Cleaning with compressed air

Improper or playful use of the high-pressure hose may cause severe injury to internal organs and eardrums. Never allow compressed air to contact or enter anyone's body. Always use proper safety equipment such as face masks and goggles.

Cleaning with compressed air is the least acceptable method of removing loose foreign material. This method is used to remove dry, loose foreign particles and dust from inaccessible locations. Use clean, dry air not over 30 psi. High-pressure air is at a pressure of 30 psi or greater.

Cleaning with hot water or steam and cleaning compounds

Hot water or steam methods can be used to remove residue of seawater as well as dirt, grease, or oil. NSTM Chapter 300 lists three types of  authorized cleaning compounds: cleaning compound P-D-220, powdered salt water soap, or steam cleaning compound.

The hot water method uses heated fresh water and approved cleaning compounds in a hot water wash tank equipped with a means of heating and circulating the liquid. The temperature of the liquid should be maintained at 194^oF (90^oC) by use of steam or electric heaters.

Place the stator in the tank in the position that allows for maximum circulation of the liquid through the stator bore. When using an installed agitator tank, lift the cover and begin filling the tank with water. When the water level is satisfactory, cut in the steam or electric heaters to bring the water up to temperature. Raise the basket using the compressed air provided and place the parts to be washed on the screen. The stator bore should be in the vertical position to receive the most agitation and cleaning effect. It may have to be rotated 180 degrees during the cleaning process. Add the proper amount of cleaning agent (see NSTM Chapter 300), lower the basket, shut the cover, and start the agitation.

After washing, the parts must be flushed with clean, fresh water in the same manner. A sample of the rinse water draining from the stator should be collected and checked for salinity to determine if the cleaning process is complete.

Insulated gloves must be worn when steam cleaning to protect the operator from being burned or scalded.

Take care to keep live steam from being directly applied to windings. The temperature of the solutions at the windings should not exceed 194^o F (90^o C). The compressed air pressure should not exceed 30 lb/in^2.

For steam cleaning, the mixture of water and compound is heated in a boiler and a hose and nozzle are used to direct the steam at the windings.

Thoroughly flush the stator with fresh water upon completion of hot water or steam methods of cleaning to remove all traces of cleaning agents prior to drying and testing.

Cleaning with Type 2 cleaning solvent

Type 2 dry cleaning solvent is highly flammable. Its use requires the strictest observance of all safety precautions pertaining to open flames, smoking, or spark producing activity. Use only in a well-ventilated environment. Ensure that solvent containers are tightly sealed any time they are not in use.

Type 2 dry cleaning solvent is the only solvent authorized for cleaning electrical insulation. The solvent's cleaning efficiency, as well as the ill effects to personnel, are less than the chlorinated solvents.

Never spray solvent because it may form into pools and damage the insulation.

Use a clean, lint-free cloth to apply the solvent to a small area of the stator windings. Examine the area to determine if any adverse effects have occurred. Continue to wipe the windings if no adverse effects are noted. Wipe dry with another clean, lint-free cloth. Repeat the wiping and drying steps as necessary.

Motor drying and testing

This process is necessary to ensure that all of the water has evaporated from the stator prior to raising the temperature above the boiling point of water (212^oF).

Place the winding in a cool air circulating oven. Set the temperature control to 200^oF (93^oC). Allow the temperature of the winding to reach 200^o F ± 10^oF. Maintain that temperature for 2 hours, then set the oven temperature to 220^oF (104^oC).

Allow the windings and the oven to reach 220^oF ± 10^oF (104^oC ± 6^oC), and maintain this temperature for 4 to 6 hours.

Remove the windings from the oven and let them cool to room temperature.

Conduct a phase resistance balance test. Record the results. Rewind the motor if unsatisfactory test results are obtained.

Measure insulation resistance with a megohmmeter. Record the results. If the reading is less than 25 megohms, the stator must be rewound.

Varnish should only be applied when it serves a purpose. Unnecessary application of varnish can result in a heavy layer of buildup that interferes with heat dissipation and causes surface cracking.

If the reading is 26 megohms or greater, dip and bake the stator. For procedures, refer to the lesson on testing and varnishing rewound motors. Conduct a polarization index test. Conduct a dc high-potential test. Conduct required tests after dipping and baking: JQR 251.03 Megger; JQR 251.38 Measuring System, Precision Resistance; and JQR 251.31 Tester, Surge, Portable. Reassemble the motor, conduct operational tests, and return the motor to service if all tests are satisfactory.