Safety, Tools, Weld Faults & OAW

Question 0

Explain why oxygen is dangerous.

Answer 0

Oxygen readily supports combustion and may react violently with some materials.

Question 1

Which one of these gases is produced using the air liquefaction process?

A) acetylene
B) oxygen
C) propane
D) hydrogen

Answer 1

B) oxygen

Question 2

For efficient welding and cutting operations, oxygen must have a minimum purity of:

A) 80%
B) 93%
C) 98.6%
D) 99.5%

Answer 2

D) 99.5%

Question 3

Oil or grease in contact with pure oxygen can:

Answer 3

Oil or grease in contact with pure oxygen can react violently and cause an explosion.

Question 4

Explain how acetylene gas is produced.

Answer 4

By mixing calcium carbide and watering an acetylene generator.

Question 5

Define the term acetylene generator.

Answer 5

A machine used to produce acetylene gas (C2H2) by bringing specific amounts of granulated calcium carbide and water together under strictly controlled conditions. The vaporous acetylene gas is collected from the generator as it is produced and placed into specially designed cylinders for storage and use. Acetylene generators can be found in large industrial plants and gas supplier depots where acetylene gas is manufactured.

Question 6

Fill in the blanks with the correct numbers associated with acetylene.

A) the critical pressure is __________kPa (__________psi)
B) the maximum safe working pressure is __________kPa (__________psi)
C) the explosive limit in air is from ________% to __________%
D) the explosive limit in pure oxygen is from __________% to __________%

Answer 6

A) the critical pressure is 193 kPa (28psi)
B) the maximum safe working pressure is 103.5kPa (15psi)
C) the explosive limit in air is from 2.5% to 80%
D) the explosive limit in pure oxygen is from 3.0% to 93%

Question 7

List 4 fuel gases used for heating & cutting.

A) ______________________________
B) ______________________________
C) ______________________________
D) ______________________________

Answer 7

A) acetylene
B) propane
C) natural gas
D) propylene

Question 8

List 2 methods used for storing oxygen:

A) ______________________________
B) ______________________________

Answer 8

A) they may be stored as a liquid in a cryogenic container (like a thermos bottle)
B) they may be stored as a gas in high-pressure cylinders

Question 9

Name the safety device used on oxygen cylinders. What is the bursting pressure?

Answer 9

It is a metal rupture disc that has a bursting pressure of about 22000kPa (3200 psi).

Question 10

Compare the pressures and contents of a full-size oxygen cylinder with that of a half-size cylinder.

Answer 10

The pressure will be the same for both cylinders, but the volume of gas is the half-size cylinder will be half that of the full-size cylinder.

Question 11

Explain why fuel gas cylinders gave left-handed threads while non-fuel gas cylinders have right-hand threads.

Answer 11

This is a safety feature that ensures the equipment is not interchanged.

Question 12

Explain why an acetylene cylinder is filled with a porous material.

Answer 12

The porous material prevents a large volume of free acetylene gas from accumulating under high pressure, thereby keeping the acetylene stable.

Question 13

State the location and purpose of fusible plugs.

Answer 13

Fusible plugs are located on the top and bottom of acetylene cylinders. In case of fire they melt approximately 100 degrees celcius (212 degrees ferenheit) providing a controlled release of gas, thus helping to prevent an explosion of the cylinder.

Question 14

State 2 safety precautions used to prevent acetone loss.

Answer 14

A) keep acetylene cylinders in a vertical position during storage and use.
B) DO NOT exceed the draw limit.

Question 15

What should be done before the cylinder valves protective caps are removed?

A) cylinders should be pressure-tested.
B) cylinders should be secured
C) cylinder valves should be cracked
D) equipment should be lubricated and ready for installation .

Answer 15

B) cylinders should be secured

Question 16

In order to protect the regulator gauges:

A) only use regulators having a pre-set stage.
B) release the adjusting screw before you open the cylinder valve.
C) engage the adjusting screw to allow u restricted gas flow.
D) only use gauges equipped with heavy duty bourbon tubes

Answer 16

B) release the adjusting screw before you open the cylinder valve.

Question 17

Which type of regulator fitting requires a fibre washer?

Answer 17

Flat-faced fitting found on some acetylene regulator/cylinder valves

Question 18

Why are the cylinder valves cracked before regulators are attached?

Answer 18

In order to remove dust or dirt from the cylinder valve

Question 19

How should you check for leaks on oxyfuel equipment?

A) use an open flame
B) use a spark lighter
C) spray with anti spatter solution
D) apply a suitable leak detection fluid

Answer 19

D) apply a suitable leak detection fluid

Question 20

When shutting down an oxyfuel outfit, you should:

A) close the cylinder valves & bleed the system
B) close the torch valves and bleed the system
C) back off the regulator screws & bleed the system
D) roll up the hoses and remove the welding tip

Answer 20

A) close the cylinder valves & bleed the system

Question 21

Regarding shutting down an oxyfuel outfit, answer true or false to the following:

A) hoses are rolled up
B) torch valves are closed
C) regulator adjusting screws are disengaged
D) cylinder valves are closed
E) shutdown is done at the end of each work shift

Answer 21

All the above statements are true.

Question 22

What are regulators used for oxyfuel welding and cutting operations?

Answer 22

Regulators are used to reduce source pressure to a working pressure and maintain a constant delivery pressure.

Question 23

What precaution should be taken when regulators are to be stored for extended periods of time?

Answer 23

Turn in the working pressure adjusting screw enough to release the spring pressure on the diaphragm, moving the valve stem pressure on two steps.

Question 24

List 2 types of regulators and briefly explain the operation of each type.

Answer 24

single-stage - reduces source pressure to working pressure in one step.
Two-stage - reduces source pressure to working pressure on two steps

Question 25

What does the term creep mean as it relates to welding equipment regulators?

Answer 25

Creep is a condition where the high-pressure valve is not seated and gas is leaking into the low-pressure side, causing an uncontrolled pressure rise in the low-pressure chamber

Question 26

How would you safely repair an acetylene hose?

Answer 26

Cut out the damaged area and splice using compressed gas association approved fittings of yellow brass, iron or steel.

Question 27

The oxygen hose is usually coloured ___________.

Answer 27

Green.

Question 28

Which hose fittings have left handed thread?

Answer 28

Fuel gas fittings.

Question 29

List 2 types of welding tips and the type of flame each produces.

Answer 29

1) swedge bore gives a long, pointed flame.

2) Straight bore gives a round, bulbous flame.

Question 30

List 2 tools that may be used to properly clean a dirty tip.

Answer 30

1) tip cleaners

2) tip drills

Question 31

What is the difference between a backfire and a flashback?

Answer 31

A backfire occurs in the mixture and tip and a flashback occurs beyond the mixer into the hose and regulator on the low pressure side.

Question 32

List 4 causes of backfires and burn backs and 2 means of avoiding them.

Answer 32

Too little gas speed, obstruction of gas flow, loose or faulty connections between the tip and mixer or a hot tip can cause backfires and burn backs. To avoid this, maintain sufficient gas flow and keep the tip clean.

Question 33

When changing welding tips to a different size, why is a need to rebalance gas pressures?

A) to ensure the tip is free of dirt
B) because the orfice size is different
C) to prevent a burn back from occurring
D) to ensure the proper gases are in their respective hoses

Answer 33

B) because the orfice size is different

Question 34

Why should the acetylene torch valve always be set to work above the smoke range?

Answer 34

This ensures that adequate gas flow is maintained and reduces the possibility of backfires and burn backs

Question 35

List the steps for balancing gas pressures using welding tips
A)
B)
C)
D)
E)
F)

Answer 35

A) rough set both regulators to the manufacturers recommended pressures and purge each line individually
B)open acetylene torch valve 1/2 turn and light. Now open valve fully.
C) now adjust the acetylene regulator so that the flame blows away from the tip but not too harshly. This adjustment must be made with the acetylene torch valve fully open. Use the regulator to adjust the flame
D) reduce the acetylene flow with the torch valve until you are just above the smoke range and the flame is burning at the tip. Then, using the oxygen torch valve, slowly add oxygen until a cone is produced. Then, alternatively increase acetylene and oxygen using the torch valves until they are at full flow.
E) with both torch valves fully open, adjust the flame with the oxygen regulator until a neutral flame is established
F) reduce flame size to midrange proportions using the torch valves; this must not be down in the smoke range.

Question 36

What is meant by the term speed of flame propagation?

Answer 36

This is the speed that a flame will travel in premixed gases.

Question 37

List 3 flame types used with the oxyacetylene process and list 2 uses for each type.

Answer 37

Carbonizing flame: low temperature brazing, aluminum brazing, hard surfacing, fusion welding of medium and high carbon steels, using low alloy welding rods.

Neutral flame: fusion welding low carbon steels, fusion welding of aluminum, fusion welding of cast iron, brazing of steels, flam cutting, heating.

Oxidizing flame: fusion welding brass and bronze, (slightly), brazing of copper and galvanized metal, ( slightly), brazing of cast iron and malleable cast iron.

Question 38

What is meant by the term 2x flame?

Answer 38

This means that the cone and the feather are both the same length.