MAN B&W fuel pump cut-off method

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rohan.kochhar
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MAN B&W fuel pump cut-off method

Postby rohan.kochhar » Thu Sep 19, 2013 10:38 pm

Suppose you get into a situation where in your high pressure pipes installed on the M/E fuel pumps starts leaking and you need to cut-off the fuel pump for that particular cylinder, yes it can be done by lifting the roller off the fuel cam, but the hitch here is that you are maneuvering into a port and its advisable here not to stop the engines. Now my question here is; is it possible to lift the roller off the fuel cams without stopping the engines ? The manual clearly specifies that the engine has to be stopped for lifting the roller off the fuel cams using the specified tool.

My second similar doubt is regarding the puncture valve actuation on the fuel pump.
Now the case is that we want to cut off a particular unit, and still continue maneuvering.No issues with the fuel pump here, but an issue with unit cylinder. So is it possible to manually actuate the puncture valve for the unit in question, without stopping the engine ? To add to the query is it also possible to pull the fuel racks to a zero position and have the plunger aligned such that the helix on the plunger communicates with the cut-off holes on the barrel.

My query relates to MAN B&W 11K98-MC engine.

Hope to get some good insight on this..!

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Big Pete
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Re: MAN B&W fuel pump cut-off method

Postby Big Pete » Fri Sep 20, 2013 1:19 am

On the older engines the simplest and safest way to shut the fuel off the engine was to disconnect the fuel pump from the fuel rack and pull its delivery back to minimum, that way the rest of the engine keeps running as normal, and you have little risk to the person doing the job. I have jacked up the fuel pump on some engines in the past when they were running, but there is a risk of personal injury, so why do it, if you don't have to?


BP
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JK
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Re: MAN B&W fuel pump cut-off method

Postby JK » Fri Sep 20, 2013 3:52 am

I have seen it done on a MAN medium speed, by the biggest fellow in the engineroom. The problem is, if you don't get it the first try, then you do have problems and the engine has to be shut down.
We had changed the flexible fuel supply lines from the manifld to the pump, to a new type because the old type were failing but the new ones failed even faster.
Happy daze....I had forgotten about this until now. With the engine running, the supply line could be renewed and the pump put back into operation.

rohan.kochhar
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Re: MAN B&W fuel pump cut-off method

Postby rohan.kochhar » Fri Sep 20, 2013 4:14 am

Thank you Big Pete for sharing your view..
Yes i completely do agree with you that the personnel at the end, who's trying to adjust the fuel rack of the unit in question is definitely at high risk; cause the governor is at play when the engine is running, especially when maneuvering. So the job is better done with the engine stopped.

I'll just quote something relative to what you've just mentioned, from the MAN B&W manual.
Now what this specifies is; 'The toothed fuel rack is linked together with the regulating gear of the engine through a spring loaded connection. Thus in event of a sticking pump plunger the remaining fuel pumps will not be blocked.' Now this seems like an inbuilt safety feature, which naturally comes across the mind..as the governor control will give its signal and, the communicating links will come in play. But when such a case of the plunger being stuck, it does cause concern with the other units and the only way out would be to disconnect the links immediately. Also since the plunger is stuck, we do need to get the roller off the fuel cam since the stuck plunger would be causing unnecessary resistance, and could definitely damage the rest of the linkages in concern. Here advisable to stop the engine, lift the roller off the cam and then close the fuel inlet to the pump.

Now in my case what i was trying to explain is that, when there is an abnormal leakage from the head of the fuel pump or consider the high pressure fuel pipe connection on the head was not torqued to the required value which causes a sudden burst of oil from that connection, so here you definitely want the inlet to the fuel pump for that individual unit, shut immediately; to stop purging of the fuel oil from that connection. For this i would have to shut the F.O inlet connection to the pump, since the fuel oil circulating pump is still running, and before being able to do so i need to have No reciprocating motion of the plunger to avoid further damage to the barrel and plunger surfaces, as it is this oil that gets in between the two providing the required lubrication.

now here is where i come to a stall, is it possible to do so while the engine running..?

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Re: MAN B&W fuel pump cut-off method

Postby rohan.kochhar » Fri Sep 20, 2013 4:25 am

Hello JK,

That was the case with the tool on-board my ship, it seems some one had already tried it out and, while we were about our inventory rounds we found the tool damaged..to be more specific 'bent'. So it is more of a hit-and-try case and only an experienced hand can get by. So now i get it as to why the manual specifies 'Stopped Condition Only.'

Thank you JK for sharing your experience.

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JK
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Re: MAN B&W fuel pump cut-off method

Postby JK » Fri Sep 20, 2013 5:16 am

I've only saw it, over 20 years ago, so memory is fuzzy because I was a deck up. But timing was important and you have to get the plunger up in the first try. The engineer had been on the ship for years and was immensely strong. (So much so, that when I did my first set of rounds after relieving his watch, I would carry a valve wrench to loosen the commonly used valves, so I could open them without rupturing myself.). I can't comment on how experienced you would need to be as it is something I never considered trying as I am rather attached to my various body parts and function.
It seems to me, one of the other engineers tried it and never got the plunger up and he ended up with the tool madly jumping up and down with the plunger motion.
I chose the safe route and shut the engine down which caused much angst as they lost 30 minutes out of the schedule :roll:

I should add, this was a MAN 52\55A medium speed 4 stroke, running 400 RPM, if I remember correctly

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Big Pete
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Re: MAN B&W fuel pump cut-off method

Postby Big Pete » Fri Sep 20, 2013 10:53 am

Hi again Rohan,

As JK says you have to be strong to lift the fuel pumps while the engine is running, (I am 6 ft tall and more hundreds of pounds than I care to think about).

If you disconnect the toothed rack on the fuel pump and move it to Zero delivery, that is very easy and safe to do while the engine is running. The Governor movements are small, relatively slow, and in a straight line so your fingers won't get trapped if you are careful.
Because it is a positive displacement pump, no fuel should go past the pump barrel & plunger into the HP fuel pipe or the "Head" of the pump, unless the pump is very bady worn or damaged. Even if it does the pressure should not be sufficient to open the fuel pump Delivery valve. Some fuel will be retained inside the pump to lubricate it. There is no need to shut off the fuel inlet & outlet valves to the pump. Indeed it is probably better to leave them open to ensure some flow through the pump for cooling and lubrication.
It should be possible to change a leaking HP fuel pipe while the engine is running, either with the fuel rack for the cylinder brought back to zero or the pump lifted off the cam so that it is no longer "stroking".

I wouldn't like to dismantle the head of the pump while it was still stroking on zero delivery, or to change the fuel pump while the engine was running, that has a higher risk of personal injury. Hoever if the cam follower is hung up and the inlet and outlet valves to the fuel pump are disconnected, it should be possible to change the fuel pump, being very careful about how you do it. There may be a problem with the forced L.O. supply fitted to some fuel injection pumps.

All the above very much depends on a thorough reading of the manuals and understanding how it all works, usually you are "Hanging Up" the cam follower rather than the fuel pump, so it should be possible to change the fuel pumps without danger, so long as you can disconnect the fuel and L.O> from that pump.

BP
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Re: MAN B&W fuel pump cut-off method

Postby jimmys » Sun Sep 22, 2013 5:31 am

A number of medium speeds had what is called a spragging gear on the fuel pumps and this could be used to shut fuel of one unit or all the units. Its a few years since I have seen them and I cant remember what engines. Certainly the system is still around.
In the engines I sailed with it was a simple task, you inserted the tool and nothing happened till you jacked and it was leverage and lift when the follower was off the cam. The Pielsticks burned holes the size of your fist in the valves and the tool was in the control room all the time.
A good dose of the PC4V on heavy oil soon learns the engineer how to jack a fuel pump.

regards
jimmy

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Re: MAN B&W fuel pump cut-off method

Postby hugerich » Sun Nov 10, 2013 10:02 am

Bear in mind I was a first trip cadet when I saw this, but as I remember there was actually a piston on each fuel pump connected to an air supply, and when you operated a lever air was lead to this piston which lifted the roller off the cam, easy as that. If I remember it was a 10k90MC-C. Although, I actually have a copy of the K98MC manual here on my computer and it has references to the same feature as I saw, if you also have the manual it is plate 909-10.1.

In regards to just stopping the fuel supply without lifting the follower, would this have problems in regards to sticking of the plunger in the barrel? However, I suppose in a situation where fuel is blasting all over the engine room a stuck fuel pump wouldn't be the biggest problem!

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Re: MAN B&W fuel pump cut-off method

Postby hamal » Wed Dec 17, 2014 2:46 am

In a 1 - 2 hours max. maneuvering I will shut the fuel pump's supply and open for 1 - 3 strokes, every 10 mins if M/E is running on HFO or every 2-3 minutes on MDO / LSMGO depending on M/E rpm and fuel lubricity additive (for LSMGO).
For longer maneuvering (Suez, Panama, Magellan Str., Danish Str., etc.) I would try to disconnect the control air from the puncture valve, I will plug the connection from the control air line and I will supply 7 bar compressed air to the fuel pump's puncture valve. Meantime, I will push the Master to arrange for a safe anchorage / stoppage.
Also, the fuel rack disconnection seems to be ok.
In all the cases, cooperations with the Master is a MUST.


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