Propane Tanks Explained
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< (In-Line Sensor is less satisfactory than In-tank float sensor see below)
Should I buy a in-line gauge
to tell when the 20 pound tank is empty.
Long answer and more information than you might want is below.
About LP Gas *
Liquid propane (LP) is a petroleum product that is a gas at regular
environmental pressures and temperatures. Under moderate pressure
inside The Tank, LP is a liquid that readily vaporizes to become gas as the
pressure is released. For this reason, commonly available, add-on pressure
gauges don't actually tell you how much liquid propane you have left. They
will tell you when the pressure's running low, but by then it may be too late
if you've already started grilling.
Two inside tank float sensors that work well for an external gauge
is a product on the market that gives an accurate,
reliable measurement of the level of liquid propane left in the tank.
Explanation of propane tanks magic in more detail:
Seems the bottom line is that the propane inside the bottle has a set known
temp of magic transformation. Liquid propane’s boiling point is –44°F
(-43°C). That is the point where the liquid begins to turn to vapor. Just as
in boiling water, the more heat that is introduced to the process, the more
rapid the transfer of vapor. When propane gas is pressurized, it readily
turns to a liquid state. As liquid propane is contained in a pressure vessel
(tank), the following events will occur:
• The liquid in the tank begins to boil.
• Vapor is produced which is contained in the tank.
• The increase in vapor causes a corollary increase of the pressure in the tank.
• Soon the pressure in the tank builds to a high enough level to stop
the boiling off of the LP. The pressure in the tank has in effect caused the
boiling point of the LP to be raised.
The mixture of liquid versus gas in the tank will remain in this state of
balance until either of the following two conditions is met:
1. Gas is released from the tank causing internal pressure in the tank
to drop, which allows the liquid to boil off more gas.
2. The temperature of the tank changes. If the temperature in the
tank increases, the resulting effect is a lowering of the boiling point of the
LP and more vapor will be produced.
See pdf file here of the above information and more including
a chart of the correlation between temperature and tank pressures. *** Key file to look at ***
How can I tell how much LPG is left in the cylinder?
There are a number of ways to check this:
, a cylinder can be weighed to check how much product is left in
the cylinder. The weight of the LPG remaining in the cylinder is total weight
of the cylinder plus the LPG, less the empty weight or tare weight, of the
cylinder. (The regulator and any other fittings should be removed prior to
weighing the cylinder).
, some cylinders have gauges which show the amount of
LPG contained within the cylinder. The in-line gauges
are less desirable
than the in-tank gauges
that have floats that sense exact liquid level.
(This in-line gauge is one that is the FULL / EMPTY gauge for 25 bucks.)
See The Tank
advertisements for in-tank float gauges.
, liquid crystal gauges, which stick to the outer surface of the
LPG cylinder are available, and these show the level of the liquid LPG within
the cylinder by indicating a colour change at the interface between the
liquid and vapour levels caused by the temperature variation.
, if the cylinder is being used, then it may be possible to see
the level of the LPG in the cylinder by observing the level of the sweating
on the cylinder wall.
, it is possible to see the level of the LPG liquid within a cylinder
by pouring boiling water down the side of the LPG cylinder. The liquid level
is revealed where a condensate or frost line occurs.
What does a 20lb propane cylinder weigh when empty?
17-18 pounds, depending on the manufacturer.
How long on average does a 20 lb propane gas grill tank last?
1 gallon of Propane ~= 4.23 lbs ~= 91500 Btus
1 lbs of Propane ~=22000 Btus
20 lb tank of propane holds approx 4 gallons of propane (366000 BTUs)
Your grill will last 366000 BTUs/ Grill BTU output hrs
More information on Liquefied Petroleum Gas (LPG)or(LP)
Frequently asked questions on Liquefied Petroleum Gas (LPG)or(LP)
Refilling Propane Tanks - cheaper than exchanging
Refilling your own barbecue tank is cheaper than going to an exchange
location. When you exchange your tank at a gas station or convenience
store, not only does it cost more than getting it refilled at any
, but you also llose the propane left in your
exchanged tank. With us, you pay only for the propane you buy.
Convert grill from propane to Natural gas (LP to NG)