Two interconnected salt water circulating systems, one for use with the diesel engines and the other with the main motors, are provided on the IX-C submarine.  Salt water is used directly for cooling engine components and lubricating oil without intermediate fresh water.  All parts of both systems subject to circulating water pressure are built to withstand a test pressure of at least 142 psi (corresponding to the design depth of the vessel).  Certain fittings and piping are subject to higher test pressures.  
          A minimum of pumps is used with the systems.  Each diesel has an attached circulating water pump that services the diesel engine, its lub oil cooler, and all parts of the exhaust system; and then discharges to the compensating system head box.  The main motor components requiring cooling receive their circulating water from one detached circulating water pump.  The latter services the air coolers, main motor bearings, thrust bearings, Junkers air compressor, stern tube glands and distiller; and then discharges to sea.  The standby pump in the engine room can service either of the systems.  A separate attached pump is used to supply the circulating water to the electric air compressor.  A small hand circulating pump has also been connected to the systems.  
June, 1946
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  1.  Introduction  
          Some of the details of the circulating water arrangements that are associated with lub oil cooling have been covered under the S45 section, lubricating oil systems, of the IX-C report.  
  2.  General Description  
          Very simple salt water circulating systems are installed on the type IX-C submarine.  All units requiring cooling are cooled by these systems as the separate fresh water cooling arrangements used with the diesel engines on U.S. submarines have not been installed.  
          The cooling water for the diesel engine comes from one of two sea suctions in the engine room.  The sea chests are fitted with blow and venting connections.  The water passes through a strainer to a common suction line for the attached, standby, and hand circulating water pumps.  The discharges from all four pumps feeds into a common distribution manifold.  
          The discharge from each attached pump also leads directly to the lub oil cooler and thence to the diesel engines.  The water passes through the water jacket on the engines, through the inboard and outboard exhaust valves, the muffler, the exhaust throttling valve, the spark arrester and thence to the head box.  A recirculating line runs from the water jacket discharge to the pump suction line.  A "hot" salt water line for showers, etc. leads from the inboard exhaust piping.  
          The distribution manifold permits one of any of the circulating water pumps on either diesel engine system or by means of the cross-connection line on the units in the maneuvering room.  A hull valve at the bulkhead isolates the circulating water piping in the two rooms.  
          The salt water for the main motor and compressor circulating water pumps comes from a separate sea suction in the maneuvering room.  The sea chest is fitted with a blowing connection.  A wire mesh filter is installed in the suction line.  
          The main motor circulating water pump discharges to a common supply line.  All units to be cooled, with one exception, receive their circulating water direct from this line.  The cooling water piping for the Junkers compressor and its inboard exhaust valve is in series while  
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  that for the air coolers, main motor bearings, main thrust bearing, stern tube gland and distiller forms a parallel arrangement.  The supply to all units is controlled by individual suction and discharge stop valves.  The discharge from all units runs into a common discharge line that, in turn, leads through a stop-check and a hull valve to sea.  
          The circulating water from the pump on the air compressor services the compressor and then passes via a sight gauge and check valve to the common discharge line.  A safety valve is placed between the gauge glass and check valve.  
          Several direct leads, as well as portable hose fitting, are provided in the salt water piping to permit complete flushing of the entire system with anti-corrosive oil.  The details of this flushing arrangements are covered under the S19 section of the IX-C Report.  
          In addition to the sight gauge on the electric compressor discharge piping, gauges have also been fitted on the salt water line leading from the Junkers compressor and on a lub oil cooler vent line.  These permit ready detection of leakage from the units serviced to the salt water piping.  
          All parts of the circulating water system are designed to withstand a basic test pressure of 142 psi, the designed depth pressure.  This requires that circulating water to the main motors must be secured before this depth is reached as a pressure in excess of the above is reached at designed depths by the differential pressure of 21.3 psi from the main motor circulating water pump.  The test pressure on the standby, compressor and main motor circulating water pumps on the air coolers is 142 psi or greater, while that of the piping, inboard valves, filters, safety valves and other fittings is set at the lower value.  Hull valves and the connecting piping are designed to withstand a test pressure of 2-1/2 times the designed depth or 355 psi.  
          For the most part, salt water piping and fittings are made from galvanized steel.  Hull valves in some cases are made from a special brass composition.  "Warm" salt water piping used with the main motors is made from half hard copper.  
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  3.  Individual Components  
          a)  Attached cooling water pump (Diesel)  
Type - 2 cylinder piston pump
RPM - 235
Capacity - 408 G.P.M.
Test pressure - 142 psi
          b)  Standby cooling water pump (engine room)  
Type - Centrifugal
No. - 1
Test pressure
142 psi
RPM 3000 3550 3000 3550
Volts     110 170
Power (HP) 11.5 22.2 10.5 17.5
Delivery (GPM) 308 574    
Press. head (psi)
66 lbs.
          c)  Main motor circulating water pump  
Type - Centrifugal
No. 1
Test pressure
142 psi
RPM 1650 1900 1650 1900
Volts     110 170
Power (HP) 1.72 3.16 1.7 3.25 (KW)
Delivery (GPM) 88.0 139    
Press. head (psi)
79 lbs.
          d)  Main motor air coolers  
Weight - 430 lbs.
No. - 2
Dimensions - 33.4 x 25.0 x 15.3 (ins.)
Air inlet temp. - 1`58F
Air exit temp. - 95F
Water flow - 19.4 GPM
Temp. water in - 77°F
Tamp. water out - 95°F
Operating press. - up to 142 psi.
Test pressure - 256 psi
Air flow - 49.5 CFS
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          e)  Circulating water piping  
1.  Piping for cold water - galvanized medium steel
2.  Piping for warm water - copper piping (half hard)
        a.  Characteristics
                At least 99.5% cu.
                Tensile strength - 35,500 psi
                Elastic limit       - 21,300 psi
                Elongation        - 9% in 5 dia.
3.  Test pressures - 142 psi
          f)  Salt water filters  
Engine Room
Maneuvering Room
Filter material
Gal. steel
Gal. steel
Mesh material
Phosphor bronze
Phosphor bronze
Wire mesh (dia.)
.030 ins.
.026 ins.
   "       "     (spacing)
.160 ins.
.040 ins.
  4.  Conclusions  
          There are no particular noteworthy features in the circulating water systems installed on the IX-C.  Although the system layout is simple in most respects, it provides a desired wide flexibility in the use of the four main circulating water pumps.  Detection of leakage from several prevalent sources of trouble is possible from the installation of sight gauges on the discharges from these units.  
          The limitation imposed on the use of the main motor circulating water system by the test pressure is a weakness in the system.  Not only must the system be secured when going to deep submergence, but pressures arising from leaky valves after it is secured may readily cause rupture of vital inboard piping.  This is particularly true with the piping used for cooling the main motor and main thrust bearings.  
          The use of salt water cooling for the diesel engines and the lub oil cooler is more hazardous and subject to less temperature control than is the use of fresh water for this purpose.  A measure of compensation arises from the fact that the diesel engines are of lower speed and more rugged design, and that lub oil operating pressures exceed circulating water pressures on the lub oil cooler.  
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