U/W Cutting and Welding Flashcards
(32 cards)
What are the 2 methods of U/W cutting being used?
Oxygen-Arc
Shielded Metal-Arc
Can the diver ever be in-between the ground and the electrode?
NO- diver must avoid becoming a-part of the electrical circuit
What is the only approved clamp for grounding work underwater?
C-type clamps
What are the 2 different types of electrodes used for Oxygen-Arc cutting?
- Steel-Tubular (manufactured by Arc-Air)
-Exothermic types (Arcair’s Sea-Jet and BROCO’s Ultrathermic)
- Exothermic (types like Arc-Air’s Sea Set & Broco’s Ultrathermic)
What current is used for U/W Cutting?
DC only
AC not authorized
What is the polarity set to for U/W Cutting?
Why is this method. prefered?
Straight. Polarity (electrode negative)
Preferred method because it cuts plain & Low Carbon steel easily
Can compressed air be substituted for O2 in U/W Cutting?
NO- Hydrocarbons can. contaminate the O2 regulator. and hoses with oil residue
For cutting underwater what shall the O2 purity be?
99.5%
*A one percent decrease in
oxygen purity will result with a 25 percent reduction in cutting speed.
What are the cutting amperage for both Arc-Air Steel Tubular electrodes?
Sea-Cut?
Tuff-Cote?
300-400 AMPS
What are the characteristics of. a steel tubular electrode?
- Steel tube with a water proofed flux coating
- 14 inches long
- 5/16 inch outer. diameter
- Bore diameter slightly less than 1/8. inch or 0.112” Bore
- 1 1/2” - 1 3/4” steel exposed
What purpose does flux coating serve for the steel tubular electrode?
- Promotes easy maintenance & storing of the rod
- It liberates gasses, thus forming a protective bubble. around the arc
- Serves as an electrical insulator protecting the diver in wet conditions
- prevents arcing from the side of the electrode when working in confined quarters
What are the advantages of steel-tubular electrodes?
- Simple cutting. technique
- Cut. metals 2 inch thick
- Neat, trim, narrow cuts are produced
- Within 400amp welder capacity
- There is less electrode waste because electrode must be in constant contact with metal being cut to sustain an arc
What are the disadvantages if the steel-tubular electrode?
- Burn time is short (approx 1 min per electrode)
- Narrow gap produced is difficult t o locate in poor vis
- Welding machine is required
- Higher amperage requirement deteriorates electrode holder more rapidly then exothermic process
The hand should never be closer than ___ iches from the electrode?
4 inches
Prior to beginning a cut how does the DV check oxygen flow
Purge for 20 seconds through the hose
6-inch stream of O2 u/w should be observed for the electrode tip
What do you do once the electrode has been consumed to within ___ inches?
3 inches
Call for switch off
Tap twice to make sure the current is off
Don’t operate the torch without what installed?
the flashback arrestor
What size inner diameter O2 hose is needed for cutting?
3/8 inch
Advantages of The Exothermic Electrode Cutting Process.
a. The cutting technique is very simple and readily mastered.
b. They will cut thin metal when the power is off.
c. Cutting is performed rapidly.
d. They will cut all ferrous and non-ferrous metals.
e. They are applicable to all metal thicknesses.
f. They will burn through concrete, rock, coral, marine growth and other non-conductive
materials when the power is off.
g. The power required is within the capability of a 200-ampere welding power source.
h. A 12-volt battery can be used as an ignition source.
Disadvantages of The Exothermic Electrode Cutting Process.
a. Larger volume of oxygen is required than with steel-tubular electrodes.
b. Burning time of the electrode is short; 45 to 55 seconds.
c. Contact with the work is not required to sustain ignition, thus electrode waste can occur.
When cutting with electrical power opposed to only oxygen what increase in cutting rate can be realized?
20% increase
The exothermic process develops tip-temperatures in excess of…
10,000 degrees
Will Kerie cable cut rock or concrete above or below the water line?
No
