Page 178 - Machinery Component Maintenance

160 Machinery Component Maintenance and Repair

(c) After rinsing with water in step six, immerse piping in a hot
phosphoric bath. The suggested concentration is three to six
ounces of iron phosphate per gallon of water, heated to 160-
170°F, with pH range of 4.2 to 4.8. The immersion time is three
to five minutes or longer, depending on density of coating re-
quired. Remove and dry thoroughly, blowing out with hot air.

CAUTION: Hydrochloric acid in contact with the skin can cause
burns. If contacted, acid should be washed off im-
mediately with water. Also, if indoors, adequate
ventilation, including a vent hood, should be used.
When mixing the solution, always add the acid to
the water, never the water to the acid.

On large piping (where a man can work inside), the pickling procedure
can be omitted if the piping is cleaned mechanically with a wire brush,
vacuumed and then thoroughly inspected for cleanliness. Time and trou-
ble taken in the beginning to insure that the piping is clean will shorten
the break-in period, and may save a number of expensive shut downs.

Temporary Line Filters

When first starting, it is advisable to use a temporary line filter in the
intake line near the compressor to catch any dirt, chips, or other foreign
material that may have been left in the pipe. But clean the pipe first. Do
not depend on a temporary line filter. If the gas or air being compressed
may, at times, contain dust, sand, or other abrasive particles, a gas scrub-
ber or air cleaner must be installed permanently and serviced regularly.
Even though the previous cleaning procedure has been carefully fol-
lowed on the compressor piping, a temporary filter (such as Type PT
American Filter or equal) should be installed in the suction line to the
suction bottle to remove particles 230 microns (0.009 in.) in diameter or
larger. If the compressor is an "NL" (nonlubricated) design, the filter
should be designed to remove particles 140 microns (0.0055 in.) in diam-
eter or larger. Provision must be made in the piping to check the pressure
drop across the filter and to remove the filter cell for cleaning. If the
pressure drop across the filter exceeds 5 percent of the upstream line
pressure, remove the filter, clean thoroughly and reinstall. The filter cell
should be removed and left out only when the inlet line is free of welding
beads, pipe scale, and other extraneous matter.