Explanation of Gaseous Vapor Fuel Pressures
Liquid Propane Fuel Pressure
And the deferences between Low Pressure & High Pressure
Types of Gaseous Vapor Fuels Available
Are Propane, Natural Gas, & CNG
Customers often ask what the difference is between Low Pressure & High Pressure
So we thought this page would be helpful for everyone to get a better idea of the differences
20 Pound Grill Tank Cylinder
Most people think a 20 lb cylinder is low pressure because it's a small tank, but this is not true. Propane makes its own vapor pressure naturally, and will have the same amount of pressure as a 1000 gallon storage tank. Grill Tanks draw the vapor pressure from the top of the tank, the liquid propane inside the tank will then boil to restore the pressure drawn off, or better said, to keep the vapor pressure the same as it was before you started to draw the vapor out of the tank. Propane weighs 4.24 pounds per gallon, so if you take 20 divided by 4.24 you will see that there is 4.72 gallons of liquid propane, or Liquefied Petroleum Gas which is what LPG stands for, some people often think that LPG stands for Low Pressure Gas, not true. You would need a High Pressure Kit or a Tri Fuel Kit for both High & Low Pressure.
Natural Gas Meter
Natural Gas usually goes through the gas line along the road or street and to your meter, at about 2 pounds of pressure. After your natural gas has passed through the meter and regulator, it's normally at about 5 to 7 inches of water column, which uses a Low Pressure Kit
100 Pound Propane Cylinder
The 100 lb cylinder works exactly like the 20 lb, you draw the vapor off the top of the tank and the liquid propane boils to keep the vapor pressure the same in the tank, making more vapor to use for your cooking stove, or small furnace, or for your generator. It's a taller tank, and to figure out how many gallons of liquid is in the tank (propane weighs 4.24 pounds per gallon) so you take 100 divided by 4.24 which equals 23.59 gallons when the tank is full. The 100 pound cylinder has high pressure in it until you install a regulator to bring the pressure down to normally 11 inches of pressure, once this is done, you then have Low Pressure Propane Vapor. You would need a High Pressure or Tri Fuel Kit that does both High & Low Pressure for this tank, unless your propane company has already installed a regulator on the tank.
500 Gallon Propane Storage Tank
Some homes have a large storage tank on the property to supply propane for their furnace, cooking stove, water heater, or generator. This tank is designed to draw the vapor from the top of the tank, although there is commonly a liquid draw port at the bottom of the tank too, do not open this, leave that for your propane company only to use if they need to. There is high pressure in this tank and when the vapor is drawn from the top of the tank for your home, the liquid will boil to replace the vapor pressure that has been drawn from the tank as you use it. The propane company installs regulators on your storage tank so that when the line comes into your home the pressure has been reduced to 11 inches of water column, which is about equal to 6 ounces of pressure or Low Pressure Propane. If you plan to connect to the low pressure line before it enters your home, you would use a Low Pressure Kit.
Propane Tank Pressure can vary depending if the tank is in the sun or in the shade
and depending if your tank is gray or light blue or white can make a minor difference too
Fork Lift Truck Tanks
Fork Lift Truck tanks are designed for Liquid Draw, you can also purchase a special vapor draw tank as well, but most commonly this tank is liquid draw. When liquid propane is drawn from the tank it must go through a vaporizer such as a model J or Cobra which have engine coolant ports so the hot water from the engine will keep the vaporizer from freezing when the liquid changes to a vapor as propane goes down to 44 degrees below zero at its point of vaporization, which would happen inside the vaporizer, if there is no engine coolant passing through the vaporizer it would completely freeze up and the engine will shut down. The Liquid Draw Tank is also commonly used on Concrete Saws, Concrete Trowels, and Welders which have air cooled engines, for his type of engine conversion we use a High Pressure Kit along with Air Heated Vaporizers such as the Beam 11A17 which has air fins and when located near the engine where there is warm air flow, the warm air flow will remove the 44 degrees below zero from the air fins keeping it from freezing up.
Compressed Natural Gas CNG Tank
CNG Tanks are designed to hold up to 3600 pounds of pressure, normally filled at 3000 pounds or so. This type of tank requires a special compressor to pressurize the tank with natural gas with enough fuel to last or to get the job done. This type of pressure requires a special regulator to handle that much pressure, it's the HPR-3600 Pressure Regulator.
Pressure Facts - We take advantage of the fact that pressure "attempts to escape", and we use the pressure to move gas along the pipe or tubing to the engine. Outside temperature greatly affects container pressure. Too low container pressure means that not enough gas is able to get to the engine. The table below shows vapor pressures for various outside temperatures.
Environmentally Sound Fuel Systems
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