Gas Turbine: Measurment, Defectation And Repairing

Inraduction. Measurment. Diagnosing the rotors unbalancing. Diagnosing of shafts misaligment. Maintenance classification. Corrective maintenance. Frequency of maintenance. Tipical maintenance procedures. Repair procedures. Conclusion. Reference.

In simplest terms, preventive maintenance can be defined as that maintenance performed on a gas turbine engine to allow the engine to meet all operating requirements during its life cycle. Ideally, preventive maintenance eliminates unscheduled engine repairs; practically, however, it minimizes the amount and degree of engine repairs.

Preventive maintenance can be as simple as changing of a lube oil or fuel oil filter, or as complex as a complete engine overhaul. For all U. S. Naval marine gas turbines, a three-level concept of preventive maintenance has been adopted. Those three concepts are (a) organizational, (b) intermediate, and (c) depot.

Organizational maintenance (also called shipboard maintenance) is that maintenance which is done on a gas turbine engine in its installed configuration, and is performed by ship's personnel. The maintenance is normally limited to external parts of the engine with the exception of internal combustion section inspections. With the organizational maintenance concept, all external engine accessories, such as fuel pump, fuel control, starting system, and exhaust thermocouple harness, can be removed or replaced. In addition, certain internal combustion section components can be removed and replaced. Those replacement components are normally limited to combustion burner cans, fuel nozzles, fuel nozzle manifold assemblies, and nozzle guide vanes or nozzle guide vane assemblies. With certain configured engines, removal of first-stage turbine blades is also possible. Intermediate level maintenance is that maintenance performed on an engine which, due to the type or quantity of maintenance action required, must be removed from the ship. The removal of either the power turbine portion or gas generator portion (or both) is included in this concept.

The removal and replacement of all main engine bearings is included in this concept. A complete operational check of the rebuilt gas turbine to ensure that the engine is functioning normally is the final phase in the intermediate maintenance level concept. The check of the rebuilt gas turbine is limited to operation of the gas generator only, due to the absence of a load absorbing capability at heavy maintenance bases. The back pressure imparted by the power turbine on the gas generator is simulated by means of a calibrated exhaust nozzle on the gas generator.

Depot level is that maintenance which is performed on the gas turbine engine by a shore side overhaul activity. Overhaul includes complete disassembly, inspection, repair and reassembly of all engine assemblies, subassemblies, and accessories. The engine is disassembled down to the last nut and bolt. For bearings, this includes disassembly of the inner and outer races and all balls and rollers.