CWS Welding Equipment & Maintenance — Questions and Answers

Question 1: Which power source output characteristic is normally used for SMAW?

Pulsed constant voltage only
Constant voltage (flat)
Rising voltage
Constant current (drooping) (Correct answer)

Correct answer: Constant current (drooping)

SMAW uses constant current so amperage stays fairly stable as the welder's arc length changes.

Question 2: A power source is rated at 300 A at a 60% duty cycle. What does this mean?

It delivers 180 A continuously
It runs at 60% efficiency at 300 A
It can weld at 300 A for 6 minutes out of every 10 minutes (Correct answer)
It can weld at 300 A for 60 minutes per hour without rest

Correct answer: It can weld at 300 A for 6 minutes out of every 10 minutes

Duty cycle is the percentage of a 10-minute period a machine can run at rated output without overheating.

Question 3: A machine is rated 200 A at 60% duty cycle. About what duty cycle is allowed at 150 A?

About 45%
About 80%
About 60%
About 100% (Correct answer)

Correct answer: About 100%

Allowable duty cycle = (rated A / actual A)² × rated duty cycle = (200/150)² × 60 ≈ 107%, capped at 100%.

Question 4: On a constant-voltage GMAW power source, what mainly controls welding current?

Voltage setting
Gas flow rate
Wire feed speed (Correct answer)
Travel speed

Correct answer: Wire feed speed

With CV output, raising wire feed speed raises the current the machine supplies to melt the wire.

Question 5: In short-circuit GMAW, raising the inductance setting usually does what?

Raises open circuit voltage to make arc starts easier
Increases the wire feed speed
Changes polarity to DCEN
Slows the rate of current rise, giving a softer arc with less spatter (Correct answer)

Correct answer: Slows the rate of current rise, giving a softer arc with less spatter

Inductance limits how fast current rises during each short circuit, which cuts spatter and makes the puddle more fluid.

Question 6: What is the main purpose of open circuit voltage (OCV) on a welding power source?

To set the welding current
To cool the transformer
To control the shielding gas solenoid
To start and re-strike the arc (Correct answer)

Correct answer: To start and re-strike the arc

OCV is the voltage across the output terminals when no arc is burning, and it is needed to start the arc.

Question 7: What is a key advantage of inverter-based power sources over conventional transformer-rectifier machines?

Inverters only work on single-phase power
Inverters need no preventive maintenance
Smaller size, lighter weight, and better electrical efficiency (Correct answer)
Inverters can't be damaged by voltage spikes

Correct answer: Smaller size, lighter weight, and better electrical efficiency

High-frequency switching lets inverters use much smaller transformers, which reduces weight and improves efficiency.

Question 8: A crew must run welding leads much farther than usual at the same current. What cable change is correct?

Use a smaller-diameter cable to reduce weight
Coil the extra cable to shorten its effective length
Use a larger-diameter cable (smaller AWG number) (Correct answer)
Keep the same cable but raise the voltage

Correct answer: Use a larger-diameter cable (smaller AWG number)

Longer runs increase resistance and voltage drop, so you need a larger conductor to carry the current properly.

Question 9: A loose or corroded work (ground) clamp connection is most likely to cause what?

Erratic arc, voltage drop, and overheating at the connection (Correct answer)
Better arc stability on thin material
Higher deposition rates
Lower shielding gas use

Correct answer: Erratic arc, voltage drop, and overheating at the connection

A poor work connection adds resistance, which causes heat, voltage loss, and an unstable arc.

Question 10: Under AWS D1.1, at what minimum temperature must low-hydrogen SMAW electrodes be kept in a holding oven after removal from hermetically sealed containers?

150°F (65°C)
450°F (230°C)
250°F (120°C) (Correct answer)
120°F (50°C)

Correct answer: 250°F (120°C)

D1.1 requires low-hydrogen electrodes to be stored in ovens held at 250°F (120°C) or higher.

Question 11: Which drive roll type is generally recommended for feeding soft aluminum GMAW wire?

Smooth V-groove
Knurled V-groove
Serrated flat roll
U-groove (Correct answer)

Correct answer: U-groove

U-groove rolls cradle soft aluminum wire without shaving or deforming it.

Question 12: A GMAW wire feeder keeps 'birdnesting' at the drive rolls. Which is the most likely equipment cause?

Inductance set too low
Wrong polarity on the work lead
Shielding gas flow set too high
A kinked, dirty, or wrong-size liner, or a clogged contact tip (Correct answer)

Correct answer: A kinked, dirty, or wrong-size liner, or a clogged contact tip

Resistance downstream of the drive rolls makes the wire buckle and tangle at the feeder.

Question 13: When should a GMAW contact tip normally be replaced?

Only when the shielding gas is changed
Only once a year during scheduled maintenance
When the bore is worn oval or spatter causes erratic feeding and arc wander (Correct answer)
Whenever the wire spool is changed, regardless of condition

Correct answer: When the bore is worn oval or spatter causes erratic feeding and arc wander

A worn or spatter-fouled tip transfers current poorly and lets the wire wander, which destabilizes the arc.

Question 14: Which equipment setup is commonly used to feed aluminum wire reliably over longer distances in GMAW?

Knurled drive rolls with high tension
Water-cooled SMAW stinger
Standard push feeder with a steel liner
Push-pull gun or spool gun (Correct answer)

Correct answer: Push-pull gun or spool gun

Push-pull and spool guns shorten or assist the feed path, so soft aluminum wire doesn't buckle.

Question 15: Above what working pressure should acetylene never be used?

15 psig (Correct answer)
25 psig
50 psig
5 psig

Correct answer: 15 psig

Free acetylene becomes unstable and can decompose explosively above 15 psig.

Question 16: Under OSHA 29 CFR 1910.253, oxygen cylinders in storage must be separated from fuel-gas cylinders by at least what?

50 feet in every case
20 feet, or a noncombustible barrier at least 5 feet high with a 1/2-hour fire rating (Correct answer)
10 feet, or any wooden partition
5 feet with no barrier

Correct answer: 20 feet, or a noncombustible barrier at least 5 feet high with a 1/2-hour fire rating

OSHA requires 20 ft of separation or a 5-ft-high noncombustible barrier rated for at least 1/2 hour of fire resistance.

Question 17: What is the main function of a flashback arrestor on an oxyfuel outfit?

To regulate cylinder pressure down to working pressure
To raise the flame temperature
To mix oxygen and fuel gas evenly
To stop a flame front from traveling back into the hose, regulator, and cylinder (Correct answer)

Correct answer: To stop a flame front from traveling back into the hose, regulator, and cylinder

Flashback arrestors quench a reverse-traveling flame and usually include a check valve to prevent gas backflow.

Question 18: Why should acetylene cylinders be stored and used upright, with withdrawal limited to about 1/7 of contents per hour?

To prevent oxygen contamination
To raise flame temperature
To keep acetone from being drawn out of the cylinder (Correct answer)
To keep the fusible plug cool

Correct answer: To keep acetone from being drawn out of the cylinder

Acetylene is dissolved in acetone, and drawing gas too fast or from a horizontal cylinder pulls acetone into the regulator and torch.

Question 19: What is the correct method to check oxyfuel or shielding gas connections for leaks?

Apply oil to the threads and look for seepage
Listen for hissing only
Pass a small flame around each fitting
Apply an approved leak-detection solution and watch for bubbles (Correct answer)

Correct answer: Apply an approved leak-detection solution and watch for bubbles

Approved leak solutions show leaks safely, while flames and oil create fire or explosion hazards.

Question 20: Before attaching a regulator to an oxygen cylinder, what practice is recommended?

Briefly crack the cylinder valve to blow out dust and debris, standing to the side (Correct answer)
Lubricate the regulator threads with light oil
Open the cylinder valve fully before connecting
Tap the valve with a hammer to seat it

Correct answer: Briefly crack the cylinder valve to blow out dust and debris, standing to the side

Cracking the valve clears contaminants that could ignite in high-pressure oxygen, and oil must never touch oxygen fittings.

Question 21: A GTAW welder sets shielding gas flow far above normal and gets porosity. What is the likely cause?

Turbulence at the nozzle pulls air into the shielding gas (Correct answer)
High flow raises the hydrogen content of the tungsten
High flow changes the machine polarity
Too much argon makes the weld too cold

Correct answer: Turbulence at the nozzle pulls air into the shielding gas

Too much flow makes the gas turbulent, which draws in atmospheric air and contaminates the weld.

CWS Welding Equipment & Maintenance

Which power source output characteristic is normally used for SMAW?

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