LP Gas Properties

Properties of Propane

Formula C3H8

Boiling Point, ºF -44

Specific Gravity of Gas (Air=1.00) 1.50

Specific Gravity of Liquid (Water=1.00) 0.504

Lbs. per Gallon of Liquid at 60º F 4.20

BTU per Gallon of Gas at 60º F 91502

BTU per Lb. of Gas 21548

BTU per Cu. Ft. of Gas at 60º F 2488

Cu. Ft. of Vapor (at 60º F) Gal. 36.38

Cu. Ft. of Vapor (at 60º F) Lb. 8.66

Latent Heat of Vaporization at Boiling Point BTU/Gal. 773

Combustion Data: Cu. Ft. Air Required to Burn 1 Cu. Ft. Gas 23.86

Flash Point, ºF -156

Ignition Temperature in Air, ºF 920-1120

Maximum Flame Temperature in Air, ºF 3595

Limits of Flammability Percentage of Gas in Air Mixture; At Lower Limit – % 2.15

At Upper Limit – % 9.6

Octane Number (ISO-Octane=100) Over 100

Vapor Pressure of LP Gases

Temperature (°F) Approximate Pressure (PSIG)
-40 3.6
-30 8
-20 13.5
-10 23.3
0 28
10 37
20 47
30 58
40 72
50 86
60 102
70 127
80 140
90 165
100 196
110 220

 

Approximate BTU Input For Some Appliances

Appliance Approximate Input (BTU per Hour)
Range, free standing, domestic 65,000
Built-in oven or broiler unit, domestic 25,000
Built-in top unit, domestic 40,000
Water Heater, (Quick Recovery) automatic storage–
30 Gallon Tank 30,000
40 Gallon Tank 38,000
50 Gallon Tank 50,000
Water Heater, automatic instantaneous
(2 gal. per minute) 142,800
(4 gal. per minute 285,000
(6 gal. per minute) 428,400
Refrigerator 3,000
Clothes Dryer, Domestic 35,000
Gas Light 2,500
Gas Logs 30,000

 

Vaporization Rate – 100 Lb. Propane Cylinders (Approximate)

Lbs of Propane in Cylinder Maximum Continuous Draw in BTU Per Hour At Various Temperatures in Degrees F.
0°F 20°F 40°F 60°F 70°F
100 113,000 167,000 214,000 277,000 300,000
90 104,000 152,000 200,000 247,000 277,000
80 94,000 137,000 180,000 214,000 236,000
70 83,000 122,000 160,000 199,000 214,000
60 75,000 109,000 140,000 176,000 192,000
50 64,000 94,000 125,000 154,000 167,000
40 55,000 79,000 105,000 131,000 141,000
30 45,000 66,000 85,000 107,000 118,000
20 36,000 51,000 68,000 83,000 92,000
10 28,000 38,000 49,000 60,000 66,000

This chart shows the vaporization rate of containers in terms of the temperature of the liquid and the wet surface area of the container. When the temperature is lower of if the container has less liquid in it, the vaporization rate of the container is a lower value.

Vaporization of ASME Storage Containers

Determining Propane Vaporization Capacity “Rule of Thumb” Guide for ASME LP-Gas Storage Containers Where

D  = Outside diameter in inches

L  = Overall length in inches

K = Constant for percent volume of liquid in container

LP Vaporization

 

% of Container Filled K Equals *Propane Vaporization Capacity at 0°F (in BUU/hr.)
60 100 D X L X 100
50 90 D X L X  90
40 80 D X L X  80
30 70 D X L X  70
20 60 D X L X  60
10 45 D X L X  45

*These formulae allow for the temperature of the liquid to refrigerate to -20ºF (below zero), producing a temperature differential of 20ºF for the transfer of heat from the air to the container’s “wetted” surface and then into the liquid. The vapor space area of the vessel is not  considered. Its effect is negligible.