1.1.2

1. 1.1.2 Identifying the Physical Properties of Propane • A basic knowledge and understanding of propane’s physical properties and characteristics is the first step in proper and safe handling of propane. • In this module you will: • Identify the specific gravity of propane liquid and vapor • Identify the effects of pressure and temperature on propane • Identify how to verify the presence of propane odorant and minimize the possibility of odorant fade

2. Propane’s Specific Gravity The specific gravity of a liquidis the comparison of the weight of a given volume of one liquid at a certain temperature with the weight of the same volume of water at the same temperature. Water = 1.0 The average specific gravity of commercial propane liquid is 0.504 at 60°F.(Check the specific gravity listed on Bills of Lading that document propane deliveries to the bulk plant to verify the product is propane, not butane.)

3. The specific gravity of a vaporis the comparison of the weight of a given volume of gas at a certain temperature with the weight of the same volume of air at the same temperature. Air = 1.0 The average specific gravity of commercial propane vapor is 1.50 at 60°F.(Propane vapor is 1½ times heavier than air.) Important to know when trying to find the source of a propane leak. Propane is likely to settle in low areas & concentrate if there’s no air movement.

4. Effects of Temperature Change on Liquids, Example: Water When water (or any liquid) is heated, it will expand in volume. To increase the temperature of the water, heat must be added. Heat is measured in British thermal units (Btus).

5. Effects of Temperature Change on Liquids, Example: Water A Btu is the amount of heat needed to raise the temperature of 1 pound of water 1° F. To raise the temperature of 1 pound of water 100° requires 100 Btus. To raise the temperature of 3 pounds of water 100° requires 300 Btus. To raise the temperature of 1 pound of water from 60° to 212° requires 152 Btus.

6. Effects of Temperature Change on Liquids, Example: Water Once the temperature of the water at atmospheric pressure reaches 212° F, it begins to boil, producing water vapor. After the water begins to boil, heat measured in Btus can be increased, but the measured water temperature will remain at water’s boiling point212°. The added heat is now “hidden”—Latent Heat.

7. Effects of Temperature Change on Liquids, Example: Water • When water (or any liquid) is heated above its boiling point in an open container, vaporization will occur. • Additional heat added is called latent heat of vaporization, because the measured liquid temperature will not increase.

8. Effects of Temperature Change on Liquids, Example: Water • In a closed container, such as a pressure cooker, the measured temperature will increase, and boiling will stop. • Energy in the form of pressure offsets the heat energy, increasing the measured liquid temperature and vapor pressure.

9. Effects of Temperature Change on Propane • Propane must be stored in closed • containers because of its low • boiling point -44°F. • At higher temperatures, it • vaporizes, and will boil off. • Besides that, it is flammable and must not be exposed to • air except under controlled conditions.

10. Effects of Pressure Change on Propane Propane systems work because of temperature/pressure equilibrium. When appliances call for gas, container pressure drops, and vaporization happens to supply demand.

11. Effects of Temperature Change on Propane • As with water, propane liquid expands • with increases in temperature, but in • comparison…. Propane expands in volume 17 times more than water over the same temperature increase. • To accommodate liquid propane expansion, containers • are filled to only about 80% of their capacities.

12. Effects of Temperature Change on Propane Propane storage containers are equipped withat least one pressure relief valveto protect the container from excessive internal pressure. One cubic foot of propane liquid boils off into approximately270 cubic feetof propane vapor.

13. To obtain additional information about propane or any chemical in your workplace, you can read the • Material Safety Data Sheet (MSDS). • MSDSs give manufacturer information about • physical properties, • health effects, • first aid, • safety precautions and personal protective equipment, & • other facts about chemicals used in businesses and industry.

14. Odorants: Verifying Their Presence • Ethyl mercaptan, the most common LP-gas odorant is added at a minimum rate of 1 pound per 10,000 gallons of propane. • NFPA 58 requires propane marketers to verify the presence of odorant in propane delivered to the bulk plant. A documented “sniff test” meets that requirement.

15. Odorants: Maintaining Their Effectiveness • Ethyl mercaptan, the most common LP-gas odorant can temporarily be chemically bound up by rust (iron oxide) coating the walls of containers or piping that has been open to the atmosphere. • Purging new containers and piping that have been open to the atmosphere using propane vapor can reduce the possibility of temporary odorant fade.

16. Time to See If You Got the Key Points Regarding the Physical Properties of Propane • Complete the Review on Page 12. • See if you are ready for the Certification Exam by checking off the performance criteria on page 14.