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5.2 Exterior Cleaning
The Gauge is going to get soiled during use. While this causes no harm,
removing loose material at the end of each working day will prolong the
cosmetic appearance.
Occasionally it would help if the exterior were cleaned with an industrial
grade detergent and water. Heavy scrubbing may damage the finish on
labels but will not harm the other materials.
The source rod and index rod may be sprayed with silicon ok and the excess
wiped off with a cloth. The source rod is 440C stainless steel and while
no pitting can occur, surface rust may form initially due to iron molecules
brought to the surface by heat-treating. Light rubbing with an abrasive will
remove it and after several times, it will no longer occur.
Cleaning the top seal around the source rod will aid in preventing soil from
working into the bearing, which is located below the seal.
5.3 Sliding Shield Cavity
A sliding shield of tungsten covers the gamma source when it is retracted
to the “SAFE” condition. After prolonged use, the small amount of soil
carried into the cavity with each retraction will accumulate in this cavity. If
not periodically cleaned, the abrasion from the soil will increase the force
required to push the rod out and could cause jamming of the shield which
will result in faulty STANDARD COUNT repeatability. Ultimately the soil will
damage the seals between the cavity and the bearing.
The bottom plate, which contains a scraper ring to remove soil from the rod
when it is retracted, can be removed by using a hex key to take out the two
screws. Lay the Gauge on its side or end with the bottom pointed away from
personnel and the rod in the “SAFE” position to prevent exposure from
the source. Remove the screws and pull the plate away from the base. The
sliding shield is held in place by a spring. Be careful not to let the spring fly
off when removing the shield
Clean the parts with a damp cloth and clean the cavity with a stiff brush.
Finally spray the parts and cavity with dry silicon spray.
The cavity, and bottom plate are impregnated with Teflon and do not require
extensive lubrication. If excessive wear has occurred to the bottom plate and
scraper ring, they may need to be replaced.
Push the spring into the hole in the sliding shield and replace it in the cavity
with the sloping side towards source and the spring compressed against the
end of the cavity. If the sliding shield does not fully close it may be necessary
to stretch / replace the spring. Replace the plate and screws being certain
that they are tight and the heads of the screws do not extend above the
surface of the plate.
