Abstract:
An apparatus and method are provided for removing a blade from a dovetailed slot in a wheel of a rotating machine. At least one device is adapted to apply a pushing force on a first surface of a blade. A turntable for supporting the wheel has indexing capability to advance the wheel by a predetermined amount. The device can be used to remove one or more blades from the wheel.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority based on U.S. Provisional Application No. 61/141,851 filed Dec. 31, 2008. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates generally to a compressor and more specifically to an apparatus and method for removing compressor blades. 
     A conventional gas turbine generally operates on the principle of compressing air within a compressor and then delivering the compressed air to a combustion chamber where fuel is added to the air and ignited. Afterwards, the resulting combustion mixture is delivered to the turbine section of the gas turbine where a portion of the energy, generated by the combustion process, is extracted by a turbine to drive the compressor via a shaft. 
     In multi-stage compressor sections, stators are placed at the entrance and exit of the compressor section, as well as between each compressor stage, for purposes of properly directing the airflow to each successive compressor stage. As a result, stators are able to enhance compressor performance by appropriately influencing airflow and pressure within the compressor section. 
     Stators generally consist of an annular array of airfoils or vanes. Stators are typically formed in segments as stator vane segments consisting of one or more airfoils supported by the base. The base includes a dovetail to maintain the stator vane unit within the casing. These stator vane segments are individually mounted to the compressor casing to form an annular array, so that the airfoils project radially between an adjacent pair of compressor stages. A rotor with blades occupies the space between the stator vanes. The rotor blades or airfoils are also connected to the rotor wheel via dovetail connection. 
     After prolonged use, the blades or airfoils of the compressor may need to be repaired or replaced. Some known methods for removing compressor blades from compressor wheels have relied on manual labor. In one method, a first person rests a V-shaped block mounted on the end of a long handle on the leading edge of a blade. A second person then swings a heavy sledgehammer and hits the back of the V-shaped block. This is repeated multiple times until the blade is removed from the wheel. This process is then repeated for the rest of the blades, and is a time consuming and may be a potentially hazardous activity. Another known method uses a hand-held pneumatic jack-hammer to bear on the blade until it is removed. This requires significant physical effort on the part of the jack-hammer operator and may also carry risk of injury. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Briefly in accordance with one aspect of the present invention, an apparatus is provided for removing a blade from a dovetailed slot in a wheel of a rotating machine. At least one device is adapted to apply a pushing force on a first surface of a blade. A turntable for supporting the wheel has indexing capability to advance the wheel by a predetermined amount. The device can be used to remove one or more blades from the wheel. 
     In another aspect of the present invention, a method is for removing a blade from a dovetailed slot in a wheel of a rotating machine. At least one device is provided to apply a pushing force on a first surface of a blade. A turntable is provided for supporting the wheel, and has indexing capability to advance the wheel by a predetermined amount. The device can be used to remove one or more blades from the wheel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
         FIG. 1  illustrates a perspective illustration of a sound-reducing enclosure used to house the apparatus used to remove a blade, according to one aspect of the present invention. 
         FIG. 2  illustrates a perspective illustration of the apparatus, contained within the enclosure of  FIG. 1 , used to remove a blade, according to one aspect of the present invention. 
         FIG. 3  illustrates a perspective illustration of a portion of a compressor wheel positioned to have a blade removed, according to one aspect of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following embodiments of the present invention have many advantages, including providing an apparatus and method to quickly and safely remove compressor blades, and to reduce the need for serious physical effort by maintenance personnel. In addition, the present invention also reduces the environmental noise in the workplace during a blade removal operation. 
       FIG. 1  illustrates one embodiment of the present invention and shows a substantially sound proof enclosure  100  that contains a blade removal apparatus. The doors  110  may be opened to gain access to the interior of enclosure  100 , and are preferably sized to permit passage of a compressor wheel. The sound proof enclosure  100  limits and reduces the ambient noise outside the enclosure to under about 80 dbA. Any suitable noise reducing materials or insulating layers can be used to construct the enclosure  100 . The enclosure  100  can also incorporate a safety interlock to prevent operation with the door open. 
       FIG. 2  illustrates a view of one embodiment of the apparatus used to remove blades of a compressor wheel though the open doors  110  of enclosure  100 . The apparatus  200  has a variably indexable turntable  210  that can receive and support a compressor wheel  215 . Not all compressor wheels have the same number of blades so the rotation of turntable  210  can be adjusted to index by the correct angle to advance one blade at a time. The indexing mechanism can be digitally controlled and adjusted. 
     The apparatus  200  also comprises a device, such as a hammer  220 , for example, a pneumatic hammer (hereinafter referred to as a “hammer” which is not intended to limit the invention in any manner) that may use an air-cooled hardened bit to bear on the blade during removal. The air cooling can help to reduce the temperature of the workpiece and the tool during use. The hammer  220  can be advanced by a hydraulic device that advances the hammer as the blade is removed, thus keeping constant pressure on the blade. The hammer  220  can be rotated in two or more planes and advanced or retracted relative to the blade being removed. This enables the apparatus  200  to be used for a wide variety of blade and wheel sizes. 
     Means for communicating power to the hammer  220  may be provided in multiple ways. The hammer  220  may be powered by high-pressure gas through a gas flow path. The high-pressure gas may be supplied by umbilical from outside the enclosure. Alternately, hammer  220  may be powered by an electric solenoid supplied by electric power through an umbilical. An alternate power method could also include ultrasonic or subsonic acoustics, or explosive charge. The hammer can also be an impact hammer, pneumatic hammer or hydraulic hammer. A hydraulic ram may also be connected to hammer  220  to assist in the removal process. 
     Remote operation of some or all of the apparatus mechanisms can be provided. For example, a control panel on the exterior of enclosure  100  may be provided, and enable the turntable  210  to be indexed remotely from outside the sound-proof enclosure  100 . The hammer  220  can also be operated remotely from outside the sound proof enclosure. In alternative embodiments, a processor can be connected to the apparatus  200  via wired or wireless connection, and be used to control some or all of the components of the apparatus  200 . 
       FIG. 3  illustrates a view of the hammer  220  contacting one of the blades  305  of compressor wheel  215 . The hammer can be manipulated to drive blades  305  out of wheel  215  from either above (as shown) or below. 
     A method of removing a blade  305  will now be described according to one aspect of the present invention. A compressor wheel having multiple blades can be transported into enclosure  100  and mounted on turntable  210 . A clamping mechanism (not shown) can be used to secure the wheel  215  to turntable  210 . A lubricant, such as a penetrating lubricant, can be applied to the blade and dovetail joint to assist in the removal process. The apparatus can be programmed with the proper indexing value to advance the wheel one blade at a time. 
     The hammer can be positioned either above or below the blade to be removed. The hammer can be positioned by any suitable sensor (e.g., electrical or optical) or by manually sighting through a window of enclosure  100 . A series of initial blows from hammer  220 , while maintaining substantially continuous contact with the blade, sets the blade in motion, which may be continued by the force of a hydraulic ram. The operation can be continued until the blade is removed from wheel  215 . The turntable  210  then shifts the next blade into position and the process can be repeated until all blades are removed. 
     A single head apparatus has been described, but it is to be understood that a multiple head apparatus (e.g., an apparatus having two or more hammers) can be employed. In addition, any blade or airfoil in a compressor or turbine wheel may be removed or installed with the apparatus and method of the present invention. 
     Additionally, means (not shown in the Figures) may be provided for dispensing a penetrating lubricant, if so desired, to assist in freeing the blade from the dovetail. Such a penetrating lubricant could be provided from an outside source via umbilical and communicated through a nozzle. 
     While various embodiments are described herein, it will be appreciated from the specification that various combinations of elements, variations or improvements therein may be made, and are within the scope of the invention.