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Publication Date: 2014-Sep-03
Document File: 8 page(s) / 1M

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The invention proposes a stakeless patch ring design. The patch ring is designed such that the patch ring fits on rotor centering feature rabbet and a locking mechanism helps the ring remain in its location during operation. The technique enables self-retention capability of patch ring for rabbet repairs on rotor for both male and female rabbets.

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The present invention relates generally to a gas turbine and more particularly to a technique to repair gas turbine rabbet.

In general, compressor rotors of gas turbines have independent wheels which are mounted with blades and buckets. The independent wheels are aligned and centered together using a centering feature called rabbets. Rotor discs are assembled together using these rabbet features by means of positive interference. The rotor disc experiences high rotational speed and axial growth during operational conditions. Such high rotational speed and axial growth is due to high thermal gradients which results in wear out of rabbet and loosened interference fit of rabbet. Due to interference loss, rabbets slide axially on top of each other resulting in damage of rabbet surfaces. The damage is sometimes of a considerable order. Similar kinds of scenario are observed in rotors of gas turbines which are operated for long duration of time and in case wheels are disassembled.

Conventionally, the rabbet surfaces are restored by providing coating or installing a patch ring which helps rotor to achieve interference fit. Patch rings are axially retained using 2-4 stakes spread circumferentially. However, the stakes are not enough to axially retain the patch ring during operation and disassembly.

Generally, there is a loss of external staking because of which there is a risk of axial movement of patch ring which results in vibration issues. Also, in case of rabbet repair on FSS and turbine shaft which mates with couplings, patch ring slides off from the rabbet when the couplings are disassembled at site.

Figure 1 depicts field issues with the conventional design.

Figure 1

As depicted in the above figure, the patch rings repair is used for rabbets on compressor wheels, FSS, MJ and shafts which are connected to couplings on site. Staking is not enough to axially retain patch ring during operation and disassembly. Staking is not an elegant way of retention. Mating rabbet is scored due to axial movement of the patch ring.

A conventional technique uses diaphragm patch rings for rotary machines. The technique assembles a diaphragm assembly by configuring a diaphragm bore portion to receive the diaphragm patch ring. The technique forms a diaphragm patch member sub-assembly by coupling the diaphragm patch ring to the configured diaphragm bore portion.

Another conventional technique relates to a bearing support assembly which transmits vibration force from the rotor assembly to the support structure.

However, the above mentioned techniques do not provide means for repairing rabbet.

Therefore there is a need in the art to provide a technique that provides positive retention mechanism for patch ring for rabbet repair.


Figure 1 depicts field issues with the conventional design.

Figure 2 depicts the proposed stakeless patch ring design.

Figure 3 depicts to the idea applied to a comp...