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

In a flashback, immediately close torch valves to cut gas flow, then close cylinder valves; water must never be applied to a gas-fed flame as it creates additional hazards.

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

Holding the inner cone 3–6 mm from the work ensures efficient preheat transfer to the steel without overheating the tip or allowing spatter to clog the tip orifices.

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

Acetylene cylinders are filled with porous material saturated with liquid acetone in which acetylene is dissolved; tipping the cylinder allows liquid acetone to flow into the regulator, damaging it and causing a fire hazard.

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 is a minor event — a momentary 'pop' and flame extinction at the tip, usually caused by tip contact with the work — while a flashback is a serious event where the flame travels back through the hoses toward the cylinders.

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

Proper procedure requires closing the cylinder valve, bleeding residual pressure from the hose and regulator, and replacing the protective valve cap before the cylinder is moved, stored, or returned.

Red Seal Welder 456A Practice Test

Red Seal Welder 456A Practice Test

456A Oxyfuel Welding & Cutting 3