4-68. PURGING TANK (Con't).
c. STEAM CLEAN PURGING (PREFERRED METHOD)
DO NOT perform purging operations in an electrical storm or if a storm is
threatening. Keep open flames or other sources of ignition, such as
welding and cutting torches and ordinary electrical equipment, away
from area where purging operation is in progress. Sufficient fire extin-
guishers must be present and manned. Failure to follow this warning will
result in serious injury or death to personnel.
Connect bonding and grounding connection before beginning purging
operations. Maintain bonding and grounding connection until after all
purging is completed. DO NOT connect semitrailer grounding cable to
semitrailer grounding stud. Connections must be made to clean, un-
painted surfaces. An unbonded and ungrounded or improperly bonded
and grounded semitrailer could produce a spark. The resulting explosion
will cause serious injury or death to personnel.
Personnel engaged in purging operations must not wear wool, nylon,
silk, rayon, or other clothing that generates static electricity. Wear clean
cotton clothing with no metal zippers. Remove all contents from pock-
ets. Wear rubber boots and gloves to keep fuel off skin. Use cotton
cloths for cleaning purposes. Before climbing onto semitrailer, grasp
static ground wire to discharge all static from body.
Give IMMEDIATE medical attention to personnel exposed to hydrocarbon
or toxic vapors. Signs of distress are weakness, nausea, coughing or
intoxication, nosebleed or cramps, or other unusual symptoms. Quali-
fied personnel able to administer artificial respiration and simple first aid
must be present.
Should an emergency arise requiring entry into a tank which is not vapor-
free, or which has an oxygen content less than 19.5%, personnel enter-
ing must have an attached lifeline and wear protective respiratory equip-
ment in the form of self-contained breathing apparatus or a full
facepiece mask with a pressure supply of breathable air. Another per-
son, also provided with respiratory equipment, MUST be stationed at
manhole opening and remain there with full ability to watch personnel
inside tank and summon assistance in the event a rescue operation is
needed. Personnel MUST NOT enter a tank which is in the explosive
If semitrailer is left overnight after purging procedure, retest with com-
bustible gas indicator set to ensure a SAFE reading. Tanks may recharge
themselves with seepage of undetected pockets of vapors. Failure to
follow this warning may result in serious injury or death to personnel.
(1) Ground semitrailer to steam cleaner. Ensure that semitrailer bonding and grounding