Underwater Cutting

Question 1

What are the 2 methods of U/W Cutting being used?

Answer 1

Oxy-arc

Shielded Metal Arc

Question 2

What are two different types of electrodes used for Oxy-arc?

Answer 2

Steel-tubular (by Arc-air)

Exothermic (By Broco)

Question 3

What current is used for U/W Cutting?

Answer 3

DC, never AC.

Question 4

What polarity is used for U/W cutting? Why?

Answer 4

DC Straight polarity (electrode negative). Preferred because it cuts plain and low-carbon steel easily.

Question 5

How long is a Steel tubular electrode?

Answer 5

14 inches long.

Question 6

What is the outer diameter of a steel tubular electrode?

Answer 6

5/16 inch.

Question 7

What purpose does flux coating serve for the steel tubular electrode?

Answer 7

Promotes easy maintenance and storing
Liberates gasses, forming a protective bubble around the arc
Serves as an electrical insulator to protect the diver.
Prevents arcing.

Question 8

A diver is most at risk to severe shock if performing cutting/welding while only ______ in water.

Answer 8

partially immersed.

Question 9

The “_____” zone is the most hazardous.

Answer 9

Splash

Question 10

Gas produced by Cutting/Welding are rich in _____ and _____, and will explode if trapped and ignited.

Answer 10

Oxygen and hydrogen

Question 11

Oxygen cutting is only ____ percent efficient, resulting in _____ percent pure oxygen being released and potentially trapped.

Answer 11

60/40

Question 12

Hydroweld switch is Electrode (Negative/Positive) and Ground (Negative/Positive.)

Answer 12

Electrode Negative

Ground Positive.

Question 13

During U/W Cutting, the welder is set between _____ amps.

Answer 13

70-80 amps.

Question 14

Exothermic rods burn for how long?

Answer 14

Approx. 45 seconds.

Question 15

What is the standard for oxygen purity while cutting?

Answer 15

99.5% purity or greater. Commercially available should be 99.9%.

Question 16

A 1% less purity O2 results in ____% less effective cutting.

Answer 16

25%

Question 17

When the cutting electrode has been consumed within ___ inches, stop the cut and “Tap,Tap,Tap. Okay Red.”

Answer 17

3 inches.

Question 18

What type of knife switch may be used? What type is preferred?

Answer 18

Single/Dual pole. Dual is preferred.

Question 19

Welding/cutting lenses are required, what lense shade numbers are recommended?

Answer 19

10 & #12.

Question 20

Hand distance from electrode tip should be no less than ___”

Answer 20

4”

Question 21

Ultrathermic electrodes only require ___ amps

Answer 21

150.

Question 22

Cutting pressure is ____ psi over bottom pressure.

Answer 22

90psi.

Question 23

Prior to cutting, hold the oxygen trigger down for ____ seconds and ensure a ____” minimum stream of bubbles emerges from the electrode tip.

Answer 23

20 seconds, 6 inches.