Well, duh. Point is, they don't use "complicated instruments" as
claimed by someone else.
They actually sell a "gas gauge" for 20 pound BBQ tanks. It's a
foolish thing to buy for a few reasons. You can buy a second tank for
about the same cost as the gauge. The advantage of a second tank, over
a gauge is that you can run tanks until empty, then simply swap out
the empty tank for the full spare and still finish cooking your
dinner. With a gauge, you still have to judge whether you have enough
for the meal you are about to cook. When you get near "low", and you
are planning a party, you have to start guessing if it is enough to
last you, or go get a refill on a tank that's not empty.
Actually, it's near a constant pressure until the last few
drops of liquid is used. The liquid "boils" off until the
vapor pressure reaches 51 to 172 psi in the tank, depending
on liquid temperature (32 to 100 degrees F range shown) See
"(S)tandard(T)emperature(P)ressure" in a chemistry book. A
pressure gauge would make a much better thermometer. ;-)
Weight or depth of liquid in tank is best way of determining
if you will make it thru that last steak.
empty (tare) weight is stamped on the tank, add 80%(20%
vapor space) of 4.24 (lb/gal) times 5 (gal) to tare for a
full tank weight. The (O)verfill(P)rotection(D)evice valve
is a float in the tank that shuts off the valve when the
liquid reaches its maximum safe full level. Filling a tank
is easy, connect supply hose, and fill until the flow stops.
Charge for the gallons on the gauge (usually around 4.2
gal) or a flat 5 gal refill fee. ;-)
Be safe, several years ago, two 20 gallon "stove" tanks
laying flat in the back of a pickup in the hot Texas sun
exploded like missiles. Appeared the tanks were improperly
filled, with no vapor space for expansion.
I have eight tanks at two houses, three at one house, and two at a cabin.
Sometimes I have taken up to eight of them in to be filled. Sometimes on
the rentals, I will pull a tank when it's low so it doesn't run out while
the guest is there and I'm out of town. When you get eight tanks filled,
how does one keep track of how much has gone into each? And how does the
geek know if he is filling to the suggested 80-85%?
On one tank fills, it's pretty easy to get it close. After that, going
through eight tanks, and using up to 35 gallons, I think the only way to
properly fill is by weight. The rolling numbers will tell the eventual
grand total, but only weight will tell you how much is in a partial that
you're adding to. PLUS, sometimes if they're flat empty some suppliers will
refuse to fill unless they perform an additional purge. (translates $)
So, although filling tanks isn't up to rocket trajectory mathematics, it is
not really simple. Well, it really is, but most of today's idiots don't
have a clue. And I hate to stand there and wonder if this guy is
overfilling or even knows what he's doing. Yes, they do have the overflow
screw to tell them, but do you like to be standing out there with all that
gas around, and a couple of tons more in the tank? I don't.
Whatever winds yer clock. I actually prefer fillers who have "complicated
equipment". Their help is better than some pimply little girl who's had
fifteen minutes training and a ten minute attention span.
Paper and pencil? Is that too high tech and complicated? How about a
He doesn't need to know that. All he needs to know is the weight
stamped on the tank. The OPD will prevent him from even screwing that
up if he falls asleep during the fill process. That's why they made
Steve. Filling a standard 20# propane tank properly, even when doing
20 at a time, is VERY simple. The tanks by law, have the weight they
should be when full stamped on them. All you do is place the tank on
the scale, and fill it until it is at the stated weight. If you have a
partial fill and they sell by the pound, rather tnan by the tank, you
just write down the before and after weights and do simple subtraction
with a pencil on a paper bag. The OPD Blocks overfilling. It doesn't
divert to the atmosphere. Forget any "rolling numbers". Not needed,
and I've yet to see any place that even looks at gauges when they have
them. They measure by weight only, regardles of the number of tanks..
There is TARE or just a T stamped on the collar (handle). That is the tare
weight, or the weight of the empty container. The contents are rated at
pounds, but sold as gallons, so add it up. Propane weighs approximately 4.2
pounds per gallon according to Wikipedia. Or take a bathroom scale, and
weigh the tank. Use a calculator and subtract tare weight. Or ask your kid
to do the math for you.
Just an FYI update...
I typically go with Blue Rhino replacements from Walmart, but I was in
a hurry and bought an AmeriGas replacement at Home Depot.
Here's the info from the tanks & labels:
- Tare Weight - 17.0 lbs
- Net Weight - 17.0 Lbs Propane
- Tare Weight - 17.5 lbs
- Net Weight - 15.0 Lbs Propane
I don't recall the exact prices, but I can just about guarantee that
the Home Depot price wasn't 13% percent cheaper!
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