Original Date: 10/18/1999
Revision Date: 01/18/2007
Information : Repair Scheme Development
Procurement of new turbine engines, engine modules, and components is very expensive. Orenda Turbines recognizes that it is more economical to repair a component, if possible, than to discard the defective part and replace it with a new component even when the repairs are not covered by existing instructions. Consequently, the development of new repair schemes has become a significant element in Orenda Turbines’ repair/overhaul philosophy and capability.
As engine components age over years of operation, unserviceable conditions will arise that are not covered by existing repair instructions. Therefore, new repair schemes must be developed which can produce a viable and cost- effective repair. At Orenda Turbines, this approach works best when the number of components requiring repair is fairly large. The typical scenario involves waiting until several components are rejected for the same unserviceable feature, which ensures that the first incident is not unique. Next, the defective component is reviewed by a group of experts, and a scheme is devised to repair the defect. Depending on the customer and the nature of the defect, it may be necessary to obtain authorization to proceed and validate the repairs on one or more of the rejected components. With approval and a plan of action, a repair scheme is developed to carry out the trial operation. Depending on the complexity of the repair, several trials may be required to achieve a viable repair scheme and a serviceable component. Most repairs are simple enough that proof testing is not necessary. Engineering principles dictate whether additional testing is required to validate the soundness of the repair.
Orenda Turbines has demonstrated its Repair Scheme Development capability on numerous engine components, typically at a fraction of the cost of buying a new component. Three examples include:
Combustion Liner Assembly The customer presented a repair scheme for its combustion liner assembly that was inadequate and lacking in detail and tooling. Orenda Turbines changed the scheme and redesigned the tooling, making it possible to repair the assembly for approximately 15% of the cost of a new part.
F404 Oil Tank Assembly This repair involved end-cap replacement which needed to meet stringent welding requirements for aluminum structures. Orenda Turbines introduced a backing ring that permitted the welding process to be conducted while maintaining the integrity of the weld and the affected components (Figure 2-1). The new techniques enabled the company to produce a repaired assembly for less than 5% of the cost of a new part.
Combustion Chamber Case This situation involved severe wear at the forward end where the outlet guide vane fits to the casing, thereby affecting the land and the groove. Orenda Turbines created repair activities for both components. The scheme was implemented with great success and is in place today, producing a repair cost of only 10% of the cost of a new part.
Figure 2-1. F404 Oil Tank Assembly
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