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© 2012 Delmar, Cengage Learning
Chapter 5Hazards of Liquids
© 2012 Delmar, Cengage Learning
The Hazards of Liquids
• Physical: combustible, compressed, explosive, oxidizer, and pyrophoric.
• Chemical: carcinogens, mutagens, teratogens, reproductive toxins, caustic or acidic.
• Biological: insects, bacteria, fungi, and molds.
© 2012 Delmar, Cengage Learning
Physical Hazards Associated with Liquids
• Combustible liquid has a flashpoint between 100°F and 200°F
• Flammable liquid has a flashpoint below 100°F
• Pyrophoric – ignites spontaneously with air at temperatures below 130°F
© 2012 Delmar, Cengage Learning
Health Hazard Associated with Liquids
• Carcinogens – liquids that are known cancer-causing substances.
• Mutagen – chemical that is suspected to have the properties required to change or alter the genetic structure of a living cell.
• Reproductive toxin – chemical that inhibits the ability of a person to have children.
© 2012 Delmar, Cengage Learning
Pressure and Pressurized Equipment
The primary variables a process technician works with are:
•Temperature
•Flow
•Level
•Analytical
•Pressure
© 2012 Delmar, Cengage Learning
Figure 5-1 Pressure Control Loop
© 2012 Delmar, Cengage Learning
Figure 5-2 Process System
© 2012 Delmar, Cengage Learning
Flammable Liquid Storage
• Metal cabinets
• Tanks and vessels
• Nitrogen blanket can be used to keep flammable liquids under pressure
© 2012 Delmar, Cengage Learning
Spontaneous Combustion
Spontaneous combustion is the result of a slowly developing chemical reaction that produces its own heat.
© 2012 Delmar, Cengage Learning
Figure 5-4 Fire Tetrahedron and Chemical Reaction
© 2012 Delmar, Cengage Learning
Hazards of Steam
• The most common hazards associated with steam are physical exposure to live steam, contact with heated equipment, non-uniform heat transfer, and equipment over-pressuring.
• High-pressure steam discharged from a small opening has enough energy to cut through solid materials.
© 2012 Delmar, Cengage Learning
Hazards of Water
• When water flashes to steam at 100°C it expands 1,500 to 1,600 times its original volume.
• Uncontrolled mixing of water with hydrocarbons can generate high-pressure conditions that can damage systems.
© 2012 Delmar, Cengage Learning
• Foamover occurs when water vaporizes under hot, heavy oil or asphalt. The foam can expand to 20 or 30 times the original volume of the product pumped in.
• Water and acid do not respond well with each other. Pour acid into water; never pour water into acid.
© 2012 Delmar, Cengage Learning
Figure 5-5 Uncontrolled Mixing in a Heat Exchanger
© 2012 Delmar, Cengage Learning
• Vacuum towers operate below atmospheric pressure which lowers the boiling point of water. The volume expansion is much greater in low-pressure situations.
© 2012 Delmar, Cengage Learning
Figure 5-6 Pressure Effect
© 2012 Delmar, Cengage Learning
Hazards of Light Ends
• Viscosity – Can easily escape from enclosed systems
• Frostbite – When light-ends contact human skin, heat is absorbed.
• Thermal expansion – Overheating must be avoided.
• Hazard of air – Air and light-ends mixed can lead to an explosion.
© 2012 Delmar, Cengage Learning
Acids and Caustics
• Acids – Have a pH between 0 and 7.0 and turn litmus paper red.
• Caustics – Have a pH between 7.0 and 14.0 and turn litmus paper blue.
• Acids donate a proton to a base.
© 2012 Delmar, Cengage Learning
Figure 5-7 pH Scale