Boom?

MaxMercy

We've all seen home owners push the reset button on a burner "a couple of times", but I've read that when firing up the burner after several lockouts for no ignition, the warning is to *not* shut the burner off while burning off the old oil lest we risk an explosion. Is this true and if so, what's the explanation?

Jamie Hall

Flashback in the boiler. You fire up the system after the homeowner has pushed the button half a dozen times (boom). Then after a bit you shut it off -- but there is still unburned oil vapourizing from the now nice and hot liner, flue passages, and what have you. At some point, if this just isn't your day, that vapour concentration will reach the ignition point and the whole boiler -- now full of fumes -- will explode. If you're really lucky, it will just blow the breaching and doors off...

retiredguy

At a building in MT union, Pa. I once had the occasion to visit a job where the burner that was direct fire oil did not light the oil and a screwed up control allowed the burner to run for many hours spraying the #2 fuel oil into the firebox. The boiler was an H B Smith 350-10 steam boiler. When I arrived at the job site after driving from Pittsburgh, Pa. I found that the burner was still spraying oil into the firebox and the brick chamber was saturated with oil to the point that oil was running out of the firebox and making it's way to the floor drain. On those boilers the chamber was lined with 2" of a rockwool soft insulating board plus 2" of firebrick. My dilemma was how to light this oil with the least possible danger to myself and the boiler. I decided to throw into the chamber a few pieces of cord wood and a whole bunch of newspaper, light the newspaper and hope everything went OK. The paper lit as did the wood and the oil burned in the firebox all the rest of the day and up until about 2:00 am. The burner was lit and and put back into service after replacing the bad control. It was "touch and go" for awhile but the end result was OK.

EdTheHeaterMan

As a professional who is making the repair to the ignition problem on a "Saturation" (what we call it when the combustion chamber has a significant build up of unburnt oil soaked into the chamber), I have the following procedure that I was taught years ago.
1. remove as much oil as possible from the chamber/heat exchanger/boiler using a vacuum cleaner while it is still cold.
a. pour oil dry into the chamber and vacuum out
b. replace the combustion chamber if excessive
c. vacuum soot and scale from heat exchanger
2. Find a way to stop the oil flow while keeping the burner fan operating.
a. Disconnect electricity to solenoid valve.
b. remove bolts from pump in order to slide it off the burner coupling.
c. install a valve in the high-pressure line
3. Have a fire extinguisher ready and a phone ready to call the fire department
4. Repair ignition problem and start burner. Adjust the combustion air to full open on the burner.
5. Observe the progress of flame and if flame is too large for the equipment, turn off the fuel to the nozzle but keep the burner fan running. (see #2 above) This way you will have combustion air for the soaked in fuel in the chamber to burn it off.
6. Once the flame reduces in size (or if the flame never gets too big) continue to operate the burner with fuel to the nozzle until the burner will stop and no flame is present from unburnt oil in the chamber.

Only needed the fire extinguisher once in 45 years, and only had the fire department show up once in 45 years, and that was because someone else called when they saw the smoke from the chimney.

You got to use common sense and understand the fire triangle. SAFTEY FIRST !

MaxMercy

I like Ed's idea of running the burner without fuel.

Jamie Hall said:

Flashback in the boiler. You fire up the system after the homeowner has pushed the button half a dozen times (boom). Then after a bit you shut it off -- but there is still unburned oil vapourizing from the now nice and hot liner, flue passages, and what have you. At some point, if this just isn't your day, that vapour concentration will reach the ignition point and the whole boiler -- now full of fumes -- will explode. ..

So the vapor concentration will be less if we keep the burner running as opposed to just than letting the oil burn itself out in the mostly stagnant air?

And just to be clear, I'm talking three or four resets, not a horror story like Ed and retiredguy are talking about! Wow. Scary stuff.

I trained my mom many years ago to push the reset only once and call me either way.

Jamie Hall

The trouble with letting the oil burn itself out in mostly stagnant air is that it won't. You will very quickly reduce the oxygen content if the air isn't moving, which will lead to a build up of flammable vapours -- above the explosive limit at least in parts of the boiler. Should enough oxygen reach them, and there be an ignition source, things will get exciting.

However, I missspoke, and should have used the term "flashover", not "flashback", which may have been confusing. Wikipedia, for once, has a rather good writeup on the phenomenon: https://en.wikipedia.org/wiki/Flashover . In a burner, it would usually be a rich flashover.

MaxMercy

Thanks, makes sense.

EdTheHeaterMan

@MaxMercy There are very few "Horror Stories" type of saturations. most are like you said, "Push the reset several times" The trouble is, you never know until it's too late, and if not prepaired, then you have a problem. My brother ended up at a burn center with 1st-degree burns (not a big deal but looked really bad, hair singed, face blackened). It was a boiler #3 on a commercial customer that was down for a week, before they called the oil company to get it fixed. "How many times did you reset it?" answer "A couple"
But what they did not say was that they did it (and wrote it done on the boiler log) every shift (3), every day (6) for the entire time it was down.

"Boiler 1 operational, pressures within range, Boiler 2 operational pressure within range. Boiler number 3, off line, reset burner, cycled without ignition. reset again, boiler still off line."

Same log entry 18 times. That is 36 resets

My little brother owned the oil company with my big brother. and we joke about it today, but my little brother follows the procedure now.

Steamhead

If you read @Firedragon 's books, he calls this "facing the dragon". I've yet to hear a better description

kevink1955

It's over 30 years ago but I still remember it like yesterday. I was the maintenance superfisor for of all places a Fire Department. I got a no heat call for 1 of our Firehouses . When i got there I found a 60 degree boiler (OOS for at least 12 hours) with the burner motor still running and pumping oil (2gph) with no ignition. I shut the burner down and called the contract oil company.

They arrived a few hours later and replaced the transformer and were about to restart the burner when I informed the tech that judging by water and building temp the berner had been pumping oil for at least 12 hours (24 gal in the chamber). He said no problem and lit it off.

The thing went off with a roar and the next thing we knew we had the owner of the oil company across the street (who lost the service bid last year) in the basement with us reporting flames coming out the top of the chimney. The chamber was roaring but it was contained and the chimney fire went out so the oil co said let it burn.

About 6 hours later the building was up to temp and thermostats satisfied. Pumps stopped with a roaring fire still going in the chamber, The water temp was rapidly approaching boiling and the tech had no idea what to do. He was on the phone with his boss who told him to just let it burn out.

I was not about to let it boil so I started to jump circulator controls to force them to run, that brought the water temperature under control. At that point we asked the tech to leave and we (the Fd) took control. That thing burned for over 24 hours and the building was almost 90 degrees before it burned out.

We brought the previous oil co (from across the street) in to go over the boiler. We checked service records and found that the week before the oil co wrote a ticket that said "adjusted bimetal stack control"

As far as to could figure the tech had bent the bimetal in the old stack switch when they found the boiler cold the week before.

Needless to say the oil co contract was terminated and we went back to the old oil co who had serviced the boiler for at least 30 years and we lived happily ever after till they converted to gas and removed the 1930's asbestos covered monster and replaced it with a 2 section Hydrotherm

I have since retired but the Hydrotherm is still there, I am told they want to replace it with a new HVAC system, forced air heating and cooling. I will never be the same, the truck bays have large cast iron radiators now, I can only imagine how uncomfortable forced air will be. Plus the radiators are used to dry fire gear (coats, gloves etc) try that with forced air

SuperTech

There should be laws against removing cast iron radiators and baseboards, the people who do this do not understand the mistake they are making and need laws to protect them from their own stupidity. 

JUGHNE

I have been involved in a small Fire Dept for 42 years.
This ends up putting you in the position of maintaining the heating systems.
We have had major additions and then eventually completely new building.
We use hanging NG radiant infrared heaters. I specified 4 130,000 BTUH units, 30' each.
One will maintain the building, the others are there for redundancy and that seldom needed time when 30-40 tons of ice covered trucks return to thaw out.
With that and 10 overhead doors it is hard to imagine FAF recovering.

In floor heating would have been the best but considering the costs and maintenance (also who would have been stuck with doing it) the infrared was the best bang for the buck. This is volunteer and no permanent personal in the building.

I think they would be disappointed with FAF, depending upon the DD temp. But the AC would be good in the summer.

Jamie Hall

Those big infrared heaters are perfect for your application -- or for agricultural stock and equipment barns. Or, for that matter, pretty much anywhere where the air exchange and heating loads tend to be somewhat (!) unpredictable.

JUGHNE

Our old building had 2 hanging infrared heaters installed in 1999.
They never failed nor required any attention or repairs.
They were the higher end units....sealed ball bearings etc.

kevink1955

I agree that infrared would be a good choice but with all the ducting and sliding tracks for the vehicle exhaust system there is no ceiling room left. It's a narrow building built in 1930 so there is very little room between the trucks. I have retired and while I miss the job I do not miss the politics and problems

STEVEusaPA

Here’s the way I handle an oil soaked boiler, from the master himself...
https://fueloilnews.com/2016/05/26/a-few-tricks/

weedhopper

^^^ I saved that, will read.
Coming from a large condo with gas heat, electric A/C and a service plan my knowledge of the systems was to pick up the phone. I never used it but I knew that if I wanted quick service all I had to say was " I think I smell gas"

So the old Erie boiler in the house we bought was on it's last legs and had a history of lockouts. We were having conversations with out new heating guy about replacing the boiler, in the meantime he made some adjustments and repairs.

I had pushed reset a few times in the past with success but one time my wife informed me we did not have hot water. I was doing other stuff and my brain was otherwise occupied when I opened the peephole in the larger door and saw a glow inside the firebox.

Anyone with a brain would have let it cool down or called the repair guy, or both. So I hit reset and BOOM !

The explosion blew the door open and the basement filled with smoke and soot, the door was hanging by one hinge and the firebox was on fire. Ran to the top of the stairs and flipped the emergency switch to off.

That was an old boiler, original to the house in 1956 and had zero safety features to prevent the kind of dumb move I made.