Tores mailbox VIIC and VIIC/41 operation and technical details

[SnakeDoc]

The image attached seems to qualify for the "b" valve going to FBT 4 port side because it is far enough ahead of the Q Tank. It looks to be low enough to fit into the scheme of things, and it has a means to limit the valve movement.  There is a red metal stake that extends into the valve hand wheel spokes which will limit the valve selection...  Hopefully Mr. Tore or Maciek will have a definitive answer to your question instead of my 'SWAG"...

The red medal stake is the drive shaft of the FBT 4 flooding valve.


--
Regards
Maciek

[Don Prince]

Hi Maciek,


I believe you are not looking at the red metal stake that I was referring to...


Regards,
Don_

[SnakeDoc]

Hi Don,

I believe you are not looking at the red metal stake that I was referring to...

Indeed, I was looking on wrong stake. However the element you are referring to is (in my opinion) the MBT 3 blowing line check-valve.


Note that this element is located at the (curved) top of MBT 3 (it is not pressure hull). If it would be stake for the selector valve in question, it had to penetrate MBT 3 walls two times (it would not be desired).


--
Regards
Maciek

[Don Prince]

Hi Maciek,


Your photo is much better than mine.  However, I was thinking of something like this...


Regards,
Don_

[NZSnowman]

Hi Maciek,


Your photo is much better than mine.  However, I was thinking of something like this...


Regards,
Don_

From this viewpoint, the line look like its working its way up pressure hull.

[NZSnowman]

Simon- Don.
Sorry being late in answering. We  never or very seldom used the fuel mode of the saddle ballasttanks, as we operated the VIICs as Coastal submarines. Hence I have not a personal experience of operating same. Transfering a ballasttank into fuelconfigurating requires some preparation. Of course the ventducts have to be shut, the blowing pipe both HP air and exhaust has to be locked shut, but nevertheless the compensating water pipe is in place and in ballasttank configuration you have to take measures to prevent blowing air into the compensating system.
In the bottom of the external ballast/fuel tanks the compensating water is checked by a selectorvalve D on the plan 8 this valve has two positions either open directly to the bottom of the tank and shut to the sea (fuelmode) or (in ballast mode) via a recess in the tank ( to prevent possible oilspill) to the sea and shut to the tank. My rough sketch below might explain the idea.The selector valve sits on the top of the pipe in the tank like some of the fuel testingvalves but are operated from outside the pressurehull ( not in the controlroom). The system prevent, in ballast mode, that  the compensating system don`t get higher pressures than the head of the compensating expansion tank in the towercasing regardless of the depth of the submarine and is not influenced by HP airblowing of the ballasttank.  Tore

Hi Tore, Don & Maciek.

Does this valve need to be in the saddle tanks?

If you place this valve under the deck and right next to the saddle tank this seem to me a have a few advantages than being within the saddle tank (Fig. 1). Can be easily accessible and easier for maintenance.

I also checked my U-boat plans and there an opening in the saddle tank between frame 38 & 39. You can see this opening on U-995 (Fig. 2) (It has been welded up in the photo). This is very likely the opening to the sea.



Figure 1.


Figure 2.

[Don Prince]

Hi Simon,


That all looks like a possibility...  However, I am very concerned about conjecture at this point.  I still can't understand the hand wheel gear driving a worm shaft that seems to go to a pipe.  That makes no sense to me. To say the least, I'm very confused at this point about the selector valve for the saddle tanks... 


Hello Mr. Tore,


While searching through my U-995 CD I found the drive shaft for the FBT 2 saddle tanks Kingston valves.  I have attached the image.


Regards,
Don_

[SnakeDoc]

Hi Gentlemen,

Your photo is much better than mine.  However, I was thinking of something like this...

From this viewpoint, the line look like its working its way up pressure hull.

The HP line goes up and then to stb, to the blowing distributor.

That all looks like a possibility...  However, I am very concerned about conjecture at this point.  I still can't understand the hand wheel gear driving a worm shaft that seems to go to a pipe.  That makes no sense to me. To say the least, I'm very confused at this point about the selector valve for the saddle tanks... 

This is not a worm gear. This is how the valve is constructed. I have attached the photo of another valve from the bow torpedo room and another from control room (FBT 4 hull blowing valve stb).


--
Regards
Maciek

[Don Prince]

Hi Maciek,


Thanks for the info about the valve...  I was thinking of a mechanical hand wheel with a worm gear shaft.  It looks like you are right about the valve in question, and it's attached to the upper area of MBT 3; I'm not sure where it goes? Perhaps to an air pressure gauge? That would be one means to know the pressure inside MBT 3 when blowing the tank...  Is what looks to be a red spring latch just a reminder that they had better know what they are doing before changing the valve setting?


I'm still not sure where the selector valve is physically located for FBT 2 and 4; inside the saddle tanks or above and under the deck like Simon suggests?  I guess I have a lot of questions...  It seems the more I learn about the Type VII, then there is the more I don't know...


Regards,
Don_

[SnakeDoc]

It looks like you are right about the valve in question, and it's attached to the upper area of MBT 3; I'm not sure where it goes? Perhaps to an air pressure gauge? That would be one means to know the pressure inside MBT 3 when blowing the tank... 

This is line going to the blowing manifold. See the attached drawing (I marked the line with green color).


--
Regards
Maciek

[Don Prince]

Hi Maciek,


Great work...  You convinced me that this line is for blowing MBT 3! It seems like such a small air line to blow such a huge ballast tank (MBT 3).  Comparing the size of the blowing line to the size of the venting valves (2) for MBT 3 in the venting trunks... Since the blowing line is such a small diameter have you ever read as to how long it took to blow MBT 3 (even partially blow)?

With the differential in vent and blowing diameters, then diving time would be faster, and surfacing time would be much slower...


I see there are two blowing valves for MBT 3 Port and Starboard...

Regards,
Don_

[SnakeDoc]

Don,

Great work...  You convinced me that this line is for blowing MBT 3! It seems like such a small air line to blow such a huge ballast tank (MBT 3).  Comparing the size of the blowing line to the size of the venting valves (2) for MBT 3 in the venting trunks...

The diameters of the blowing lines: internal 17 mm, external 20 mm.
As a point of interest, the regulating tanks and Q-tanks blowing lines diameters are: internal 22 mm, external 26 mm.

Since the blowing line is such a small diameter have you ever read as to how long it took to blow MBT 3 (even partially blow)?

No, as I recall, I have never met such data. But knowing the flooding holes cross-area and blowing air pressure and amount, the time could be possible to estimate.
If I remember correctly, Mark has made such calculations.

With the differential in vent and blowing diameters, then diving time would be faster, and surfacing time would be much slower...

I'm not sure if flooding cross-area did not have greater influence on blowing and flooding time than vent and blowing lines diamater.

I see there are two blowing valves for MBT 3 Port and Starboard...

Yes, you are right. I was not able to locate stb valve. If both valves were located symmetrical, the stb one should be located near the aft diving plane operating station. But there are oxygen bottles on the deck. So I guess, that the stb valve is located near (under) the blowing distributor.


--
Regards
Maciek

[tore]

Simon.
I guess you are right in assuming the selectorvalve for the compensatingwater could be outside the saddletank.In spite of an extra pipe it is much simpler and eliminates the stuffingbox for the valvespindle. You suggestion for the valvecasing could be correct I enclose an image of a selector valve in the fuelsystem.
Tore

[tore]

Don.
The image of your blowingvalve is indeed the port blowingvalve for MBT3. As you know you have a central bulkhead in MBT3, allthough the bulkhead is not  pressure/watertight the tank still requires two blowingvalvs as well as two ventvalves.
 What you assumed was a wormdrive is the housing for the checkvalve which is incorporated in the blowing valve casing. This is the classical ballasttank blowvalve and all the blowvalves have a non return/checkvalve.
Tore

[tore]

Simon.
Compensating water selector valve saddle fuel/MBT 2&4. May be an execution as below and possibly a removable T bar extension?
Tore