Oxy Acetylene Flashcards
What is the typical weight and height of a gas bottle??
1.6m tall and 69kg
How do u identity what’s in a gas bottle??
By label is the only sure way
What should be in each bottle when they are in use??
A key
What should you not use cylinders for?
Never use for rollers
How are cylinders moved over short distances?
Churned
What way should cylinders be stored?
They should be upright and out side in a well ventilated building,
Are cylinders stored together?
Empty and full cylinders should be segregated and OXYGEN should be kept separate from flammable gases
Y is the gas channel offset?
This is done to prevent the cylinder taking off like a missile, instead it will go around in circles and different directions
What are valves designed to do?
The are designed to withstand a fall bending at the weak point
What gases are most commonly used in welding processes??
OXYGEN which is supplied in a black or grey bottle and a white collar and a right handed thread and ACETYLENE which is maroon bottle and a left handed thread
What are the hose colours for the gases?
OXYGEN is blue ACETYLENE is red
What pressure are the bottles charged to?
OXYGEN 230 bars ACETYLENE 17.5 bars and is unstable if any more
What gases make up the atmosphere?
Nitrogen 78% oxygen 21% argon , carbon dioxide, neon , helium, methane, krypton, hydrogen, xenon
Oxygen does not burn! But supports and encourages combustion, if oxygen is present a fire will burn VERY AGGRESSIVELY
Materials that do not burn, may burn in an oxygen enriched atmosphere
What can oxygen react explosively with??
Oils, greases, tarry substances, some solvents such as soap, butter, and some hand cream
What is oxygen specific gravity??
1.1 and is heavier than air so oxygen will drop and gather in the lowest point and make it a fire hazard
What is inside a acetylene bottle??
Porous filler (kapok) 8-10%. Acetone 42% acetylene 36%
What is the porous mass in a bottle?
This is know as kapok and is a charcoal like substance
What does the kapok do?
This is a safety precaution that slows down the acetylene decomposing and slows it down from exploding in the bottle as it is impossible for the reaction to spread quickly throughout the whole mass
What would happen if the acetylene bottle got a sudden blow or heated in a fire??
The bottle would start to heat up and mean it is becoming unstable and the atoms are beginning to split which gives off heat and the pressure increases and likely to explode
What are the procedures carried out if a bottle got a blow and started to heat up??
Do not move the bottle…. Get a spray of water on the bottle…. Evacuate the building…. Ring the fire service And advise them about the gas…. Contact. B.O.C for further advice
If bottle has received a blow but is NOT hot what should u do?
Remove to a safe place outside and check every 5 min for 2 hrs or immerse in water . If in any doubt open the valve to let the gases into the atmosphere and leave it that way and contact the supplier
What does acetylene react explosively with?
With copper or products which contains more than 70% copper
How would u know there was acetylene gas in the air?
It has a garlic smell and also is an asphyxiate
What heat does acetylene burn at?
It produces a flame of 3200 *c when mixed with oxygen at its hottest
What is acetylene ignition temp?
406” ~ 440” this means if it reaches or comes in contact with this temp it will explode without a spark
What is the specific gravity of acetylene?
0.9 making it lighter that air so it will collect in a ceiling or roof where it will wait for an ignition source ( acetylene only needs between 2% and 82% of air volume to become explosive)
If a bottle is on it side what should u do?
It should be upright and not used for a minimum of one hour to prevent the liquid acetone leaking out
What is acetone used for??
It is an affinity for acetylene and is uses for the safe bottling of acetylene
What is chemical symbol of acetylene?
C2h2
1 bar = 14.7 ibs/sq” = 101.3 km/m2
1.000 newtons = 1kilo Newton (kn)
What are regulators used for?
They are used to reduce the pressure of either oxygen or acetylene from high pressure to lower pressure at the blowpipe. ( a regulator or reducing value is a must)
What is two stage regulators?
This makes sure the pressure stays the same all the time and never drops irrespective of the bottles pressure
What is single stage regulators??
It’s a cheaper regulator in which the gas has to be altered or adjusted manually if welding for a long time.
What should be done before threading on the regulator??
You must carry out SNIFTING to make sure that the socket is not blocked with anything
How is SNIFTING done?
It is done by opening the cylinder for a split second Nd closing very quickly with a special key.
What should you wear when SNIFTING?
Eye protection and gloves and never look directly into the cylinder when doing it,
What gas should never be SNIFT?
Hydrogen
What are flashback arresters?
They are for preventing the flames getting into the cylinder if the torch backfires or if the torch was on fire
Where are flashback arrest ord fitted?
They are fitted on both oxygen and acetylene cylinders
What are the types of flash back arrestors? And how many?
There are 2 different. Disposable types and re settable types
What are connected to the hoses?
One end is connected to the flashback arrestors at the cylinder end , the other is connected a hose check valve at the welding blowpipe end
Where are hose check valves connected??
Between the welding blowpipe and the hose
What is a hose check valve??
They are a spring loaded non return valve designed to close in the event of back fire
What is the blowpipe?
The blowpipe is a simple mixing device That usually come In different sizes 1.2.3.5.7.10 etc. the greater the number the larger the hole
What is used to open the valves on cylinders??
A spindle or bottle key
How much should the valve be opened on the cylinders??
1/2 turn and the key should always be left in the oxygen bottle,
What are the rules when working in a confined space ?
1, never work on your own 2, a lot torch is always lit outside and passed to you 3, always leave cylinders outside 4, it should be adequately ventilated 5, fire equipment should be available
When working on an enclosed vessel what should you do?
Make sure the vessel is empty of petrol or oil etc 2, make sure it is throughly cleaned out and steam cleaned if needed 3, fill the vessel with water or sand to within 1 inch of the weld point
What should you do if a torch overheated or seriously back fires??
Put the blowpipe into a bucket of cold water leaving the oxygen running to prevent water entering the blowpipe
What is a backfire?
It’s a mini explosion occurring within the torch
Why do backfires happen?
Because the nozzle has got to hot
Why do the nozzles over heat??
Incorrect angle to the work piece (60’ - 70’) 2, insufficient gas flow to cool the nozzle 3, blocked or dirty nozzle
What is a flashback?
It is when a backfire gets past the torch and into the hoses or in to the bottle it is now called a flashback
What is the lighting up?
When the equipment is initially set up and before lighting up it should be checked for leaks but never check with a flame
How do you extinguish the flame when finished?
The acetylene valve should be turned off first on the blowpipe this will allow the flame to go out, the oxygen valve is then turned off
If the equipment is not in use for long periods of time what should you do??
The valves on the cylinder should be turned off, both blowpipe valves should be opened fully until gas has stopped flowing then closed again
How do you start up the blowpipe?
1-open the acetylene valve ignite it and adjust it till it stops smoking, 2- then oxygen is added and adjusted to make a natural flame
What are the melting points of copper and steel?
Steel is 1926’c and copper is 1080’c
What are the 3 types of flames ?
NEUTRAL - equal amount of oxygen and acetylene. CARBONISED- to much acetylene. OXIDISING- to much oxygen
