Gas and Oil Home Heating Furnaces - Beckett blast tube is melting.

Hello... I've been searching the web trying to find some answers and I came across this site. I've been using the search and have learned a few things in the process, but still haven't found what I'm after.

I have an oil burner with a Beckett gun, with a short blast tube, F head. My problem is I keep going through blast tubes, I've replaced
it 3 times in 4 years (?). The bottom half of the forward most end of the tube has been melted, sagged and bulged outward, one time burned through. The adjustments all seem to be correct, so my assumption was that the nozzle was dripping fuel into the blast tube while it was off. The fuel would later burn and cook the end of the tube.
However I've replaced the whole nozzle/tube/electrode assemble a few times and still have this same problem.

I was hoping someone would have some input as what is causing this and how to go about remedying it.

Any ideas?

The most common cause of burned off air tubes is the tube being inserted too far into the combustion chamber.

In warm air furnaces, another common cause is a cracked heat exchanger. It could be a lack of draft thru the furnace causing heat to be trapped.

What is the make, model, & age of the furnace? When was it last professionally serviced?

It's a Axeman-Anderson - VESTA (http://www.axeman-anderson.com/vesta.html). 4 years old I guess. I did the install and had someone come setup/adjust the gun.

It doesn't have a heat shield, but he whole blast tube isn't burning up (I've seen that before on other burners), it's just one spot about 6 o'clock at the end of the tube. The rest of the tube and nose escutcheon look like new. I wish I'd saved some of the old ones to photograph. They develop what looks like a bubble, or a sag in the metal.

Often when the burner fires up, it will run for a second, stop burning, then a second later re-light and run for the rest of the cycle. Almost as if there's air in the end of the line (every time). That also lead me to thinking that it was leaking fuel into the blast tube somehow, but I've changed the nozzle/tube/electrode assembly probably 3 times in the last two years without any change in the "miss" or with the tubes "melting" in one small spot.

You are getting heat on the nozzle causing expansion of the oil in the drawer assembly. When the oil expands, it dribbles out & eventually will burn a tube exactly as you explain. If the air tube does not have the flange welded in place, check the insertion depth. This particular boiler is terrible. Don't expect to get more than 15 years or so out of it, at least so has been my experience with them.

Do you have a two pipe system for your fuel?

Yes it's a two line system.

The flange is moveable.... where would I get the specs for the depth? Any time I've had it off, I put it back where it was. Maybe the guy set it wrong from the start.

Other than checking the depth, would it be of any help to get a heat shield for the tube?

Normal insertion depth is 1/4" back from the inside face of the chamber. The way I measure is to use a piece of wood or metal I can get thru the burner opening & hold it against the inside of the chamber then measure from there to the boiler jacket.

Your double firing is probably caused by an air leak somewhere in the fuel system & the two pipe system is masking it. This is another reason I hate two pipe systems but I won't get on that soapbox right now. To cure the problem do away with the return to the tank & install a Tigerloop. Latest News -Tigerloop (http://www.westwoodproducts.com/latest_news_tigerloop.htm)

Here is an article which explains why air removal is so important. Granted the article is from the people who sell the Tigerloop but the article is accurate.
Tigerloop Article (http://www.westwoodproducts.com/tigerloop_article.htm)

You are getting heat on the nozzle causing expansion of the oil in the drawer assembly. When the oil expands, it dribbles out & eventually will burn a tube exactly as you explain. If the air tube does not have the flange welded in place, check the insertion depth.


Grady... I pulled the gun and it was in about 2" or so too far. Thanks for the info on that.

Is there anything else to check to help reduce the dribbling fuel problems of the Becketts?

Are you sure? 2" into a combustion chamber is a long way.

Another way to help get rid of the after drip is to get rid of the two pipe & install a TigerLoop.

Yeah... it was about 2"(+/-) in past being flush. (luckily the tube on there now looks to still be in good shape, not melted/bubbled)

I've been looking into the Tiger loop a bit and may give it a shot when funds allow. (after the holidays)

Thanks again for your help.

The end of the burner tube should never protrude into the chamber. In general, flush with to 1/4" back from the inside face of the chamber is what is normally used.