Frozen underground fuel line?

WisconWaterfowler

I work for a fuel company and do the furnace work for the fuel oil and propane furnaces.

I had a call this afternoon after a customer had run out of fuel in his 500 gal underground

tank. Fuel was delivered and he opted to bleed the line himself. I was called after he couldnt get the line bled. I took the line off the filter cup just inside the basement wall and turned the valve on, no fuel. I attempted to blow the line back with a compressed air cartridge thinking the line had gotten plugged as a result of running out of fuel. Could not get any air through the line. With such a solid plug, I'm assuming water was drawn into the line and froze. Today has been the first time the passed few days the temperature has risen above -10 or so, and -30 with the wind chill. If the line is frozen, how can one aid in thawing the line out aside from an additive?

STEVEusaPA

Some thoughts/questions

1. If it's an underground tank, isn't it a 2 pipe system, or one pipe with a tiger loop?

2. Blowing back the line.

a) I would never use a CO2 cartridge. Too much pressure, too easy to split the fuel line.

b) Maybe there was a check valve?

3. How deep is the fuel line buried? Is it below the frost line?

I'd believe it's plugged before I would believe its frozen. Not freezing is maybe the only benefit to bury a tank. An additive won't help.

Or maybe a frost heave kinked the line.