Gas BBQ propane tank question

[T_R_Oglodyte]

Today I fired up the grill for the first time this season today. Just before putting the cover on it for the winter. I had connected a fresh propane tank. I had the tank filled at local gas station - not a cylinder exchange arrangement.

Shortly after startup, the gas flow decreased. I checked the tank and connections, and the pressure regulator on the end of the hose and the hose itself were coated with ice. There was also frost on the threaded connection to the tank, but the tank itself was normal temperature. When I disconnected the hose from the cylinder there was pressure in the connector itself - as the thread disengages propane started leaking out and when i I removed the hose there was a little "pop" accompanied by shot of propane from the end of the hose.

So it's evident that the cylinder was delivering liquid propane through the threaded connection and into the pressure regulator , and the propane was vaporizing in and downstream of the pressure regulator. But the question comes as to why the cylinder is delivering liquid instead of vapor? My thought is that the tank must have been overfilled so that there is little or no headspace inside the tank. If that's the case, then I presume the best solution is to just draw down the tank, perhaps by running one burner at lowest setting for awhile. Then as headspace develops in the tank the tank should start acting normally.

But I'm not that familiar with the mechanics of propane tank connections, which is prompts my question. Is an overfilled the only explanation? Or might there be some other problems in the fittings that would cause a tank to deliver liquid instead of vapor?

 

[CO skier]

Google is amazing.

Propane 101, Propane Regulator Facts

Propane 101 and Propane Regulator Facts from GasHosesandRegulators.com

gashosesandregulators.com

My propane tank and regulator ice up and the propane output is dropping.

What can I do when the propane tank and regulator freezes?

 

[T_R_Oglodyte]

Google is amazing.

Propane 101, Propane Regulator Facts

Propane 101 and Propane Regulator Facts from GasHosesandRegulators.com

gashosesandregulators.com

My propane tank and regulator ice up and the propane output is dropping.

What can I do when the propane tank and regulator freezes?

I googled that, and that does not describe my situation. I am very familiar with icing up of the tank as described in the article. That happens when you're drawing too much propane out of the tank. Been there, done that. And that always has ice on the side of the tank.

As noted in the article in normal operation, the heat of vaporization for the propane being removed is taken from the liquid propane in the tank, cooling the propane in the tank. If the temperature of the propane drops below freezing, the system ices up, as noted. But in that circumstance the propane tank itself will be frosted or icy, because the propane is below freezing temperature.

That does not describe my situation. As I noted the temperature of the tank is normal.

What is unique about this is that there is no ice on the tank, and even with minimal gas flow the icing still occurs in the hose. Also, when I disconnect the threaded coupling there is back pressure at the pressure regulator.

Given the that icing occurs only down at the threaded connection and downstream, the back pressure when I disconnect, and the fact that the propane in the tank is still at normal temperature, I don't seen any conclusion other than that propane is leaving the tank as liquid, not as gas., and it is then vaporizing in the pressure regulator and the connector.

So what could be causing liquid propane to exit from the top of the tank?

 

[sdbrier]

I agree that the tank is over full. I would just let some out and see if it continues. As modern valves have a safety closing valve you simply cannot open the valve and let it out. You could remove hose from the the inlet side of the regulator. Remove tank and take to an open safe place. When you open it if you get some liquid and not all vapor it is too full. Bleed it until it’s just vapor. Then put it back together. Just my .02 worth.

 

[buzglyd]

Propane grill? I expected more out of you.

 

[CO skier]

Given the that icing occurs only down at the threaded connection and downstream, the back pressure when I disconnect, and the fact that the propane in the tank is still at normal temperature, I don't seen any conclusion other than that propane is leaving the tank as liquid, not as gas., and it is then vaporizing in the pressure regulator and the connector.

So what could be causing liquid propane to exit from the top of the tank?

An overfull tank is a good explanation, which would mean the overflow valve failed, and you have a defective and dangerous propane tank.

Process of elimination and safe diagnosis options:

1) Try the warm water down the side of the tank trick to determine where the vapor space meets the liquid phase. No temperature difference top to bottom? Overfilled tank. If the vapor space is at the top shoulder of the tank, then it is likely not overfilled.

or try

2) Borrow (or buy a spare tank from grocery store or The Home Depot displays). Plug it in; if it works, then the old tank is a defective and dangerous propane tank. Take it to a propane dealer. If you get the same icing phenomenon with the new tank (unlikely), it must be the regulator, somehow.

 

[Cornell]

I’d like to ask a tangential Q here. I’m moving in a few months and will have a gas line for my grill so I will no longer be using tanks. Do I need a different fitting / adapter for the gas intake on the grill when I make this switch ?

 

[sdbrier]

I’d like to ask a tangential Q here. I’m moving in a few months and will have a gas line for my grill so I will no longer be using tanks. Do I need a different fitting / adapter for the gas intake on the grill when I make this switch ?

if you are moving to an area that has natural gas, then yes you’ll need a different regulator. If you’ll be on an lp bulk tank you won’t need to change it.

 

[Passepartout]

I’d like to ask a tangential Q here. I’m moving in a few months and will have a gas line for my grill so I will no longer be using tanks. Do I need a different fitting / adapter for the gas intake on the grill when I make this switch ?

More importantly, you'll need different orifices in the grill. The local natural gas co. can set this up. There should be no charge to do this.

 

[JeffC]

Check with the manufacturer to see if they have a conversion kit for your grill. If not you can try a universal kit, but these can be hit or miss as to how well they work. If your new house doesn’t have a piped hookup for the grill you’ll need to have a plumber install one.

 

[bbodb1]

Propane grill? I expected more out of you.

Wasn't a troglodyte using a gas propane grill one of the scenes in 2001: A Space Odyssey?

 

[BJRSanDiego]

Today I fired up the grill for the first time this season today. Just before putting the cover on it for the winter. I had connected a fresh propane tank. I had the tank filled at local gas station - not a cylinder exchange arrangement.

Shortly after startup, the gas flow decreased. I checked the tank and connections, and the pressure regulator on the end of the hose and the hose itself were coated with ice. There was also frost on the threaded connection to the tank, but the tank itself was normal temperature. When I disconnected the hose from the cylinder there was pressure in the connector itself - as the thread disengages propane started leaking out and when i I removed the hose there was a little "pop" accompanied by shot of propane from the end of the hose.

So it's evident that the cylinder was delivering liquid propane through the threaded connection and into the pressure regulator , and the propane was vaporizing in and downstream of the pressure regulator. But the question comes as to why the cylinder is delivering liquid instead of vapor? My thought is that the tank must have been overfilled so that there is little or no headspace inside the tank. If that's the case, then I presume the best solution is to just draw down the tank, perhaps by running one burner at lowest setting for awhile. Then as headspace develops in the tank the tank should start acting normally.

But I'm not that familiar with the mechanics of propane tank connections, which is prompts my question. Is an overfilled the only explanation? Or might there be some other problems in the fittings that would cause a tank to deliver liquid instead of vapor?

Steve, you have an interesting problem. I'm hoping that when you figure it out, that you repost it.

One way to bleed liquid or gas out of your tank is to take a screw driver and loosen the gas vent. When the tank is being filled, the operator will crack it open a little and it'll hiss. When it sputters, that indicates the the liquid is at the right height. Cracking it open should vent the gas. You probably want to wear a pair of leather gloves in case you let the spray hit your fingers.

One way I check the tank is to shake it sideways. If it is "full" (not over-filled) is to rock it back and forth. If I can feel the liquid sloshing around I figure that it is full. I suspect that if it is 100% liquid that it'll feel heavy but no "sloshing".

 

[isisdave]

You can also weigh it. The tare weight should be stamped into the collar. If not, the "usual" weight is 17 pounds.

I think a full tank holds about 20 pounds of propane.

 

[easyrider]

Today I fired up the grill for the first time this season today. Just before putting the cover on it for the winter. I had connected a fresh propane tank. I had the tank filled at local gas station - not a cylinder exchange arrangement.

Shortly after startup, the gas flow decreased. I checked the tank and connections, and the pressure regulator on the end of the hose and the hose itself were coated with ice. There was also frost on the threaded connection to the tank, but the tank itself was normal temperature. When I disconnected the hose from the cylinder there was pressure in the connector itself - as the thread disengages propane started leaking out and when i I removed the hose there was a little "pop" accompanied by shot of propane from the end of the hose.

So it's evident that the cylinder was delivering liquid propane through the threaded connection and into the pressure regulator , and the propane was vaporizing in and downstream of the pressure regulator. But the question comes as to why the cylinder is delivering liquid instead of vapor? My thought is that the tank must have been overfilled so that there is little or no headspace inside the tank. If that's the case, then I presume the best solution is to just draw down the tank, perhaps by running one burner at lowest setting for awhile. Then as headspace develops in the tank the tank should start acting normally.

But I'm not that familiar with the mechanics of propane tank connections, which is prompts my question. Is an overfilled the only explanation? Or might there be some other problems in the fittings that would cause a tank to deliver liquid instead of vapor?

Just take it back and get another is pretty easy and safe. My brother in law had an overfilled tank relief valve spew while he was smoking salmon. Lucky he was in the house because it exploded and left a crater in the driveway and messed up his Treger.

EDIT
Ok, I got part of this wrong. It wasn't a Tregar, it was a Webber. It wasn't the relief valve, it was a small garbage container with plastic in it set on fire by smoker wood chips in foil that burned the hose between the tank and smoker causing the tank to explode. I did get the crater part right.


Bill

 

[T_R_Oglodyte]

Thanks for the input folks. I also recall that when I did get it going for short periods, the tank was making kind of gurgling sound - that also suggests overfilled, with liquid level right up to the outlet.

For those familiar with industrial freezer systems, the pressure relief valve was acting exactly as an evaporator. Receiving liquid under pressure on the high side, and discharging at reduced pressure on the low side, causing the liquid to flash to vapor across the valve. Same ice build as I see in the evaporators inside a cold storage unit that handles frozen goods.

One way to bleed liquid or gas out of your tank is to take a screw driver and loosen the gas vent. When the tank is being filled, the operator will crack it open a little and it'll hiss. When it sputters, that indicates the the liquid is at the right height. Cracking it open should vent the gas. You probably want to wear a pair of leather gloves in case you let the spray hit your fingers.

That's one of the tricks I was wondering about. I'll take that as my next step after just trying to burn off some of the excess with a burner on low setting.

 

[CO skier]

That's one of the tricks I was wondering about. I'll take that as my next step after just trying to burn off some of the excess with a burner on low setting.

Using fire to solve a problem involving a propane tank sounds like a Darwinian experiment to me. How will the regulator handle liquid propane?

Using the bleeder valve until mist appears, instead of liquid, sounds like a much better idea.

 

[T_R_Oglodyte]

Using fire to solve a problem involving a propane tank sounds like a Darwinian experiment to me. How will the regulator handle liquid propane?

Using the bleeder valve until mist appears, instead of liquid, sounds like a much better idea.

Exactly the way it did when the whole situation started. If liquid propane reaches to pressure regulator, it vaporizes in the regulator. As long as vaporization occur before the burner, the everything goes normally. And if the rate at which I'm taking propane is low enough that the pressure regulator and the hose connection can provide enough heat to vaporize, the burner keeps going until the excess propane is burned off.

If the regulator and the hose can't provide the heat, they ice over and the system shuts down - exactly same scenario when the tank itself ices over.

The only think I'm going to do differently is to start up using only one burner on low setting, instead of cracking open all four burners at full fire to get the grill and grates hot enough for searing.

 

[T_R_Oglodyte]

The only think I'm going to do differently is to start up using only one burner on low setting, instead of cracking open all four burners at full fire to get the grill and grates hot enough for searing.

I did as described above. The grill had been sitting overnight, so everything was back to ambient temperatures and all the frost and ice was long gone.

The grill is a 4-burner Weber, so I started only one burner, the one furthest from the tank, and after ignition I set it to minimum. My thinking was that since I needed to rely on the pressure regulator and the hose to provide the heat of vaporization for the propane, I should make the length of connection as long as possible in order to maximize the heat transfer capability of the connection between the tank and the burner.

Immediately the pressure valve started to get cold, and soon frost started forming on the pressure regulator. I set a timer to check every 15 minutes.

For the first hour, frost remained on the pressure regulator, and soon begain extending along the hose downstream of the pressure regulator. The layer of ice on the regulator wasn't nearly as thick as last night, when the ice on the regulator had been almost 1/8-inch thick. Also, tonight the frost on the hose only extended a few inches past the regulator, whereas last night the entire length of the hose that I could observe (about 12 inches) was coated with ice.

Based on that I figured that liquid propane was still getting into the regulator, but my draw rate was low enough that the regulator and the first few inches of hose had enough heat transfer capability to provide the vaporization heat load.

At about the two-hour mark, I noted that the frost had retreated down the hose back to the pressure regulator, and the frost on the regulator was thinning. A half an hour later, the frost had disappeared entirely, and the pressure regulator was pretty close to ambient conditions.

So I turned the grill on full blast - all four burners at full fire - and let it rip for about 15 minutes. Everything was working normally. Burners received their full fuel supply, and the regulator was close to ambient. Clearly not frosting as it did at the start, when one burner at min fire caused frost to form within 15 minutes.

***************

Based on all of the above I conclude that the cylinder was overfilled - no headspace. Without head space, the cylinder was delivering liquid propane instead of propane gas. The situation was resolved when I was able to burn off enough propane to create adequate vapor head space inside the cylinder.

One burner at minimum fire on a 4-burner Weber is a pretty low setting. That didn't even heat the grill above 90 °F over more than two hours as I was burning off the excess propane. But that was key - for my approach to work, the propane vaporization heat load needed to be low enough that the pressure regulator and hose connection could sustainably vaporize the propane before it reached the burner. If that draw had still been too much for the regulator and hose to vaporize, then I would have had to find a method to bleed some propane out of the tank.

 

[T_R_Oglodyte]

re the above - my hunch is that the person who filled the tank was tardy in closing the gas sent during fill, resulting in the tank being completely filled with propane and no head space.

 

[BJRSanDiego]

Thanks Steve for the final feedback.

In theory, the OPV valve should have prevented the over filling. There is a float that is supposed to shut off the input when it gets full. But perhaps it is defective and leaking. Secondly, there is a bleed off screw that is supposed to release some gas to help the liquid refill. there is a tube that goes down and when the liquid level reaches the tube, it starts to "spit". In order to get fully filled, this screw is left partially open. If it is closed, then it may not be possible to completely fill the tank. So, the bleed screw was open. But when the liquid level gets high enough, it changes from venting gas to spitting gas and liquid.

So, my guess is that that OPV or OPD is not stopping the overflow. Also, the bleed screw should have been spitting liquid and the person filling it just ignored it. Two mistakes/problems.

The tank is supposed to hold 20# of propane. That equates to 4.2 gallons of propane. So, the next time you get it filled, if it is over 4.2 gallons, then you've got the same problem again.

Thanks for responding. Interesting issue.

 

[T_R_Oglodyte]

Thanks Steve for the final feedback.

In theory, the OPV valve should have prevented the over filling. There is a float that is supposed to shut off the input when it gets full. But perhaps it is defective and leaking. Secondly, there is a bleed off screw that is supposed to release some gas to help the liquid refill. there is a tube that goes down and when the liquid level reaches the tube, it starts to "spit". In order to get fully filled, this screw is left partially open. If it is closed, then it may not be possible to completely fill the tank. So, the bleed screw was open. But when the liquid level gets high enough, it changes from venting gas to spitting gas and liquid.

So, my guess is that that OPV or OPD is not stopping the overflow. Also, the bleed screw should have been spitting liquid and the person filling it just ignored it. Two mistakes/problems.

The tank is supposed to hold 20# of propane. That equates to 4.2 gallons of propane. So, the next time you get it filled, if it is over 4.2 gallons, then you've got the same problem again.

Thanks for responding. Interesting issue.

Thanks and this why I posted the question. I know enough chemistry to know that the tank had to be discharging liquid instead of gas. But apart from the pressure regulator, I am unfamiliar with design elements. And, the TUG community being what it is, I was sure that someone would know that information. And I would get better, more on-point, insight than I was likely to get anywhere else.

Love this TUG community. !!!!!

 

[Zenichiro]

This doesn’t have anything to do with answering the issue but I still thought it a good place to post this.

Mopeka TankCheck LPG Tank Check Dual Sensor with Monitor Kit

LPG Tank Check Dual Sensor with Monitor Kit - AP 024-1000 - Fuel Efficiency

www.campingworld.com

The Mopeka TankCheck actually works well for checking the fuel level of LP tanks. I have 3 currently. They monitor the fuel level and you get an app that keeps track of them.

 

[LannyPC]

Does anybody here do charcoal grilling? We are contemplating the idea of getting one in addition to or in place of our gas grill. One big question I have. Does it cost more to fuel a charcoal grill or a propane grill for grills of approximately the same size. IOW, what generally costs more, fueling with charcoal or fueling with propane?

 

[Passepartout]

While I have no numbers to share, I grill a couple times a week, year round. A 5 gal propane tank lasts me 6-9 months and costs $25ish to refill. If I were using charcoal briquets, it would take 7-10 lbs by the time you light it, let it burn down to coals you can cook over, do your meal, then it just continues to burn down to ash that you have to clean out before the next use. There is a LOT of waste of time, fuel, cleanup that you avoid with propane. I DO have a wood pellet smoker/grill. It lights with a push of a button, takes about 15-30 minutes to get up to 'cooking temperature. I use a 'rule of thumb' of about a pound of pellets an hour. So like a couple racks of ribs will take 4-5 hours, and a 25 lb bag of pellets is around $15, so $5 or so will smoke/grill the ribs.

My gut feeling is that overall, propane is cheapest (unless you have natural gas), followed by pellets- though the grill itself has some cost, and charcoal, while cheapest to get into initially, probably has the higher long-term cost. That said, the flavor imparted to meat grilled over charcoal is heavenly! Each has it's place. In a perfect world, I'd have one of each and a Kamado cooker as well.

Jim

 

[Gypsy65]

Does anybody here do charcoal grilling? We are contemplating the idea of getting one in addition to or in place of our gas grill. One big question I have. Does it cost more to fuel a charcoal grill or a propane grill for grills of approximately the same size. IOW, what generally costs more, fueling with charcoal or fueling with propane?

I have an outdoor kitchen that I built a couple years ago with a built in gas grill
I purchased a rectangular box specific for my grill that holds charcoal that sits down below the grates
You light that burner and it starts the charcoal with no fluid
When lit you turn off the burner and use the charcoal

Works great when we have the extra time which is usually most of the time

As far as cost?
It’s usually a taste thing. Charcoal normally has more flavor