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20 Cards in this Set

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  • Back
When under water welding how does the diver avoid becoming part of the electrical circuit?
By positioning the ground in relation to the diver so that at no time does the diver or his equipment get between the ground and the electrode.
Why do you never use AC current for underwater cutting or welding?
Electrical shock produced by AC current prevents voluntary
relaxation of the muscles controlling the hand. Consequently, the diver may be unable to let go if his body or equipment accidentally enters the electrical circuit.
No habitat welding will be performed in an air environment at depths greater than ___ FSW?
Why
- 60 FSW
- Oxygen partial pressure increases with water depth, thereby creating a fire hazard in habitat environments.
Habitats shall be filled with an inert gas at depths greater
than 60 FSW.
60 FSW
Why is very high strength steels, like HY-80, are not recommended for wet welding
Because of cracking problems stemming from the intense heat produced by the welding process followed by rapid cooling of the weld metal by the ambient water.
What is a Tong Test Ammeter?
The tong test ammeter is a portable instrument that will
quickly measure current flowing in a circuit without making electrical connections. It is used to check the amperage.
Wha is a Tong Test Ammeter used for?
use while setting-up and during electric underwater cutting and welding operations.
How long should the "leg" be on a fillet weld up to 3/8 inch thick? Greater than 3/8 inch?
A fillet weld should have a leg length equal to the plate thickness up to 3/8-inch plate.
For plate thicknesses 3/8-inch and greater, a minimum of 3/8-inch leg length is required on all wet welds.
When wet welding what Electrode Polarity is used?
Wet welding Electrode Polarity is usually conducted using STRAIGHT POLARITY, sometimes referred to as DC ELECTRODE NEGATIVE,
Why is DC ELECTRODE NEGATIVE used when wet welding?
DC ELECTRODE NEGATIVE results in longer life of the electrode holder.
What type of gloves are used for wet welding?
Thick, gauntlet-type rubber gloves worn over a pair of playtex-type gloves afford the best protection against electrical shock. They should be secured at the wrist
to prevent slag from getting inside the glove.
True or False? When wet welding in cold water, wetsuit gloves in good condition, worn over surgical gloves can be used?
True.
Name conditions adverse to underwater welding.
a. Diving apparel
b. Where a steady platform cannot be provided from which to weld.
c. Adverse currents,
d. Low temperature,
e. Where the metal thickness is less than 0.20 inch.
f. Where the fit-up is poor. A 1/8-inch gap should be considered the maximum permissible for a quality wet weld
g. As the depth increases, due to the increase in hydrostatic pressure.
h. Where the visibility is extremely low and the diver has no groove to follow.
Name the three types of underwater welding?
Cofferdams and caissons
Mini-habitat welding
Shielded metal arc welding
What are the two basic techniques used today in shielded metal arc wet welding?
Self-consuming technique and the manipulative or weave technique.
What clamp should be used as the grounding clamp for underwater cutting or welding operations?
For diver safety, only C-type clamps should be used as grounding clamps for underwater cutting or welding operations.
Where is a dvier at most risk for severe electrical shock. completly submerged or paritaly submerged (in the splash zone)?
A diver is at risk to severe electrical shock when performing a cutting or welding operation while only partially immersed in water. Hence, the splash zone is the most hazardous location in which a diver can be placed.
What are the dangers of gases produced by underwater cutting and welding?
Gases produced by underwater cutting are rich in oxygen and hydrogen and will explode if trapped and ignited.
How does the underwater cutting and welding processes generate explosive gases?
When cutting or welding, hydrogen and oxygen are dissociated from the water and will travel separately as bubbles. These bubbles can collect in a trapped or confined space overhead. As the hydrogen and oxygen gases combine they will ignite, causing a popping sound.
What size welding cables are used for underwater cutting and welding? What is the exception?
Use only welding cables that are a minimum of 2/0 extra flexible. An exception is the
electrode holder lead, which can be 1/0. The 1/0 lead is more flexible and will aid the
diver in maneuvering the electrode holder.