Tores mailbox VIIC and VIIC/41 operation and technical details

[Don Prince]

Hello Mr. Tore,


As I learn more about these valves, I believe I have to go back and revisit the Negative Buoyancy tank blowing valve.  I have labeled 3 valves related to the air pressure to blow the tanks.


A.  This valve is a manually controlled pressure valve that sets the blowing pressure to 25 Bar from HP
B.  This is the red hand-wheel valve that is used to provide blowing air to the Negative Buoyancy tanks
C.  This is a pressure relief valve to limit the air pressure


See the attached drawing...  Comments?


Regards,
Don_

[Don Prince]

Hello Mr. Tore,


Can you tell me if this is correct?



High Pressure = 200+ Bar
Ballast Tank Blowing Pressure = 25 Bar
Low Pressure = 12 Bar
Negative Buoyancy Tank Blowing Pressure = 25 Bar
Regulating/FRO Tanks Pressure= 10 Bar
Regulating Tanks Pressure = 10 Bar


Regards,
Don_

[tore]

Hello Mr. Tore,


As I learn more about these valves, I believe I have to go back and revisit the Negative Buoyancy tank blowing valve.  I have labeled 3 valves related to the air pressure to blow the tanks.


A.  This valve is a manually controlled pressure valve that sets the blowing pressure to 25 Bar from HP
B.  This is the red hand-wheel valve that is used to provide blowing air to the Negative Buoyancy tanks
C.  This is a pressure relief valve to limit the air pressure


See the attached drawing...  Comments?


Regards,
Don_

Don.
The is a classical blowing arrangement for a VIIC.
  A is the mainblowing valve (red handwheel stb side) not set to any pressure but, controlled manually by the blowing man for port and stb. Q within the pressure range set by the reliefvalve C and checked by reading the manometer.
 B is not a blowing valve and has no special valvecone for pressure regulation, it is a shut off valve to the common venting and blowing pipe between port and stb. Q. This valve is shut when the system is in venting configuration.
Tore

[tore]

Don.
I am not sure I understand fully what kind of figures you want to check. There are a number of different pressures figures. Operating pressures, reliefvalve pressures, testpressures and differential pressures. Fi. the MBT blowing pressure 25 bar is not the usual blowing pressure. Blowingpressure is manually controlled to the pressure required within a pressure range I believe up to 25 kg/cm2 and I guess the max ballasttank blowing panel is having a relief valve pressure set to 30 kg/cm2. I don`t remember all the figures but I guess most of these figures are mentioned in your book U boat information translated by Maciek.
Tore

[Don Prince]

Hello Mr. Tore,
 
I was thinking again...  This setup looked like the Blowing Manifold for the ballast tanks; where there are 2 HP input lines with manually adjustable pressure valves.  A primary and a backup line in case the primary line freezes.   They reduce the HP pressure and use the individual blowing (on/off) valves for blowing the ballast tanks.  This setup looked exactly like the Q tank setup; where you could set the blowing pressure with the manually adjustable pressure valve and then use the on/off valve to blow the Q tanks.  That way you would not need to set the pressure each time you blow the Q tanks.


However, you are the expert and I am just the student who continues to ask many questions to learn about the U-Boat.  I don't believe I will ever be at the point where I don't have questions???  Thank you for the quick response...


I have just uploaded to dropbox the latest version of Skizzenbuch.


Updated pages:
90 - 91 Junkers
98 - 101 Bow and Stern Buoyancy Tanks
189 - 191 Blowing Manifold
212 - 213 Oxygen
348 Corrected U-995 Info
349 - 350 Listening Devices -  GHG, Balkon, KDB, and UT
359 added external views of Bold


Regards,
Don_

[Don Prince]

Hello Mr. Tore,


I was looking through my photo files and I noticed several things about Kaura / U-995....


The photo at with the mountains in the background; there is no lower gun deck, only the upper one.  Was that removed when it became the Kaura S309?


There is a photo of Kaura with people lined up and assending the stair case to the stern hull entrance.  In addition, there is a Norwegian flag on the pole beside the stair case.  Was Kaura a museum boat before it went back to Germany?  It surely looks so...


Regards,
Don_

[tore]

Don.
When the Norwegians introduced the VIICs and VIIC/41 submarines as Nato subs. their operation would be different from the germans. The AAguns or foredeck gun would not be necessary, in addition the boats had schnorchel and spent more time submerged. The guns and wintergarden created a considerable drag submerged, reducing the underwaterspeed. So we removed both the wintergarden and guns and designed a new aft towercasing. It is not a copy of the old VIIC tower from the 1940/41 as can be seen on the photo below.
U 995 museum.
I assume the photo you are referring to is the one below. The U 995 was never a museum in Norway,after my time on board she had a refit and was not used as a frontline sub.any more, but more like a training and research vessel before she was faced out and laid up, I guess in 1962. As from 1965 there were confidential talks and plans to return the submarine to Germany as war memorial. It took a long time before it became a reality as it was still a touchy subject still close to the war. In the early 70ties she was converted to a museum in Kiel and the official handing over sermon took place at Laboe October 2nd. 1971. the photo of the event is below.
Tore

[tore]

Don.
 I have checked you Skizzenbuch (5) and have a few small remarks.

There is a misprint in paragraph 1 mentioning bow buoyancy tank instead of stern buoyancy tank.
On page 101 you have a double description of the Junker which is a bit confusing in addition it has become a two cylinder diesel. The correct text would be: The Junker compressor is driven by a single cylinder opposed free piston, two stroke diesel............
The whole Junker exhaustvalve arrangement is an assumption as we have no original drawing or description of  the design.
Tore 

[tore]

Don .
The venting system of a submarine is one of the most important systems and I just had a look into your description of the system in your Skizzenbuch. On page 281 it seems to me that you have mixed up the MBT 3 emergency shutoff ventvalves with ordinary vents. I have made a sketch based on Plate 16 and 28 below which give an explanation of the system.
The venting of MBT 3 is done via two ducts going through the port and stb. regulating tank and then outside the pressurehull to the port and stb main ventvalves operated from the controlroom. The saddle tanks 2 and 4  have a similar arrangement however the venting ducts goes directly outside the pressure hull and  2 and 4 stb merge into a common ventvalve as port tanks do as well. In the ducts, at the point where these ventducts leaves the tanks there are emergency shut off valves which normally do not take part in the venting of the tanks, they are normally always open and only used in the event of a damage to the outside duct.
A third valve is placed in the MBT 2 and 4 ducts, coloured green on the drawing. These are the isolating gatevalves, shut when the saddletanks are in fuelconfiguration. Otherwise they are always open.
Tore

[Don Prince]

Hello Mr. Tore,


Is that page 281 of the current Skizzenbuch file loaded into dropbox currently?  Almost every time I make changes, the page numbers change.  Currently Page 281 just contains drawings from u-historia about the MBT 2 and MBT 4 hull valves, and the MBT 2 dual residual valve and hand-wheel in the control room.


Page 282 deals with MBT 3 and the commom trunk valve that is operated via a lever in the control room which is also from u-historia.


Regards,
Don_

[tore]

Don.
Yes, I believe you have copied the drawings and may be the text. What is confusing is probably that the emergency shut of valves are called vent valves, giving the impression that they are used in the normal tankventing operation, whereas they are practically never used for venting. They are emergency valves. See drawing below.
Tore

[Don Prince]

Hello Mr. Tore,


I am not permitted to change their drawings, byt I will add a note about the errata.  I will poat a new Skizzenbuch late this evening which will have 10 additional pages as well...


Regards,
Don_

[tore]

Don.
As the emergency valves  have a purpose in the system it is absolutely worth while to explain. A ventpipe outside the pressurehull only hidden by a fragile casing is very susceptible to for inst. aircraft machinegunfire, a puncture of a ventpipe shall cause all the air to escape from the ballasttank which might have a serious consequence that's why these valves are important yet very rarely used.
Tore

[Don Prince]

Hello Mr. Tore,


Thanks for the explanation...  I just assumed the valves were redundant vent valves.  I sure am getting an education!


Regards,
Don_

[Don Prince]

Hello Mr.Tore and Maciek,


I uploaded to dropbox the latest version of Skizzenbuch with the following changes:


Plate 17: Blowing pages 190 - 199
Plate 21: Sanitary Systems pages 226 - 227
Page 291 - Emergency valves
Page 295 - Drawing of valves and locations
Page 327 - Toggle Switchboard


Regards,
Don_