Tores mailbox VIIC and VIIC/41 operation and technical details

[tore]

Karel. You could not pick a more complicated item. When the Junker free piston compressor was installed in the aft torpedoroom of the VIICs they experience problem with the exhaust back pressure of the Junker compressor. In order to solve this, they made an interlock with the aft buoyancy tank vent so you could not open the exhaustvalve unless  the buoyancy tank vent was shut, preventing the stern to be too low in the water, hence the complicated arrangement as can be seen on the image below. However your question as to the location of the vent handle you`l see same on my images, as you see, this vent cannot be  operated from the control room.
Tore

[maillemaker]

Hi Tore!

Thanks for the replies on the snorkel.

So if I am interpreting the illustration correctly, the snorkle rests directly on the pressure hull when in the lowered position.

So, on my Revell 1:72 model, I am building the pressure hull and saddle tanks under the deck in that region, and I will omit the "box" structure provided with the kit, except for the hinge section.  I will build in appropriate deck supports around the opening.

Steve

[tore]

Steve, I guess you`ll be well off with such a solution.
Tore

[maillemaker]

So what would you say is a ballpark number of valves that had to be manually opened/closed every time you dove or surfaced the boat?

It seems very complicated!

Steve

[tore]

Steve. All the valve were manually operated. Kingstons, vents, exhaustvalves etc. I guesstimate some 30- 40 vents/valves altogether including valves for HP blowing and exhaust blowing.
Tore

[maillemaker]

Steve. All the valve were manually operated. Kingstons, vents, exhaustvalves etc. I guesstimate some 30- 40 vents/valves altogether including valves for HP blowing and exhaust blowing.

Cool.  How many people were required generally to operate all the valves?  Seems like a lot of coordination is required!

Steve

[tore]

Steve.
 Diving would require some 7-10 people operating the vents manually, further 3-4 men in the engine room shutting the hull valves. Surfacing, one man, the control room engineer at the blowing panel as many of the HP air valves were adjusted on beforehand allowing only the main blowing valve to be operated. No men at the vents as the vents are shut when submerged, however in war time the vent operators would be stand by at diving stations. Each man knew exactly what he should do, the drill was done during the work up periode and you did not give any other order than dive, dive, dive, the coordination was done on beforehand. 
Tore

[maillemaker]

Diving would require some 7-10 people operating the vents manually, further 3-4 men in the engine room shutting the hull valves. Surfacing, one man, the control room engineer at the blowing panel as many of the HP air valves were adjusted on beforehand allowing only the main blowing valve to be operated. No men at the vents as the vents are shut when submerged, however in war time the vent operators would be stand by at diving stations. Each man knew exactly what he should do, the drill was done during the work up periode and you did not gave any other order than dive, dive, dive, the coordination was done on beforehand.

Fascinating stuff!  Did the German u-boats have a "Christmas tree" like the US subs to indicate the status of all the valves?

Steve

[tore]

Steve.
Christmas trees were common on the VIICs, below is an image of the blowing panel, as you probably know the VIICs used HP air for blowing the ballast tanks, the blowing christmas tree consisted of a common blowing valve for all the ballasttanks, each tank could be individually adjusted  as nessesary by a separate valve after the main blowing valve, which of course resulted in a lot of valves. In order to save HP air you only blew the main ballast tank partly by hp air and continued blowing the residue by exhaust from the main diesels. The system required a constant adjusting of the exhaustblowing as the resistance varied because the ballasttanks were situated at different depth and thus the counterpressure varied, if not adjusted the exhaust would only work on the tank having the lowest counterpressure. Thus you must be able to distribute the exhaust to the right tanks. This panel or christmastree if you like, is situated outside the pressurehull having the adjusting valve wheels on top of the blowing panel as can be seen on the image.You started to exhaust blow the the MBT 2 & 4 being closest to the surface (least resistance ), then shut the valves to MBT2&4, continued with 1 and 5 now having the lowest resistance and as the submarine ascended shut the  MBT 1 and 5  and finishing up with the MBT 3 the (deepest tank highest resistance ) now having an acceptable resistance, until you was completely surfaced. This required a constant surveillance by the operator and a frequent adjustment of the valves in the exhaustblowing panel.
Tore

[VIC20]

below is an image of the blowing pane

Your forgot to add the image. 

[tore]

You was too quick, I had the image loaded but it was too large and I had to make it smaller hope everything is OK now.
tore

[maillemaker]

Hi Tore,

That is not the kind of Christmas Tree I was talking about - on US subs they had a series of red and green lights (like are on a Christmas tree, thus the name) that indicate the open/closed status of hull valves.

Here is one from the USS Drum (Gato class):



Steve

[maillemaker]

Tore:

In your picture of the VIIC Christmas Tree, why do some valves have rope windings on the handle?  Do they get hot/cold from the air passing through them?

Steve

[tore]

Steve. I thought you used the same valvecluster nomination as the offshore oilexplore people which is a stack of valves on top of an underwater oilwell. No the VIICs did not have your type of xmastree the closest I can get is the light controlpanel for the essential hullvalves as on the image below.
Tore

[tore]

Steve. The valves on the blowing panel were of a special construction having a valve cone designed as a reduction valve. The green handle wheels were the HP group valves direct connected to the HP flasks max. 205 bar. or slightly in excess of 2900 lbs/sq.inch. The main blowing valves reducing the pressure from max.205 to max. 25 bar and the distribution valves reducing the pressure to appropriate adjusted pressure for the relevant ballast tanks. The rope windings on the handles are insulation, this can be seen in particular on the exhaust blowing panel. The dieselexhaust valves gets hot, the HP air reduction valves get cold.
Tore