456A Oxyfuel Welding & Cutting 3

Question 1

What is the correct immediate action if a flashback occurs during oxyfuel welding?

Accepted Answer

Close the torch valves immediately, then close the cylinder valves

Answer

Increase oxygen pressure to clear the hoses of flame

Answer

Remove the torch tip and inspect for blockage

Answer

Submerge the torch in water to extinguish the internal flame

Question 2

What is the recommended inner-cone standoff distance when starting an oxyfuel cut on mild steel plate?

Accepted Answer

The inner cone approximately 3–6 mm (1/8–1/4 in) from the steel surface

Answer

The inner cone should lightly touch the steel surface for maximum heat transfer

Answer

Approximately 50 mm (2 in) away to prevent tip overheating

Answer

Distance is not critical and does not affect cut quality

Question 3

Why must acetylene cylinders always be stored and used in an upright position?

Accepted Answer

To prevent liquid acetone from entering the regulator and valve

Answer

To prevent damage to the regulator from the cylinder's weight

Answer

To ensure the pressure gauge on the regulator reads accurately

Answer

To comply with valve thread orientation requirements under CSA standards

Question 4

How does a 'backfire' differ from a 'flashback' in oxyfuel equipment?

Accepted Answer

A backfire is a brief flame pop and extinction at the tip; a flashback is flame traveling into the hoses

Answer

A backfire occurs at the cylinder valve; a flashback occurs at the torch tip

Answer

A backfire involves excess oxygen; a flashback involves excess acetylene pressure

Answer

They are identical events described by two different trade names

Question 5

What is the correct procedure when an oxyfuel cylinder is empty or no longer required on the job site?

Accepted Answer

Close the cylinder valve, bleed the hose and regulator, then replace the valve protection cap

Answer

Remove the regulator and leave the valve open slightly for ventilation

Answer

Leave the regulator attached and transport the cylinder to storage as-is

Answer

Mark the cylinder 'MT' with tape and leave the valve cracked open

Question 6

On a two-gauge oxyfuel regulator, what does each pressure gauge indicate?

Accepted Answer

The high-pressure gauge shows cylinder contents pressure; the low-pressure gauge shows delivery (working) pressure

Answer

Both gauges show working delivery pressure at two different reduction stages

Answer

The high-pressure gauge shows delivery pressure; the low-pressure gauge shows cylinder pressure

Answer

Only one gauge is functional; the second is a backup in case of primary gauge failure

Question 7

What minimum shade filter lens is recommended for oxyfuel welding according to Canadian safe work standards?

Accepted Answer

Shade #5

Answer

Shade #2

Answer

Shade #10

Answer

Shade #12