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Propane fuel line freezing! Need your opinion!


Why would propane fuel line freeze after about 30min run time on a 8.5 kw, approx 12 hp emergency...

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  #1  
Old 01-23-2010, 11:26 AM
Arkie Arkie is offline
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Question Propane fuel line freezing! Need your opinion!

Why would propane fuel line freeze after about 30min run time on a 8.5 kw, approx 12 hp emergency gen?
The unit is being operated in the Colorado ice storm last few days and they said it was CONVERTED to propane!

Anyone got any idea for a quick SAFE solution to keep the propane fuel line from freezing?
They have no electric power other than this gen when it runs!

I do not at this time have any idea as to the size of the Propane tank, the size of the fuel line, etc!

I just told them I would ask here and see if I can get them some info ASAP?

Thanks
Arkie
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Old 01-23-2010, 11:41 AM
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Default Re: Propane fuel line freezing! Need your opinion!

At work we have propane oil heaters for road repair. We use liquid propane on them. The lines on them get frozen layer of frost on the outside of the steel lines, but have never froze solid. Could it be that they are using the wrong type of propane? There is liquid form and gas form.
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Old 01-23-2010, 12:35 PM
Arkie Arkie is offline
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Default Re: Propane fuel line freezing! Need your opinion!

JK: you asked this!

Could it be that they are using the wrong type of propane? There is liquid form and gas form.

I do not know for sure, but since it's a small gen set-up and converted from gasoline to propane, I would assume that this would be vapor line from the supply tank with a vapor regulator at approx 6 oz or so and then a demand vacuum reg at the engine area! (Im not familiar with the small engine propane systems so I'm just assuming!
We use Liquid supply line to our 85KW gens and then use water heated vapor regulators at the engine for liquid to vapor conversion!
I was wondering why they did not just switch back to gasoline, if they did not do any jet mod's to the carb?
Could they just re-connect the gasoline line, re-gap the spark plug and just turn off the propane supply??

The question I was asked is "why is our propane fuel line freezing up after 30 minutes of run time?" I said, really do not know, maybe line too small, I'll ask smokstak for ideas???
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Old 01-23-2010, 02:53 PM
Ed Radtke Ed Radtke is offline
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Default Re: Propane fuel line freezing! Need your opinion!

If its just frost on the outside of the line it wont pose any problems except for thawing and making things wet.A frosted line is just a simple refrigeration system.Also,if the line is long enough the gas may be condensing at some point along the way and then re-vaporizing when it comes to a warmer area.
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Old 01-23-2010, 03:07 PM
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Default Re: Propane fuel line freezing! Need your opinion!

Right about the frost on the outside of the line! They indicated that the fuel line freezes internally after about 30 min of run time and shuts off the fuel supply!

I was wonding if they might take their line loose at the tank and inject about couple teaspoons of de-natured alchol in their lines to rid of possible moisture in the lines and regulators???? (I assume on this small gen they are using a vapor feed)
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Old 01-23-2010, 03:25 PM
Merritt Merritt is offline
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Default Re: Propane fuel line freezing! Need your opinion!

are they sure the lines them selves are freezing and its not just the regulator thats freezing up? like maybe a diaphram is getting stiff in the cold weather and not operating correctly.

im going to assume they are withdrawling vapor off the tank its self... if it is being operated in weather that is too cold, there wont be enough heat available to vaporize propane in the tank its self (especially if its a small tank) to feed a vapor type demand regulator.

just a few ideas...
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Old 01-23-2010, 03:32 PM
pegasuspinto pegasuspinto is offline
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Default Re: Propane fuel line freezing! Need your opinion!

The line should not freeze (internally or externally) unless they are pulling vapor, and the tank itself is also frozen. (In vapor draw, the evaporation, and hence cooling, happens in the tank-the vapor is cold, sure, but only as cold as the tank itself is) OR, they are pulling liquid, and at some point it's trying to vaporize in the line, and that part of the line is getting cold.

I think we need more details, pictures, etc to solve this problem!

Robert
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Old 01-23-2010, 03:47 PM
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Default Re: Propane fuel line freezing! Need your opinion!

Quote:
Originally Posted by Merritt View Post
are they sure the lines them selves are freezing and its not just the regulator thats freezing up? like maybe a diaphram is getting stiff in the cold weather and not operating correctly.

im going to assume they are withdrawling vapor off the tank its self... if it is being operated in weather that is too cold, there wont be enough heat available to vaporize propane in the tank its self (especially if its a small tank) to feed a vapor type demand regulator.

just a few ideas...
I thought the same about the regulator freezing and told them to try some de-natured alchol injected into the line before the reg to rid of moisture!

I was also assuming they are drawing vapor! I do not know the size of the tank! What size minimum tank would you recommend for a 12hp motor and freezing temps! or could vec exhaust pipe be use to warm the tank maybe?????
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Old 01-23-2010, 03:48 PM
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Default Re: Propane fuel line freezing! Need your opinion!

Need to know if this is a vapor or liquid system?
What engine is used, is it liquid cooled?
I ran into a liquid system that was freezing up. Found several gallons of water inside the porpane tank. It appears that either the tank on the truck delivering propane or the main tank was not properly returned to service after hydro testing. I blew as much water I could out of the tank by removing the line and opening the tank valve, then jacked up one end of the tank and blocked it up. This moved the water away from the liquid pick up tube in the tank. It then ran until the propane company replaced the fuel tanks. I don't think the same symptoms would occur with a vapor system.
Mikey
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Old 01-23-2010, 04:03 PM
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Question Re: Propane fuel line freezing! Need your opinion!

I just now talked to one of the guys and he said that they only have the small BBQ type tanks at about 10 lbs capacity as the fuel supplys and the 3/8 inch line starts frosting from the carb to the reg which is located at the tank and the gen quits!
I told them they probably need a bigger tank for the cold temps and they might try sitting the supply tank in vicinity of a vec exhaust so as to just warm the tank, because the tank may be getting too cold to produce vapor! I told them to use common sense and sit the tank so as the heat would only keep it warm enough that they could still hold their hand on the tank when it's at it's warmest!

Any ideas????
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Old 01-23-2010, 04:53 PM
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Default Re: Propane fuel line freezing! Need your opinion!

Arkie, there is no easy quick fix for your customer, if they don't have the different items below on hand, or cannot go out and get some. Back up power that is relied on as essential in a time like this should have been fully tested in advance, since being converted/modified.

"Give me six hours to chop down a tree and I will spend the first four sharpening the axe." Abraham Lincoln

Get a different (larger) regulator, and larger hose from regulator output-to-carb. I don't like the tiny (approx 3" dia.) gas grill regulators, as the BTU capacity is just too small. The "RV" regulators used on campers for years (approx 4-4.5" dia.) work much better. I experimented some years ago with my RV's propane tank, regulator, a BBQ grill regulator, and an Onan JC genset. Could not carry full load with the small reg, but the RV reguator worked fine.

I would also recommend a larger tank.

Frost=rapid change from liquid to vapor. If your small line is frosting over heavily, you're overtaxing the regulator and the line is too small--your vaporization process is completing in-transit to the carb. Plus the current weather at the time didn't help. (see next paragraph.)

Since the conversion, I am speculating if this is the first time its had to do an extended run during cold/inclement weather. Windy, icy, drizzly, rainy weather (with humidities as high as 98%) will contribute to excess frost build up on anything colder than the ambient.

eric
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Old 01-23-2010, 05:10 PM
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Default Re: Propane fuel line freezing! Need your opinion!

Eric:
Thanks I'll pass on the info about the larger RV type 4-4 1/2 regulator!
They indicated they had previously tested the unit ok during warmer weather under load and all ok!

I indicated that they need to try a larger propane tank for cold weather operation, because the smaller tank may not vaporize enough during cold weather for the engine fuel demand!
This is why I told them to try warming the existing small tank using vec exhaust! If the warming of the portable propane does not make it run, I would suspect the regulator???
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Old 01-23-2010, 05:41 PM
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Default Re: Propane fuel line freezing! Need your opinion!

you may want to try and use a 100lb tank (people put them on the side of the houses to fuel stoves and dryers and what not), i think the 20lb bbq tank may be too small, especially in the cold weather and especially if they are pulling a lot of load on the generator...


ive seen garretson KN regulators (http://www.propane-generators.com/garretson.htm) used on some 10KW generators, in warmer weather, infact my neighbor has one on an 8.5kw honda. they are meant to have a large diameter low pressure hose to the gas mixer (carburetor)

we really would need pictures and specs on the system in order to give you proper information...

i would say for now, try and keep the whole system as warm as possible until they can get the system worked out... i kind of doubt the fuel is freezing, i think its another problem elsewhere in the system...
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Old 01-23-2010, 05:43 PM
JCarroll JCarroll is offline
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Default Re: Propane fuel line freezing! Need your opinion!

The real problem is starting in the tank. A 20 pounder simply can not absorb enough heat through the wetted surface (area liquid propane is touching).

They really should have two 100 lb cylinders & use a two stage double inlet regulator. That way when one cylinder cools to far the regulator will switch to the other cylinder. Also don't need to shut down the generator to change tanks.

For now they should place the little cylinder in the cooling air discharge - not to much to worry about with the heat they need to boil the liquid propane into vapor - just don't exceed 100 or 110 degrees Fahrenheit. To late if it hits 120. Warm the bottom of the tank.
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Old 01-23-2010, 05:47 PM
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Default Re: Propane fuel line freezing! Need your opinion!

Maybe sit a heating pad under the tank and turn it up just enough to keep it warm.
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Old 01-23-2010, 06:13 PM
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Default Re: Propane fuel line freezing! Need your opinion!

I sent word for them to try using the gen's warm air or a 120v heating pad so as to keep the small supply tanks when the engine is running! If that don't make it operate they probably have a bad regulator!
They said cannot get vec out or close to the tank to use the vec exhaust! Snow is too deep!

I asked them too let us know the outcome!

Thanks and Later!
Arkie
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Old 01-24-2010, 10:19 AM
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Default Re: Propane fuel line freezing! Need your opinion!

What is a vec?

Propane boils at -44' F - under the snow is +32 F....

It takes 773 BTU's per gallon or 184 BTU per pound (Latent heat of vaporization) to convert propane from a liquid at -44 F to a vapor at -44' F.
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Old 01-24-2010, 11:08 AM
Tony Kautza Tony Kautza is offline
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Default Re: Propane fuel line freezing! Need your opinion!

As an old propane guy I can agree tank size and line size are critical 12hp under load takes a health supply of vapor if they are going to run this for any amount of time a pair of 100lb tanks would be minimum you only have about 20 gallons in a tank if it was filled properly I don't know if they can skimp on these like they can a 20lb tanks a 100 gallon tank or a 250 would be better and you know what you have in them with 100lb tanks you should use a 2 stage auto switch regulator so a least it tells you that one tank is empty also don't skimp on line size bigger is better to a point hope this helps Tony K
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Old 01-24-2010, 02:28 PM
pegasuspinto pegasuspinto is offline
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Default Re: Propane fuel line freezing! Need your opinion!

http://www.northerntool.com/webapp/w...6873_200396873

two of those would do the trick, tho $600 will buy a lot of (bigger) propane tank.

Make sure the LP is HD95 spec, if you got a tank full of butane, nothing will help.
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Old 01-24-2010, 03:05 PM
Tony Kautza Tony Kautza is offline
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Default Re: Propane fuel line freezing! Need your opinion!

yea that butane is the bastard gas as Ed Hill would say. Did not have to deal with it up north but some of the mixes in some areas seem to get a lot Tony K
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