Tweco PC250 - Manual (Page 5)

5
FIRE OR EXPLOSION CAN CAUSE DEATH, INJURY AND PROPERTY DAMAGE! Fire and
explosion can be caused by hot slag, sparks, or the plasma arc. Be sure there is no combustible or flam-
mable material in the workplace. Any material that cannot be removed must be protected. Ventilate all
flammable or explosive vapors from the workplace. Do not cut or weld on containers that may have
held combustibles. Provide a fire watch when working in an area where fire hazards may exist.
Hydrogen gas may be formed and trapped under aluminum workpieces when they are cut underwater
or while using a water table. DO NOT cut aluminum alloys underwater or on a water table unless the
hydrogen gas can be eliminated or dissipated. Trapped hydrogen gas that is ignited will cause an explo-
sion. Remember, cutting by nature produces sparks, hot spatter, molten metal drops, hot slag and
hot metal parts that can start fires, burn skin and damage eyes.
ARC RAYS CAN INJURE EYES AND BURN SKIN! Plasma Arc Rays can injure your eyes and
burn your skin. The plasma arc process produces very bright ultra violet and infra red light. These arc
rays will damage your eyes and burn your skin if you are not properly protected. To protect your eyes,
always wear a welding helmet or shield. Also always wear safety glasses with side shields, goggles or
other protective eye wear. Wear welding gloves and suitable clothing to protect your skin from the arc
rays and sparks. Keep helmet and safety glasses in good condition. Replace lenses when cracked,
chipped or dirty. Protect others in the work area from the arc rays. Use protective booths, screens or
shields.
Use the shade of lens as suggested in the following per ANSI/ASC Z49.1:
Minimum Protective Suggested
Arc Current Shade No. Shade No.
Less Than 300* 8 9
300 - 400* 9 12
400 - 800* 10 14 *
* These values apply where the actual arc is clearly seen. Experience has shown that lighter filters
may be used when the arc is hidden by the workpiece.