Tores mailbox VIIC and VIIC/41 operation and technical details

[Don Prince]

Hello Mr. Tore and Simon,

Sometimes I over think things, but I will just ask the question... This excellent Simon drawing shows the red pipe directing Cooling Water from the mufflers to the header tank. If only one (1) Diesel engine is running and CW is flowing to the header tank, it would also be back flowing CW into the opposite muffler. I believe if there was a one-direction check valve in each muffler line (or in the muffler itself), then this would eliminate the waste of Cooling Water.

If both diesel engines were running, then both supply CW to the header tank.

Question - Do you know if there was such a one-direction check valve in the muffler line?

Regards,
Don_

[NZSnowman]

Don, a good questions. I only guessing, I imagine some of the CW would escape but most would make it to the Header Tank.

I also have a question about the Cooling Water from the mufflers to the header tank.

I estimated the size of the two pipe coming out the mufflers at 75 mm. Does this mean that the pipe from the joint of the two pipes to the header tank is 106 mm (e.g. almost double the flow) or is it the same size pipe all the water to the Header Tank?

[tore]

Simon
As it is only a headertank I guess the pipe is 75 mm.
Tore

[Don Prince]

Hi Simon,

After looking at the Cooling Water line size (75 mm) and the obviously smaller size of drain lines placed at the top side of the muffler, I would think that the Cooling Water pressure would easily force CW up to the header tank (those drain lines at the top of the muffler also serve to get any air out of the muffler CW chamber). CW flowing from the muffler will keep the muffler temperature at an acceptable level depending on the outlet pipes diameter.

Just my opinion - I do not believe the pipe diameter is increased going to the header tank. The header tank serves as a reservoir for the fuel tanks water compensating system, and this system is only drawing water when fuel is being transferred to the day tank. So, you have CW overflow drainage at the header tank and CW drainage at the two (2) muffler drain pipes.

However, all is dependent on Mr. Tore comments...

Regards,
Don

[Don Prince]

Hello Mr. Tore and Simon,

Has anybody thought about a repository for all of the information in Tores Mailbox, personal documentation, with regards to the Type VII C U-Boat. The documentation that I have on my computer that went into the creation of Skizzenbuch and the coming Addendum Booklet (doc, pdf, photos, and drawings), and the many drawings that Simon has spent thousands of hours creating?

Mr. Tore started this adventure on January 12, 2012, and is in his 90s, and I will turn 80 next year, and of course I believe Simon is about half our age... However, Simon can create engineering type 3D drawing from U-Boat remains sitting on the ocean floor.

Do we have options for preserving our work for future U-Boat enthusiasts?

Kind regards,
Don_

[tore]

Don and Simon.
The coolingwater has generally a common seawaterinlet via the inlet crossoverpipe and a common outlet via the exhaustcooling headertank. Both the inlet and the outlet can be selected if need be, however normally you use a common inlet and a common outlet for both engines.  As the coolingwater discharge for both engines are commonly connected by the headertank, both port and stb.systems have the same discharge head and need no checkvalve as they are hydraulically ballanced by the headertank. Ref. plate 10 below.
Tore
 

[Don Prince]

Hello Mr. Tore,

On sheet 10 (Fuel Oil Compensating System) that you previously posted, valve (a) shut stops high pressure in a dive from over pressurizing the internal fuel oil tanks. However on sheet 13 (Cooling Water System) I did not note a shut-off valve at the muffler side with all the different cooling water jackets and bends leading to the diesel engine; is there one? There is a shut-off hull valve on the port and starboard side taking sea water to the diesel engine water pumps.

A second question - on sheet 13, would they normally leave valve (h) open to allow both the port and starboard engines to draw cooling sea water from either hull valve. That way they could isolate either filter and replace/clean it while running both diesel engines...

Regards,
Don_

[NZSnowman]

I have worked out the alignment of the main pipe from the Muffler to the Header Tank base of a single war-time photo. The alignment is different than I previously believed.

Base on the inlet openings on the Saddle Tanks and Pressure Hull, I have a high level of certainty that these pipes entering the Saddle Tanks and Pressure Hull are around 55 mm. These are the pipes from the Header Tank to the MB & RFO Tank 2 & 4 and Engine Room.

Its also about the only way this pipe can make it to MB & RFO Tank 2, there very little space for pipes in this area (in fact I don't think I could get a 75 mm to MB & RFO Tank 2 without restructuring the deck height).

If we say these are smaller pipes entering the Saddle Tanks and Pressure Hull, do you think the main pipe from the Header Tank to the 4 way pipe connector is the same size (55 mm) or should be it be bigger at 75 mm?   

[Don Prince]

Hi Simon,

Interesting... Plate 10 does indicate that the pipe from the header tank going to MB & RFO Tank 2/4 and to the pressure hull are smaller. The pipe coming from the header tank to the mufflers and the over-flow drainage pipe are larger.

The capacity from both running diesel engines water pumps would be about 96 cubic meters of cooling water per hour; Therefore I believe the larger diameter pipe from the mufflers may be required, as well as the larger diameter overflow pipe from the header tank.

Regards,
Don_

[tore]

Don and Simon.
Sorry I have been away for a few days. I guess Simons observation that the common CW pipe from the two silencer to the headertank is larger than the direct makeup lines between the headertank and silencer is correct, the overflow of the headertank must be able to handle the full coolingwater capacity of both engines. I guess the supply pipe from the headertank through the pressurehull would be 55mm diam all the way including the shutoff-  and reliefvalves inside the pressurehull.
Tore

[Don Prince]

Hello Mr. Tore,

I took the drawing of the bow torpedo tube and door and added the two(2) drawings below to illustrate the outer door opening with the drawings below. What do you think?

Regards,
Don_

[Don Prince]

Hello Mr. Tore and Simon,

As you know, I have been working on an Addendum Booklet to supplement Skizzenbuch with our later discussions and any needed updates or corrections. I believe that we all have done a pretty good job with the initial Skizzenbuch, and the Addendum Booklet is currently scheduled for a release date of December 1, 2020. I have uploaded my latest version of the Addendum Booklet in dropbox, and I believe I only need to replace the image on page 47 with an update. If there is anything that I have missed, or needs to be included, then please advise...

Kind regards,
Don_

[NZSnowman]

Hi Simon,

Interesting... Plate 10 does indicate that the pipe from the header tank going to MB & RFO Tank 2/4 and to the pressure hull are smaller. The pipe coming from the header tank to the mufflers and the over-flow drainage pipe are larger.

The capacity from both running diesel engines water pumps would be about 96 cubic meters of cooling water per hour; Therefore I believe the larger diameter pipe from the mufflers may be required, as well as the larger diameter overflow pipe from the header tank.

Regards,
Don_

The largest pipe I could get to fixed was 60 mm, so I will go for that.

Don and Simon.
Sorry I have been away for a few days. I guess Simons observation that the common CW pipe from the two silencer to the headertank is larger than the direct makeup lines between the headertank and silencer is correct, the overflow of the headertank must be able to handle the full coolingwater capacity of both engines. I guess the supply pipe from the headertank through the pressurehull would be 55mm diam all the way including the shutoff-  and reliefvalves inside the pressurehull.
Tore

I used a online flow rate calculator and it said to match the same flow of both engine, the minimum size the pipe would need to be was 100 mm.   

[Don Prince]

Hello Mr. Tore and Simon,

I attached the photo of the mufflers and the pipe to the header tank, and the bend pipes from the diesel engines.  What I have noticed is the bend pipes are much smaller in diameter than the pipes to the header tank. Therefore, the flow capacity going to the mufflers is restricted to some degree, but the larger pipe size from the mufflers seems to reduce the CW pressure going to the header tank.

Remember, the 48 cubic meters of water per hour provided by each diesel engine water pump also flows towards the aft of the U-Boat to cool the thrust bearings plus other items in the aft torpedo room and exits at the aft drain port to the sea (Attached Plate 13 drawing). So, the CW pipe to the header tank doesn't need to be such a large diameter (i.e., 100 mm).


Simon, is there anything in the muffler photo that would allow you to determine the size of the bend pipes and the muffler pipes?

My Thoughts,
Don_

[NZSnowman]

Fuel Oil Compensating System


Fig. 1. Overview of Fuel Oil Compensating System (red).




Fig. 2, 3 & 4. Aft section of Fuel Oil Compensating System (red). Have not found any evidence of the true pipe alignment or the type or location of the drain valve 'e'. I have photograph evidence that indicates that the line back to the header tank runs along the starboard side of the boat. There a deck hatch just forward of the exhaust valve (orange) so I located the drain valve 'e' below this hatch.




Fig. 5, 6 & 7. Mid section of Fuel Oil Compensating System (red). Have not found any evidence that the pipe runs down the inside of the air inlet pipe but highly likely as there no room for piping on the starboard side. Have not found any evidence where the '4 way' pipe junction is located. We know where the inlets are on the saddle tanks so base on that and the deck hatches, I have located again under the hatches valve 'b'. You can also see I have located the exhaust blowing valve 'h' under the same hatch (orange).



Fig. 8 & 9. Header Tank of Fuel Oil Compensating System (red). Have not found any evidence of the layout of the header tanks but this layout seems most likely (I still need to fixs the Header Tank outlets). I found evidence the pipe running forward on the starboard side of the CT.

I need to do more research on how the piping goes around the CT, the alignment of the overflow pipe, and the alignment of the piping inside the saddle tanks to the expansion tanks.

A good start to the Fuel Oil Compensating System, I been working on this system for about four years now, so it great to see it nearing completion.