EMD 645 Blowdown Procedures

[jbmccormick]

Specifically with regard to the blowdown valves after shutdown.

During the cold start procedures, I understand that the blowdown valves are opened, the engine turned over to remove any possible condensate, the valves shut then the motor started normally. When the operation is completed the motor is shut down but no action is taken with regard to the blowdown valves.

The engineer on the vessel has been keeping these blowdown valves open.

My question is whether this is important or not and if it is, is there any citation to a manual or other authority to this respect?

I fully realize that I am not an expert and I am only questioning this because it is different from what I have seen in the past.

Any feedback will be greatly appreciated.

Best regards always,

James B. McCormick

[Big Pete]

Good question jbm,

I think what you are calling "Blow Down Valves" are what I would call indicator cocks, fitted for taking peak pressures, power and draw cards etc, as well as for venting any water from the cylinder head caused by condensation or leakage.

The advantages that I can see in leaving the cocks open when the engine is stopped, are that any corrosive gases and moisture left in the cylinder will dissipate, and the engine is ready for a "slow blow" prior to starting.
This has been the normal operating procedure in my experience.

If it becomes neccessary to start the engine in a hurry, because of some emergency, this often done without blowing the engine over. Leaving the cocks open would then delay starting the engine.

When I came to Sea, all engines with indicator cocks were first turned on the turning gear, then given a "slow blow on air" i.e. the air start valve was opened, but the manual valve was throttled in to restrict the cranking speed of the engine, and prevent major damage if a cylinder was full of water.

Now that most engines can be remotely and automatically started, this is no longer Universal, however, it is still good Engineering Practice, if the engine has been stopped for more than a few hours.

I hope this clears things up for you, and I am sure you will get more opinions posted.
It is always good to question what you are told, there are a lot of misunderstandings and half truths at Sea, and you have to navigate through it all to find out what the best thing to do is.
For years I used to lap in fuel injector nozzles to the valve body, because that is what I had been shown when I first came to Sea, then it was explained to me why that is a really bad idea.
I also used to dismantle boiler burner nozzles to clean them, before it was explained to me that that also was a really bad idea.
Hopefully we all learn with experience, except the idiots who think they know everything.

BP

[JK]

We usually rolled the engine over every hour when on 10 minute standby, every watch for 30 minute standby and every morning before the first start of the day.
I have seen an engine started with all the cocks open when we snapped all the mooring lines and went down river. It was not pretty.

[jbmccormick]

Thank you BP and JK for your insight.

The descriptive answer definitely helps my understanding. I had been taught that the indicator cocks (thanks also for correcting me - this is why us deck officers aren't "allowed" in the Engine Room!!! ) should remain closed in order to prevent condensation from building up in the first place. The slow blow procedure prior to lighting off (except in emergency) was a precaution "just in case".

This explanation makes the issue much clearer to me and makes good sense. There are advantages and disadvantages to both methods (keeping open vs. closed) and I am sure would depend entirely on the mission.

Out of curiosity, what was the "official" recommendation from the manufacturer?

JK, I can't help but imagine flames shooting out from the indicator cocks when that incident happened! I'm sure it was not pretty from down below or from topside!

I found this site accidentally through a google search and I am very glad I did. Thank you all again.

Jim

[JK]

I can't recall if the manual specifically outlines the frequencies.
That ship I worked on 20 years ago and that had the most strigent requirements of all I worked on, because the engine was a PITA nightmare, (the older fellows called it Hitler's revenge).
Some of the ships we blew down the engines in the morning and they were on autostart all day, other ships the engines were never on autostart, but started locally. Others you started in the MCR.

[The Dieselduck]

I've work quite a bit with EMD of late, and the procedure for me as always been blow before you start, if the engine has been shutdown less than 24 hrs. More than 24 hrs, then a manual barring of the engine would be a very good idea - after a pre-lube period of course. I don't remember ever seeing the actual procedure from EMD, apart from blowing through.

Its good practice because you can catch a few problems just from doing it. We had one engine, never a sign of problem, after about 12 hrs shut down, be blew the thing over, and one cylinder was spiting out diesel. The injector was broken and the cylinder was filing with fuel. On another, a little oil was blow out, steady though, the valve guide was leaking lube oil. So blowing over is a pretty good idea on any vessel, EMDs are not different.

On newer vessel, like BP and JK mentioned, and in my experience, the engine go through an automatic "kick", every half hour. The manufacturer, Wartsila, figures that was good enough for them, so a blow through was not necessary before start up. Which means the engine was available on very short notice at all times with little need for manpower or intervention - pre lube and pre heat was constant, fuel supply was in constant recirc mode. Any abnormal condition during or before its "roll" set off an alarm and disable the auto start feature.

[Big Pete]

Hi James,
I thought I posted an update earlier, but it must have been lost in transmission, from the ship.

Further to the other answers:-

Like JK, and probably most other long time engineers, Ihave seen an engine started with the cocks open, not pretty, the whole engine room disappears in a cload of smoke and flames, and everyone rushes to close the cocks before the fire alarms go off, usually unsuccessfully!!!

Incidently, if the engine is smoking and you are unsure which cylinder is the culprit, one way to check is by opening the indicator cock and allowing the exhaust to escape through a white rag, for a second or so. It is often easy to tell that one cylinder exhaust is much dirtier than the others.

Condensation could only form inside the engine cylinder if that was colder than the ambient air outsid the engine. This could possible happen during cold lay up, just as it can happen inside fuel tanks. During the day everything warms up, and the air in the tank or cylinder expands, forcing some out. During the night the air cools and contracts, and more air is sucked into the cylinder or tank. If this air has a high humidity, it can condense overnight, just as dew or frost can form on land.

This should never happen when the ship is in service, because almost all modern engines are kept warm when stopped, this also helps to reduce leakages from pipes and cylinder liner seals, caused by repeated expansion and contraction, as well as minimising thermal stresses when the engines are started.

The main reason for blowing the engine over is to prevent the cylinder head being blown right off the engine if it is cranked over with a cylinder full of water. Causing severe damage to anyone or anything, nearby, as well as to the engine itself.
Water can get into the cylinder from:
Leaking charge air cooler or turbocharger casing, filling the inlet or exhaust manifold with water that then passes through open cylinder head valves into the cylinder.
Cracked cylinder head, leak between fuel injector pocket and cylinder head, cracked water cooled valve cage, cracked piston crown (water cooled piston).
There can also be leakage from fuel injector coolant, diesel oil, lube. oil or water depending on type.
As Martin says there can also be fuel leaking from the injector, and Lube oil leaking past the "O" rings in the valve guides.
The cylinder can also fill with lube oil if there is a crack in the piston crown of an oil cooled piston.

JK:- Was Hitlers revenge a Pielstick by any chance?? These were originally designed for German "U" boats in WWII, and after the war the "Intellectual Property Rights" were acquired by the French S.E.M.T ( Society Etudes Mechanique et Thermodynamic) if I remember correctly: they only had an Academic and theoretical interest in the engine and licensed it's production to engine builders. The older Polish crew that I sailed with on one ship fitted with them, always called then "Herman Goering's Revenge".

I think we have pretty much covered this topic between us. I hope you continue to enjoy the "Duck".
BP

[Madzng]

SEMT = Simple Engineering Made Tricky....

Sailed with a few SEMT and Crossley Pielsticks - never seen an engine leak so much. But it was the small Deutz engines that I briefly sailed with that were regularly called "Hitlers Revenge..."

I guess every engineer has his own nemesis...

[JK]

BP, the engine was a MAN 52/55A-specifically the engine of the ship to the right. The 2nd use to say it sounded like a farrier beating out horseshoes on a anvil LOL

[Mitsui]

Hi everyone

I remember an engine block we had (as souvenir ), in the engine room of a new tanker ship.It belonged to one of the three yanmar D/Gs' we had.During standby,2nd eng tried to start the engine from the control room,confident that nothing could go wrong,since everything was almost new.The engines had a combined air cooler/heater with an automatic air-directing valve which guided the air to the cooler or heater,depending on the temperature.
This unit was leaking, cylinders flooded with water and when "START" button was pressed...parts where flying everywhere.
After that,we had strict order from chief engineer, never to start the engine remote.And a direction from company was to cut off the heater unit.
Every time i had to go down to start a generator, the broken block was there to remind me:Prior to start, blow off! it does no harm

[JK]

Hands up, those of you that have seen the engine that was pre-lubed too long and then rolled over on air with the cocks open!!
It makes an ungodly mess of the flat.
Anyone who has sailed with a 2 stroke Fairbanks Morris, has seen this happen.

[Big Pete]

I was thinking about Mitsui's story, Some engines have water detectors and alarms fitted in the charge air manifold scavenge space to pick up this sort of problem.
Blanking of the charge air heater would make the engine less efficient at low load .
All engines have to be type approved, in order to comply with the MARPOL exhaust gas pollution regulations, any unauthorised modification (Like this) or use of Grey market spares, renders the owner and senior Officers liable to prosecutuion.
All part of the criminalisation of our job.
BP

[Mitsui]

I am against any kind of change that is made to original settings,without justified reason and serious study.
Engineering is science and we are not dealing with toys,sure you all know that.
Of course there are exceptions,and i've heard many cases,either as design flaws or shipyard defects.Error is a human feature...the point is to learn from them
Perhaps the company was instructed by yanmar to cut out the heating element until a revision is made.Chief told me that it was temperature difference that made the pipes fail and leak.
The ship was new,so the coolers-heaters were not misstreated by crew.
However,i don't agree with the tactic "oh,there's auto-start button in ecr,i can safely use it since it is designed to be here".
The intake manifold did not have a water sensor,and if 3rd engineer didn't know,chief&2nd should.
Lucky they didn't have an accident.

[Wyatt]

We only blew down if the engine was shut down more than 24 hours, just like mentioned earlier. But seeing as there are usually only one engineer on watch nowadays, when you blew over, did you ever wonder what was happening on the side of the engine you could not see? As to leave the IC open or closed, I would agree that if preheat was not available, I would side with keeping the cocks closed, but on our vessels all engines had preheaters which we always used, 645's were always a bitch to start when cold, especially the old style power packs on the tugs in the Arctic. The new design by GE have proven to be excellent starters, cold or hot. I also used the charge air manifold drains as indicators of water leaks inside the engine, but you had to remember to close those little bastards or you will have a mess on your hands from the oil splash back from the drip buckets. We had a fuel leak on an injector once, and it filled the sump with fuel, a real pain in the arse!
Cheers
Wyatt