Tores mailbox VIIC and VIIC/41 operation and technical details

[tore]

Don.
I just had a brief look at your latest Skizzenbuch new text starting from page 141. On page 142 you are showing the lube oil cooling system naming the coolers luboilcannister filters. On this drawing the filters are not shown. I guess I made a mistake when I commented on your mixing up the double  fuelfilters with the luboilfilter posting the wrong image of Simons luboil system. Down below is a right image from Simon and the traditional lubeoil scheme where I have tried to indicate the positions of the lubeoil filters. I guess you should reduce the dimension somewhat down to say 200 mm  diameter. The filters are usually placed before the coolers as you have less resistance when the oil is warm. To show all the systems on top of each other makes it difficult  to read and understand and might be confusing. Reverting hopefully tomorrow.
Tore

[Don Prince]

Hello Mr. Tore,


There are two electric piston pumps located on the right top and bottom of Simon's drawing (look like round circles). I believe these are the diesel engine water cooling pumps.  If one water cooling pump fails, then can 1 water cooling pump cool both diesel engines?  It looks like they could function in that way...


The basket type filter on the initial lube oil loading line serves to catch the nuts and bolts.  So, did they replace the 2 basket type filters with 2 knife type filters that were placed very close to the valve chest?

Does the labeling look correct on the attached photo?  What is the large red cap for at the bottom of the photo?

Regards,
Don_ 

[tore]

Don.
In order not to get confused I take one question at the time. The "round circles" on Simons image are not electric driven pistonpumps, but the well known port screw "Imo" spareluboil/ fueltransfer pump and the other the spare electric driven seawater centrifugal pumps as indicated on my image below. Please note that the original seacoolingwater scheme has a mistake as the suction for the electric driven seawaterpump has a suction connecion to the main crossover seawaterpipe . The pump can indeed be used as spare coolingwaterpump for both engines.
Tore.

[tore]

Don.
The attached piston coolingwater pumps are located well below the floorplates and are not easy to see. Below is an image of the double pistonpump driven off a gearwhweel on the crankshaft just aft of the vibrationdamper on the front of the engine.
Tore

[tore]

Don.
 Basket strainers. If you mean the lubeoil filter before the lubeoilcoolers I don`t think they are replacement. In the old systemplan you`ll see there is a differential manometer to survey the pressuredrop over the filter, so I guess it could be classified as the main lubeoilfilter.
Tore

[Don Prince]

Hello Mr. Tore,


These filters and pumps are really getting to me.


1. I now understand the water cooling pumps (location) are an integral part of the diesel engine.
2. I now understand the lube oil pumps (location) are also a integral part of the diesel engine.
3. Is there a way to disable the lube oil pump mechanically so it's not running when you want to change it out?
4. Did you change out a lube oil pump while the diesel engine was running?
5. If so, is the lube oil pump configured in a by-passed, or isolated mode, so it may be changed and not get pressurized lube oil feed from the aux. Lube oil pump if it's supplying lube oil to the running engine?
6. What are those 2 electric lumps for in the opposite corners of the forward bulkhead used for?
7. If a water cooling pump fails can it be replaced on a war patrol?
8. Is there any possible valve chest switching to allow one pump to supply cooling water to both diesel engines?


I should know or be able to figure this out this stuff on my own, but I just don't want to get this wrong...


Regards,
Don_

[tore]

Don.
Labeling photo. I am afraid you have to correct the labeling. Below you`ll find my corrections, but you really have to go into the lubeoilsystem to have a correct understanding.
Tore

[tore]

Don, your last questions. Again you have to study the whole lubeoilsystem to have a complete understanding as there are many options to operate the system. You can indeed run the main engine disabeling the attached coolingwaterpumps, I have done that myshelf when the port engine coolingwaterpump broke down. If the drive of the pumps are mechanically OK, you can operate the valves so you are able to connect one of the systems to the other f.i. operate the port engines attached pump to serve the stb as well or to operate the system by the electric centrifugal seawaterpump. Normally you dont`carry a complete pump with drive and casing as spare due to spaceproblems, we had to get a new from base as the piston conrod got loose, smasing the casing. You cannot be sure to be able to continue a war patrol on two engines if you have a brake down, it all depends on the collateral damage, that is the drawbackof attached auxilliaries.

Tore 

[tore]

Don.
I am not sure if I understand your question 6. about two electric lumps?
Tore

[SnakeDoc]

Hi Don,

6. What are those 2 electric lumps for in the opposite corners of the forward bulkhead used for?

If you mean electric pumps in the forward port and forward stb corner of the Diesel engine room, the one in the port corner is auxiliary/emergency lubricating oil pump (and transfer fuel oil pump). This pump was used to force lubricating oil through all friction surfaces of the engine, before it is started up (and when the individual lubricating oil pump driven from the crank shaft is not running). Of course, it was also used when the crank shaft driven pump is out of order.
When used as fuel oil transfer pump, this pump transfers fuel from external fuel oil tanks (tankers, depot ships and so on) to the boat's fuel oil tanks.


In the stb corner is the auxiliary cooling water pump, used when the individual cooling pumps driven from crank shafts are out of order and to cool down the diesel engines after they were stopped (and when individual cooling pumps also were not working).


These pumps are vertical shaft, centrifugal pumps. The parts visible above deck plating are the electric motors, the pumps themselves are below deck. Such arrangement (similar to all other pumps) is to protect motors from splashes and water (even if pumps are flooded due to high water level in bilges, the motors are safe).


--
Regards
Maciek

[tore]

Done.
I guess I did not answer your question on the atteched luboilpump which is a gearpump. It goes the same way as for the attached piston coolingwater pump. you can remove the pump in case of damage and isolate the pipesystem connected to the pump. In such case you use the electric driven screw lubeoilpump on the port side and direct the oilflow as indicated on my image below shortcutting the attached gearpump.
Tore

[SnakeDoc]

I would like to make some comments to my previous post:

6. What are those 2 electric lumps for in the opposite corners of the forward bulkhead used for?

If you mean electric pumps in the forward port and forward stb corner of the Diesel engine room, the one in the port corner is auxiliary/emergency lubricating oil pump (and transfer fuel oil pump). This pump was used to force lubricating oil through all friction surfaces of the engine, before it is started up (and when the individual lubricating oil pump driven from the crank shaft is not running). Of course, it was also used when the crank shaft driven pump is out of order.
When used as fuel oil transfer pump, this pump transfers fuel from external fuel oil tanks (tankers, depot ships and so on) to the boat's fuel oil tanks.

One more use: taking the lubricating oil into the boat's tanks.

These pumps are vertical shaft, centrifugal pumps. The parts visible above deck plating are the electric motors, the pumps themselves are below deck. Such arrangement (similar to all other pumps) is to protect motors from splashes and water (even if pumps are flooded due to high water level in bilges, the motors are safe).

The auxiliary lubrication pump is not centrifugal type (as I have written before) but worm type pump, with one main rotor (driven by electric motor) and one auxiliary rotor (rotated in the opposite direction), both in vertical arrangement. The oil is pumped up from the bottom.



The auxiliary cooling pump is centrifugal type pump, not self-suction, i.e. it has to be flooded to work (but it is not a problem, because the water level is always above the pump).


--
Regards
Maciek

[SnakeDoc]

Regarding the previous post about filters, I have attached some images of the filters (not necessarily used on U-Boats, but from that period).


--
Regards
Maciek

[Don Prince]

Hello Mr. Tore,

Page 123 - The Büchi turbo charger was never used at lower loads; the tuning of the exhaust/inlet cams was adapted to higher exhaust pressure even on U-Boats without a schnorchel.

1. Should that be the roots supercharger was never used at lower loads?
2. I thought the Büchi turbo charger was always engaged on the MAN diesel engines
3. Did the Germans tune the exhaust/inlet cams to adapt to higher exhaust pressure for schnorchelling?
4. I believe a MAN diesel engine would have the Büchi turbo charger engaged while schnorchelling, but I'm not sure that a GW Diesel engine would have the Roots supercharger engaged while schnorchelling because of the 6 knots speed restriction (stress/snap the schnorchel mast).

Regards,
Don_

[tore]

Don.
I guess it is a misunderstanding stating the Buchi turbocharging system was never used at lower loads. This relates to the Roots blower. The Roots blower required a lot of energy to operate and did not contributed to a higher efficiency of the GW diesel to compensate for the higher power requirement,  hence you only increased the fuelconsumption, so you disengaged the blower at lower loads. The Roots blower was merely a device to boost the max. power of the engine when higher output was required. The MAN turbocharger utilised the energy in the exhaustgases thus using the waste heat energy to operate and hence contributed to a general higher efficiency e.g. lower fuelconsumption and could not be disengaged.
On the non reversible GW engines you had only one set of valvecams. I don`t know for sure but assume on the MAN turbocharged engine you possibly had two sets of cams using adopted cams on the reversing shaft, this might be due to the exhaust gas turbine.
When schnorcheling you primarily was charging the batteries, using low speed propulsion on E motors  as we had speed restrictions.
Tore