Abstract:
A kit is provided to measure the depth to which the tip of a probe should be set inside an assembly such as a combustion can. The acquired depth is then transferred to a set of probes for installation. The fixtures and the associated process ensure that the probe will be in a proper position for accurate measurement and to eliminate inconsistencies in measurement due to probe insertion to different depths.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to fixtures and a method for accurately setting probe depth and, more particularly, to a fixture and method for accurately setting dynamic pressure probe depth in a combustion liner. 
     As part of the monitoring controls and diagnostic tools for an operating combustion system in a rotary machine such as a gas turbine, it is necessary to measure and acquire various data including combustion chamber dynamic pressure. This data is used to confirm proper operational health of the combustion system, and is also used to tune the gas turbine engine so that it is operating with an appropriate balance between combustion dynamics and emissions. 
     The combustion dynamics measurement probe holder should be inserted to the combustion can so that the tip aligns itself at a certain depth relative to the combustion liner. Typically, the tip is set about 0.030″ back from the inside of the liner. The depth of the tip should be identical for all probes used in the turbine. 
     One way of achieving identical probe depth is to remove the combustion can cover and combustion hardware so that the tip of the probe can be set by measuring its position relative to the inside wall of the combustion liner. Thus, currently, after each combustion can of the turbine is disassembled, the probe depth is set visually. It would be desirable to provide for an accurate and consistent probe tip placement without requiring removal of the combustion hardware and disassembly of the combustion cans of the turbine. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The invention provides fixtures and a method for setting the depth of the combustion dynamics probe tip repeatably and accurately in all combustion cans of the turbine. 
     The fixture of the invention is provided in accordance with an exemplary embodiment as a kit of tools or fixtures for measuring and transferring probe depth. A first, measuring fixture of the kit measures the depth to which the tip of the probe should be set. The acquired depth is then applied to the probe(s) for installation. In an exemplary embodiment, the measurement acquired by the measurement fixture is transferred to a second device that can apply the measured depth to the probe itself. This process ensures that the probe will be placed in a proper position to accurately measure, e.g., the dynamic pressure of the combustion process and eliminate any inconsistencies in measurement that would result from having the probe tips inserted at different depths. 
     Thus, the invention is embodied in a kit for setting probe depth, comprising a measurement fixture for measuring a target probe insertion depth through a wall of a component, said measurement fixture including a shaft and a tip portion provided at a distal end of said shaft, and an indicator for indicating said target depth on said shaft; and a transfer fixture for transferring a depth indicated by said indicator of said measurement fixture to a probe holder device. The transfer fixture including a housing defining a receptacle for receiving said shaft and said tip portion, the receptacle having an adjustable depth to selectively correspond to the depth indicated by the indicator of the measurement fixture, whereby a probe holder device may thereafter be disposed in said transfer fixture to a depth corresponding to said indicated depth and marked. 
     The invention is also embodied in a method of accurately placing a probe to a target depth comprising: providing an assembly for receiving the probe comprising a first, liner wall and a second, casing wall, a receptacle being defined in the first wall for receiving a tip of the probe; providing a measurement fixture having a shaft and a tip portion projecting from said shaft a distance corresponding in length to a target length of the probe inwardly from an outer surface of said first, liner wall; disposing the measurement fixture through an orifice defined in said second, casing wall and inserting said tip portion into said receptacle to abut said shaft of said measurement fixture against said outer surface of said liner wall; providing an indication of a position of said shaft at a predetermined point with respect to said second, casing wall; providing a transfer fixture including a housing having a receptacle of variable depth for receiving the measurement fixture; inserting said shaft into said receptacle so that said position indicator is aligned with a predetermined, complimentary portion of the fixture; adjusting a depth of said receptacle so that a bottom of the receptacle engages the tip portion; removing the measurement fixture; inserting a probe holder device into said receptacle so that the probe tip engages the bottom of the receptacle; and marking said probe at a point corresponding to said complimentary portion. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic elevational view of a measurement fixture in accordance with an embodiment of the invention; 
     FIG. 2 is an elevational view of the main body of the measurement fixture of FIG. 1; 
     FIG. 3 is a schematic cross-sectional view of a measurement barrel provided according to the FIG. 1 embodiment of the invention; 
     FIG. 4 is a cross-sectional view of a lock nut of the measurement fixture provided in accordance with the FIG. 1 embodiment; 
     FIG. 5 is a schematic illustration of the step of measuring target probe depth using the measurement fixture of FIG. 1; 
     FIG. 6 is a schematic cross-sectional view of a transfer fixture according to an embodiment of the invention; 
     FIG. 7 is a schematic view partly in cross-section showing the transfer of target probe depth from a measurement fixture to transfer fixture; 
     FIG. 8 is a schematic view partly in cross-section of the transfer of the measured target probe depth to a probe holder; and 
     FIG. 9 is a schematic view partly in cross-section showing the probe device coupled to the casing. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In a turbine, the combustion dynamics probe holders need to be mounted to the combustion can so that the probe tips are all disposed at a certain depth with respect to inside the combustion liner, a certain depth relative to the combustion liner. Typically, the tip is set about 0.030″ back from the inside of the liner, although this invention is not limited to that placement and can be used to place the tip beyond, aligned with, or recessed from a surface, such as the inner surface of a combustor liner. As noted above, the prescribed depth should be identical across all probes used in the turbine. To provide for reliable, repeatable probe tip placement, a kit is provided in an embodiment of the invention for determining the proper placement of the probe holder with respect to the combustor casing and liner. 
     In an exemplary embodiment of the invention, the kit includes a measurement fixture  10  for measuring can depth, and a transfer fixture  12  for transferring the measured can depth to the probe device  14 . 
     In the illustrated embodiment, the measurement fixture  10 , which for convenience may be characterized as a male measurement fixture, includes a tip portion  16  corresponding in axial length to a desired or target length of the probe tip inwardly with respect to a reference surface, which in the exemplary embodiment is the outer surface  18  of the combustion liner  20  (FIG.  5 ). Referring to FIGS. 1 and 2, the male measurement fixture further includes an elongated main body or shaft  22  which extends from a shoulder  24  defined with the tip portion and is adapted to span the distance between the reference surface at least to an access/insertion point that is remote from it, e.g., from the combustion liner  20  through and beyond the coupling or other fitting  28  provided on the combustion casing for coupling the probe device  14  to the combustion casing  26 . In the illustrated embodiment, access/insertion point is a coupling provided on the combustor casing outer wall, more specifically a Swagelok® fitting  28 , although it is to be understood that the invention is not limited to such coupling devices. 
     Since the illustrated measure fixture is adapted to interface with a Swagelok® connector assembly  28 , as described in greater detail hereinbelow, Swagelok® ferrules  30 , 32  are used to mark or indicate the target probe depth on the measurement fixture  10 . For that reason the shaft includes a smooth, unthreaded portion  34  that extends from the shoulder  24  through the casing  26  and connector fitting  28  (for sliding placement of the ferrule(s)  30 , 32 ) and a threaded portion  36 . It is to be understood, however, that if the target probe depth is indicated, recorded or marked on the measurement fixture in another manner, such as by noting indicia or physically marking the shaft of the measurement shaft, or solely by the position of the distal face of the measurement barrel  38 , then the shaft  22  may be threaded along a greater extent of its length or along substantially its entire length. In addition to a measurement barrel  38 , a lock nut  40  is provided on the measurement fixture for locking the barrel in a target position, as described in greater detail hereinbelow. 
     Referring to FIG. 3, in an exemplary embodiment, the measurement barrel  38  has an inner bore including a smooth surface portion  42  and a threaded portion  44 . The smooth surface portion is provided to slidably engage the smooth shaft  34  of the measurement fixture whereas the threaded portion  42  is adapted to threadably engage the threaded segment  36  of the measurement fixture. Providing a smooth surface portion as illustrated limits the proximal displacement of the barrel with respect to the measurement fixture main body  22 . This ensures that the ferrule(s) slidably disposed on the shaft of the measurement fixture will not undesirably engage the threaded portion  36  of the shaft. It is to be understood, however, that the smooth surface inner diameter portion of the barrel is an optional feature of the structure. In an exemplary embodiment, the measurement fixture  10  is about 8″ long, the tip portion  16  is about 0.125 inch, and the threaded portion  36  is about 2 inches long. Furthermore, in an exemplary embodiment, the diameter of the tip portion  16  is about 0.25 inch and the diameter of the shaft  22  of the measurement fixture is about 0.75 inch. A head  46  is provided at the proximal end of the measurement fixture for retaining the measurement barrel  38  and lock nut  40  on the shaft  22 . In an exemplary embodiment, the head has an outer diameter of about 1.2 inch and may have a knurled surface to facilitate handling. 
     Referring to FIG. 3, the measurement barrel  38  advantageously has a total length generally corresponding to the threaded portion  36  of the measurement fixture but the threaded inner bore of the barrel is less than the total length of the barrel by an amount generally corresponding to the length of the lock nut  40  so that if, e.g., the lock nut has a length of about 0.3 inches, the threaded portion of the barrel is about 1.7 inches. In this way, when the barrel is fully engaged with the threaded portion of the shaft and the lock nut  40  is interposed between the barrel  38  and the head  46  of the shaft the threaded portion of the shaft will be fully covered and the barrel will project distally of the threaded portion. Of course the size of the barrel and lock nut is not critical and may be varied, it being understood that, desirably, when the barrel and lock nut are fully engaged with the threaded portion, the threads are covered so that engagement of the ferrule(s)  30 , 32  and the threads  36  will be avoided. 
     Referring now to FIG. 5, to measure the target probe depth, the measuring fixture  10  is inserted through the probe connector  28  provided on the combustor casing  26  to dispose the tip  16  in/through the receptacle  48  defined in the combustion liner  20 . The measuring fixture is advanced until the shoulder  24  defined between the tip portion and the shaft engages a reference surface  18 , which in the illustrated embodiment is the outer surface of the combustion liner  20 . The tip portion advantageously has a length that corresponds to the distance that the probe tip desirably extends inwardly from the reference surface. This distance will generally correspond to the liner wall thickness. The tip portion length may be fixed or, if adjustment is desired, the tip portion length can be varied, for example, by providing a threaded tip portion that may be threaded in or out for adjustment or by providing interchangeable tip portions. 
     The measured target probe depth is then indicated, recorded or marked on the measuring fixture at a predetermined point with respect to the combustor casing  26 . In the illustrated embodiment, the predetermined point is the proximal end of the Swagelok® connector and the depth is indicated by the location of front and back Swagelok® ferrules  30 , 32  that are slidably disposed, in advance, on the shaft  22  of the measuring fixture. Thus, once the fixture is inserted so that the shoulder  24  abuts surface  18 , the measurement barrel  38  is rotated to be advanced distally. In the illustrated embodiment, this advances the front and rear ferrules  30 , 32  until they are snug with the Swagelok®  28 . Once the ferrules and barrel are in position to indicate the target probe depth, the lock nut  40  is advanced distally to lock the barrel. The outer surfaces of the barrel and lock nut may be knurled to facilitate manipulation. 
     It is to be understood that if a connector other than a Swagelok® is provided to secure the probe device with respect to the combustor casing, then the measuring fixture may be marked in another manner. For example, the target depth may be indicated simply by the location of the distal face of the barrel  38  when advanced to engage the respective connector assembly or the combustor casing wall, whichever applies. In the alternative, indicia may be applied to the measuring device as by applying a physical mark, tape or the like to indicate the depth from the tip to a point that is at a determined location with respect to the combustor casing outer surface. As noted above, where a marking method other than ferrule placement is used, the shaft  22  of the measurement fixture need not have a smooth portion  34  and may be threaded along a greater extent of its length. 
     Referring now to FIGS. 6 and 7, in an embodiment of the invention, a transfer fixture  12  is provided for transferring the target depth determined by the measurement fixture  10  ultimately to the probe device  14  that is to be secured to the combustor, or other assembly measured by the measurement fixture. For convenience, the transfer fixture  12  may be referred to as a female ferrule setting fixture. As can be seen, the transfer fixture includes at a first, open end thereof, a connector  50  corresponding to the connector  28  provided on the combustor casing. Thus, in the illustrated embodiment, a Swagelok® fitting  50  is secured at a first end of the fixture  12 . The fixture  12  defines an internal receptacle  52  having a length or depth that is adjustable so that it may be adjusted to correspond to the depth measured or indicated by the measuring fixture. In the illustrated embodiment, the depth of the receptacle of the transfer fixture  12  may be adjusted with threaded bolt  54  which is threadably engaged with the fixture housing  56  to selectively determine the depth of the receptacle  52  of the fixture. In the illustrated embodiment, the threaded bolt has a head  58  with a knurled surface to facilitate its displacement with respect to the fixture housing  56 . A lock nut  60  is further provided for locking the bolt with respect to the housing  56 . The housing may be faceted to have flat faces as at  62  so that it can be clamped during the measured depth transfer process. 
     With reference to FIG. 7, the measurement fixture  10 , once marked, is slidably inserted through the connector structure  50  into the transfer fixture until the indicator thereof is aligned with a complimentary portion or feature  64  provided on the connector  50 . In the illustrated embodiment, the ferrule(s)  30 , 32  and/or measurement barrel  38  are used to mark the measurement fixture  10  and, thus, the measurement fixture is inserted into the transfer fixture  12  until the ferrules  30 , 32  are snug with the Swagelok® fitting  50 . The depth setting bolt  54  is then adjusted so that the measurement fixture tip  16  engages the depth setting bolt  54 . The lock nut  60  is then tightened to lock the depth setting bolt&#39;s position. As will be understood, the distance between the tip of the depth setting bolt  54  and the complimentary feature  64  corresponds to the distance between the target depth of the probe tip, e.g., inside the combustion liner and the proximal end of the Swagelok®  28  of the combustor casing. 
     Once the depth setting bolt  54  has been adjusted and set, the measurement fixture  10  may be removed and held for reuse during subsequent probe measurement and placement, and the transfer fixture  12  may now be used to mark the target depth of the probe on the probe device or holder itself. More particularly, referring now to FIG. 8, the probe device  14  that is to be coupled to the combustor casing  26  is inserted through the connector structure  50  until the probe tip  70  abuts the depth setting bolt  54 . With the probe so disposed, and the ferrule(s)  72  is displaced so as to align with the complimentary portion  64  of the connector assembly, the fitting  74  is then tightened as shown by arrow T to lock the ferrule(s)  72  in place at the correct position on the probe device shaft  78 . With the target depth thus recorded or marked on the probe device  14 , the fitting  74  can be released and the dynamics probe device removed for engagement in due course with the combustion casing. Because the ferrule  72  has been locked in position on the shaft of the probe device, when the probe is inserted through the connector of the combustor casing, as shown in FIG. 9, engagement of the locked ferrule(s)  72  with the Swagelok® connector  28  of the combustion casing  26  indicates that the probe tip  70  is properly disposed with respect to the combustion liner  20  and the fitting  74  may then be tightened to secure the probe with respect to the combustor casing. 
     By way of non-limiting example, in the illustrated embodiment the probe device  14  is a T-shaped holder of the type disclosed in U.S. patent application Ser. No. 09/989,102 the entire disclosure of which is incorporated herein by this reference. The invention may also be used to mark and position probe devices of the type disclosed in co-pending U.S. patent application Ser. No. 10/374,719, titled DYNAMIC PRESSURE PROBE HOLDER AND METHOD OF OBTAINING A DYNAMIC PRESSURE SIGNAL, the entire disclosure of which is incorporated herein by this reference. The invention may also be used to measure and mark insertion depth for other probes and instruments having a target depth with respect to a reference surface that is remote from an access/insertion point. 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.