CONFIDENTIAL REPORT 2G-21
S48-5
     
 
FORMER GERMAN SUBMARINE TYPE XXI
 
 
 
 
CIRCULATING WATER SYSTEMS
 
     
 
SUMMARY
  
     
          The circulating water setup on the XXI consists of a circulating water main and independent systems in the maneuvering room, engine room and control room.  Each of the 3 systems can either supply circulating water to the main or receive from it.  An emergency tie-in is also provided for reciprocal service with the main drainage system.  
          The circulating water main and the systems within the maneuvering room and control room, with the single exception of that part connected to the electric air compressor, are designed to be operated at deep submergence.  Individual units connected to the main and the diesel engine components within the engine room are not designed to withstand this pressure.  
     
     
     
     
     
 
June, 1946
 
 
 
 
PORTSMOUTH NAVAL SHIPYARD, PORTSMOUTH, N. H.
 
     
     
     
 
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  REPORT 2G-21
S48-5
     
 
CIRCULATING WATER SYSTEMS
 
     
  1.  Introduction  
          Those parts of the IXC circulating water systems, described in Report 2G-9C-S48-5, that have been adopted on the type XXI submarine will not be discussed in detail in this section.  
          For some of the components within the systems test pressures as originally specified in the building specifications were not attainable and had to be consequently reduced.  The test pressures listed herein will be those obtained from latest available information.  
     
  2.  General Description  
          Much additional cooling service is required of the circulating water systems on the type XXI submarine beyond that required on the IXC.  Consequently considerable change on system layouts has been made.  
          Three independent systems, each of which has its own individual sea suction and discharge, have been set up to service most of the equipment.  The remaining units receive cooling water from a circulating water main that runs from the control room to the after end of the maneuvering room.  (The main divides into port and starboard lines at the after engine room bulkhead.)  The pumps from any of the individual systems as well as the centrifugal drain pump can put pressure on this main.  In addition, all units, with the exception of the air conditioning condensers, can be serviced from the main.  
          The system within the maneuvering room services the main motor and the reduction gear components.  It is normally set up with the port circulating water pump (attached to the main motor reduction gear) supplying circulating water to the port units, i.e. the gear lub oil cooler, the two main motor air coolers and the stern tube, and with the starboard attached pump servicing the corresponding starboard units.  A standby pump is also installed to provide additional or emergency service, and can discharge to either or both circulating water mains.  All three pumps can take their suction from a common suction line that connects port and starboard sea suctions, and has a connection to the vessel's main drain.  All piping and units  
     
 
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  REPORT 2G-21
S48-5
     
  in the main motor circulating water system are tested to withstand a pressure of 455 psi for tightness and 568 psi for strength.  A valve in each circulating water main serves to isolate the main motor circulating water piping from that forward.  These valves are normally secured on going to deep submergence.  
          The diesel engine circulating water system is simpler than that on the IXC.  The pump discharge manifold has been eliminated and the two attached pumps discharge directly to the lub oil cooler and diesel engine.  The two attached pumps have interconnected port and starboard sea suctions.  The hand circulating water pump has a suction to this cross connection.  Either of these three pumps can also take a suction from the engine room bilges.  They have, as well, a discharge connection to the circulating water main.  The operating pressure on the system is set at 28 - 35 psi while the test pressure on all inboard parts is limited to 142 psi.  
          The third independent circulating water system has a sea suction in the control room for the three units serviced, and a separate sea discharge in the control room for the compressor and the cold storage condenser and one in the engine room for the air conditioning condensers.  The compressor and cold storage units can be serviced by the small circulating water pumps provided for each or by water from the circulating water main.  However, the 3 air conditioning condensers can only be serviced by the 3 individual pumps provided.  The test pressure on the electric compressor circulating water piping is limited to 213 psi while that for the remainder of the system is increased to 455 psi, permitting its use at deep submergence.  
          The distiller, Junkers compressors, and lub oil purifiers receive circulating water direct from the circulating water main.  The piping for these units is not designed to take deep submergence pressures, that for the Junkers is limited to 85.2 psi.  
          Pressure is normally put on the circulating water main by either of the maneuvering room or engine room pumps.  The emergency connection to the line from the centrifugal drain pump discharge is in the control room.  The test pressures on the circulating water main and its branches, up to the first stop valve on each branch, is 455 psi for tightness and 568 psi for strength.  That of the branches outboard of the stop valve is as heretofore specified.  
     
 
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  REPORT 2G-21
S48-5
     
  3.  Individual Components  
          a.  Attached circulating water pump (diesel)  
 
No.
-
 2
Type
-
 Two stage centrifugal
RPM
-
 2050
Delivery
-
 365 GPM
Press. Head
-
 56.8 psi
Test press. pump and piping
-
 142 psi
 
          b.  Attached circulating water pump (reduction gear)  
 
No.
-
 2
Weight
-
 114 lbs.
Type
-
 Single stage centrifugal
Delivery
-
 approx. 264 GPM
Press. Head
-
 56.8-71 psi
Power
-
 approx. 26 HP
 
          c.  Standby circulating water pump  
 
No.
-
 1
Type
-
 Centrifugal, with self-priming feature
 
 
Characteristics:
Pump
Motor
Weight
185 lbs.
495 lbs.
Volts    
110
170
RPM
3000
3500
3000
3500
Power
12.3
19.3 (HP)
10.5
17.5 (KW)
Delivery
308
440 (gpm)
Press. head
42.6
61 (psi)
 
     
  4.  Conclusions  
          The circulating water systems on the type XXI submarine are provided with extreme flexibility at an undesirable sacrifice of safety.  The designers have permitted a desired wide interchangeability in the use of the various pumps within the several circulating water systems and have set up an emergency exchange of service between the pumps in the circulating water and the main drainage system, features which are not possible with the completely independent engine room, maneuvering room and control room systems on U.S. submarines.  However, in providing wide flexibility added reliance has been placed upon operating personnel to insure that excessive pressures are not placed on low pressure equipment during deep submergence.  The possibility of the pressure arising from either open or leaky valves is greater because of the presence of the necessary interlocking valves between the systems.  
     
 
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