Tores mailbox VIIC and VIIC/41 operation and technical details

[SnakeDoc]

Tore,

I have rather general question about operation of diesel engines. From the basic experience with car engines I know, that
color of the fumes may indicate some problems with the diesel. For example white smoke can mean leak from the cooling
system and blue smoke - that engine burns the lubricating oil. The black fumes can indicate, that there is inadequate amount
of air to fuel combustion - or to much fuel - for example due to injectors failure.
Do the marine diesel engines behave in the same way? How about GW engines? What kind of problems influence the
color of the fumes? Did you experience some of them? Were there some repairs/adjustments possible while at sea?
I know, that this was not so important while snorkeling,  but when U-Boats cruised most the time on the surface, the machine
crews paid attention to the color of the fumes.

--
Thanks, regards
Maciek

[Don Prince]

Hello Mr. Tore,


In addition to Maciek's question about the diesel exhaust; did they purposely run a rich mixture while blowing the ballast tanks to provide a layer of un-burned diesel fuel as a means to protect the tank's lining from corrosion?


Regards,
Don_

[Don Prince]

Hello Mr. Tore,


Now I'm interested....


"Tore"
A.   shut to the settlingtanks and engines as shown on plate 9.
B.   the unusual, daytank shut and fuel goes straight to the fuel supplypump on the engines,
C.   topping up port settling tank and supply to the engine supplypumps from stb. settling tank and
D.   topping up stb settlingtank and supply to the engine supplypumps from port settling tank

The drawn position of e valve is shut (closed).  If it were rotated 90 degrees where the valve line/separator was not parallel with the tank, then we would have condition B; fuel going straight to the engines?

Now here is where I have a problem; does e valve have more than one activating lever/wheel, etc.? Something has to cause the diverting of the direction fuel can flow.  In the drawing where you are topping up the port side and drawing fuel from the stb side, how do you stop the fuel flow into the port side when the tank is full without affection the stb side fuel supply to the engines?

The one possibility I see is using the valve f ahead of the filter to the incoming fuel line. That way the one settling tank supply can be stopped without affecting the other settling tank that is providing fuel to the running engines...

Confused as usual...

Regards,
Don_

[tore]

Maciek and Don
 Running of the GW diesels. As both a car- and GW diesel generally are fourstroke engines, the combustion is pretty much the same. So the colours of the exhaust would be following the same rules. On a submarine however you have a wet sparkarrestor after the silencer which created some white watervapour pretty much like cooling waterleakage in a car engine. A bad atomizing of a fuelinjector or an overload,( lack of oxygen in relation to fuel) created a black exhaust. The exchange of fuel nozzles or HP fuelpumps is relatively simple on a large diesel and was a quick routine job at sea, spare fuelinjectors and pumps were always on board. Contrary to the car engine we checked the combustion in another way. Each cylinder has an indicatorcock e.g. a cock having a direct connection to the combustion chamber, every morning I personally checked the cylinders combustion by looking at the colour of the combustionjet on each and every cylinder. In this way an experienced eye could pick a cylinder not having an optimal combustion. If a further check would be required you could attach an manometer to the cock and check the combustionpressure before carrying out repair. This is a much more accurate check than looking at the exhaust. Black exhaust could be a problem when schnorcheling. Particularly when starting the engine as it was some residue water in the exhaustpipe. This water created a  backpressure in the exhaust pipe which could open the reliefvalve on the exhaustmanifold filling the engineroom with black exhaust, rather unpleasant.
Blowing the ballasttanks by exhaust. I know somewhere in the literature it is mentioned that an advantage of the exhaustblowing was rustprevention of the ballasttanks. We never paid attention to that, in fact the ballastanks were nice and clean painted with a yellow zinc chromate and very little corrosion.  Certainly we would not like to foul up the engine by running the engine with an incomplete combustion.
Tore

[tore]

Don.
I understand your confusion as the description of the selector cock is incomplete. The supply cock "f" is indeed used for topping up the system. The supply from the bunker fuel tank is much faster that the consumption of the engines so it goes relatively fast to top up the settlingtank and cock "f"cock is commonly the shut off cock for that operation.
A word on "closed" and "shut". In the RN submarine english the word closed is not used, in order to prevent misunderstandings for an important word, shut is generally used.
Tore

[tore]

Maciek.
Combustion check.
Perhaps I should mention that in addition to the checks I mention, the GW engines were equipped with individual exhaust thermometer for each cylinder which would register any unormal combustion as well. Proper monitoring of the combustion was important for many reasons and hence the surveillance was good.
Tore

[SnakeDoc]

Tore,

thank you for your answers.
When you started diesel engines after submerged cruise (that is when engines were cold) - did you run them for a some time with low load to get them warm gradually (except emergency of course)? I have met following figures: after start about 10 minutes KF, then 5 minutes LF, then 5 minutes HF and so on.

--
Thanks, regards
Maciek

[tore]

Maciek.
From an ideal point of view it would have been nice to run the engines as indicated by you. However when you surface you normally would like to obtain full buoyancy as quick as possible, particularly at heavy weather and swell. This because the metacentric height change from negative to positive when you break the surface and you are in an unstable situation. Hence you start the engine and run same at the load required for blowing the ballasttanks with a somewhat higher exhaust backpressure rather than an ideal warming up load. Otherwise normal surface cruising, starting with cold engines, we did not use the engine telegraph with strict speed commands, but communicated with the bridge verbally leaving the gradual increase in output to the desire of the engineer on watch, only to be overruled by the engine telegraph if the bridge had to.
Tore

[Don Prince]

Hello Mr. Tore and all,


My observations on Plate 8a (venting, sounding, test piping) are as follows:


1.  Maciek provided an excellent drawings on how to measure the remaining fuel in internal FO tank 1 and 2.  No questions...


2.  I don't see any means to measure the contents of fuel oil in any of the saddle tanks (D2, Regulating and RFO tank 1, and D4) in the Type VIIC.  I believe I seen a drawing from a Type XXIII that had a means to measure the external fuel tank contents.  Am I correct?


3.  D4 has the ability to drain fuel (from the top) into a collector bucket.  Why?


4.  D2 has the ability to drain fuel (from the top) into the FO Collecting tank. Why?


I have a question about the FO Collecting tank.  It looks like there is some type of a collecting valve that permits the input lines to feed the tank.  I assume it is manually or some how opened; it can't just be an open collector?  Otherwise, the measuring gage feeding the collector from D2 would be worthless because the collecting tank has a goose neck vent.


One question specifically for Mr. Tore -  When times were difficult and the captain needed to stretch his fuel oil supply, was the fuel oil in the FO Collecting tank re-cycled and used to power the engines?


Regards,
Don_

[tore]

Don.
Your no 2. question. measuring fuel from saddletanks. I think you have seen some drawings either from the IXC type or XXI. The system works as follows: a relatively small diam. pipe goes almost from the tankbottom to the top. A few cm. from the top is a 3 way selector cock which i believe can be operated from inside which either connect the pipe to the upper part of the tank or to the inside of the pressurehull via a hullvalve to a graded draincontainer. When measuring, you first put the selector cock to a equalizing position e.g. connected to the fluid on top of the tank and let the level stabilize in the small measuringpipe. Then the oil level in the pipe is at the same level as the tank. Then the cock is turned to a measuring position, the connection to the top of the tank is shut and the hullconnection is open. The inside cock is opened and the compensatingwater force the oil contents in the pipe into the measuring container.The hullcock is shut as soon as the compensating water starts to come. The the container has now an accurate oil level measurement of the saddletank which by tables can be transferred into oil volume. I have tried to make a sketch below.
3 and 4. You never squeeze the last drop of fuel into your fuelsystem, f.i when when you want to drain the external fuel/ballasttanks to convert same into just plain ballasttanks all the fuel on the top must be drained. You avoid letting the last drop go overboard and create an oilslick danger, thus you drain the last drops into contaminated oil collectingtanks and containers, not into the bilge.
The VIICs did not have a fuel separator or clarifier only gravity settlings and filters thus we did not use any contaminated fuel from the collecting tank.  We did not worry about environment in those days but the danger of being traced by an oilslick was allways in our heads and great care was taken to prevent fueloil contaminating the compensating watersystem and bilges.
Tore

[Don Prince]

Hello Mr. Tore,


Thank you for your response...


Q2.  I know how it works on the Type IX and XXI, but this is not available in the Type VIIC?


Question about the FO Collecting tank -  How is the collection valve controlled?  It looks like it has to have a shut state, otherwise the pressure measuring gage could not measure the fuel pressure?


Regards,
Don_

[tore]

Q 2. I cannot remember we had this system on the VIICs.
Fuel drain collecting tank pressuregauge. I am not sure I understand the question, I believe the the "valve" is a connection point on the top of the tank receiving the fuel drains by gravity and otherwise having no pressure. Could you explain which fuelpressure gauge you are referring to?
Tore 

[Don Prince]

Hello Mr. Tore,


On Plate 10 left side, there are two sampling pipes from D2 port and stb that connect to a collector (one above and one below).  There is also a measuring device going to the same collector with a valve.  All of this goes into the FO Collecting tank. 


In the other drawings of the FO Collecting from the top on Plate 9, there looks to be a circle with 4 inputs.  If that circle were just an open collection point in the FO Collecting tank, then the measuring device would never be functional because the FO Collecting tank has a goose neck to equalize the tank pressure with the internal hull pressure.


Is that some type of a valve in the FO Collecting tank with the 4 inputs?


Regards,
Don_

[tore]

Don
If I have understood you correct this time, I believe plate 10 shows the compensating water (green) entering the pressurehull via the normal hullvalve a, drains e and d as well as reliefvalve f. then to the inner fueltanks 1 and 2. Before entering the tanks each have a overpressure and underpressure reliefvalve which for tank no 1 has a drain via a funnel to the  (yellow pipe) fuel collecting tank in the engineroom. Se my sketch below.Tank 2 has a similar drain in the control room. Would that be it? I don`t believe it is a valve (or four) on the FO collectingtank.
Tore

[Don Prince]

Hello Mr. Tore,


I have marked 2 pipes as the A side and the B side on the drawing as follows:


1.  The B side looks to contain the pressure water from the Header Tank. 
2.  The A side has a collection funnel and drains directly into the FO Collecting tank. 
3.  The FO Collection tank has a goose neck vent to equalize the air pressure in the tank.


If this is the configuration, then I don't understand how the Measuring Container can ever collect anything.


If there is an over pressure event on the B side of the pipe and the over pressure relief valve opens, then the contents goes directly into the FO Collecting tank and nothing would get measured. 


Perhaps, I do not understand the function of the measuring device...


Can you enlighten this poor sole?  Do you have a photo of it?


Kind regards,
Don_