USS Cassin Young DD-793 - Basic Operation


Two GE Double Reduction Turbines.



Four Babcock and Wilcox Boiler


Steam Pressure:

615psi/Temp-490°FSat: 850°FSH



Ship Service- Two GE 290KW

Emergency- One GE 100KW


Power: 60,000 total SHP, from General Electric double-reduction geared turbines on 2 shafts with 3 blade screws


Liquid Load - Approximate

Fuel Oil- 137,740 gal  (Navy Special Fuel Oil (NSFO) (Bunker, No. 5 oil) 80/20 mix of #6 oil and diesel fuel)

Diesel Oil- 6,772 gal

Feed Water- 18,016 gal

Potable Water- 16,939 gal

Fueling at sea: Oil delivered at 250 Deg F and 1,667 GPM.


How the Engines Work

The ship’s engineering plant is composed of a boiler that burns fuel oil to convert water to steam, a turbine that uses the steam to turn a propeller, and a condenser that cools the steam back to water for re-routing back to the boiler. In order to provide enough power to the turbine, the steam generated in the boilers is superheated to 850 deg under approximately 615 lb./sqft of pressure.


Engineering Plant: 1/3 of the entire hull length. 1/2 of the entire hull volume. 


Range: 6,500 miles at 15 kn, standard displacement Speed: 36 Knots / 41 Miles Per Hour



Turbine sets for Sumner-Gearing: Cruising: 1,000 HP at 10,101 RPM. HP: 23,000 HP at 5,676 RPM.

LP (ahead): 6,000 HP at 4,780 RPM. LP (astern): 6,000 HP at 2,571 RPM.

Power astern vs. forward: Astern power is approximately 20% of forward power, or 6,000 each shaft.  


Steam pressure: 615 PSI, from Babcock & Wilcox M-type boilers.


Steam temperature: Saturated = 490 deg F (615 PSI) Superheated = 850 deg F (565 PSI)


Boiler water capacity: 5,200 gallons each at normal water level and 9,600 gallons if completely pressed up. 

NOTE: Boiling point of water decreases 1 degree F for every 450 foot rise in elevation. Typical home pressure cooker operates at 15 PSI and 250 Deg F at sea level. 


Reduction gears manufactured by Falk Corporation.

Special note...Reduction ratios for Sumner-Gearing class and 350 max speed (instead of 397) were: 

Total reduction for cruising turbine to prop shaft: 28.860:1.

Total reduction for HP turbine to prop shaft: 16.217:1.

Total reduction LP turbine to prop shaft: 11.794:1


Generators: Two GE Turbo-generators 290 KW (now 350 KW) One diesel-generator 100 KW.


Shaft speed: 397 rpm (max).


Turbines manufactured by: General Electric in Schenectady, NY


Speed on one shaft: 18-20 KN full out


Endurance, approximate figures:

797 miles at 34 KN (34 knots is considered max sustained speed using 170 gallons per mile and 5,727 gallons per hour).  3,193 miles at 13 KN (13 knots is economy speed using 42.8 gallons per mile and 556 gallons per hour)


Tactical turning diameter: As built: 950 yards @ 30 KN

With new rudder: 630 yards @30 KN

Improved time for 180 Deg turn: was 59 seconds, from 88 seconds. 

Comparison: Iowa class BB, 814 yards @ 30 KN / 76 seconds for 180 Deg turn.