Preliminary Requirements

Safety Requirements

WARNING

IT IS THE RESPONSIBILITY OF THE OPERATOR TO OBTAIN AND OBSERVE THE MANUFACTURERS MATERIAL SAFETY DATA SHEETS FOR CONSUMABLE MATERIALS INFORMATION SUCH AS, HAZARDOUS INGREDIENTS, PHYSICAL/CHEMICAL CHARACTERISTICS, FIRE, EXPLOSION, REACTIVITY, HEALTH HAZARD DATA, PRECAUTIONS FOR SAFE HANDLNG, USE AND CONTROL MEASURES AND ALSO TO TAKE LOCAL REGULATIONS IN TO CONSIDERATION.

Procedure

1. SUBTASK 70-53-03-440-001 procedure

   1. General Precautions.

      1. Wear a clean pair of gloves, made of lint-free material, when handling bearings.

      2. When you assemble inner races of bearings on their mating shafts, expand the inner race with controlled heating.

         1. The inner race of demountable bearings and complete bearing assenbly of nondemountable bearings can be raised to the necessary temperature by immersion in a controlled hot oil bath or with an oven or induction heater.

         2. Check shafts and bearing races for size and trueness before heating to prevent abnormal fits.

      3. It is important to keep the area clean regardless of whether you use a hot oli bath, an oven, or an induction heater.

         1. HOT OIL BATH.

            1. This used to be the typical heating method for bearings and other parts because of the anti-corrosion characteristics of oil. There are now environmental and safety concerns which make other methods a better choice.

            2. Be sure to put a cover on the tank to minimize contamination of the oil by airborn dirt and abrasives. It is important to change the oil and clean the tank regularly as necessary.

            3. Do not permit bearings to rest on the bottom of the tank because the settlings can cause contamination and the bearing temperature will be much greater than the indicated oil temperature. A heavy screen or series of rods that extend at least 3 inches (76.2 mm) above the tank bottom will keep the bearings surrounded by oil at an equal temperature and will permit any dirt to settle to the bottom of the tank.

            4. The hot oil bath of CoMat 10-077 APPROVED ENGINE OILS temperature must not be more than 250 deg F (121 deg C) unless specified differently in the Engine Manual.

         2. OVEN.

            1. An oven may not increase the temperature the temperature of the part as fast as an induction heater, but there is less potential to increase the temperature of the part too much. An oven gives an equal amount of heat to large or complex parts and thus minimizes distortion and thermal stress.

            2. A film of oil must be on each part before it goes into the oven. Oil prevents corrosion before, during, and after assembly.

            3. The oven temperature must not be more than 250 deg F (121 deg C) unless specified differently in the Engine Manual.

         3. INDUCTION HEATER.

            1. An induction heater increases the temperature of a part quickly and does not have the environmental concerns of the hot oil bath, but to know how to get the correct temperature takes experience. Be sure to follow the manufacturer's warnings and cautions.

            2. IAE has induction heater experience with units (Models TIH 020, TIH 050, TIH 100 and TIH 120) supplied by SKF Industries, units (Models 1x and 4x) supplied by Eddytherm and units (Foucault 22 ESD swingarm (PWA 89127)) by Foucault International Corporation. This equipment (or use units with equivalent features and safeguards) is available from the sources that follow:

               C4298

               75957

               2M749

               IAE442

            3. IAE has confirmed that magetism can be induced by induction heaters. IAE has had negative experience with trapping contamination in a non-separable ball bearing due to remaining magnetism. Therefore, after induction heating, be sure to examine bearings for any remaining magnetism (Ref. the SPM TASK 70-11-22-300-503). Limits for remaining magnetism are plus or minus 3 gauss.

            4. There frequently is a degaussing feature built into the induction heater, but it may be inoperative (no indicating device to define if or when the degausser is functional or if degausser is indeed present).

            5. Excessive remaining magnetism is undesirable because magnetism can attract unwanted particles which can cause wear and surface distress in bearings and similar critical components.

            6. A film of oil must be on each part before the induction heater is used to increase the temperature of the part. Oil prevents corrosion before, during, and after assembly.

            7. Bearing temperatures must not be more than 250 deg. F (121 deg. C) unless specified differently in the Engine Manual. Be sure to wear insulated, clean, lint-free gloves when you touch heated bearings.

      4. Before installing main bearings, wipe excess oil from journals with a clean lint-free cloth or paper wiper and apply a thin film of CoMat 05-063 DRY FILM LUBRICANT. Force must not be used in assembly of parts; if there is any difficulty, disassemble parts and inspect them for burrs or other interference.

      5. When a roller bearing is installed, rotate rollers with respect to outer race. This will reduce possibility of hang up of rollers and will also increase sensitivity of detection of hang up.

      6. When it is necessary to hold roller bearings in place, apply a minimum amount of CoMat 10-041 PETROLATUM, WHITE to rollers immediately before assembly. Position rollers radially inward against inner race, where they will be held by the petrolatum during assembly.

      7. Manufacturer's number on bearing races must face the operator, as bearing is installed, unless otherwise specified in procedural text.

      8. Large spannernuts used to secure main bearings or seals to shafts and housings frequently have small burrs at spanner slots which, if installed in reversed position, scar faces of bearings or seals. Spannernuts found in this condition must be deburred.

      9. Remove or protect prepacked bearings when washing assembly where such bearings are used.

   2. Selective Fit of Main Shaft Bearings.

      1. Bearings that meet all requirements of bearing inspection sections of Overhaul Manuals except ID or OD dimensions may be used by selective fit of mating parts within engine to achieve clearance index limits.