Filling Propane Tanks

According to API Table 53/54, a mass of liquid propane at 60F will expand in volume by about 5 Percent when warmed up to 86F.

ktmrfs wrote:

Since LPG can be a mixture of propane, butane and isobutane, all of which have different specific gravities, how does this affect a fill by weight?

same as volume, see NFPA sec 4 and/or appendix F
1998 version
https://www.nfpa.org/assets/files/aboutthecodes/58/58-98-pdf.pdf

Fortunately the sg does not change day to day.

42% of WC weight is based on sg ~.51
80% of WC volume is based on 40F AND sg ~.51

youtube fires with cylinder show venting ROAR then the valve shuts to reopen again to another roar ...

Worthington tanks. Costco. Around 1985.

Had the tanks "filled" in Nogales in January. Cold weather demands propane not butane. Tanks were carried in open bed of pickup.

Got to near the turnoff to San Blas. Temperature in the high 80's.

One relief valve popped. I pulled over on the exit lane the beginning of the toll road to Tepic. Shut the engine off and exited the truck.

Several minutes later the 2nd tank relief valve vented but it was not a controlled release - it was a catastrophic venting. Emptied the tank in under a half minute. The first tank took something like 3 or 4 minutes to empty.

Both valves were ruined.

A friend, who was a propane installation guru before he retired quipped "Venting too frequently ruins valves and allows 100% discharge of contents". Worthington tank said exactly the same thing a few months later.

My 83 gallon motorfuel tank* on Quicksilver has a full size relief valve and so does my 100 pound cylinder - "Vince" said 100 pound cylinders with this type of relief valve (a brass hex around 2" across) are rare as hen's teeth.

*It serves solely as vapor duty

Sure spooked me. Mixed with air in just the wrong way, propane makes a Fuel Air Explosive that makes dynamite look like a ladyfinger.

Since OPD type tanks refuse to fill down here, I have no OPD 20 lb pots. Gas depots fill by weight and they do open the liquid level valve. With two quarts of process oil inside a tank, using tare weight only is hazardous.

Oil? Ever pick up a really heavy empty pot? Those lube oils used in refinery process streams to lube valves and pumps eventually turns to goo inside the pot, cylinder or tank. MEK, or lacquer thinner will dissolve the goo. A quart for a 20 lb pot, a gallon for a 100 lb cylinder.

Process oil/goo absorbs LPG odorant. Spilled oil will smell like an intense propane leak. Skin, clothes, wood, soil, water, all absorb the smelly goo. Tank cleaning is obnoxiously demanding because of how to deal with the smell.

dougrainer wrote:
Since people do not care to research the issue, here is a simple version of what can happen with a slightly overfilled tank and THIS has happened and documented. A lot of RV'er transport 20 or 30 lb DOT tanks in there Motorhome or Towable(usually 5th wheels) storage. So, it is 70 degrees when filled and they overfill the DOT tank and you throw it in the RV and take off. You go to a climate that is 95 plus and camp out. The interior storage heats up and the LP heats up. Then its system blow out valve opens and spews LIQUID LP inside your RV. What happens when that LP reaches an Ignition source? There are lots of them inside and up in a RV. Most would blame the Norcold 1200 refer if it had one:B Same thing can happen in your enclosed Pick up bed or the trunk or interior of your car. I have seen enough REAL evidence in 40 years that I believe what Texas mandates and what we practice is the BEST way to handle LP. Doug

That is beyond silliness, it’s well into fantasy.

A 20 or 30 pound cylinder uses ,as per DOT regulations, a CG-7 spring loaded over-pressure valve. It begins to open at 360 psi, and is fully open at 480 psi, but it recloses at 240 psi, the design working pressure of those tanks.

Propane doesn’t expand much with temperature, it does however produce more vapour and therefore pressure. At 60 deg. F. propane is at 92 psi, at 130 deg. F. that has only risen to 257 psi, which is still about 100 psi BELOW the pressure relief valves opening point.

Beyond all of that, the pressure relief valve is at the TOP of the tank, thus if it opened would mean that ONLY vapour would come out, besides the fact that propane boils at -42 deg. F. and so it would in this ‘overheated’ situation be some 150++++ deg. F. hotter than that and so could not be a liquid once it’s not contained in a pressurized vessel.

Even if the cylinder were drastically over-filled, not “even slightly over-filled”, could the ‘spew liquid LP’ be remotely possible.


Rant over.

dougrainer wrote:
Since people do not care to research the issue, here is a simple version of what can happen with a slightly overfilled tank and THIS has happened and documented. A lot of RV'er transport 20 or 30 lb DOT tanks in there Motorhome or Towable(usually 5th wheels) storage. So, it is 70 degrees when filled and they overfill the DOT tank and you throw it in the RV and take off. You go to a climate that is 95 plus and camp out. The interior storage heats up and the LP heats up. Then its system blow out valve opens and spews LIQUID LP inside your RV. What happens when that LP reaches an Ignition source? There are lots of them inside and up in a RV. Most would blame the Norcold 1200 refer if it had one:B Same thing can happen in your enclosed Pick up bed or the trunk or interior of your car. I have seen enough REAL evidence in 40 years that I believe what Texas mandates and what we practice is the BEST way to handle LP. Doug

Don’t know of any RV or Motor Home that has the propane tank located inside a closed compartment all are at least open on the bottom, some even have louvered doors. That would keep the vapor outside the RV, there could still be ignition sources within reach of the vapor, but it isn’t inside of the RV.
Now some person may carry a container inside said RV, but doing so is a lack of common sense.

dougrainer wrote:
I find it funny a person from OREGON defending an unsafe LP fill practice. HIS state (New Jersey also) has not allowed their own drivers to fill their Auto's for almost 70 years as an UNSAFE practice. This is what Oregon stated in 1951 to pass the Law.

"Back in 1951, when Oregon first mandated that only trained station workers could put "Class 1 flammable liquids" into cars, the state mainly didn't want people accidentally blowing things up".

So, HOW many people in the other 48 states have blown themselves UP in 70 years filling the Auto Gas tanks????? :B Stay in Oregon and let the rest of us live normal lives:W Doug

well, oregon is sort of a no self serve. Motorcycles can and usually are self serve, have yet to have a pump jockey that would even fill my motorcycle, and same for "classic cars", I routinely self serve my 1997 model year roadster, and if you are in lightly populated areas, many stations are self serve after hours. And then there is diesel which is not a a class 1 flamable, so I've never been stopped from filling my truck.

That said, I'm not in favor of the NO self serve, but it probably will be a long time before it gets changed.

And for filling propane, while fill by weight is the best way, I'd probably have to drive 25 miles or more to find anyone that fills by weight or even has a scale to fill by weight. right or wrong my experience is that the fast majority of refill stations use the bleed valve. same when I'm on the road in or out of state. It's been rare when a refill station fills by weight.

And I'd never ever let someone fill by the OPD float alone. I've never had a tank that stopped filling by the OPD valve when using the bleed valve and stopping when it started to spit.



I'm not defending any practice, just stating what I've experienced.

I just watch to make sure they shut if off as soon as the bleed valve starts to spit liquid.

Since people do not care to research the issue, here is a simple version of what can happen with a slightly overfilled tank and THIS has happened and documented. A lot of RV'er transport 20 or 30 lb DOT tanks in there Motorhome or Towable(usually 5th wheels) storage. So, it is 70 degrees when filled and they overfill the DOT tank and you throw it in the RV and take off. You go to a climate that is 95 plus and camp out. The interior storage heats up and the LP heats up. Then its system blow out valve opens and spews LIQUID LP inside your RV. What happens when that LP reaches an Ignition source? There are lots of them inside and up in a RV. Most would blame the Norcold 1200 refer if it had one:B Same thing can happen in your enclosed Pick up bed or the trunk or interior of your car. I have seen enough REAL evidence in 40 years that I believe what Texas mandates and what we practice is the BEST way to handle LP. Doug

I find it funny a person from OREGON defending an unsafe LP fill practice. HIS state (New Jersey also) has not allowed their own drivers to fill their Auto's for almost 70 years as an UNSAFE practice. This is what Oregon stated in 1951 to pass the Law.

"Back in 1951, when Oregon first mandated that only trained station workers could put "Class 1 flammable liquids" into cars, the state mainly didn't want people accidentally blowing things up".

So, HOW many people in the other 48 states have blown themselves UP in 70 years filling the Auto Gas tanks????? :B Stay in Oregon and let the rest of us live normal lives:W Doug

ktmrfs wrote:

dougrainer wrote:

owenssailor wrote:
At the places I have filled tanks in Canada it has always been by weight. In the US it has always been done using the screwed out vent valve.

Using the vent valve is a much better option id filling a tank that is not completely empty since the propane is metered.

Not True. Certain States, (Texas is one) have extensive STATE rules for Natural and LP Gas. IF some of the posters that do not believe WEIGHT is the safest way, they need to RESEARCH the subject before claiming weight is not needed. I have been Licensed By the RAILROAD COMMISSION for 38 years in the State of Texas. I am licensed to WORK on LP systems and to FILL Tanks and Bottles. This is who regulates LP in the state. We have to go for training before you get Licensed and we have to go for training every 3 years to keep you current. They always bring up actual stories and Pics of what happens when a DOT tank is overfilled and conditions cause it to vent due to too much liquid. Does not always happen obviously, but when it does you do not want to be around. Doug

Since LPG can be a mixture of propane, butane and isobutane, all of which have different specific gravities, how does this affect a fill by weight?

I am not aware of BUTANE being retailed in the USA anymore. Mexico, yes. Isobutane,is used as a refrigerant. Do not know who would fill or if you can have containers that can be refilled . Butane has gone away because it does not function well in very cold climates. They used to produce Butane in the summer and LP in the winter, but like I stated, not aware of any retailer that can get or would sell Butane in the USA. Weight of Butane is 4.86 lb per gallon. Weight of LP is 4.23 lb per gallon. So, you can get MORE LP liquid volume in a DOT cylinder than Butane liquid volume. LPG is NOT a mixture of various gases. Each variant (LP/Butane/Isobutane) is produced and not mixed at the Oil refinery. That does not mean local retailers will contaminate their existing storage containers with mixed fuel. Not smart. Doug

I live in the MD suburbs of DC. Locally, the sources of which I am aware fill 20# Cylinders by weight exclusively.

Seems the safest way to me. Of course, YMMV.