C4 - LT#1 Oxy Fuel Equipment Flashcards
The process of gas cutting requires what?
Two gases and a source of ignition
What gas has the highest flame temperature?
Acetylene gas
What is the first step in putting out a fire in the hoses of an oxyacetylene outfit?
Close both the oxygen and acetylene cylinder valves
What CRITICAL point of free acetylene is:
28 PSI (193 KPA) pressure at 21 celsius. If the temperature is increased, the pressure becomes critical at a LOWER temperature.
The safety devices on an acetylene cylinder are ______ activated
Heat activated
Oxygen valves are opened all the way, acetylene valves are opened
1/4 to 1/2 the way
Liquid fuel cylinders are designed to allow the liquid to _______ when the cylinder valve is opened and gas escapes
Boil off or vaporize
When cylinders are too low on gas to be used, they should be marked
MT
Cylinder valves should always be _____ open momentarily before the regulator is attached and _____ when your work is finished.
Cracked open before attaching the regulator and close when your work is finished.
To increase the working pressure, the pressure adjusting screw is turned _______?
Clockwise
A grooved hex nut indicates
A left-handed / acetylene regulator
The gauge with the higher numerical calibrations indicates:
Cylinder pressure
The gauge with the lower numerical calibrations indicates
Working pressure
The color of an oxygen hose is usually
Green / black
The colour of the fuel gas hose is usually
Red
An RFCV placed between the torch and hose has the arrow pointing toward the; between the hose and regulator, it is pointing toward the
Torch, hose
When you are using the combination torch for the cutting process, the ____ valve is used to adjust the amount of oxygen mixed with the acetylene for preheating
Preheat oxygen valve
If a flashback occurs, the _____ and the _____ valves must be shut down as soon as possible
Torch and cylinder
What is one of the main hazards of oxygen?
It accelerates combustion rapidly and raises the combustion temperature of fuel gases, which can cause hazards if the oxygen content is above standard atmospheric % (20.8)
The acceleration of combustion is called:
The oxidizing effect. Materials that are not combustible in air will burn readily in oxygen-enriched atmospheres.
If oil or grease is brought into contact with pure oxygen under slight pressure, what can occur?
An explosion
Acetylene is a compound formed by uniting:
Two atoms of Carbon with two atoms of hydrogen to form C2H2
The resulting flame temperature of acetylene + oxygen is
up to 3,300 celsius
What does the term unstable mean, in acetylene is an unstable compound.
Unstable means likely to break down (decompose) or undergo a physical change without much provocation or cause. This point is called the “critical point”
The “critical point” of free acetylene (explosive and unstable) is:
28 PSI at 21 degree celsius
Which fittings are safe with acetylene?
Yellow brass, iron, or steel
What is the advantage of MAPP?
Relatively inexpensive when compared to the cost of acetylene. Safer to use and may be safely compressed. Flame temp of 2 900
What is the advantage of cuts with natural gas?
It can be piped in. The main constituent of natural gas is methane. Flame temp. of 2540 celsius.
What is the main advantage of propane gas?
Safe and easy to handle, it is widely used because of its ability to produce clean cuts at a low cost. Requires 4 1/2 volumes of oxygen to one volume of fuel to produce a neutral flame. Temp is 2540 celsius
What is stored in acetylene cylinders to charge the average PSI to around 250 (from the dangerous pressure of 15)
Agamassan - a porous material such as asbestos, charcoal, diatomaceous, a stable liquid to absorb the acetylene gas and is used in the cylinder them safe at high pressures. One volume of acetone will absorb 20 volumes of acetylene gas
Should you use grease or oil to lubricate regulators, torches, cylinder valves, or other oxy-fuel gas equipment?
No, never
The working pressure of acetylene must be kept below how many PSI?
Below 15 PSI to prevent unstable gas from exploding
What do oxy-fuel hoses consist of?
2 or 3 layers of rubber, with a strong fabric between each rubber layer for reinforcement
What are the causes of backfire?
1)Obstruction of gas flow at the tip
2)hot tip from being too close to the work
3) working pressure too low
4) faulty connection between the torch and the welding or cutting attachment
What is a backfire?
the torch burns back into the welding or cutting tip, making a popping sound. Gases pre-igniting inside of the tip.
What is a flashback?
When the backfire goes beyond the tip, through the hose to the regulator. The torch handle may become hot.
What are the causes of a flashback?
1) Incorrect adjustment of torch valves
2) grossly unequal oxygen and acetylene working pressures
3) clogged tip along with excessive oxygen pressure
4) failure to purge the lines before igniting the torch
What is a Reverse Flow Check Valve?
A device that prevents gases from flowing in reverse inside the torch or hose.
What are causes of reverse flow?
1) Using plugged or obstructed cutting or welding tips
2) bleeding the lines by turning off cylinder valves while torch valves are still open
3) no pressure from either the oxygen or acetylene cylinders while the torch is in use
If a rubber hose is ruptured or catches fire, what must you do?
Turn off the supply of oxygen and fuel gas, before attempting to put out the fire using a smothering fire extinguisher
During the cutting process, steel is reduced to:
Iron oxides
What is a gas cylinder of acetylene composed of?
A porous filler such as asbestos, charcoal or balsa wood, then filled with liquid acetone into which the acetylene is dissolved
MAPP gas is the compound:
Methylacetylene propadiene
Gas cylinders, once emptied are emptied out first, then refilled, why?
In the case the remaining gas is contaminated
How to safely store acetylene cylinders?
1) Not near radiators or any other source of heat
2) Storage room must be well ventilated
3) Should be used and stored in an upright position
4) Once a cylinder is empty, it is to be stored in the appropriate location and marked MT
What is a manifold system?
When large volumes of acetylene are needed and a single cylinder may not provide enough acetylene at the rate required, if the draw limit is exceeded, the liquid acetone will be drawn
Manifold system connects a number of cylinders together so that the draw limit is increased.
What is a manifold system?
When large volumes of acetylene are needed and a single cylinder may not provide enough acetylene at the rate required, if the draw limit is exceeded, the liquid acetone will be drawn
A manifold system connects a number of cylinders together so that the draw limit is increased.
