Figure 10-63.  Combustion case inspection.  Cleaning the hot section is not usually necessary for a repair  in the field, but in areas of high salt water or other chemicals  a turbine rinse should be accomplished.  Engine parts can be degreased by using the emulsion-type  cleaners or chlorinated solvents. The emulsion-type cleaners  are safe for all metals, since they are neutral and noncorrosive.  Cleaning parts by the chlorinated solvent method leaves the  parts absolutely dry. If they are not to be subjected to further  cleaning operations, they should be sprayed with a corrosion- preventive solution to protect them against rust or corrosion. The hot section, which generally includes the combustion  section and turbine sections, normally require inspections at  regular intervals. The extent of disassembly of the engine to  accomplish this inspection varies from different engine types.  Most engines require that the combustion case be open for  the inspection of the hot section. However, in performing this  disassembly, numerous associated parts are readily accessible  for inspection. The importance of properly supporting the  engine and the parts being removed cannot be overstressed.  The alignment of components being removed and installed  is also of the utmost importance. After all the inspections  and repairs are made, the manufacturer’s detailed assembly  instructions should be followed. These instructions are  important in efficient engine maintenance, and the ultimate  life and performance of the engine. Extreme care must be  taken during assembly to prevent dirt, dust, cotter pins, lock  wire, nuts, washers, or other foreign material from entering  the engine.  Certain materials may be used for temporary marking during  assembly and disassembly. Always refer to manufacturer’s  information for marking parts. Layout dye (lightly applied) or  chalk may be used to mark parts that are directly exposed to  the engine’s gas path, such as turbine blades and disks, turbine  Parts may be found where localized areas have been heated  to an extent to buckle small portions of the chamber. Such  parts are considered acceptable if the burning of the part  has not progressed into an adjacent welded area, or to such  After long periods of engine operation, the external surfaces  of the combustion chamber liner location pads often show  signs of fretting. This is acceptable, provided no resultant  cracks or perforation of the metal is apparent. Any cover  or chamber inadvertently dropped on a hard surface or  mishandled should be thoroughly inspected for minute  cracks that may elongate over a period of time and then open,  creating a hazard. Combustion chambers should be replaced or repaired if two  cracks are progressing from a free edge so that their meeting  is imminent and could allow a piece of metal that could  cause turbine damage to break loose. Separate cracks in  the baffle are acceptable. Cracks in the cone are rare but, at  any location on this component, is cause for rejection of the  liner. Cracks in the swirl vanes are cause for rejection of the  liner. Loose swirl vanes may be repaired by silver brazing.  Cracks in the front liner emanating from the air holes are  acceptable, provided they do not exceed allowable limits.  If such cracks fork or link with others, the liner must be  repaired. If two cracks originating from the same air hole are  diametrically opposite, the liner is acceptable. Radial cracks  extending from the interconnector and spark igniter boss  are acceptable, if they do not exceed allowable limits and if  such cracks do not fork or link with others. Circumferential  cracks around the boss pads should be repaired prior to re-use  of the liner. Baffle cracks connecting more than two holes  should be repaired. Inspect the combustion chambers and covers for cracks by  using visible dye or fluorescent penetrant inspection method.  Any cracks, nicks, or dents are usually cause for rejecting the  component. Inspect the covers, noting particularly the area  around the fuel drain bosses for any pits or corrosion. When  repairing the combustion chamber liner, the procedures given  in the appropriate engine manufacturer’s overhaul instruction  manual should be followed. If there is doubt that the liner is  serviceable, it should be replaced. vanes, and combustion chamber liners. A wax marking pencil  may be used for parts that are not directly exposed to the gas  path. Do not use a wax marking pencil on a liner surface or  a turbine rotor. The use of carbon alloy or metallic pencils  is not recommended because of the possibility of causing  intergranular corrosion attack, that could result in a reduction  in material strength and cracking. Inspection and Repair of Combustion Chambers  Marking Materials for Combustion Section Parts 10-50