Class A propane tank refills

[chindog]

I was looking at my notes I scribbled down during the Escapees RV Bootcamp, and during a presentation on fire safety, I had made a note to not let the propane tank get below half full. Now it is several months later, I can't remember why the tank should not get below half full. Anyone know the answer to this?

Thanks.

 

[AFchap]

Because you may run out? No idea actually. I've been using LP in vehicles since my early teens on the farm and have never heard or observed/paid attention to such a warning.

[Kirk W]

That is a good question and a thought that I've not heard of before. I have tended to run ours low by intention at times to prevent the buildup of the odorant that is added to propane as that can happen in tanks after long term use.

 

I'll do a little checking to see what I can find out.

[wildmandmc]

i believe its so tank not have to get purged. plus in the event (cold weather). loose elec. propane will run your furnace, hot water. ect.

[Fulltimer51]

i believe its so tank not have to get purged. plus in the event (cold weather). loose elec. propane will run your furnace, hot water. ect.

 

Why would the tank have to be purged??

[Kirk W]

i believe its so tank not have to get purged. plus in the event (cold weather). loose elec. propane will run your furnace, hot water. ect.

That only happens if you leave the tank sit open with no gas in it and vent it completely or when the bottle/tank is new. I also once saw a propane service take one of the 100 gallon tanks used for a small house that had sat for a very long time and invert it with the valve open for several hours and when I asked it was to drain out a collection of oils and odorants from long term use and storage. That was followed by a purge process before it was placed back into service.

 

I did send a note to Mark to see if I can find out what this was about. If it was during a fire safety presentation, I'd think that would have been by "Mac the Fire Guy" I would think.

[TXiceman]

There is absolutely no reason to only use the first half of the tank and then fill leaving 1/2 tank unused. I have no idea why they would male such a statement. We have a 5th wheel with the auto change over between the two 40# tanks. We always let the one tank run down to empty and switch to the full tank before filing the empty tank.

 

Even running the tank to empty, there should be a slight positive pressure pressure from the residual propane. What you do not want to do is to completely vent the tank to atmospheric pressure.

 

When we had a motorhome we frequently ran the propane tank down to near empty.

 

Maybe be was talking about the gasoline tank. It is not a good idea to run it down to the bottom as there is more tendency to pick up trash in the bottom of the tank. But you have a fuel filter to stop the trash from getting to the engine.

 

Did the instructor leave you an email address to contact him with any questions? I would sure be curious to hear the reason behind such a statement.

 

Ken

[chindog]

I'm not sure who the presenter was. It may have been Mark Nemeth. Mac the fire guy was not at the bootcamp I attended, so the fire safety presentation was done by someone else.

[Kirk W]

I got a reply back from Mark and he says it is fine to share it with you all. I will quote below:

 

In a fire, Mac says the fuller it is, the better, because full tanks will take longer to heat up to the safety valve pressure. A mostly empty tank will apparently pop off very quickly because the small volume of liquid propane heats up fast.

 

I didn’t come up with this, but it does make sense.

 

--

 

Mark

[Yarome]

Without seeing some type of study, that line of logic wouldn't persuade me to change how I run my tanks. My own thought being that if a fire is intense enough to cook off a small amount of propane in my tank I would, more than likely, have already vacated the area. Having a tank more than half full 'would' more than likely take longer to over pressure, but then you've got a lot more fuel being combined with the fire. It would seem to me that a limited amount of LP would be preferable to a nearly full tank... even if it took a few more minutes before it popped the OPD.

 

I would wonder though... even if a small amount of fuel would vaporize more quickly, wouldn't it have more space for expansion before over pressurizing than a full tank would? Wouldn't there be a much quicker pressure build up occur even at a lower temperature in a full tank? Would the mitigating factors cancel each other to the point where it really wouldn't make a significant difference in how long it took? If so... I revert back to the thought that it would be better to have a limited amount of fuel in such an event.

[RVTEN]

Now everyone will worry about there tank getting below half.

[Ronbo]

In the event of a fire, when it starts venting it will continue until it is empty. By the time it starts venting the rv is already a total loss so it doesn't matter, the fed will expect it to start venting.

[gjhunter01]

It's OK to run a motorhome LP tank empty the same as you would run a grill 20 lb tank empty. The only place you don't want to run a LP tank empty is when it is a residential/commercial type tank, usually 250 or 500 gallon type. By law, those systems need to be pressure checked for leaks before refilling which is usually for a fee depending on the LP company.

There is no harm or benefit to running a portable LP tank empty. Some company's charge a flat rate to fill a 20 or 30 lb bottle, so it makes sense for the tank to be empty.

I have drained and opened up 50 year old tanks and never once observed any kind buildup in them??

Greg

[nana25k]

Now everyone will worry about there tank getting below half.

X2.

[Dale P]

Mac, is Mac the Fire Guy. An ex fireman, who rel knows his stuff

[patty98311]

I am a retail dispenser to fill portable propane tanks(campground, propane dispenser, store, and gas station) we just competed our every 3 year training license requirement by the state on filling propane tanks. There were no warning requirements on allowing tanks to not be allowed to go below 1/2. While new tanks use to all be purged prior to original/first time fill this may be required but there was no mention of it any were in any of our training literature. We used to do purges some years ago but we took our system down 3 years ago as we had not used for a long time and have even dropped that part of the license as it requires more paperwork anyway. I personally would think it is probably due to the gross inaccuracy of propane gauges to ensure you don't run out.

[chindog]

I got a reply back from Mark and he says it is fine to share it with you all. I will quote below:

 

 

Thanks for tracking that down, Kirk!

 

 

 

Now everyone will worry about there tank getting below half.

 

Then my work here is done!

[Ray,IN]

I was looking at my notes I scribbled down during the Escapees RV Bootcamp, and during a presentation on fire safety, I had made a note to not let the propane tank get below half full. Now it is several months later, I can't remember why the tank should not get below half full. Anyone know the answer to this?

Thanks.

 

I adhere to the recommendation to never allow your fuel tank to go below 1/2 tank, but we use propane so little I only refill it when it get down to 1/4. tank.

[Ray,IN]

It's OK to run a motorhome LP tank empty the same as you would run a grill 20 lb tank empty. The only place you don't want to run a LP tank empty is when it is a residential/commercial type tank, usually 250 or 500 gallon type. By law, those systems need to be pressure checked for leaks before refilling which is usually for a fee depending on the LP company.

I have drained and opened up 50 year old tanks and never once observed any kind buildup in them??

Greg

That's odd, I let my 1,000 G propane tank run empty last year. I called the company, their driver came out and filled the tank with just under 800 G of propane, no mention of any pressure check.

[Kirk W]

 

The only place you don't want to run a LP tank empty is when it is a residential/commercial type tank, usually 250 or 500 gallon type. By law, those systems need to be pressure checked for leaks before refilling which is usually for a fee depending on the LP company.

That my vary by what state you are in. I was getting my neighbor's 100 gallon tank filled for her when it registered as empty but the appliances were still working. When I called the supplier for her I was told that as long as the pilot lights were still burning they would fill the tank but if the pilots were to go out they would require us to let them do a pressure drop test on the line before filling it. That is in TX.

[TXiceman]

If you size relief vales per API (American Petroleum Institute) you consider the amount of liquid in the tank and you do get to take credit for the insulation on the tank if there is any when you size the valves for being located in a fire. I have sized many on propane refrigeration systems and they have to be sized based on the maximum amount of liquid that the vessel could contain.

 

Mark's concern and belief for 1/2 tank is unfounded. As for the amount of vapor relieved, you are better off with a smaller amount of liquid. The lager volume of liquid will take slightly longer to heat up, but as soon as a tank is in a fire, the liquid will start vaporizing and once it reaches the relief valve setting it will relieve the pressure until the pressure drops to some where about 10% under the relief valve setting.

[gjhunter01]

Yes, as Kirk stated as long as there is pressure in the system it is not considered empty, but you are running on fumes. For legal reasons if a residential system was empty (no pressure) and it gets refilled it has to be pressure tested to determine the system does not have a leak in it. When a tank is refilled a pressure test is performed and the operator and owner need to sign off with a copy being kept for records. A house blew up in North Houston a couple of years ago after a empty refill and no record of a pressure test being done, it was a pretty serious event for the LP company.

If a tank is involved in a fire and the relief valve pops, it's game over until it burns itself out, no reason to hang around.

Greg

[mohamer]

A lot of Propane and Natural Gas systems no longer have pilot flames.

Now what to do if the tank says it is empty????????????

[Kirk W]

If the level indicates empty you need to fill as soon as practicle since you don't want the pressure inside to drop too low or it will need to be purged in order to get them to fill it. But the key is not what an indicator of level says but the internal pressure.

[gjhunter01]

If there is no pilot light in the house, we would ask the owner to turn on the stove or one of the LP appliances. If it lights up then we are good to go and fill the tank. If it don't light up then a pressure test is required. We can pressure the system by opening and then closing the valve on the delivery truck without actually filling the tank with propane. Then we close the main house feed valve and see if the system loses pressure over a 5 min period with a pressure gage attached to the system.

What's amazing is that it would be the same customers that would run out 3-4 times during a winter. It takes about a half hour per test, time better spent delivering LP to customers on auto fill.

 

Greg