Winco MD6L - Manual (Page 10)

60706-121 PAGE 8
method is the most practical for removing loose, dry
particles because it does not redeposit them on other
parts of the equipment as is done when compressed air
is used. Also, a vacuum cleaner is capable of removing
dust from coils and from grooves between wires that is
otherwise inaccessible to a wipe cloth.
Substances such as grease and oil can best be
removed by wiping whenever possible with a cloth or a
brush, and flushing inaccessible windings and other
areas with a minimum volume of trichloroethane*
solvent. Flush windings with trichloroethane beginning
at the top or 12 o’clock position and proceeding to the
bottom or 6 o’clock position, on either side. After
cleaning and drying (which is rapid with trichlo-
roethane), take megger readings to determine whether
resistance has increased to above the acceptable 200
megohm level. If resistance is still low, clean the
affected areas again.
*WARNING: PERSONAL DANGER
The explosive and fire hazards of trichloroethane are
negligible and it has the least toxic effect of all the
chlorinated hydrocarbons; however, avoid prolonged
skin contact with the solvent and perform cleaning
operations in a well ventilated area. If the solvent is
splashed on the skin, wash off with soap and water. If
splashed into the eyes, flush with water and get medical
help. Avoid prolonged breathing of fumes.
4. Drying insulation - It is sometimes necessary
to dry insulation in order to recondition electrical
equipment that has been submerged or splashed with
water. It may also be necessary to dry equipment that
has absorbed moisture from the air after standing idle
for an extended period of time.
Heat and circulation of dry air, or the application of a
vacuum, is required in order to effectively remove
moisture from insulation. Heat may be provided by
either of 2 methods or a combination of both.
a) By external application of heat.
b) By circulation of electrical current at low
voltage through the conductors.
The best method to use on a specific case depends
upon local conditions and the facilities/equipment
available. Do not use the second method until after
insulation has been partially dried by the first method.
Regardless of heating method used, keep a close
check on temperature of the insulation. This can be
done by means of temperature detectors, either
permanently or temporarily installed, or by thermom-
eters so placed that they can be easily read at the
(297k) ambient temperature and moisture is suspected,
dry the insulation as described later in this section.
Note: Measurement of insulation resistance is an
important part of an adequate program for the mainte-
nance of electric equipment. The measured values of
insulation resistance serve as a useful guide in deter-
mining whether or not insulation is defective. Drying,
revarnishing, or overhauling may be necessary to
prevent failure.
a) Check windings, connections, load
cables, and other components for
excessive dirt and grime. Clean if
applicable.
b) Make sure all mounting bolts have
been installed and are tight. Refer to
applicable portions of the text for
torque specifications.
c) Make certain no foreign objects are
lodged in the generator. Remove all
tools and shop clothes from the
vicinity of the Generator Set.
d) Be sure that all covers and guards
are reinstalled.
3. Cleaning - Cleanliness is of primary importance
in preventive maintenance. Do not allow dust, moisture,
oil, or other substances to remain in or on the equip-
ment. The importance of keeping all insulation clean
cannot be over emphasized. Dust, dirt and other foreign
materials tend to block ventilating ducts and retard
dissipation of heat, which in turn, leads to local over-
heating. If the particles are allowed to build up, the
windings may eventually be short circuited or grounded.
Abrasive particles may puncture insulation. Iron dust is
especially harmful because the particles are continually
agitated by magnetic pulsations. For these reasons,
equipment must be kept clean, both externally and
internally, and particularly, all air ducts must be kept
clean and unobstructed.
There are four (4) acceptable methods of cleaning
insulation associated with electrical equipment:
a) Clean with a vacuum cleaner with
suitable plastic attachments.
b)
Wipe clean with a cloth.
c) Blow off with direct stream of filtered,
oilless low pressure compressed air.
d)
Clean with solvent and soft bristle
brush.
Of the methods listed above, the vacuum cleaner