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

Beam: 14 .75 ft. (4.5 m)

Molded depth: 7 .58 ft. (2.31 m)

Length of longest compartment: 17 .6 ft.

(5.36 m)

Displacement: 25 .2 long tons (25.6 metric

tons)

CFR Commercial would require one

power-driven pump of 10 gpm (38 lpm) and

one portable hand pump, or one fixed hand

pump of 10 gpm (38 lpm) and one portable

pump of 5 gpm (19 lpm). Minimum bilge pipe

diameter is 1 inch (DN 25 mm).

ABS would require one power-driven

pump of 25 gpm (95 lpm) with the minimum

pipe diameter found by the ABS formulas,

but not less than Table 18-2: a 1-inch (DN

25 mm) ID pipe, in this case.

The main suction line for ABS would be

Inspecting the pipe tables in Appendix B, we

find that 1^1 / 2 - inch schedule 40 pipe has an ID

of 1. 61 inches. This is within^1 / 4 inch of the

calculated pipe ID. Use 1^1 / 2 - inch schedule 40

pipe.

Or

Inspecting the pipe tables in Appendix B, we

find that DN 40 mm schedule 40 pipe has an

ID of 40.89 mm. This is within 6 mm of the

calculated pipe ID. Use DN 40 mm schedule

40 pipe.

The ABS branch line for the longest com-

partment would be

Inspecting the pipe tables in Appendix B,

we find that 1^1 / 4 - inch schedule 40 pipe has

an ID of 1. 38 in. This is within^1 / 4 inch of the

calculated pipe ID. Use 1^1 / 4 - inch schedule

40 pipe.

Or

Inspecting the pipe tables in Appendix B, we

find that DN 32 mm schedule 40 pipe has an

ID of 35.05 mm. This is within 6 mm of the

calculated pipe ID. Use DN 32 mm schedule

40 pipe.

Note that smaller compartments could

use smaller branch-line diameters, but not

less than 1 inch (25 mm) ID for this vessel.

It’s usually best, however, to make all

branch lines the same diameter (the one

required for the largest compartment) to

simplify installation, maintenance, and

repair.

Bilge-Piping Material

CFR Commercial states that bilge and fire-

main piping are piping for vital systems. CFR

Commercial requires that all such piping be

steel or stainless steel. The exception is for

aluminum boats, which may use aluminum

pipe, schedule 80 wall minimum.

Estimating Flooding Rate

from Hull Damage

Both the CFR and ABS minimum recommen-

dations for bilge-pump capacity seem too low

1

17 .6ft.c ompa rtme nt le ng th

(14.75 ft.be

+

aam 7.58 ft.molded depth)

1,500

1. 51 in.ID

+

=

PART SIX: PLUMBING SYSTEMS WITH NOTES ON FIRE SUPPRESSION

25 2. 16

5 .36 m compartment length (4.5m

bea

+

mm2.31 m molded depth)

36 .7 8 mm ID

+

=

TABLE 18-2. ABS BILGE-SYSTEM REQUIREMENTS

Minimum Capacity Minimum Pipe
Vessel Length per Pump Inside Diameter

Below 65 ft. (19.8 m) 25 gpm (240 lpm) 1 in. (25 mm)
65 ft. (19.8 m) or 50 gpm (184 lpm) 1.25 in. (32 mm)
greater but less than
100 ft. (30.5 m)
100 ft. (30.5 m) or 66.6 gpm (240 lpm) 1.5 in. (38 mm)
greater but less than
150 ft (45.7 m)

1

46 ft.WL (14.75 ft.beam 7.58 ft.depth

+

+ mmolde d)

2,500

= 1. 64 in.ID

25 1++.68 14 m LOA (4.5 m beam 2.31 m depth mollded)

= 41 .4mmID