Hypertherm XPR170, Instruction Manual

Page: 223 / 438

Operation
6
XPR300 Instruction Manual 809480 223
Processes for special applications
Underwater cutting
Underwater cutting can suppress the acoustical noise, smoke, and glare that plasma cutting
produces. Underwater cutting also decreases the heat-affected zone on the workpiece. On mild
steel, it also decreases cutting speeds and produces a rougher cut edge with increased dross.

You can expect the acoustical noise levels to average less than 70
decibels for many processes during underwater cutting of metals that are
up to 75 mm (3 inches) below the water surface.
Make sure to satisfy the following conditions before you do underwater cutting:

Do not cut under water with fuel gases (H
2
-mix) or F5. An explosion can occur.

Do not cut non-ferrous alloys under water or on a water table, unless you have installed the
correct safety equipment from your table manufacturer or cutting machine supplier.

Consult with your cutting machine supplier, the table manufacturer, and other experts prior
to cutting non-ferrous alloys to implement a risk assessment and mitigation plan that
eliminates the risk of detonation by preventing hydrogen accumulation.

Do not cut a workpiece that is more than 75 mm (3 inches) below the surface of the water.
It can negatively affect cutting system performance.

Do not use True Hole
®
processes underwater. True Hole processes are not compatible with
underwater cutting.

True Hole cutting on a water table is possible only if the surface of the
water is lowered to at least 25 mm (1 inch)
below the bottom surface of
the workpiece. For information about True Hole processes, contact your
cutting machine supplier or regional Hypertherm Technical Service team.

Make sure that the torch is perpendicular (at a 90° angle) to the workpiece.
WARNING
UNDERWATER CUTTING CAN CAUSE AN EXPLOSION
Underwater cutting with fuel gases or underwater cutting of non-ferrous alloys can cause
an explosion.
• Do NOT cut under water with fuel gases (H
2
-mix) or F5.
• Do NOT cut non-ferrous alloys under water or on a water table, unless you can prevent the
accumulation of hydrogen gas.
Failure to remove accumulated hydrogen gas can result in an explosion during cutting
system operation.