Tores mailbox VIIC and VIIC/41 operation and technical details

[Don Prince]

Hello Mr. Tore and Maciek,


I believe I resolved the problem of a photo of the water cooling pump on the starboard side.  It's really impossible to get a good wide angle shot of a pump that's a bit down below the diesel engine room floor and large horizontal pump blocking the view.  So, I improvised...


Regards,
Don_

[tore]

Hello Mr. Tore,


You would only change-out a failed attached gear pump when the diesel engine is shut down, is that correct?


Regards,
Don_

Don, yes.
Tore

[tore]

Don.
The large aux. lubeoil pump would require electricity which in spite of batteries was not always available, hence a small handpump to handle small quantities during maintenance work.
Q 1. It works for drawing ( green) fresh luboil in small quantities from port lubeoil storagetank the way cock2 is positioned. Would probably be used for filling the small daytank.
Q 2. It works. But remember the pipes are small, low capacities. it would probably be used for maintenance work on the engines like turning the engine manually.
Cock "n" to the lubeoil daytank could be shut. Generally fresh oil was used for the oilcans but if you would need larger quantities for maintenance work you would use used oil, but not contaminating the daytank with such oil. Indeed you could draw lubeoil in small quantities from the sumptank of each engine, remember the engines are of the dry sump type, but if you would take a sample of the luboil in the system of a relevant engine, you could use the handpump.
As I have stated before there are numerous ways to operate the systems describing one on the cost of others might be confusing and should be mentioned as an example of many.
Tore.

[karel]

Tore and Maciek. Thank you for answering my question.

I have another one about rudder gauge. I attached the screenshot and you can see there are red lines marked at number 25.  https://www.dropbox.com/s/hijz49wot1x8y4a/rudder.jpg?dl=0
Can you tell me what this means? If i had to guess then rudder max turn angle was 25 degrees?

[SnakeDoc]

Hi Karel,

I have another one about rudder gauge. I attached the screenshot and you can see there are red lines marked at number 25.  https://www.dropbox.com/s/hijz49wot1x8y4a/rudder.jpg?dl=0
Can you tell me what this means? If i had to guess then rudder max turn angle was 25 degrees?

 The rudder maximum deflection is 25° when electrically driven and 35° when manually driven.

--
Regards
Maciek

[karel]

Hi Maciek. Thank you. This makes sense.
 
Can you tell me where the manual rudder was located?  In the aft torpedo room?

[Don Prince]

Hello Mr. Tore,


Last question on the engines and oil, How do you turn those huge engines over manually?

I think I going to bed...  It's 5:05 AM!  I'm like a vampire, I sleep all day and work all might!

Regards,
Don_

[SnakeDoc]

Can you tell me where the manual rudder was located?  In the aft torpedo room?

You are right, the main rudder manual control station is located in the aft torpedo room. There is an hand-wheel provided, which is coupled with the rudder drive shaft. When not used, the control column and hand-wheel is moved to the stowed to the port side (between the electrically driven air-compressor and main switchboard port), as currently on U 995 display (white slanted column and red hand-wheel):


See also this photo from U 570 aft torpedo room.
http://uboatarchive.net/U-570/U-570Photo32.htm
Here, the hand-wheel is detached from the column.


If there was a need to use manual control, the column was moved to the center-ilne, as on this photo from U 505 aft torpedo room:


--
Regards
Maciek

[karel]

Much appreciated Maciek

[Don Prince]

Hello Mr. Tore,


I was reviewing Skizzenbuch and I came across the info on the day tank and the fuel oil system.  We noted that valve "e" had an unusual position that allowed fuel oil to go directly to the attached fuel pump on the diesel engine.


Could it be possible... If the attached fuel pump failed, then the auxiliary lube oil pump could draw fuel oil from a selected fuel oil storage tank. Then fuel oil is directed by valve "e" to the by passed attached fuel oil pump and on to the fuel injectors to fire the cylinders and keep the engine running.


Of course, the attached fuel pump would need to be changed when the engine is shut down.


Does this sound logical?


Image attached.


Regards,
Don_

[tore]

Don.
I guess you should consider the fueltransfersystem independently from the daytank/headertank system. You filled the daytank normally by the compensatingwaterpressure using the head of the compensatingwater tank in the wintergarten casing, thus no use of the electric driven aux.luboil/fuel transferpump. As soon as the day-headertanks were filled the tanks were shut off from the compensatingwatersystem, hence no compensating pressure in the system. Usually one tank was selected  for supply, the other for setling. The daytank in the engine supplymode would generally initiate sufficient natural supplyhead to the attached gearpump. If the attached gearpump failed, the head of the daytank would probably not be sufficent for to overcome the pressuredrop over two filters in series and you would use the compensating system pressure as an emergency substitute for the attached fuelsupplypump. In that case you are shortcutting the day/setlingtanks and have a direct supply connection from the fuelstorage tanks to the dieselengine fuelsystem at the cost of no setlingtank.. Of course you might use the emergency fueltransfer pump as well but as you have to add compensatingwater anyhow I guess that would be superfluous.
Tore

[Don Prince]

Hello Mr. Tore,


I obviously forgot to consider the header tank into the equation in the instance of a fuel pump failure.  That's why I have you as the expert! I didn't realize they turned off the header tank pressure to the internal fuel oil storage tanks on the surface (I only thought they did that when they dived the U-Boat); that would make sense because that would be one less valve to worry about when a dive situation is called for! However, the header pressure to the external tanks in the compensating mode to FBT 2 and FBT 4 can not turned off. (I don't think?).

I need to STOP guessing!



Mr. Tore, I have searched the internet for many hours today and I cannot discover what the head pressure from the fuel oil pump is to the injectors.  If you know the answer to that question, then you can set me straight. It looks like the header pressure can vary depending upon the height of the water in the internal fuel oil storage tanks. So this may affect the head pressure to the injectors as well???  Internal tank 1 has the height level much higher because of the side walls, but Internal tank 2's height is limited to the control room's deck.  Would Internal tank 2 be the only tank to select to by pas the fuel pump if it provided adequate head pressure to the injectors?


Regards,
Don_


PS - I did fine this gem of info...

A standing order states that when using Schnorchel U-boats may only use fuel from the external tanks.  Fuel is pumped from the internal tanks by using diesel cooling water, the pressure varying with the depth of the boat; if the boat is at 14 meters (46 ft.) the pressure is 1.4 atmospheres.  If fuel is pumped from the internal tanks with cooling water at this pressure the tanks are subjected to a pressure greater than that for which they are designed.
 
By approximate and experienced handling, however, ("cracking" the appropriate valve) fuel can be pumped from the internal tanks, but accidents are likely to occur and this may have been the reason for the order.

 

[tore]

Don.
In order not to create confusion I guess you should have a correct understanding of the system. The fueltanks (bunker)are for storage and are seawater compensated from the diesel engine coolingwatersystem. The compensating pressure when the submarine on the surface is obtained by the head of the compensating tank in the wintergarten casing and do not relate to the coolingwaterpressure. When the submarine is submerged, the higher differential pressure in the external fuel storage tanks is still only obtained by the headtank. However if you open the compensating water board valves to the internal tanks you introduce the external ambient sea pressure to the internal tanks which might exceed the designed pressure for the internal fuelstorage tanks. For safety reasons the internal tanks have reliefvalves to prevent damages in such events. You might however, if you are experienced, be able at schnorchelling to crack the compensating water hullvalves so you throttle the pressure within safe limits in the internal fueltanks.
The fuel in the bunkertanks is generally transfered by using the compensating waterpressure, say to the day/setlingtanks in the engineroom. The latter tanks are not watercompensated and thus have a venting into the internal pressure of the submarine. Hence the supply to the gearpump on the main engine is done by the head of the day tank. The attached gearpump purpose is only to supply fuel by a common fuelpipe to the independent HP fuel injection pumps for each cylinder. As you have the double fuel filters on the front of the engine and the knife filter before the supplypipe to the HP pumps, the attached gearpump has to force the fuel through these filters.
Below is an image of the venting pipes of the fuel day/head tanks in the engineroom.
Tore

[Don Prince]

Hello Mr. Tore,


What you stated makes sense and I believe that I grasp your explanation...  The only question I have is does the internal storage tanks (especially Tank 2) have enough head pressure to permit fuel to skip the gravity tank and flow through the valve "e" central passage and supply fuel oil to the engine with a by passed failed pump? The failed pump can no longer draw fuel from the gravity tank, so this flow path does not exists anymore for that pump...


Kind regards,
Don_

[tore]

Normally the attached gearpump has sufficient pressure (some 2 m. wc.)from the daytank head at the suction side to supply the required amount fuel. Storage tank 2 has compensating waterpressure just as the other storagetanks, controlled by the head of the compensating tank in the wintergarten casing as long as the hullvalve for the compensatingwater is open. Surfaced the head in the storage tanks (some 5 m. wc.) would be sufficient to fill the daytanks.
 If the attached gearpump has a failure and had to be short cutted, the head of the daytank is probably not sufficient to force fuel through the filters in the supply pipe to the HP fuelpumps, hence you use the full compensating pressure ( some additional 2.m wc. to the daytankhead) to force the fuel through the fuelfilters and you to use the compensating water head directly to the fuelsupply pipe shortcutting the daytank, a indicated on my image below.
Tore