This invention is related to development of novel innovative methodology on reclaiming rear bearing support assembly of gas turbine engine.

Background of invention:

The typical Rear Bearing Support assembly is a major component of gas turbine engine integrated at the rear side of the engine. It supports two bearing, one for gas generator shaft & other for power turbine shaft through bearing housing, which also houses the power turbine nozzle guide vane & power turbine. Rear Bearing Support assembly consist of casting having two detailed components outer casing and inner bearing housing made up of super alloy, "WASPALLOY" which are welded together to form the assembly.

There are many cases of rejection of Rear Bearing Support assembly of gas turbine engine due to thermal cracks. These cracks are noticed during detailed inspection of gas turbine engine received at repair agencies for repair or overhaul. Due to high rejection of this component for thermal cracks and due to its sophisticated nature, lead time for procurement of this component is very high. Repair agencies have to wait for months together to carry out the repair and overhaul task, leading to delay in delivery of engines to the customers. Hence to avoid delay in delivery of engines and saving in terms of unit cost, a need arose to develop novel innovative methodology on reclaiming Rear Bearing Support assembly.

Summary of invention:

A novel method is introduced that comprises of the following features: The technology involves reclaiming of Rear Bearing Support assembly by removal of thermal cracks. It is observed that the Rear Bearing Support assembly is getting cracked at seam weldinig joining location of outer casing and inner bearing housing (refer Figure 1).

The innovative novel methodology on reclaiming the Rear Bearing Support assembly consist of identification of thermal crack zone, removal of material from thermal crack zone and rebuilding the material by welding. Crack test by non destructive dye penetrate method carried out to assess the reclaimed area. Exhaustive qualifications consist of structural and dynamic analysis has been carried out to assess the structural integrity and dynamic characteristic of the gas turbine engine under prevailing operating conditions. The basic design of the gas turbine engine has been kept undisturbed, with no additional weight / mass penalty. The life of the components is increased and the component is made available for reuse.

Objective of invention

1. Main objective is to design and develop a novel methodology on reclaiming the Rear Bearing Support assembly.

2. To develop novel methodology on reusing the defective components.

3. To make available components of gas turbine engine in due course, to meet production task in time without delay. As the repair agency has to wait till new component for replacement is available.

4. To innovate simple solution, where basic design of the gas turbine engine is kept undisturbed, with no additional weight/ mass penalty.

Detailed description of the invention

The innovative novel methodology on reclaiming the Rear Bearing Support assembly has been developed by carrying out number of trials on affected components. Test specimens were made from the actual Rear Bearing Support assembly to simulate the real conditions. Weld material details, welding parameter and pre & post heat treatment parameters are developed and set.

Based on the test specimen novel methodology is developed. Novel methodology on reclaiming the Rear Bearing Support assembly comprises of following procedure:

• Identification of thermal crack zone by non-destructive fluorescent dye penetrate test method to access the nature and depth of crack..

• Removal of material from thermal crack zone for weld preparation.

• Solutions treatment-heat at 1080°C for 4hrs.

• Carry out welding using WASPALLOY filler material as per details given below.

Method of Welding

Machine

Torch

Electrode

Tip Angle

Electrode Protrusion

Filler Wire

No.ofTracks

Tack Weld Current

Tack Diameter

Final Current

Argon Flow to torch Argon Flow to Back

Tig Manual (Butt) 350 Miller Synchrowave. WP-20

1/16" Thoriated Tungsten 45°

8-10 mm Waspalloy 4

35 Amps 2mm 40 Amps 15 litres/minute 10 litres/minute

Inspect the weld surface in such a way that the surface should be free from rough edges, beads and protrusions. If such features exist suitable polishing operation should be carried out. Carry out inspection by n on -destructive fluorescent dye penetrate test after weld to ensure proper Weld penetration.

Re-Solutioniseat 1080°C for 4hrs, Argon fan cool.

Stabilise-reheatat 845°C for 4 hrs, Argon fan cool.
 
Age harden - reheat at 760°C for 16hrs, Argon fan cool.

Carryout final visual inspection.
Figure 2 and Figure 3 shows the location of reclaimed Rear Bearing Support assembly.

Analysis carried out

N on-destructive Florescent dye penetration test carried out Pre and post welding operation. Validation of the reclaimed Rear Bearing Support assembly is carried out by exhaustive static and dynamic analysis by assembling the support assembly on engine and carrying out endurance performance run on gas turbine engine, under the prevailing conditions to assess the structural integrity of the assembly. The Rear Bearing Support assembly was disassembled after exhaustive engine test run and inspected for non-destructive Florescent dye penetration test and for detailed dimensional features and found satisfactory.

Claims

I claim

1. A Novel methodology has been invented reclaims/ salvage of rear bearing support assembly of gas turbine engine discarded for thermal cracks.

2. The method claimed in claim 1 has resulted in increasing the life of component, enormous saving and availability of major costly aerospace components required for completion of repair and overhaul task in time.

3. The method claimed in claim 1 has resulted in development of methodology useful for applying across the gas turbine spectrum on reclaiming similar major gas turbine engine components.