Scavenge fires.

MWD
23rd April 2011, 21:26
Several recent threads I have read remind me of the frequency and trouble with these fires on the old B&W double acting opposed piston two stroke engines I had the misfortune to sail with as a junior
(1957) early in my time at sea.

Are such fires still a frequent occurrence on modern slow speed engines? Is scavenge belt cleaning still a frequently chore and how does one dispose of the debris under modern 'Green' legislation?

Cheers,

MWD.

lazyjohn
25th April 2011, 22:31
I can't really answer your question. however from 1971 - 1981 I sailed Doxford, Sulzer RD90 and B&W KGF. Never experianced a scavenge fire even once. Was I lucky?

Ian J. Huckin
25th April 2011, 23:04
I can't really answer your question. however from 1971 - 1981 I sailed Doxford, Sulzer RD90 and B&W KGF. Never experianced a scavenge fire even once. Was I lucky?

In a word "yes", especially with the Sulzer. But then again there are so many operating conditions that can put you in the scavenge fire danger zone.

Slow steaming on regular full output nozzles, incorrect cylinder lubrication and or poor ring maintenance...all contribute. The K series MAN engines would always experience a scavenge fire coming out of the Great Lakes...usually between Montreal and Quebec. Burning off the crap accumulated through hours of manouvering up and down the Lake system.

I seem to remember Sulzer scavenge fires when the perspex scavenge belt viewing windows would suck in and blow out like snot from a two year olds nose...rotary exh valve jobs if I remember right.

No biggy though, pull the job back, shut the fuel off that unit and increase cyl lub and let it burn out under control by varying engine revs. If it got too bad, i.e. burning paint and getting the C/Es panties wedged then stop the job, put the TG in and crank the cyc lub...that what apps are for.

The absolute modern slow speed engines probably are too well designed and built to experience this problem on a regular basis. Cyl lub is so very accurately metered in etc.

uisdean mor
26th April 2011, 10:15
Ian
Agree with all you say but would add that lub quality also played a part. Consequential issues which arose after a fire were also a work up such as damage to piston rod glands amd obviously the scavenge finger valves needing replaced. The mighty Manipur ( ex Mickey mouse boat) could only make around 1.5 knots against the Mississippi on our way up to Baton Rouge due to poor maintenance over an extended period - you name it and there was a fault - piston rings broken due to excessive liner wear had damaged the exhaust valves and the blowers - safety grid had been holed.Incorrect lub supplied to liners so scavenge fires were a daily occurence and then we had to get up the river to lay up and get some much needed maintenance completed. Handed over to 4th who was instructed to "take it easy" on reduced revs and not to exceed certain temperatures on each unit. Having ben on the plates for some 16 hours I felt the need for some fresh air and a cool drink as well as a bit of scoff. within about 15 minutes he had every scavenge on fire and the loss of power sufficient to make steerage almost impossible. Size 12 applied to delicate anatomical orifice and he was not seen for a good few hours. It was a long stand by after we got everything back under control .
So as you say - there were many and varied reasons for scavenge fires and anyone who did not experience any was certainly lucky. I am an advocate of the Sulzer engine of that era but there were a lot of things which could go wrong quite quickly.

Best regards
Uisdean.

surfaceblow
26th April 2011, 14:40
I must have lived a charmed life I spent many years working on Sulzer's RTA and B & W K Type engines but I never experienced a Scavenge Space Fire. The maintenance schedule was in the most part carried out within a few hours before required only rarely a day or two afterwards.

Joe

Malky Glaister
26th April 2011, 15:52
I had a good fire on a monster of a B&W, , the tanker BERN. I was second at the time. We had a Super with us and he was in the ER when it started
I dealt with it much as has been said and Made a cup of coffee. The wee Scots Chief came down and the super went of his head "the engines on fire and that F***ing Seconds having a coffee" to which the Chief said Hope he makes me one" Exit the super!

regards Malky

celsis
27th April 2011, 09:22
Worked on Sulzer and B&Ws and never had a scavenge fire. Mind you, the spaces were cleaned out every three to four months. A crappy job, but a job that had to be done.

uisdean mor
27th April 2011, 11:55
Scavenge fires did not normally appear during any trip when concientious engineers were on board. The fires were "usually" a result of poor maintenance and record keeping. In the 70's and early 80's there was much structural change within companies and you could be unlucky enough to sail with people who did not really want to be on that ship on that run and sad to say the side effects of that were visited upon those who followed on.
Rgds
Uisdean

Malky Glaister
27th April 2011, 12:06
Well 12 hours in port, no imobilisation permitted, month at sea and repeat voyage. No matter how conscientious you were life could be very difficult on motor ships in the 70's. Cleaning scavenges on Sulzer RD,s was very unpleasant
indeed. Nice to be in port for a couple of weeks to get it done

regards malky

lazyjohn
27th April 2011, 16:32
Well 12 hours in port, no imobilisation permitted, month at sea and repeat voyage. No matter how conscientious you were life could be very difficult on motor ships in the 70's. Cleaning scavenges on Sulzer RD,s was very unpleasant
indeed. Nice to be in port for a couple of weeks to get it done

regards malky

Couple of weeks?

We used to do two Sulzer RD90 engines (16 cylinders total), once every six weeks. Max down time approx 8 hr for scavenge spaces + bit of extra time for top end o'hauls.

Ian J. Huckin
27th April 2011, 18:28
Well 12 hours in port, no imobilisation permitted, month at sea and repeat voyage. No matter how conscientious you were life could be very difficult on motor ships in the 70's. Cleaning scavenges on Sulzer RD,s was very unpleasant
indeed. Nice to be in port for a couple of weeks to get it done

regards malky

Agreed. Was not an issue of conscietious engineers or not, was totally opportunity based. Like I mentioned earlier, we would get a scavenge fire EVERYTIME on EVERY MAN K series engine coming out of the Lakes. And we pulled units, cleaned scavenges while up there...engine design was a big factor. Loop scavenge + economical steaming = scavenge fire, no matter what.

....and we have not even discussed fuel quality, fuel nozzles, scavenge air pressure/flow etc. Big subject all around.

I'll jump in and say right now that, in general, the quality of the majority of modern sea going engineers (I hesitate to call them marine engineers) is well below what was the norm up until about the late 80s yet I bet there are less scavenge fires because engine design and operational parameters are so much improved. Cyl oil always was unique with high TBN etc but now they burn to ash rather than tar and gone are loop scavenge engines...roll on uni-flow.

PS - having a bad day at work so excuse my irritation...(Pint) needed badly!

surfaceblow
27th April 2011, 22:34
I spent a few years working on USNS vessels we would have to do slow steaming when in the practice conveys. While some of the ships were max out on the speed of the convey the ship I was on was stuck at slow to half ahead with the auxiliary blowers on. Twice a day we where permitted an hour or two of independent "steaming" So we could get up to full Nav Speed to blow out the unburnt carbon. Increasing speed at night we would get sparklers coming out of the stack which usually got the Mates pants in a twist. I could not see the point of running with the lights off when you could see the sparks from the stacks.

Being on twin screw and triple screw vessel's it is alot easier to maintain the engines based on the running hours. You are almost never totally disable at any time.

Joe

chadburn
27th April 2011, 23:09
After a period of slow "steaming" on the Deltic "Tons" you had to clear the Deck's when you opened them up to avoid being hit by lumps of Carbon.

John Farrell
27th April 2011, 23:18
Scavenge fires did not normally appear during any trip when concientious engineers were on board. The fires were "usually" a result of poor maintenance and record keeping. In the 70's and early 80's there was much structural change within companies and you could be unlucky enough to sail with people who did not really want to be on that ship on that run and sad to say the side effects of that were visited upon those who followed on.
Rgds
Uisdean


I'll agree to that totally.

uisdean mor
28th April 2011, 22:49
Yup, that as well. As Ian has said a lack of opportunity also added to the maintenance headaches.
Rgds
Uisdean

Macphail
29th April 2011, 00:18
Scavenge Fires...

I have only experienced scavenge fires whilst sailing with Blue Funnel / Glen Line during the sixties. Engines... B & W Double Acting opposed piston.
The “Clytoneus” was so prone to scavenge fires, that it had a scavenge fire engineers call klaxon alarm, it had one whilst on convoy in the Suez Canal. Black balled and always thereafter placed at the end of the convoy.
The usual procedure was to go to slow ahead, put maximum cylinder lubrication on the burning cylinders, dependant on the fire extinguishing agent fitted to the scavenge belt, could be steam, CO2 or CO2 powder. Apply if required.

When everything has cooled down, stop, put the turning gear in and inspect and clean out the scavenge belt.

It was a design problem, build up of residue in the scavenge space and piston blow past.


John.

MARINEJOCKY
29th April 2011, 00:27
Sailed with some of the hardest working and dedicated engineers, deck officers and crews on the Houlder Gaz boats and no matter how hard we all worked we could never find the switch that had to be there somewhere to go from Scavenge fires on a regular basis to no scavenge fires.

MAN KZ engines, need I say more.

Nothing like more sparks coming out of our funnel than lights at the Blackpool illuminations and that was on a gas tanker, tightened up the butt muscles especially for those on the bridge.

Satanic Mechanic
29th April 2011, 05:43
I have near OCD on scavenge cleanliness/ CLO consumption. Basically I never missed an opportunity to clean the scavenges and back in the days of Jensen I could get an engine down to around 0.9 grams specific consumption on the CLO - result extremely clean scavenges.

In the latest Alpha lubricators they can get down to around 0.5 specific.

Why the OCD - well I was subject to a scavenge fire so severe it caused the turbocharger to blow up and set fire to the engine room!!!

Its a well documented but rare phenomena - I'll leave the reasons open for the moment - you can all have some fun figuring it out if you haven't heard of it!!(Thumb)

WilliamH
29th April 2011, 08:34
Jensen??? is that the disc jokey or the motor car?

uisdean mor
29th April 2011, 08:52
well Sat Mech,
Have not heard of the incident so pure guess might be damage to lub oil feed pipe to turbo. Fire starts feeding itself and up she goes? Just a guess.
Rgds
Uisdean

Malky Glaister
29th April 2011, 09:50
I cannot remember being allowed any downtime to do scavenges or anything else. I can remember doing scavenges well enough.

By the varying comments and posts on this subject it seems that almost everyone has had it lucky or not lucky as the case maybe.

Certainly engine design and fuel quality have a lot to do with it.

Cylinder oil consumption was a bit hit hit and miss, two much bad for everything; rings liners and scavenges. Too little the same. Just right, well how do you do that? On one ship we had to do a front and back ring inspection (company instructions) daily, 12 cylinder B&W and adjust cylinder oil settings as required.

I was glad to get out eventually

regards Malky

Ian J. Huckin
29th April 2011, 16:56
[QUOTE=Satanic Mechanic; Why the OCD - well I was subject to a scavenge fire so severe it caused the turbocharger to blow up and set fire to the engine room!!!
Its a well documented but rare phenomena - I'll leave the reasons open for the moment - you can all have some fun figuring it out if you haven't heard of it!!(Thumb)[/QUOTE]

I think the run away turbo was caused purely by the production of combustion gases from the burning scavenge shite working through the engine into the exhaust. Was the job stopped or running?

As far as extinguishing scav fires, steam can dis-associate into oxygen and hydrogen....shudder, CO2 can crack liners and dry powder just does not hack it. If either method worked it only put the fire out, you then still have the "fuel" available to re-ignite if you do not have the opportunity to stop and clean.

I always advocated letting it burn out under control...as mentioned...isolating fuel to that unit, increasing cyl lub and varying engine revs. Scav fires jump around too, so just when it looks like you will soon be getting back to your scratcher it will flare up in another unit etc etc and breakfast is the only option. Did I mention scav fires only occur at night?....probably because a start gazer was looking 180 degrees in the wrong direction and saw all the fireworks coming out of the chimney....(Jester)

John Dryden
29th April 2011, 17:08
''Did I mention scav fires only occur at night?....probably because a start gazer was looking 180 degrees in the wrong direction and saw all the fireworks coming out of the chimney....''
I,ll hold my hand up to that Ian(Jester)

Pat Kennedy
29th April 2011, 22:00
Ian
Agree with all you say but would add that lub quality also played a part. Consequential issues which arose after a fire were also a work up such as damage to piston rod glands amd obviously the scavenge finger valves needing replaced. The mighty Manipur ( ex Mickey mouse boat) could only make around 1.5 knots against the Mississippi on our way up to Baton Rouge due to poor maintenance over an extended period - you name it and there was a fault - piston rings broken due to excessive liner wear had damaged the exhaust valves and the blowers - safety grid had been holed.Incorrect lub supplied to liners so scavenge fires were a daily occurence and then we had to get up the river to lay up and get some much needed maintenance completed. Handed over to 4th who was instructed to "take it easy" on reduced revs and not to exceed certain temperatures on each unit. Having ben on the plates for some 16 hours I felt the need for some fresh air and a cool drink as well as a bit of scoff. within about 15 minutes he had every scavenge on fire and the loss of power sufficient to make steerage almost impossible. Size 12 applied to delicate anatomical orifice and he was not seen for a good few hours. It was a long stand by after we got everything back under control .
So as you say - there were many and varied reasons for scavenge fires and anyone who did not experience any was certainly lucky. I am an advocate of the Sulzer engine of that era but there were a lot of things which could go wrong quite quickly.

Best regards
Uisdean.

Before she became Manipur, she was Cunard's Ivernia, running from Liverpool to New York. I joined her in the Buider's yard in Dundee and after sea trials, stayed in her for several voyages.
Right from the start she had one major engine room problem, whenever she took a heavy roll, the main engine would shut down amid much blaring of klaxons. It seems that the cooling water intake was coming clear of the sea, the pump would lose suction, and all hell would break loose down the pit.
We proceeded across the North Atlantic in a series of lurches.
We drydocked her in Gladstone drydock after voyage one and some work was done which alleviated the problem somewhat but not completely and she was still prone to shutting down in a heavy sea when I left her.
Regards,
Pat(Thumb)

Macphail
29th April 2011, 23:11
Post #22 by Ian Huckin…

Your right, the best way is to let it run its course. As a good engineer, keep an eye on everything, I found that just above dead slow ahead was the best, with maximum cylinder lubrication on the particular cylinders.
I mentioned steam saturation and CO2, because I found that they were a fitment for dealing with a scavenge fire on some vessels. I never used them to do the job.
CO2 Powder was used all the time with Alfred Holt, with injection points on each scavenge box, it was effective in putting out the fire, but not in cooling down.
Then their was the cleaning out of the scavenge belt. With all the powder in the sludge.
Hopefully all in the past.

John.

Satanic Mechanic
29th April 2011, 23:32
Couple of good attempts on the exploding turbocharger - Ian getting close - so a quick clue............

The engine starts slowing down by itself.(EEK)



Don't worry its not a trick question - just a wee chance to exercise the old engineering brain(Thumb)

lazyjohn
30th April 2011, 10:08
Sounds like unburnt fuel due to oxygen starvation of the cylinder, igniting in the exhaust/turbocharger?

I presume the slower the engine the more fuel would be opened up.

I had something similar during a period of really low speed running on a Sulzer RD.

Satanic Mechanic
30th April 2011, 11:25
Sounds like unburnt fuel due to oxygen starvation of the cylinder, igniting in the exhaust/turbocharger?

I presume the slower the engine the more fuel would be opened up.

I had something similar during a period of really low speed running on a Sulzer RD.

Thats da bunny

Yup the scavenge fire was severe enough to start using oxygen to an extent it started to starve the engine. The result was unburnt fuel entering the exhaust receiver where it ignited causing a huge pressure rise in the receiver. This pressure then of course caused the turbo charger to massively overspeed and rupture (and I mean rupture - this was a genuine explosion) result - burning oil and stuff everywhere and a fixed CO2 release being required.

Not pleasant