-Hot drawn: made by single piece of hot steel. No girth or longitudinal seams. Bottom concave and top hemisphere is thickest part (where reg is attached).

-min wall thick 0.260”

-various sizes but 2 common are full size (244ft3) and haf size (122ft3)

-serial number of each stamped near top.

-periodically hydrotested, 1.5x working pressure. Retested after 10 years then 5 after first retest.

-all connections right hand threads, valves fully open when in use

-when empty, mark MT (if you say it out loud it says empty) and put in storage.

-no fixed draw limit, can empty as slow or fast as you want.

-ambient temps affect pressure, most accuracy at 21C.

-do not use near arc welding equipment as cylinders may become grounded.

-metal rupture disk provides controlled relief from extreme pressure due to rise in temp. Usually at 3200 psig.

-hand valve has a backseating spring and seal that uses cylinder pressure to seal against top of valve stem to prevent leaks.

Acetylene cylinder

-welded design- operates at lower working pressures.

-older cylinders may be shredded asbestos, charcoal, cement, wood. 70-80% porous, may crush on impact.

-newer cylinders are made of billions of microscopic “calcium silicate” pores. Withstands up to 400psig crushing force.

-porous material is needed because in the bottle, acetylene is over the 15psig limit. To help stabilize, acetylene gas is dissolved into acetone. Acetylene only stays dissolved in small spaces so the porous material breaks it up.

-more pressure in vessel = better absorption of acetylene in acetone.

-acetylene usually pumped to 40% of volumetric capacity. Cylinder is then weighted and weight is stamped on the shoulder. When empty cylinder, this weight must be the same as stamped. If less, then acetone must be added.

-must be used in vertical position, to prevent acetone from being drawn off.

-Valves:

Key type: needs a t wrench
Wheel type: hand to open.

Only open acetylene valves 1 to 1.5 turns!!!

-Fusible plugs:

built into the cylinder (not hand valve)
Melts at 100C. Made to melt out in case of fire.

-Draw Limit:

limited to prevent drawing acetone
Must not be emptied faster than 1/7th of its volume.
If draw off happens: flame temp drops, flame pale blue with orange flecks at outer torch.
May happen if using very large tips.
If you may exceed- use a manifold system with 2 or more cylinders so they take up the difference.

Manifold systems

-if need to draw off large volumes. Multiple tanks connected together in parallel.

-built to standard of CGA (compressed gas association)

-cylinders must all have equal pressures, otherwise draw off limit can be exceeded when they equalize. This may cause a temp rise and risk explosion.

-one way check valves to prevent cylinder backflow but cannot assume they are functional!

-Never use copper or red brass fittings or tubing with acetylene. It reacts and forms a residue that can cause an explosion. Always use yellow brass or steel fittings.

Cylinder identification

-identification must conform to ANSI

-cylinders are NOT color coded

Regulators

-main 3 working parts are : spring, diaphragm, valve/seat.

-classified by :

Service (acetylene, oxygen)
Type (single stage, 2 stage)

-single stage is not as fine of a control. Mainly used when small delivery pressure changes do not greatly affect performance. Most common for oxyfuel outfits.

-2 stage regs - reduces to intermediate pressure, then reduces further. Common use is master reg on manifold systems.

-good idea to store long term with adj screw inward just enough to put spring pressure on to prevent seat corrosion.

-regulator creep:

high pressure side of reg leaks past seat and raises pressure above normal. Can trigger relief valve, damage bourdon tube.
- May be caused by: ruptured diaphragm, valve seat contamination

Gauges

-Bourdon tube may be damaged if sudden increases

Oxyfuel hose

-rubber, linen braid, neoprene and nylon

-max pressure 400psig burst

-must meet CSA spec which adopted CGA standards.

-do not try to repair!

-fuel gas is red with left hand thread, oxygen is green with right hand threads..

-available sizes: 3/16”, 1/4”, 3/8”.

most common is 1/4”!!! Determined based on flow needed(usually size of torch tip).

Reverse flow check and flashback arrestors

-reverse flow check valves usually installed at torch end. Do not use these as a replacement for flashback arrestors!

-flashback arrestors installed either at torch or regulator end, preferably both. Essentially a filter that extinguishes flame.

Torch tip and designs

3 categories of oxyguel equipment:

Combination weld and cutting torches for manual cut
- most popular as it has a welding/cutting tip AND a tip suitable for most cutting applications.
- Meant for lightweight not heavy duty cuts.
- When using this, the oxygen torch handle must be fully open and the “preheat” oxygen flow is set by the handle on the cutting tip. This ensure the full oxygen flow is applied when the lever is pressed when “cutting” oxygen is introduced. Preheat acetylene is still controlled by the handle on the torch handle.
Heavy duty cutting torches for manual cut
- Used for 6” or greater material in rough service such as demolition.
Machine cutting torches for semi auto or auto cutting
- 2 Styles:
  - Radiagraph:
    - Runs on a track to produce straight lines.
    - Ensure adequate preheat is used.
    - Operator can adjust travel speed, preheater distance, torch angle, torch inclination, and machine base distance.
  - Pipe Beveler:
    - Used to bevel round pipe in place.
    - Ensure adequate preheat is used.
    - Self centering jaws holds pipe, machine rotates the pipe.
    - Operator can adjust travel speed, preheater distance, torch angle, torch inclination and machine base distance.

-Never leave a cutting torch machine unattended

-Monitor lag or draglines, look for excessive slag buildup and for melting of the top edge and make necessary adjustments.

Cutting Tips

Smaller tip = lighter or thinner materials.
No standardized numbering system exists. Mfg specific.
Common Tips:
- Straight: normal square and bevel cuts
- Scarfing: remove minor imperfections during casting work
- Gouging: Gouging operations
- Heavy Duty Rivet/Bolt cutting tip: cutting rivet or bolt heads without damage to the PARENT material.
Cutting tips vary due to the flame propagation speed.
- Solid one piece - acetylene
- 2 piece, splined - propane or nat gas (cup on the end helps anchor the flame to the tip). Usually propane and nat gas tips are interchangeable but it depends on mfg.
- You cannot mix the tips and fuels. Using acetylene on a nat gas tip will destroy the tip.
Torch lightoff procedure (combination torch)
- open combination torch oxygen handle fully first
- Purge both oxygen and fuel gas lines individually- ensures no debris or trace gas
- With preheat oxygen closed, open acetylene 0.5 turn and ignite flame. Creep open acetylene valve more until there’s smoke.
- Begin adding pregeat oxygen via the oxygen torch valve that was closed
- To cut- depress cutting lever.
if flames unequal- need to clean torch tip
Acetylene/oxygen pressure ratio depends on your torch tip. Small one is 3 psi acetylene and 30 psig oxygen.
Starting torch cut:
- Place torch at starting point and preheat with the inner flame cone about 1/16” away from material surface. Always try to start your cut on a sharp edge. If it’s a solid roundshape, you can also try drilling a hole or use a chisel to nick the material where you want to start your cut.
- When starting point is red hot it means it is over 1600F. At this point you can introduce the cutting oxygen. Keep torch still until you penetrated the material.
- Maintain a 1/16 to 1/8” distance from preheat cones to workpiece. Do not allow flame cones to touch the workpiece.
Drag:
- Amount of Drag is the offset distance between where slag should exit theoretically vs where it actually exits.
- Drag can be expressed as % of the cut thickness (15% would mean that the exit of the cut lags behind the entry point of the cut by a distance equal to 15% of the material thickness).
Travel Speed
- Torch travel speed affects the drag in the kerf line.
- Use drag lines to determine your travel speed.
- Slow: ragged kerf because the cutting stream wanders into the plate in irregular fashion
- Fast: slag bubbles up to surface because cutting jet stream cannot blow fully through. This can also happen if the tip is too small or insufficient oxygen pressure.
Torch Inclination:
- Angle relative to direction of travel.
- Correct torch angle affects travel speed and cut quality
- Thinner material : more forehand inclination
- Thicker material : less inclination, on 3” or thicker you may want slight backhand inclination.
- Shape cutting : no angle at all
Piercing Holes:
- Can cause backfire or plug orifices if slag blows back up into tip. 2 methods help avoid this:
  - Still Torch method:
    - Best for small holes in thicker plate.
    - Tip is one size larger than normal for material
    - Set O2 pressure at min 25 psig.
    - Use heavy preheat
    - squeeze lever and RAISE the torch - allows slag to blow clear. Lower tip to continue the cut once fully pierced.
  - Travelling torch method:
    - preferred on materials 1/2” thick or less.
    - Normal pressure
    - Hold torch with slight forehand incline and preheat.
    - once at temp, squeeze cutting lever and slowly advance torch - this allows slag to blow clear. keep travelling until cut is through.
Common cutting faults:
- Examine the kerf lines. This is critical to knowing which variable needs correcting.
  - Dirty tip - rough cut with large slag on bottom
  - Fast ravel speed - slag bubbles to surface and cutting stops
  - Preheat flames too small or too long
  - Oxygen pressure too low or too high
  - Cutting tip too small or too large
  - Unsteady torch movement
  - Improperly executed stop/starts
Tip selection:
- Depth of cut = larger tip for deeper cut
- Type of material to be cut
- Condition of material - rust may make it harder
- Type of cut needed: 4 hole preheat is adequate for square cutting but 6 hole versions give a faster and more even preheat.
Cutting Methods:
- Across Cut:
  - Hold torch at 90deg to the cut line.
  - Pivot with your free hand, roll your pivot hand as the cut progresses
- Push/Pull:
  - Free hand becomes balance point. Use it to push or pull torch.
Malfunctions:
- Backfire:
  - Flame backs up into the tip. May re-establish with a pop
  - Susceptible at the cutting attachment.
  - Too little gas speed, dirty tip, partial obstructions, loose seat connections, hot tips may cause it.
- Burnback:
  - combustion steadily takes place in the tip and mixer.
  - Susceptible at the cutting attachment.
  - Black smoke, red sparks, screeching sound from tip.
  - Must close both torch valves quickly.
  - Hot tip, tip orifices that are enlarged, faulty torch body seats allowing mixing before mixer.
- Flashback:
  - Hose contains lower pressure and can burn back all the way into the cylinder.
  - Most serious malfunction.
  - Close O2 cylinder, Close Acetylene, Extinguish Fire. (In Order)
  - Grossly unequal pressures, mildly unequal pressures + obstruction, faulty operation (lighting with a mixture of acetylene and oxygen at the same time), failing to purge each line individually before lighting torch. Attempting to light with a mixture will almost certainly cause a flashback.
Gas Speed vs Flame Propagation Speed
- Gas Speed:
  - speed of premix gases leaving tip
  - lineal ft/sec
- Flame propagation speed:
  - speed of flame travel or spread
  - Usually 17 - 25 ft/s for O2 and Acetylene. If the Gas speed is less than the flame speed, the flame burns back and backfires will occur. If gas speed is much higher, the flame will lift off the nozzle.
Flame Types:
- Carbonizing Flame:
  - Rich in fuel
  - Less flame temp than a neutral flame
  - Will show a feather on the end of the cone of the preheater. This feather determines the amount of excess acetylene. If the feather is the same length as the cone - then it is a 2X flame (because the feather is 1X the cone plus another 1X. If you cannot see the feather then it is X or 1X [same thing]). X means the length of the neutral cone that would be formed if the feather were removed by adding oxygen
- Neutral Flame:
  - No excess O2 or fuel
  - Flame temp with acetylene and O2 would be 3090C
  - Occurs when the feather disappears into the cone as oxygen is added.
- Oxidizing Flame:
  - rich in oxygen
  - Flame temps can reach 3470C
  - Cone becomes shorter, sharper, and pale blue.
  - Oxygen in the flame first attacks the carbon in the steel and burns it out, then the iron.
  - When cutting, your are mainly oxidizing the material.