Dave Gerr - Boat Mechanical Systems Handbook-How to Design, Install, and Recognize Proper Systems in Boats

Large-Boat, High-Power

Blowers

When installed power increases over about

1,200 hp (895 kW), great blower capacity is

required. As noted earlier, companies like

Delta-T Systems and Gianneschi & Ramac-

ciotti supply the large blowers needed. In

such vessels, it often helps to have both inlet

and outlet blowers to achieve the desired

airflow. The inlet and outlet blower capaci-

ties should match so the engine room is not

pressurized over the surrounding air pres-

sure, which would drive unwanted engine

smells and gases into other parts of the

vessel.

Figure 16-2 shows a Delta-T axial blower—

one of four installed, two intake and two

exhaust—on a 105-foot (32 m) motoryacht,

with twin diesel engines totaling nearly

4,000 hp (2,980 kW). The temperature in the en-

gine compartment was usually under 85°F

(30°C).

Chapter 16:Ventilation of Machinery Spaces

Comparing to Detroit Diesel Minimum Vent Sizing

The minimum engine vent sizing rule I developed was originally based on exceeding Detroit

Diesel’s recommended minimum engine vent area.For instance, comparing the minimum vent

areas from Detroit Diesel’s engine spec sheets with the calculated results for the minimum vent

area from the engine vent sizing rule works out as follows:

Detroit Diesel Vent-Sizing Rule

Model Power Min. Vent Area Min. Vent Area

4-71M 180 BHP 55 sq.in. (353 cm^2 ) 55 sq.in. (353 cm^2 )

6V-53TI 400 BHP 115 sq.in. (742 cm^2 ) 121 sq.in. (781 cm^2 )

6-71TI 485 BHP 110 sq.in. (712 cm^2 ) 147 sq.in. (948 cm^2 )

6V-92TA DDEC 565 BHP 134 sq.in. (867 cm^2 ) 171 sq.in. (1,103 cm^2 )

8V-92TA DDEC 760 BHP 197 sq.in. (1,270 cm^2 ) 230 sq.in. (1,484 cm^2 )

12V-71TA 900 BHP 213 sq.in. (1,375 cm^2 ) 273 sq.in. (1,760 cm^2 )

12V-92TA 1,110 BHP 269 sq.in. (1,735 cm^2 ) 336 sq.in. (2,170 cm^2 )

16V-97TA DDEC 1,450 BHP 374 sq.in. (2,415 cm^2 ) 439 sq.in. (2,834 cm^2 )

16V-149TI 1,800 BHP 480 sq.in. (3,095 cm^2 ) 545 sq.in. (3,520 cm^2 )

16V-149TI 2,400 BHP 595 sq.in. (3,837 cm^2 ) 727 sq.in. (4,690 cm^2 )

BHP = brake horsepower, the engine manufacturer’s full rated engine power

Figure 16-1. Half-cowl side vent