K  r  i  e  g  s  t  a  g  e  b  u  c  h
  
 
Section Maschine
  
 
"U  38"
  
 
Patrol from 27.2. - 6.4.40.
  
     
 
A.) Malfunctions, type and correction:
  1.  On 3.3.40 port air compressor out of service.
  Cause:  Teeth of the drive worm for the cooling water pump were worn off.  It was assumed that the bearing was too large and so the teeth were raised during start-up.  No spare worm was on board. Makeshift cooling by establishing a hose connection to the stern tube cooling water piping. Worm wedged up so as to be disengaged, time requirement until makeshift repair:  13 hours.
   
B.) Experience:
  a)  Personnel:  Supplement for training above planned manning of 1:1 for watch-standers and failures is good for summer but because of increased oxygen consumption and greater CO2 enrichment undesirable. Instead of the standard 42 man crew 50 men were on board; as a result the specified air apace of 10 m³ for each man was reduced to 8 m³ meaning the beginning of ventilation was accelerated by about 2 hours.
   
  b)  Engine and diving installation:
  1.  Port exhaust gas valve could not be shut completely.  First determined diving to depth = 40 meters on the 2nd day after departure.  Linkage in the over deck had to be shortened.  This could only be done after 6 days due to the Sea State.  Time required:  2 hours.  Pressurizing the space between the inner and outer exhaust valve after every cleaning and repair with 10 kg/cm³ is deemed necessary.
  Central lubrication for valves has proven itself, grinding as well every 6 hours.  After 6 weeks operation somewhat sluggish, however still operable by one man.
   
  2.  On the compressor malfunction:  With the failure of the integral cooling water pump the following cooling route proved itself:  Cooling water from the diesel to the stern tube via the raised OPZ-valve (outlet of the cooling water pump for the E-motor room), standing centrifugal of the cooling water pump to the suction piping of the cooling water pump.  Instead of the zinc protected flange, fit on the flange with the hose coupling from the control room (from the emergency pressure connection) and connect it to the flanged suction line with a hose coupling (from the emergency connection) via the drinking water hose.  The valves inlet cooling pump - E-Motor room and cooling pump air compressor 2 remained closed, so that the air compressor could not take away water.  Cooling was then sufficient, so that both compressors could run at the same time
   
  3.  On the 3rd day after departure head gaskets of cylinders 3, 4 and 8 of the overhauled starboard diesel began to leak, on the 9th day the ones of cylinders 4 and 5. 
  Determination: The poorly accessible nuts on the rocker arms were only hand-tightened.  The rocker arm [illegible two words] were removed.  After tightening the nuts [illegible word] shaft jammed when reversing, meaning the [illegible word] of the the rocker arm allowed a twisting.  By [illegible word] the shaft was aligned with
 
     
     
Click the flag to view the above page from the original German KTB
     
 
- 2 -
  
     
 
  time consuming work (Work time for the first three repairs 15 1/2 hours, for the next 2 5 hours)
   
  4.  Experience with repair of the Dräger pressure reducer Type D 17/A for Low Pressure-distributor due to increase of the working pressure due to leaks at the crater [not understood term] of the auxiliary and main pressure reducer.  Carry out tightness test exactly according to Operating Instructions (Malfunctions).  In case of leaks, disassemble.  When replacing the closing piston 9 (fig. 24), the following must be observed:  The closing piston and the spring plate 8 must be screwed together easily and securely, if necessary, a slot at the end of the screw of the closing piston for screw drivers should be sawn. Replacement of the hard rubber sealing plug 11 can be carried out with on-board means.
  Assembling, testing and adjustment: First, fit the closing piston 9 with the spring plate 8 and check for easy movement in the housing, then securely tighten the locknut 5 with spring 7, insert the crater 12, tighten the screw 13.  Connect the auxiliary pressure reducer without connecting pipe 52.  Fasten High Pressure-pipe and with completely unscrewed adjusting nut 49 of the auxiliary pressure reducer slowly open High Pressure air.  Air must not escape from the outlet of the auxiliary pressure reducer or crater screw 13.  Then connect the connecting pipe 52 and the adjusting spring cover 2 with membrane, springs, etc. with adjusting spring 22 screwed out completely. Re-check for leakage at the Low Pressure-outlet.  Screw down the Low Pressure-pipe, extraction off, High Pressure air on, first slowly adjust the auxiliary pressure reducer by tightening adjusting nut 49 until the working pressure gauge shows 12.5 kg/cm², then open the extraction (Low Pressure distributor drain) and during extraction, set adjusting screw 22 until working pressure is 12 kg/cm² (ie, 0.5 lower than auxiliary pressure).  Check the Low Pressure-extractor to see if the auxiliary pressure reducer rises again to 12.5 kg/cm².  If the setting is correct, the working pressure drops by at least 1 kg/cm² during operation, when it is switched off, it briefly rises 1 kg/cm² above the set auxiliary pressure reducing pressure.  When set correctly the operating pressure drops by at most 1 kg/cm² during operation, when it is switched off, it rises briefly 1 kg/cm² over the set auxiliary pressure reducer pressure. When operating be careful that pressure reducer valve is always used and that the manual regulating valve is properly sealed, so that pressure on the Low Pressure side can not rise higher.  The installation of the pressure reducer on board must be such that the auxiliary pressure reducer and adjusting screw 22 are easily accessible (as in the case of U-64).
   
  5.  Once again the installation of a silencer for venting regulating tanks and negative buoyancy tanks is urgently requested. Due to the loud noises when venting to flood the negative buoyancy tanks during the surfacing, an Aircraft Alarm was not heard immediately after the opening the conning tower hatch, which may lead to the loss of the boat.
  The following experience was gained:
  Venting into the boat is not appropriate because:
  a)  loud noise for too long,
  b)  too long to flood,
  c)  too much over pressure in the boat,
  To a)  Communication is impossible for a long time
  To b)  Necessary negative buoyancy when the boat is surfacing or broached is not available.
  It has been requested:
  1.  Quick venting even with overpressure in the tank.
 
     
     
     
 
- 3 -
  
     
 
  2.  Quick opening and closing of the flood valve.
  3.  Filling display "Full" and "Empty" except for residual water check with electrical contacts (such as the "U-38" flooding time measuring system).
  For new boat the following changes are suggested for the negative buoyancy tanks, implementation in boats in service should be checked.
  Venting  as with ballast tanks with vent dome and compressed air as for manual operation (pace in front of the control room periscope or between the diesel air ducts), emergency shut-off valve on each side, compressed air drive with electric indication for flood valves, electric display for "Full" and "Empty".
   
  6.  Hydraulic installation.
  a)  Installation of a valve in the inflow and outflow line to the tower is requested.
  Reason:  With conning tower ramming or flooding of the conning tower shut-off possibility for the coning tower piping.
 

It is common for a control switch to stick, as a result of which oil constantly flows from the hydraulic oil bottles to the collecting reservoir. If for listening pursuit reasons it is not possible to adjust the hydraulic oil pumps, then the collecting reservoir will fill in a short time and the air cushion is lost from the hydraulic oil bottles.
  Result:  large oil contamination in the control room with loss of oil.
  b)  Move the control switch for forward conning tower periscope. Switch is currently under the conning tower hatch gets too wet and tends to stick.
   
  7.  Main switch board.
  The movable block switch unit d (inset 18 of the Operating Instructions) of the motor circuit breaker switches was by loosening of the connecting bolts attaching the feed conduit band to the block contact unit and as a result the bolted aluminum lever pieces were hot.  In order to be able to inspect and tighten these bolts during operation, the axis of rotation of pressure lever d3 must be designed as a floating axle.  In addition, the design of the lever piece from measurements appears to be advisable.  Check for erosion of the block contact (see description) and check the mounting bolts every 1/2 year.
   
  8.  The holding arms of the conning tower hatch were reinforced in the last shipyard period.  However the conning tower hatch on 3 September therefore 14 days after departure, was difficult to close and first held tight from depth 20 meters.  Apparently the port arm is higher than the starboard so that the hatch does not rest evenly.  Malfunction could not be corrected with on board means, hatch took very strong tightening to get completely tight.  Suggest attachment of a second support bracket to avoid a twisting moment.
   
  Reached depth = 50 meters.
   
C.) See Enclosures
                                                                                           Leading Engineer
   
                                                                                  signed in draft:  Dipl.Ing.Müller
                                                                                               Kptltn. (Ing.)
 
     
     
     
     
 
Enclosure to the Kriegstagebuch Section Maschine "U-38"
  
     
Sea days
Distance covered
Duration
Operation
Quantity
of the distiller
generated
nm
nm
hours min
hours min
hours min
hours min
1.
116
6
11 23
 2  56
-
-
-
2.
138
15
17 37
 6  23
-
-
-
3.
128
24
15 44
 8  16
-
-
-
4.
95
36
12 10
11 50
-
-
-
5.
122
28
15 45
 8  15
-
-
-
6.
87
32
13 44
10  16
-
-
-
7.
155
-
24  -
-  -
-
-
-
8.
167
12
19 49
 4  11
-
-
-
9.
204
4
22 29
 1  31
-
-
-
10.
199
1
23 40
-  20
-
-
-
11.
227
1
23 50
 1  10
-
-
-
12.
130
27
14 10
 9  50
-
-
-
13.
217
-
22 40
 1  20
-
-
-
14.
215
5
22 43
 1  17
-
-
-
15.
185
5
21  -
3  -
-
-
-
16.
112
34
11 50
12  10
-
-
-
17.
95
42
10  -
14  -
-
-
-
18.
108
31
14  -
10  -
-
-
-
19.
68
39
11 10
12  50
-
-
-
20
232
24
16  10
 7  50
-
-
-
21.
178
12
19  47
 4  13
-
-
-
22.
199
-
24  -
-  -
-
-
-
23.
214
2
23  35
-  25
-
-
-
24.
143
18
24  26
 9  39
-
-
-
25.
135
30
10  -
14  -
-
-
-
26.
195
5
22  30
 1  30
-
-
-
27.
185
-
24  -
-  -
4
-
0.025
28.
177
8
21  20
2  40
22
30
0.110
29.
225
27
14  25
9  35
13
-
0.100
30.
122
24
16  40
7  20
15
30
0.100
31.
103
33
11  10
12  50
12
40
0.100
32.
109
27
15  10
 8  50
14
45
0.110
33.
118
33
13  26
10  34
12
30
0.100
34.
136
35
12  10
11  50
10
-
0.050
35.
153
33
13  48
10  12
8
40
0.060
36.
52
45
09 40
14  20
6
30
0.055
37.
116
40
10  44
13  16
5
-
0.050
38.
170
-
24  -
-  -
-
-
-
39.
-
-
15  44
-  -
-
-
-
Total
5730
738
660 56
258 39
125
05
0.869
=============================================================
     
     
     
     
 
Consumption of:
  
 
Sea days
Fuel oil
Lubricating
Drinking
Potash
Oxygen
Provisions
oil
water
cartridges
m³
kg
liters
units
1/atü
kg
1.
2.657
 54.0
100
-
-
80
2.
3.718
 54.0
100
-
-
90
3.
3.742
 63.0
100
-
-
70
4.
2.585
 49.5
100
-
-
90
5.
3.720
 54.0
100
-
-
120
6.
2.718
 54.0
100
-
-
130
7.
3.964
 40.5
150
-
-
140
8.
2.853
 45.0
100
-
-
130
9.
3.220
 45.0
100
-
-
140
10.
3.613
 45.0
100
-
-
120
11.
3.712
 49.5
100
-
-
30
12.
2.631
 54.0
100
-
-
90
13.
3.370
 54.0
100
-
-
90
14.
4.637
 72.0
100
-
-
100
15.
3.930
 54.0
100
-
-
120
16.
2.280
 45.0
100
-
-
100
17.
1.770
 36.0
100
-
-
90
18.
1.997
 36.0
90
-
-
100
19.
1.533
 36.0
70
-
-
100
20
5.296
135.0
90
-
-
80
21.
5.139
126.0
50
-
-
100
22.
4.356
135.0
100
-
-
110
23.
4.114
135.0
80
-
-
80
24.
3.640
 90.0
80
-
-
130
25.
2.723
108.0
110
-
-
140
26.
4.415
144.0
100
-
-
105
27.
3.744
 90.0
90
-
-
100
28.
4.773
108.0
80
-
-
75
29.
3.080
 90.0
100
-
-
70
30.
3.567
 90.0
100
-
-
70
31.
3.076
 90.0
100
-
-
80
32.
2.950
 72.0
100
-
-
60
33.
3.080
180.0
100
-
-
100
34.
3.530
 90.0
100
-
-
70
35.
4.904
225.0
100
-
-
90
36.
1.905
 63.0
100
-
-
100
37.
3.880
108.0
100
-
-
100
38.
5.262
135.0
80
-
-
100
39.
7.003
240.0
-
-
-
100
Total
139.087
3404.5
3670
-
-
3790
=============================================================
Fuel oil inventory on departure:  176.200 m³.
Fuel oil inventory on arrival:        37,113 m³.
 
     
     
     
 
 
  Comments of the Flottille:  
  To A.) 1.):  Compressor cooling with diesel cooling water with failure of the diesel cooling pump, which has also occurred in the last period with diesel air compressor, is thought to be necessary.  See also "U-43" Kriegstagebuch-Article.  
     
  To B.) a):  The training supplement of 1/1 must be retained as a priority for training reasons. Even if long submerged cruise with short nights entail certain difficulties with air, this must be accepted. The specific airspace on small boats is below 8 m³.  
     
  To B.) b) 1.):  If the exhaust gas valve cannot be fully closed, the grinding mechanism must remain easily rotatable, so that it can be established that the valve is not in order. Pressurizing the space between both valves with 10 atü appears futile, since this outer valve is easily pressed in.  
     
  To B.) b) 3.):  Diesel head gaskets have recently been found to be leaky on several boats. As a cause of these issues, insufficient uniform tightening of the cover bolts must be assumed. A special key is to be produced so that the rocker arms do not have to be dismantled for the frequently leaking points on the two bolts under the rocker arms.  
     
  To B.) b) 5.):  Noise attenuation during venting under pressure of the internal tanks or negative buoyancy tanks is an urgent military requirement which must be considered for new construction.  In connection with this, the intended filling of the negative buoyancy tanks with fuel oil must be taken into account.  The low gain in cruising range is offset by the extraordinarily serious complication of a rapid dive maneuver in the seas with the ever-present sharp air surveillance so that this proposal is regarded as unacceptable from the Front.  
     
  To B.) b) 8.):  Concur with the assumption, that the conning tower hatch faced the sealing surface of the coaming obliquely as a result of a sharp impacts from heavy seas.  Similar issues were detected on several boats that struggled in heavy seas for a long time. Two kickbacks were also made by Kriegsmarine Werft. W'haven were deemed necessary.  
     
                                                                                                        The Flottilleningenieur  
                                                                                                                       
                                                                                                                 Kapltn.(Ing.)