456A Oxyfuel Welding & Cutting

Question 1

What type of flame is produced when oxygen and acetylene are mixed in equal proportions?

Accepted Answer

Neutral flame

Answer

A neutral flame results from an equal mixture of oxygen and acetylene, producing a well-defined inner cone with no acetylene feather, making it ideal for welding most steels.

Question 2

What is the maximum allowable working pressure for acetylene in Canada?

Accepted Answer

103 kPa (15 psi)

Answer

Acetylene becomes chemically unstable and risk of explosive decomposition above 103 kPa (15 psi), making this the absolute maximum safe working pressure.

Question 3

In Canada, what color is the oxygen hose used in oxyfuel equipment?

Accepted Answer

Green

Answer

In Canada, the oxygen hose is green with right-hand threaded fittings to clearly distinguish it from the red fuel gas hose and prevent dangerous cross-connection.

Question 4

What is the primary purpose of a flashback arrestor in an oxyfuel system?

Accepted Answer

To prevent flame from traveling back into the hoses and cylinders

Answer

Flashback arrestors contain a flame barrier and check valve that stop a backfiring flame from propagating back through the hoses toward the cylinders, preventing a catastrophic explosion.

Question 5

Which type of oxyfuel flame is characterized by an acetylene feather between the inner cone and outer envelope, and is used for welding high-carbon steel?

Accepted Answer

Carburizing (reducing) flame

Answer

A carburizing flame has excess acetylene, producing a luminous feather that adds carbon to the weld pool — useful for hard-facing and high-carbon steel applications.

Red Seal Welder 456A Practice Test

Red Seal Welder 456A Practice Test

456A Oxyfuel Welding & Cutting