© 2012 delmar, cengage learning chapter 5 hazards of liquids

© 2012 Delmar, Cengage Learning

Chapter 5Hazards of Liquids


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.


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


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.


Pressure and Pressurized Equipment

The primary variables a process technician works with are:

•Temperature

•Flow

•Level

•Analytical

•Pressure


Figure 5-1 Pressure Control Loop


Figure 5-2 Process System


Flammable Liquid Storage

• Metal cabinets

• Tanks and vessels

• Nitrogen blanket can be used to keep flammable liquids under pressure


Spontaneous Combustion

Spontaneous combustion is the result of a slowly developing chemical reaction that produces its own heat.


Figure 5-4 Fire Tetrahedron and Chemical Reaction


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.


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.


• 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.


Figure 5-5 Uncontrolled Mixing in a Heat Exchanger


• Vacuum towers operate below atmospheric pressure which lowers the boiling point of water. The volume expansion is much greater in low-pressure situations.


Figure 5-6 Pressure Effect


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.


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.


Figure 5-7 pH Scale

© 2012 delmar, cengage learning chapter 5 hazards of liquids

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