Propane pressure gauge

[GreenSailor2]

What I open the solenoid valve on my propane tank the pressure guage drops to zero. Any help on the causes?

 

[dlochner]

What I open the solenoid valve on my propane tank the pressure guage drops to zero. Any help on the causes?

Is the valve on the tank open?

 

[tfox2069]

Does the pressure valve read differently when the tank valve is open and the solenoid is off? Does the tank have any propane in it? I will say the pressure reading is pretty meaningless in my experience. I've had the tank reading just find on the pressure gauge, and then when I try to cook I can't get gas, check again and the gauge suddenly reads zero, and the tank is empty. I really don't judge anything by the pressure gauge anymore, and go by weight, always keeping a second tank full to switch to.

 

[Ralph Johnstone]

I've had the tank reading just find on the pressure gauge, and then when I try to cook I can't get gas, check again and the gauge suddenly reads zero, and the tank is empty.

Sorry, but as long as there is one drop of LIQUID propane left in the tank, the tank pressure will be exactly the same as if the tank were full. Only once that last drop changes from a liquid to a gas, will the pressure begin to drop.

The only way to determine the liquid propane remaining in the tank is to weigh the tank as you've said.

 

[FastOlson]

While the replies about liquid and pressure are technically correct, there does seem to be some useful info from having a gauge in the system. I had a gauge on the propane system on our prior boat and if nothing else it was invaluable to check the "downstream" piping for leaks. Admittedly I did, informally, keep track of how often we were using the propane, and did take the tank in for a refill well before it needed one. I recall that when I actuated the solenoid after turning on the tank valve, I could watch the gauge as a burner was used for a drop/change in indicated pressure.
Some RV users have it easier.... they can pour water down the side of their tank and observe where vapor condenses on the side to directly see the inside liquid level......
Of well, if owning a yacht was easy, anyone could buy one!

 

[Ralph Johnstone]

While the replies about liquid and pressure are technically correct, there does seem to be some useful info from having a gauge in the system.

What the gauge doesn't tell you is:

"WHO THE HELL FORGOT TO REFILL THE TANK LAST TIME THE BOAT WAS OUT"

 

[JamesG161]

The only way to determine the liquid propane remaining in the tank

Well if not in use, True.

Some RV users have it easier.

Boaters too, but I hate pouring water on a tank.



Magnetic Gauge Propane Butane LPG Fuel Gas Tank Bottle Level Indicator,Propane Tank Gauge Level Indicator 2PACK - Walmart.com
$9
Jim...

 

[dlochner]

Sorry, but as long as there is one drop of LIQUID propane left in the tank, the tank pressure will be exactly the same as if the tank were full. Only once that last drop changes from a liquid to a gas, will the pressure begin to drop.

The only way to determine the liquid propane remaining in the tank is to weigh the tank as you've said.

The main reason to have a pressure gauge to evaluate the integrity of the lines after the tank. With all the burners off, the tank valve open, open the solenoid and watch the pressure. If there is a leak, even a small one the pressure will drop. If the line is intact the pressure will remain the same.

It is also interesting to watch the pressure as it changes with ambient temperature. On really cold days the gauge would read much lower than the next really hot days.

 

[dlochner]

Well if not in use, True.


Boaters too, but I hate pouring water on a tank.

View attachment 208861

Magnetic Gauge Propane Butane LPG Fuel Gas Tank Bottle Level Indicator,Propane Tank Gauge Level Indicator 2PACK - Walmart.com
$9
Jim...

Do those magnetic gauges work on Aluminum tanks?

 

[JamesG161]

If in a bad spot on your boat, Add this too...

TELESCOPING INSPECTION MIRROR - Walmart.com

$6 and useful for other spots on your boat.

Jim...

 

[JamesG161]

Do those magnetic gauges work on Aluminum tanks?

They have stick on ones too.
Jim...

PS: Duck tape still works

 

[JamesG161]

It is also interesting to watch the pressure as it changes with ambient temperature. On really cold days the gauge would read much lower than the next really hot days.

I guess this post will tell most info on Propane.

Next I could post the Latent Heat of Vaporization so you can see if there is enough Ambient heat to cook too.

Jim... aka Chemical Engineer

 

[dlochner]

I guess this post will tell most info on Propane.

View attachment 208863

Next I could post the Latent Heat of Vaporization so you can see if there is enough Ambient heat to cook too.

Jim... aka Chemical Engineer

That graph pretty much reflects my real world observations. Around 100 PSI cooler days and around 150 psi on hot days.

We always have enough propane to cook on, two 6# tanks and a couple of 1# bottles with a hose adapter to plug into the system in an emergency.

 

[Ralph Johnstone]

Well if not in use, True.

Dissected that every way from Sunday and still can't figure out why the weight won't determine the remaining mass of liquid propane while the tank IS in use.

Enquiring minds want to know.

 

[Ralph Johnstone]

you can see if there is enough Ambient heat to cook too.

Laugh as you may, but I can remember living in a charming little burg named Fort Nelson years ago when everyone would start putting 100W bulbs against their outdoor propane tanks and wrap the whole mess in blankets when it got down to -30C (-22F). The show was over by the time it hit -40C (-40F). Actually about -35C as you still needed a few PSI to overcome the pressure reducing valve. Supper was a little slow in coming those cold winter nights.

 

[JamesG161]

Dissected that every way from Sunday and still can't figure out why the weight won't determine the remaining mass of liquid propane while the tank IS in use.

Enquiring minds want to know.

Simply put for just you Ralph. [often needed I see]

Record the changing weight with a precision scale. Let your Admiral cook while you hand weigh the tank.

Start with a full Tank and weigh each use. Then you are right.

Keep that Propane use LOG on your boat too.

By the way..
Not all fills are the same weight.


Have fun cooking..
Jim...

 

[Ralph Johnstone]

But all I ever wanted out of life was "how to determine the remaining amount of liquid propane in the tank at any given time" and you shook me to my foundation by saying it couldn't be done "while the tank was in use." HOW ? ? ? ? ?

Well if not in use, True.

Now remember, I am recovering from COVID at this time (and wasting my days away) so answer accordingly .

 

[JamesG161]

so answer accordingly [ sent with TLC]

Ok you must know the following Stable Temperatures....

Full Tank...
1) Weigh the Tank Full
2) Record that Stable Temp

Used Tank..
1) Weigh it
2) Record Stable Temperature

Now here is the key issue.
Both Stable Temperatures must be about the same or you have to use a correction calculation.

Otherwise the change is weight will yield the right amount left.
Jim...

 

[Ralph Johnstone]

I'm starting to feel like that nightmare when you're in a long train tunnel and all of a sudden, you see a light at the far end of the tunnel.

But in this case the light is receding and you've got to catch up to the light or you'll never know the truth. I keep running but it recedes further, and further, and further, and further, but I just can't catch it.

I'll never learn the truth. But I've got to keep trying.

All tanks are labelled with their MT and full weights. The odd units are the result of my using an old electronic fish scale when I check my tanks. I grab the handle of the tank using the old fish scale hook and just lift.

If the weight is now eg. 14 lb - 0 oz, I know I have three (3) pounds of propane (liquid and gas) remaining in the tank. I don't care how much liquid, I don't care how much gas, all I want to know is the total mass of propane. Any time I want to know what's in the tank, I can. Quick as that. Slam the propane locker lid and it's done. What are those two tanks laying over there ? A quick lift tells me either MT or full.

Both Stable Temperatures must be about the same or you have to use a correction calculation.

I don't care what the temperature of the tanks and their contents are, hot, cold, freezing, middling, the total mass never changes. Mass is neither added or subtracted by heating or cooling. Energy content does not change the mass.

And for the endless question, "what the #%$^%&* difference does it make if the tank is in use or not ? " Whether the tank is hot from the ambient or cold from a heavy load, my only quest in life is the weight of the propane mass (liquid and gas) at that precise moment in time.

 

[Richard19068]

I don't care what the temperature of the tanks and their contents are, hot, cold, freezing, middling, the total mass never changes. Mass is neither added or subtracted by heating or cooling. Energy content does not change the mass.

And for the endless question, "what the #%$^%&* difference does it make if the tank is in use or not ? " Whether the tank is hot from the ambient or cold from a heavy load, my only quest in life is the weight of the propane mass (liquid and gas) at that precise moment in time.

I agree.

At the risk of flogging a dead horse:

Propane Volume Basics
We will explain basic principles that affect the liquid propane volume. Therefore, you can better understand differing tank gauge readings in different extreme temperatures. Here’s an example assuming a 250 gallon propane tank has 100 gallons of propane at 60°F. The industry standard 60°F is universally recognized as the base reference point for liquid propane volume correction. In addition, the following are also true:

• A properly functioning float gauge will read 40%
• 100 gallons of propane weighs 424 pounds (4.24 lbs per gallon)

If there’s a huge temperature drop (over 20°F) the gauge will indicate that there is less propane in the tank. The gauge dial sits between 35% and 40% following the temperature decrease, so the tank still has 424 pounds of propane. While the propane volume has dropped, the amount of propane has not decreases. It has simply become more compact, which means the amount of usable energy has not decreased. If the temperature were to increase by the same respective amount, the gauge would indicate a higher volume of propane. However, there would still be 424 pounds of propane in the tank. As temperature decreases, liquids become more dense. Therefore, as temperature increases, liquids become less dense and expand. Propane is a liquid and is subject to the same rules of mother nature.