30 can therefore be removably installed with respect to the access slot 20 by manual procedures that can be executed quickly or at least more quickly than the full upper turbine casing shell 12 removal process described above.
In accordance with aspects, the manual procedures may be conducted with assistance from hoists or cranes that are generally smaller than those used for full casing shell removal. As the upper and lower turbine casing shells 12 and 11 can weigh several tons, the hoists or cranes needed for full removal must have the capability of lifting several tons or more. By contrast, the hoists or cranes that may be required to assist in the removal of the service wedge need to be capable of lifting substantially less weight (e.g., on the order of several hundred pounds or less).
During turbomachine operations, the service wedge 30 is installed in the access slot 20. The service wedge 30 can be removed from the access slot 20 to allow for small to intermediate scale inspections and repairs without otherwise removing the entire upper turbine casing shell 12 from the lower turbine casing shell 11. The access slot 20 thus provides for less costly repairs and inspections and less turbomachine downtime as well.
Although the access slot 20 may be defined by one or both of the upper and lower turbine casing shells 12 and 11, the following description will relate to the exemplary case of the access slot 20 being defined by the upper turbine casing shell 12. This is being done for clarity and brevity and is not intended to otherwise limit the scope of the application or the claims.
In accordance with embodiments, the access slot 20 may be defined by the upper turbine casing shell 12 to have a circumferential arc-length of adequate dimensions to allow access to and/or removal of specific internal components yet remain sized for fast and efficient removal. Even if the access slot 20 extends along substantially an entire axial length of the turbine casing 10 (e.g., from forward flange 40 to aft flange 41), the access slot 20 may have a relatively short arc-length and thereby allow the corresponding service wedge 30 to remain correspondingly lightweight. As the service wedge 30 is configured to be removably installed in the access slot 20 by manual procedures (with or without receiving some assistance from the aforementioned hoists or cranes), the lightweight characteristic of the service wedge 30 permits the service wedge 30 to be lifted out of the access slot 20 manually or by use of the relatively small hoists or cranes.
Of course, it is to be understood that the illustrations of the access slot 20 in the figures are merely exemplary and that other larger and smaller access slot 20 shapes and sizes may be employed as long as the corresponding service wedge 30 is sufficiently lightweight to be quickly and efficiently removable by manual or hoist/crane assisted procedures. In addition, although the access slot 20 is illustrated as having a regular shape, it is to be understood that this is not necessary and that it is possible that the access slot 20 may have a regular, irregular, angled, rounded or otherwise complex shape as shown in
The access slot 20 may be defined along a centerline 120 of the upper turbine casing shell 12 or at an offset position relative to the centerline 120. In either case, the access slot 20 may be but is not required to be defined symmetrically about the centerline 120 to thereby preserve thermal expansion and contraction characteristics of the turbine casing 10. In the case where the access slot 20 is defined at the offset position, the access slot 20 may be defined as multiple access slots 20. In this case, one of the access slots 20 may be defined at a first offset position relative to the centerline 120 and another access slot 20 may be defined at a second offset position on the opposite side of the centerline 120 from the first offset position. In accordance with embodiments, the first and second offset positions may be defined at or near flexural nodal locations (e.g., the 1:30 and 10:30 positions, respectively) of the upper turbine casing shell 12.
In the case where the upper turbine casing shell 12 defines multiple access slots 20, the service wedge 30 may be provided as multiple service wedges 30 and/or multiple dummy wedges 31. In either case, each one of the multiple service wedges 30 or dummy wedges 31 is configured to be removably installed in a corresponding one of the multiple access slots 30.
With reference to
Although the flanges 51 are illustrated in
With reference to
In accordance with further embodiments, it is to be understood that the borescope opening 15 may not be required where the access slot 20 is formed. In such cases, the borescope may simply by snaked through the access slot 20 with the service wedge 30 removed. If the borescope is required to be secured in place, appropriate tooling may be provided to do so within the scope of this disclosure.
With reference to
Although
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
