Oil Fired Boiler Burners

[Big Pete]

I had a problem on my last ship, with the boiler furnace exploding and going on fire, fortunatly no injuries or damage apart from smoke and S*** everywhere. It was a Japanese type with 2 threaded bosses on the end of the bar whch had the atomising nozzles screwed on to them. It eventually turned out that the Fourth "Engineer" had dismantled the burner to clean it, then dropped the burner bar on the deck, destroying the face to face surface and screw thread on one boss, so he had re assembled the burner with only one nozzle and refitted it to the boiler. When the Engineers tried to fire the boiler it wouldn't ignitre, so they put the burner in manual control, bypassing the safeties and repeatedly tried to start the burner without investigating why it wasnt firing, eventually they changed the whole burner for a spare and it ignited the lake of oil in the bottom of the furnace............

I found out about this when the fire alarms went off.

Apart from the the general level of incompetence and stupidity this story reveals it was TOTALLY UNNECESSARY.

You should never have to dismantle the burner nozzles to clean them. I can hear the howls of outrage when people read that statement because it was what most of us were taught to do.
However, if you think about it logically, there is a filter before the nozzle, any particle of dirt that is small enough to go through the filter will go straight through the nozzle and be burnt. Over the many years that I stripped down nozzles to clean them I never found any dirt inside them.

If you read the instruction manuals, the service schedule usually just says something like clean the burner. If there is a more detailed explanation of how to do it, it will usually say to clean the outside of the burner with a soft, Brass wire brush, rags and kerosene, a Nylon pan scourere etc. It will also usually say that the burner nozzles should not be dismantled, but replaced when worn out.

I was talking to a real Boiler expert who travelled the World commissioning Boilers in ships and Power Stations, Refineries etc, but also serviced Domestic Oil Fired Boilers when he was not travelling the World. He was telling me that these small nozzles are assembled in Ultra Clean workshops, all the workers wear hairnets and clean gloves, the air is filtered and the nozzles are assembled on special jigs inside a tank of calibration fluid that is constantly circulated through fine filters to keep it clean. They still have a high failure rate on test.
His opinion was that if you dismantled a boiler nozzle onboard ship you could only make it perform the same or worse than it was before you dismantled it, it would be impossible to make it perform better, so dismantling nozzles was a complete waste of time, no concievable benefit and probably damaging.


I had problems on another ship, with Clayton Steam Generators, these each had two 3 gallon per hour nozzles for low flame and a 6 gallon per hour nozzle that kicked in as well on high flame. The Engineer I relieved told me he had overhauled the burner the day before I joined, the unit was struggling to maintain steam pressure and after two days the flame failed and the coils were found to be choked with carbon preventing the air flow. We washed them clean and put the boiler back in service but after two days it died again. So I stripped down the burner, and then I realised what had happened.

For those who don't know, when oil fired boilers were first experimented with, there were tremendous problems with uneven combustion, smoking, blow backs etc. The eventual solution to most of these problems was to make the atomised droplets of fuel rotate as well as go forward from the nozzle, so that each individual oil droplet moves outwards in an increasing spiral, the air flow is guided into the combustion chamber with the OPPOSITE rotation to maximise mixing of the air and fuel making sure that there is always sufficient air in contact with the fuel for it to burn evenly.

These Monarch burner nozzles had a slightly different construction for the 2 sizes. One was assembled with an Allen key and the other with an ordinary screwdriver. When I stripped the burner down I found that all 3 nozzles had been assembled with the Allen Key. Each nozzle consists of a body with a hole or orifice in the end to atomise the fuel, obviously the area of the hole is roughly proportional to the designed flow rate. Behind the atomising hole, inside the body of the nozzle, is a swirler, a plate with angled channels in it allowing the fuel to flow from the outside of the body to the orifice, the cross sectional area of these channels will also be roughly proportional to the designed flow rate. The combined effect being that a proportion of the fuel pressure is converted into rotational energy and a proportion into atomising the fuel. The swirler is secured into the body by a cap. These caps are designed to be used with a specific capacity swirler, which is why one used an Allen key and the other a scredriver to assemble them.
For some unknown reason my relief had put the same capacity swirlers in both nozzle sizes which had caused the problem.
If the swirler is too big, the pressure drop across the swirler and the rotational velocity of the fuel through it will be reduced, the rotational speed of the droplets will be too low, but the pressure drop across the orifice will be too high, causing an excessive quantity of fuel to be atomised, and the droplet size to be smaller than it should be.
If the swirler is too small the opposite will happen.

So with boiler burners the rule is just the same as with fuel injection nozzles, never mix and match parts.

On a final note, I know that there are still some people out there who do not understand the correct position for the ignition electrodes. I still come across people who think that the electrodes should in the the oil spray pattern. THEY SHOULD NOT.
The spark from the electrodes should be blown into the fuel spray by the air flow, the electrodes themselves should be outside it.
Putting the electrodes into the spray is a bit like holding your arm under a shower, the spray hits your arm, the droplets combine and run off as a stream. In a burner you atomised the fuel so that it will burn well, if you put the electrodes into the oil spray, you undo the atomising and have an uncontrolled drip of oil from the electrodes that will not burn properly


I hope this gets some people thinking and I am sure it will stirr up a few replies.

BP.

[JK]

Good Lord, they bypassed the safeties?
Once upon a time, I recieved a letter from the engineers on the ship I had signed off of a couple of months before, describing the incident with their boiler. The purge cycle had been interrupted then the burner ignited. The subsequent ingnition bulged the boiler casing 6" and more importantly, bent the superheat safety over almost 90* . Can you imagine the consequence of that failing?
Back in the day, when I first went on the ships, I worked on a '49 vintage steamship with Scotch marine boilers. The fireman came up and called me in the middle of the night and said, we got a problem. I pulled on the coveralls and boots and stumbled down to the stokehold, to discover the furnace was full of heavy FO to the depth of the corrugations all the way from the ashpit door to the furnace. The corrugations were about 3-4" deep. I'm sure the old girl was smoking pure black out the stack that night. The fireman wanted to flame it off....not likely. It took a lot of effort to clean the furnace out enough with the drafts wide open, that we could light a burner.
The thing about working on that old girl was that everything was manual, you learned to light off the burner and set the drafts for optimal burning-ie less smoke out the stack and less calls from the Mates. If you made a mistake, well, flame will reach from one end of the stokehold to the other so you better stand to one side when you light it off.
We were setting the safeties and I was standing on the boiler looking down at the fireman, relaying pressures as he called them out, to the engineer adjusting the sdafety. We were coming out of the dock and the stokehold was full off shipyard guys working in the bilge putting in piping. The fireman had a line of plating put down from furnace to furnace to get around on. The burners took a shot of water and backfired out through the ashpit doors, the flame was across the stokehold. If you can imagine 2 boilers shooting flames.. I'll never forget the sight, I can even remember the firemans name 30 years on, of him trying to get to the boiler fronts to knock the burners off and the shipyard workers trying to get out of the stokehold in the opposite direction. They were rattled by us popping safeties, flame was the last straw LOL. Of course, I was pretty shattered myself the next day, of draining water off of FO and near continual boiler backfires and rumbling. We had hydrostatic testing tanks and I guess there was some cross-contamination. (Obviously)

I wasn't aware of the burners being put together in clean rooms. It was common for us to strip them to clean them. I guess that is not the modern technology though.

[mentatblur]

Hey guys, some awesome information here. Long time lurker, first time poster.

I am only a 4th class Canadian engineer, but I've worked on all the Canadian steamer lakers that are currently in service, over the last few years. I wish I could show BigPete's post to some of the "2nd's" and chiefs out there regarding burner cleaning. I'm sure the burners on all of them have been ripped apart hundreds and hundreds of times, haha. Always love hearing/reading stories like these; always a lesson to be learned for sure!

Currently working on a diesel-electric plant on another laker. This one is actually from the early 40s, originally steam, then converted over to diesel. I guess this is a common theme now on these old things. I've been on a couple other ships similar to this one... one of them even has the old water tube boilers still in place, of course not in service, all half-ripped apart.

I miss steam! Always loved being able to get to know the entire plant, and keeping everything in balance before getting any alarms. Have you guys sailed on any of the newer steam vessels? I hear they are all deep sea and LNG... guess I should get my tanker endorsement. Would definitely love to try deep sea some day.

[JK]

Welcome to the Forum, Mentatblur. Feel free to post any questions or comments. We love to hear them!

[Big Pete]

Welcome onboard mentalblur.

The Boiler I waas talking about was a water tube auxiliary boiler with a seperate exhaust gas economiser.
If they had tried to fire it on auto it would have locked out on flame failure but because they ran it on manual, the flame failure alarm was bypassed and they were able to saturate the furnace brickwork with oil.

The only ship I sailed on with steam turbines was the SS Patonga, later renamed the Strathlauder, the last of the Dorset class built from 1936 to 1953. She had Foster Wheeler D type Boiler and 3 stage Parsons turbines and a double reduction gear box, straight out of the old text books, people on board thought that the guy who wrote the book had sailed on that class.
I did my first trip as cadet on her and went back for my first trip as 5th Engineer, in the meantime she had been laid up because of the high price of Bunkers, and because she was over 20 years old, when I went back nearly everyone was new to steamers. There was no automation so there were two Engineers and two ratings on each watch. The senior rating used to watch the main boiler burners and clean the tips each watch. I found he was cleaning the burner tip with a pocket knife, poking the point of the knife into the orifice and screwing it round, totally destroying the the 90 degree knife edge at the mouth of the orifice which is required to give good atomisation in Boiler Burners and fuel injection nozzles. I ended up pointing out what he was doing to the 2nd because I thought it was wrong, and the cleaning was changed.


BP

[JK]

LOL on the knife. I went down to the stokehold and the shipyard had taken the steam cock off of the column for the gauge glass.
Same yard put the boiler blow down in with the valve screwed down and tightened the flange enough that the boiler passed a 330 lb hydrostatic test. That was special getting that fixed because it was discovered after the boiler was flashed to working pressure.
Another time, again scotch marine boilers, we had one boiler on the line, the other 2 were banked for some reason I can't remember...maybe boiler cleaning. We were tied up and I was doing the weekend. After a couple of walk arounds, I realized that the live boiler had always had the same furnace lit. I asked the fireman if he was rotating the furnaces. I just about gagged when he told me no. He wasn't long lighting off another burner and shutting down the first.


POP QUESTION:

Steam cock for the boiler glass has been taken off at the flange. What, if any, special steps you have to take during reinstall?

[mentatblur]

JK, seems you got us stumped? Or maybe no one noticed your pop question. Without looking at a book or anything, I would just say nothing special other than making sure the sealing surfaces are ultra clean? I have never had to do this before obviously. Good to get ya thinking though.. going to go look at my book now!

[JK]

A little more then that.

I'm talking gauge glasses BTW.

The flanges have to be perfectly aligned. A metal rod is machined, with no taper, to the dimensions of the glass and inserted into the cocks with the packing. Then the flanges can be tightened. If this is not done, when the boiler begins to expand as it is heated, the glass will burst as it can't take misalignment.

OK, why did I gag when I realized that only one furnace was being used in a scotch marine.
Yes, I know, we don't have them anymore, but it is such good basic knowledge of boilers, I think.

[carbob]

How old are you lot at all?? Just kidding, love to hear about the older technology. Sometimes think I was born 50 years or more too late.

I'll hazard a guess about only using one furnace in a Scotch boiler though. Would it have to do with evening (?) out the heat stresses in the unit? Perhaps the unused furnaces would 'relax' too much and start to leak. Just a thought from one who has only read the archeology books, I mean reference, books on Scotch boilers and never seen one in action.

I can remember one of the ERA's on one ship on the catwalk on top of the boilers, Sunrod boilers they were, when the safety lifted on one. I think the print of the grating is still on his face!! Another engineer used to test fire the boiler burner into a steel Drew chemical bucket, 5 gallon, when he finished overhauling it. Made for an interesting light show in the hole!!

[JK]

pretty close. Rotating the furnaces maintains natural circulation in the boiler preventing local overheating around the furnace.
The thing with the scotch marines is you had 16 tons of heated water at 220 lbs. Any leaks flashed off to steam. They had the capacity to kill everyone on the ship with a furnace or combustion chamber failure.

Safeties popping are scary, even when you know it is coming. I sailed briefly on a watertube boiler plant, it would deafen you. I was just as happy to leave there.

Ever deal with Vapowers? They were continuous coil boilers, water in one end of the coil, steam out the other. There was a modulating burner that increased or deceased the fuel, based on feed water. That is the simple explanation....I saw more then one melt down when the firing rate was more then the feed water rate.
We had one acting up, the air was a little too high on the burner flash off which meant the burner cover which was spring mounted would lift every time the burner lit (it was a temporary issue until the engineer responsible sorted it out). We had a couple of contractors onboard, they went pale ever time it happened. LOL. I suspect the engineer enjoyed seeing their reaction.

[jimmys]

I have a combined ticket steam and motor. Motor second first then steam endorsement, steam chief and motor endorsement. I do remember stoking a coalburner, single ended double furnace, she burned smokeless fuel. Triple expansion steam, exhaust overboard.
Also oil fired, Saacke burners , scotch boilers, single ended double furnace, Babcock.
T2 wavy headed boilers, I just want to forget about it. Lots lots more.

regards
jimmy

[jimmys]

The older steamships burned residual fuel, it was not a blend like today. We changed burners and cleaned tips every four hours. The first thing the watch did was a complete burner change took about half an hour. There was so much muck about the furnace front we were in with the slice to cut it away.
There was no purifiers the fuel went into the burner heated and raw. The only purifier was the lub oil one for the turbines, usually a delaval.
I spent a long time on the 12/4 and after the burner change we blew tubes, all chain driven sootblowers, you pulled the chains. If you got though the watch with only one burner change you were lucky.
Only diesel aboard was for the emergency generator and it was gas oil ordered by the drum, no diesel oil purifier. You could not risk it by the barge. It was the emergency flash up from cold.

regards
jimmy

[jimmys]

The older steamships burned residual fuel, it was not a blend like today. We changed burners and cleaned tips every four hours. The first thing the watch did was a complete burner change took about half an hour. There was so much muck about the furnace front we were in with the slice to cut it away.
There was no purifiers the fuel went into the burner heated and raw. The only purifier was the lub oil one for the turbines, usually a delaval.
I spent a long time on the 12/4 and after the burner change we blew tubes, all chain driven sootblowers, you pulled the chains. If you got though the watch with only one burner change you were lucky.
Only diesel aboard was for the emergency generator and it was gas oil ordered by the drum, no diesel oil purifier. You could not risk it by the barge. It was the emergency flash up from cold.

regards
jimmy

[JK]

Exactly what happened on the old girl every watch. We used to run with 16-18 tips, I only ever saw the 20 types go in once and we had a furnace drop. It had a small drop before, but the big tips exaberated the problem causing the boiler to be condemned.
Our emergency was a 8 cylinder, hand crank start Dorman. Two guys operated the decompression levers, one on each bank, and the rest of us took turns cranking like madmen. One Safety Sunday, the little darling refused to start, we worked our way thru the engineroom gang, then called in a couple of the big hefty deckhands. They cranked the thing over so hard and fast that I am sure we could have powered lights off of it without FO! The Donkeyman flicked the decompression levers close and off the diesel went. Too bad they never got the handle off though. All you could see were bodies diving out the door and ducking behind the uptakes, hoping the handle would stay on until the donkeyman got the engine stopped or everyone was out of the way. LOL.
Everytime I get in a discussion with co-workers, they comment that I was so skinny back then LOLOL. I was 23 and working on a steamer, every excess pound was sweated out. When I moved to the motor ships, I spent a lot of time the first couple of months shivering in the engineroom because it was so cold.
30 years later and at a desk.....well, I needn't go into specifics!!

I don't imagine this is where Bg Pete expected the topic to go. LOL. I really did not much like the watertube boiler-turbine plant I worked on next. To each their own, I guess.
What I did noticed though, is that as soon as the motor engineers find out you have a steam background, they dump the boiler work onto you, in obvious relief.

[Big Pete]

Topics go where they go, that is part of the fascination of online Fora. Serendipity.
We will be having a diet forum next!!
BP