M O D U L E 3 : T O U N D E R S T A N D B A S I C F U E L A N D C Y L I N D E R S A F E T Y W I T H R E S P E C T T O S P E C I F I C F U E L T Y P E S .

SAFELY WORKING WITH GASES

BASIC KNOWLEDGE AND PRECAUTIONS

TRIANGLE OF COMBUSTIONThe chemical, exothermic reaction – Fire

Heat – to raise the material to its ignition temperature

Fuel – or combustible material

Oxygen – to sustain combustion

CLASSIFICATION OF FUELS• Class A- Wood, paper, trash, cloth,

plastics• Class B – Flammable liquids: gas, oil,

grease, acetone• Class C – Electrical: energized

electrical equipment• Class D – Metals: potassium, sodium,

aluminum, magnesium

SAFE HANDLING OF GAS CYLINDERS• When transporting cylinders, secure vertically and with gauges

unattached.

• Do not pry frozen cylinders - use warm water because of the fuse plug on the cylinder bottom.

• Do not use valve caps to lift. cylinders.

Improper and unsafe storage

VENTILATION

• General - mechanical, 2000fpm • 10,000 ft3 per welder• ceiling less than 16 feet• around structural barriers

• Local - mechanical, 100 linear fpm in weld zone.

• When ventilation cannot meet the needs supplied, air respirators shall be used.

VENTILATIONMostly require local exhaust ventilation or airline respirators (reference OSHA standard):

• Fluorine compounds• Zinc• Lead• Beryllium• Cadmium• Mercury• Stainless steel• Chlorinated hydrocarbons

TYPES OF FUEL SOURCES

ACETYLENE – “C2H2”

• Liquefied petroleum gas -formed when calcium carbide is submerged in water or in petrochemical processes.

• A compound of carbon and hydrogen

• Used in cutting, heating, welding, brazing, soldering, flame hardening, metallizing, and stress relieving applications.

• Very unstable at pressures over 15 psi.

ACETYLENE – “C2H2” • Does not require high storage pressure

(the case with most LP gases). Is usually pressurized around 250 psi.

• Turns to liquid over 300 psi.

• Acetone liquid in cylinder lying horizontally takes at least 1 hour to settle to bottom when cylinder is set up vertically.

ACETYLENE – “C2H2”

Gases in a typical acetylene cylinder:

• Acetylene gas 36%

• Acetone 42%

• Porous filler 8-10%

• Reserve volume 10-12%

Cylinders are filled with a porous material with millions of voids to help keep pressure from building up.

Cylinders are considered “solid” compared to “hollow” in oxygen storage with fusible plugs to vent in the case of an unsafe event.

OXYGEN – “O”

• Can be separated from air by fractionated liquefaction and distillation.

• Main application is melting, and the refining and manufacturing of steel and other metals.

• Oxygen will not burn but will support combustion; therefore it is combined with “fuel” gas to produce the desired operating flame.

• Ordinarily supplied in standard steel cylinders (244 ft3) with a inlet pressure gauge on the regulator to determine cylinder contents.

OXYGEN – “O”• Oxygen is pressurized in excess of 2,000 psi and the cylinder is

hollow.

• Keep oil and grease off oxygen cylinder valves and fittings (oil and grease will burn violently).

• Protect valves of oxygen cylinders (if valves are knocked off, the cylinder becomes a “bomb”).

• Separate oxygen cylinders from fuel gas cylinders or combustible materials by a distance of at least 20 feet.

• Never use Oxygen: in pneumatic tools, to blow out dust, for ventilation, in internal combustion engines.

ALTERNATIVE FUELS• Natural Gas

• Methane is principal component (75%) with ethane (15%) and other hydrocarbons (5%) such as propane and butane.

• Colorless and odorless gas• Typically transported by pipeline but can be shipped in non-liquefied

compressed gas cylinder.

• Propane (C3H8)• Known as liquefied petroleum gas (LPG)• Colorless and odorless with Mercaptan added for leak detection (foul-

smelling odor)• Typically stored in on-site bulk storage tanks or standard cylinders

• Both used for flame cutting, scarfing, heating, flame hardening, stress relieving, brazing, and soldering.

ALTERNATIVE FUELS

• Propylene (Propene)• Colorless, highly flammable, garlic-odor compound that maintains a gas

state at room temperature and under pressure.

• Both used for flame cutting, scarfing, heating, flame hardening, stress relieving, brazing, and soldering.

IMPORTANT

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