Motors running on propane

[37chief]

I have a tractor that is setup for propane. Was originally butane. It has valves labeled liquid, or vapor. it has a water heat exchanger. I have a fork lift that runs on propane. All fuel goes through a heat exchanger to turn the liquid to a gas. I have a generator that runs on propane straight off a small tank, like a BBQ tank. I don't understand why some propane motors don't need fuel to be heated before it enters the motor. Stan

 

[Texgasser1]

I would also be interested to know that.

 

[Jim.ME]

Two different systems of removing fuel from the tanks. The BBQ tank is vapor draw vs liquid draw. Vapor can go direct to the carburetor. The liquid propane has to be converted to vapor before going to the carburetor. The water heat exchange warms the liquid for faster conversion of the larger fuel volume needed for larger engines.

 

[wore out]

I have a tractor that is setup for propane. Was originally butane. It has valves labeled liquid, or vapor. it has a water heat exchanger. I have a fork lift that runs on propane. All fuel goes through a heat exchanger to turn the liquid to a gas. I have a generator that runs on propane straight off a small tank, like a BBQ tank. I don't understand why some propane motors don't need fuel to be heated before it enters the motor. Stan

OH MY GOSH, he said MOTORS!

 

[Russ from MN]

If you need to use a lot of propane, it should be liquid withdrawn and have a vaporizer. In a cold environment sometimes it won't vaporize fast enough in the tank.

 

[Russ from MN]

OH MY GOSH, he said MOTORS!

Motors/ engines interchange doesn't bother me any more than people that keep their tractors in a barn! Barns are for livestock, tractors and machinery are kept in sheds or garages!

 

[john in la]

Motors/ engines interchange doesn't bother me any more than people that keep their tractors in a barn! Barns are for livestock, tractors and machinery are kept in sheds or garages!

That is like my parish tax office considers a pole barn what most call a carport.
Post and a roof with no side walls.
If you add walls it’s called a shed even though the roof is supported by poles.

 

[Russ from MN]

That is like my parish tax office considers a pole barn what most call a carport.
Post and a roof with no side walls.
If you add walls it’s called a shed even though the roof is supported by poles.

And your county is called a parish? Different dialects, different locations!

 

[Bob Bancroft]

I have a tractor that is setup for propane. Was originally butane. It has valves labeled liquid, or vapor. it has a water heat exchanger. I have a fork lift that runs on propane. All fuel goes through a heat exchanger to turn the liquid to a gas. I have a generator that runs on propane straight off a small tank, like a BBQ tank. I don't understand why some propane motors don't need fuel to be heated before it enters the motor. Stan

A little different, but similar. My corn dryer draws liquid from the tank and has its own vaporizer. So it's not only liquid, it's at tank pressure right from the tank to the unit. There's a regulator which draws vapor and drops the tank pressure to about 10 pounds, then the line goes from there to the buildings, where another regulator drops the pressure to about 1/2 pound. My old tank used to have the liquid draw on the bottom. The newer tank has it on the top with an internal pipe going to the bottom. The vapor is simply drawn off the top.

 

[john in la]

And your county is called a parish?

That is our Roman Catholic heritage showing its face.
Our law system is also different. We follow French and Spanish civil law rather than English common law.

 

[Pete in MD]

OH MY GOSH, he said MOTORS!

Funny comment. I remember several years ago what caused it.

 

[Rich'sToys]

On my John Deere 50 LP, you run it on vapor when you first start it up. Then, after it gets warmed up, you close the vapor valve and run it on liquid.

 

[Mcrafty1]

On my John Deere 50 LP, you run it on vapor when you first start it up. Then, after it gets warmed up, you close the vapor valve and run it on liquid.

Any idea why that method is used? It would seem if it starts on vapor it would stay on vapor as opposed to having the two methods combined? Maybe as mentioned above, the vapor system can't vaporize fast enough to supply the volume maybe? idk. If this is a thread hijack, no need to answer, I'm not looking to buy anything running on propane.

 

[Bob Bancroft]

Any idea why that method is used? It would seem if it starts on vapor it would stay on vapor as opposed to having the two methods combined? Maybe as mentioned above, the vapor system can't vaporize fast enough to supply the volume maybe? idk. If this is a thread hijack, no need to answer, I'm not looking to buy anything running on propane.

I'm only speculating. Maybe it's one of those things which depends-on the outside temperature? There will always be vapor in the tank, I suppose enough to start an engine, even on a bitterly cold day. But then maybe to be assured fuel under load, it's best to have liquid warmed by engine heat. Maybe tank size dictates how fast the vapor can boil off? When I set up my system I asked my propane supplier if the 1000 gal tank could keep liquid to my corn dryer and at the same time provide vapor to heat two buildings, heat water, and run the stove/oven? He didn't know. There's a lot of surface area in that tank to boil off. Maybe that makes no difference? Just guessing.

 

[Jim.ME]

Any idea why that method is used? It would seem if it starts on vapor it would stay on vapor as opposed to having the two methods combined? Maybe as mentioned above, the vapor system can't vaporize fast enough to supply the volume maybe? idk. If this is a thread hijack, no need to answer, I'm not looking to buy anything running on propane.

Rate of evaporation (turning to vapor) in/from the tank comes into play. If you have run a space heater or "weed burner" (vapor draw) off a 20 lb. tank in cold temperatures, you will see the tank show frost on the outside. That is cooling from the process of the liquid turning into a gas (vapor). Flow of vapor from the tank will drop off as it chills, reducing heater output. The same hold true for an engine using propane. Using a liquid draw system with a coolant heated evaporator to convert the liquid to vapor provides for a better flow during heavier draws seen with larger engines.

A system starting on vapor and changing to liquid after a warmup would be letting the coolant warm while there is vapor flow available from the tank which will drop off as the tank cools from the withdrawal. Once the coolant has warmed some the evaporator can take over, changing the liquid to vapor.

Larger tanks are often used on vapor draw uses to give more surface area for vaporization inside the tank.

 

[Geo-TH,In]

I have a tractor that is setup for propane. Was originally butane. It has valves labeled liquid, or vapor. it has a water heat exchanger. I have a fork lift that runs on propane. All fuel goes through a heat exchanger to turn the liquid to a gas. I have a generator that runs on propane straight off a small tank, like a BBQ tank. I don't understand why some propane motors don't need fuel to be heated before it enters the motor. Stan

I don't understand why some propane motors don't need fuel to be heated before it enters the motor.
I had a furnace run on straight gas. In the winter the bottom half of the tank would frost up.
I have a 150,000 BTW LP heater. Run the heater for about 30 minutes and the bottle will freeze up.
So why don't BBQ and your generator need a heat exchanger to turn liquid to a gas heat? They don't use that much LP and the tank can absorb heat from the air fast enough to not frost up.

During the gas embargo of the 70s, I knew a man that converted his F250 to Lp. He had to start the truck on gasoline to warm up the heat exchanger before using LP

 

[moresmoke]

I don't understand why some propane motors don't need fuel to be heated before it enters the motor.
I had a furnace run on straight gas. In the winter the bottom half of the tank would frost up.
I have a 150,000 BTW LP heater. Run the heater for about 30 minutes and the bottle will freeze up.
So why don't BBQ and your generator need a heat exchanger to turn liquid to a gas heat? They don't use that much LP and the tank can absorb heat from the air fast enough to not frost up.

A 20 lb LP tank can provide about 24000 btu/hr of vapor at 60F. Any more than that and the pressure in the tank drops and the flow will fall off. It takes 2545 btu/hr to make 1 HP at 100% efficiency. Rough guess is it would take about 317000 btu/hr to feed a 75 hp tractor engine. It would take about a 100 gal tank to be able to vaporize enough fuel at 60F. Or, 200 gal at 20F since there is less heat available and more surface area is needed.

By the way, when surface area is discussed in relation to vaporizing propane, it is the area of the tank wetted by propane that matters. Just like boiling water on the stove top, it doesn’t only boil on the top surface. So long skinny tanks will vaporize better than more spherical ones.

 

[TheBartman47]

On my John Deere 50 LP, you run it on vapor when you first start it up. Then, after it gets warmed up, you close the vapor valve and run it on liquid.

My 730 is also propane, but I run it almost exclusively on vapor. I've never pulled anything heavy enough to really demand full power from the engine so haven't ever needed to open up the liquid valve. I do open it occasionally just to make sure the valve never gets stuck shut or other problems with it.

 

[JMOR]

Tesla cars have motor(s).

 

[onefarmer]

All engines run on vapor, even diesels. The difference is how it gets the vapor. A small engine doesn't take much fuel so it only needs the vapor being taken of the top of the tank. Larger engines would take so much vapor that the tank would frost up as the fuel vaporizes, all the way to the point the fuel won't vaporize fast enough for the demands of that engine. So there is a vaporizer that uses the heat of the engine, usually the cooling system, to help convert the liquid fuel into a vapor. These engines would start on the vapor from the top of the tank until it's warm enough to switch over to the liquid that will be vaporized for the large demand under power.

I had a propane powered steam cleaner and it used so much fuel that after a while it would slow down the heat until it was worthless. I put it on a larger tank with more surface area and it would run longer.