C-4 Oxy-Fuel Flashcards
Oxy Fuel gasses
process of gass cutting requires two gasses and a source of ignition.
oxygen
- 8% of atmosphere
- supports combustion
- no color or oder
Hoses for oxyacetylene
made from rubber and cotton
must shut off oxygen to extinguish fire
Oil or grease and oxygen
if either is brought into contact with pure oxygen under slight pressure explosion can occur
Steel and oxygen
if brought to correct temp (red hot) and brought into contact with oxygen it can burn rapidly.
Acetylene
- compound created from two atoms of carbon and two atoms of hydrogen.
- generates high heat when burned
- widest range of flammability
- flame can reach 3300°C
- should not be stored or used at pressures over 15psi
- never use copper or red brass for fittings and tubing
use only yellow brass iron or steel
unstable gas
Acetylene
MAPP gass
- stable mixture of methylacetylene and propadiene
- shipped in low-pressure cylinders so must be used upright (liquid form)
- ## safer to use
flame temp for MAPPgass
2900°C very stable and inexpensive
Natural gas
- preferred in areas where it can be piped in eliminating handling of fuel cylinders
- not liquid form
Flame temp of natural gas
2540°C slower cuts but very inexpensive
Propane Gas
- supplied in liquid form low pressure cylinders.
- easy safe to handle
- flame temp is 2540°
Gas cylinders
- forged from one piece of high grade steel
- slightest sign of damage cylinder is withdrawn
Cylinder safety devices
- located in valve. consists of a pressure or rupture disk.
- this will burst and release cylinder oxygen into the air when excessive pressure buildup occurs.
Acetylene cylinder
filled with porous material called agamassan, asbestos, charcoal or diatomaceous earth. this filler material is saturated with acetone which has the ability to absorb acetylene gas and is used in cylinders to make them safe at high pressures
acetylene cylinder valves
turn pressure valve 1/4 turn then 1/2 turn. what handle is rotated counter clockwise (opening) pressure is released from the seal.
acetylene Cylinder safety device
heat activated plugs in top and bottom of cylinder. heat causes them to melt which then releases the cylinder content to avoid unsafe pressure rise.
Liquid Fuel Cylinders
propane and MAPP are liquids and stored in cylinders
- when shipped full there i still space above liquid for gas to occupy
- this gas escapes when valve is open
- reducing pressure on top of liquid.
- this allows the liquid to “boil off”
Oxygen Regulator
- right hand thread connection
- 0 - 4000 psi
- working pressure gauge usually calibrated from 0 - 200 psi
- OXYGEN should be printed on body and on one or booth gauges
Acetylene regulators
- left handed threads
- cylinder pressure gauge from 0 - 400 psi
- working pressure gauge from 0 - 30 psi
- working pressure gauge has red line from 15 - 30 psi
- acetylene should be printed on body and one or both gauges
oxy fuel Fittings
all fittings and connectors used in the hookup of hose to the regulators and torch body are made of brass
- this prevents sparks it its banged up against another material
- * right handed for oxygen
- ** left handed for acetylene
-
Backfire
when torch or flame burns back into the welding or cutting tip making a popping sound.
Flashback
occurs when backfire goes beyond the tip, through the hose to the regulator.
Reverse flow check valve (RFCV)
put in hoses compression spring holds the valve closed. when operator opens the regulator and torch valves, RFCV opens to permit normal gas flow then snaps shut if the flow is reversed.
