Tores mailbox VIIC and VIIC/41 operation and technical details

[NZSnowman]

Simon.
The only item left on the valve question is the purple valve. There are two valves each symmetrically placed on port and starboard side. Both have a handle of the boardvalve seawatertype so I guess that`s correct. This rules out the  single drain of the supplyline to the seacompensating head tank in the conningtower. The valves are not shown on any systemdrawings available to me, thus systems before the schnorkel. My assumption would be this is a seawatervalve installed on the schnorkel boats. The schnorkel air inlet and exhaust outlet would not require two symmetrical placed seawater valves in this position. When schnorkeling the dieselengine  sea coolingwater has not been changed  and leaves overboard in the normal way, trapped air in the outboard seacooling watersystem  could cause problems. On the old systemsketches it is an outboard ventcock in the coolingwater space for both silencers marked "n" on plate 13 and pointing forward, this cock is not accessable during schnorkeling. May be the purple valve is a modification for the schnorkeling boats enabling venting while schnorkeling? Again this is only an assumption from me.
Tore

Tore, I am not sure also

I checked the few drawings I have of the schnorkel system, and I can not see any pipes that look like drains

I off to work tomorrow so I will check my other drawings in a few days.

Maciek, do you what these valves are for?

[tore]

Simon
I guess the box you designed has a duct going down below sealevel to the outlet thus act like the sparkarrestor which is the last item before the exhaust goes overboard, otherwise the outlet outside the casing looks very much like the U 995 design having outlet above the sealevel as shown on the drawing below.
Tore

[NZSnowman]

Simon
I guess the box you designed has a duct going down below sealevel to the outlet thus act like the sparkarrestor which is the last item before the exhaust goes overboard, otherwise the outlet outside the casing looks very much like the U 995 design having outlet above the sealevel as shown on the drawing below.
Tore

Tore, would you need a spark arrestor if the exhaust outlets are always underwater?

Here the side view. You can see the box that is between the casting and the pressure hull, and the exhaust pipe running around the high pressure bottle and down to the box. 

[tore]

Simon.
I guess not if the outlet is submerged all the time. I would assume however that there would be a kind of sparkarrestor in the box indicated by you.
Below a photo showing the exhaustoutlet of the KNM Kaura at the handing over to the Germans as U 995 Oct 2. 1971.
Tore

[tore]

Simon.
I have to confess I didn`t like my yesterdays assumption of the purple valve very much. Having another look at the outboard coolingwater system it struck me the pipes as drawn on plate 13 allows full direct seaconnection to the system all the time. I do not remember the system of course, but no way you allow full seawater pressure to the inside of a submarine without a shut of valve (depthcharging- deepdiving etc.) My revised theory would be, the purple valve marked correctly as a board seawater valve  equipped as an important valve with a grease cup and a shut/open indicator could be the sea coolingwater shut off valve. The most likely place to install such a valve would be in the coolingwater bend crossing the flange of the group exhaustvalve to the mufflervalve housing. This is pretty close to the drawn purple valve. Below is my sketch showing the assumed valve. Repeating my shelf, this is an assumption. The drawback of the theory is  that the germans have omitted this essential valve on all the systemsketches, that is hardly to believe. Open for any other ideas but the system has to be capable of being shut of from the sea.
Tore

[TopherVIIC]

Hmm... I agree with Tore in that there would not be a direct sea connection without a shutoff valve... too risky. Is it a question of faulty recording? Is it a change put in after the manuals were produced? or, perhaps a post war change? Perhaps the owners of poor U-995 thought it a useful thing to try, but one not on the orig German manuals? Was the change tried as the war was winding down and people thought it not worth recording at that point? These observations bring up so many exciting questions, don't they! B-)
Christopher... hanging on the edge with curiosity...

[tore]

When the map doesn`t match with the terrain it is usually  an advantage to follow the terrain. In this case we have definitely two objects being genuine seaboardvalves having a construction of  important valves, I cannot imaging any other purpose for these valve at that place. On the other hand the German "grundlichgkeit" makes it difficult to understand why these important valves are not shown on any drawings showing the MAN or GW systems way back in time, after all this is not a late war thing, but basic submarine design. It puzzles me, may be I have overlooked something, am I getting too old? .
Tore

[TopherVIIC]

When the map doesn`t match with the terrain it is usually  an advantage to follow the terrain. In this case we have definitely two objects being genuine seaboardvalves having a construction of  important valves, I cannot imaging any other purpose for these valve at that place. On the other hand the German "grundlichgkeit" makes it difficult to understand why these important valves are not shown on any drawings showing the MAN or GW systems way back in time, after all this is not a late war thing, but basic submarine design. It puzzles me, may be I have overlooked something, am I getting too old? .
Tore

Perhaps there is a drawing map to lead us back to the path... but there are those of us who enjoy thinking beyond a drawn black and white image.

[tore]

True Christopher, hopefully we find the path. So I keep looking and pondering hoping to find the correct input  for the magnificent artwork Simon as well as you makes.
Usually we end up pretty close to the real thing, at the  same time it is fun though.
Tore

[NZSnowman]

Simon.
I guess not if the outlet is submerged all the time. I would assume however that there would be a kind of sparkarrestor in the box indicated by you.
Below a photo showing the exhaustoutlet of the KNM Kaura at the handing over to the Germans as U 995 Oct 2. 1971.
Tore

Tore, I was thinking how hot would the exhaust gases be when it reached the outlet?
 
Would it be a bad thing to have hot exhaust gases hearting up the pressure hull, in a small area?

Tore, not sure if you seen Style 6 of the exhaust outlets before, so here a few photo's and drawings.

[tore]

Simon.
As far as I can see the style 6 exhaust outlet is submerged in the area where you have a possible contact with the pressure hull, moreover the exhaustgases are considerably cooled  at the outlet. I don`t believe you would have a problem.
Tore

[NZSnowman]

Simon.
I have to confess I didn`t like my yesterdays assumption of the purple valve very much. Having another look at the outboard coolingwater system it struck me the pipes as drawn on plate 13 allows full direct seaconnection to the system all the time. I do not remember the system of course, but no way you allow full seawater pressure to the inside of a submarine without a shut of valve (depthcharging- deepdiving etc.) My revised theory would be, the purple valve marked correctly as a board seawater valve  equipped as an important valve with a grease cup and a shut/open indicator could be the sea coolingwater shut off valve. The most likely place to install such a valve would be in the coolingwater bend crossing the flange of the group exhaustvalve to the mufflervalve housing. This is pretty close to the drawn purple valve. Below is my sketch showing the assumed valve. Repeating my shelf, this is an assumption. The drawback of the theory is  that the germans have omitted this essential valve on all the systemsketches, that is hardly to believe. Open for any other ideas but the system has to be capable of being shut of from the sea.
Tore

I have not seen a valve with this style of open/shut indicator before on the Type VIIC, perhaps it could be evidence that it was not added by the Germans or very very late into the war (in Norway)

[tore]

Simon.
I believe it is a original German valve, if you look I guess you shall find more valves with an indicator, not always identical to this one, some have a threaded ring with a tap in a  pedestal slot travelling on a threaded part of the valve spindle, others have a double pointer fixed to the valve spindle, the latter you can  find as a hull fuelvalve just above the IMO motor for the fwd periscope hoist on the port side of the fwd controlroom.
The main problem is that on the systemsketches we have seen you have full seapressure directly to the seawater coolingsystem without a shut off valve for diving.
Tore

[tore]

Simon.
The mysterious purple valve.
Finally I believe we have found an explanation which hold water . The fuel/ballast tanks no 2 port and starboard have a residual venting. The venting of the fuel/ballast tanks are usually operated from the controlroom. In the fuel mode the ballasttanks 2 and 4 port and starboard are separated by gatevalves operated from deck. However the venting ducts have an emergency shut valve Right at the merger of the ventduct and the saddletank. The philosophy is that in case of damage to the ventingducts you should shut the the emergency vent valves to save the buoyancy of the saddletanks. The same philosophy must be valid for the residue venting as well, but I have found no mentioning in the literature of these emergency valves in the aft part of fuel/ ballast tanks 2 port and starboard. My conclusion is nevertheless: the purple elaborate and important valves are the emergency shut off valves for the residual venting duct of the fuel/ballasttanks 2 port and starboard. As a proof I show a picture of the emergency shut of valves for ballast/fuel tanks 4 port and starboard operated from the controlroom, as you see they are identical only the handle is removed.
Tore

[NZSnowman]

Fig. 1. Pressure hull openings.


Fig. 2. New exhaust system.