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

on the front side of the bulkhead that

can be operated by a reach rod on

deck, or aft of the bulkhead if the valve

is easily accessible from inside the boat

during normal operation.

• Submersible electric pumps can be
  used only on vessels up to 65 feet
  (19.8 m) in length and carrying not
  more than 49 passengers (other than a
  ferry), provided that the pump is only
  used to dewater one watertight com-
  partment and is permanently mounted.
  Flexible hose may be used on such
  pumps as long as it does not penetrate
  a watertight bulkhead. In addition, the
  submersible pump installation must
  comply with ABYC H-22, DC Electric
  Bilge Pumps Operating Under
  50 Volts.

Figure 18-2 shows the layout of a bilge

and fire main system. This is for an aluminum

vessel. If the vessel were of any other mate-

rial, CFR Commercial would require steel or

stainless piping.

ABS Bilge-System

Requirements

ABS Rules for High-Speed Craft under

150 feet (45.7 m) and Motor Pleasure Yachts

require two power-driven bilge pumps on

boats 65 feet (19.8 m) in length or more, and

one power-driven bilge pump and one man-

ual pump on vessels under that length. Mini-

mum required pump capacity and inside pipe

diameter are as presented in Table 18-2.

Under ABS, submersible pumps can be

used in individual compartments as long as

the boat will remain stable with such a com-

partment completely flooded, and if—in addi-

tion to the submersible pumps—one bilge

pump matching the required capacity from

Table 18-2 is installed, plus a second bilge

pump of at least half this capacity.

ABS Bilge-Piping

Diameter

ABS has formulas for determining the mini-

mum internal diameter of the main bilge-

suction pipe and also of the branch lines.

Formula 18-1. Minimum Internal

Diameter of the Main Bilge-Suction Pipe

or

Where

d =internal pipe diameter, in. or mm

L =length of vessel on the load water-

line, ft. or m

B =beam, ft. or m

D =molded depth, hull fairbody to main

deck at sheer at midships, ft. or m

NOTE: Pipe size selected should be

within^1 / 4 inch (6 mm) of the calcu-

lated size.

Formula 18-2. Minimum Internal

Diameter of Branch or Submersible-

Pump Lines

or

Where

d =internal pipe diameter, in. or mm

c =length of compartment, ft. or m

B =beam, ft. or m

D =molded depth, hull fairbody to main

deck at sheer at midships, ft. or m

NOTE: Pipe size selected should be

within^1 / 4 inch (6 mm) of the

calculated size.

CHECKING THEREQUIREDBILGESYSTEM PER

CFR COMMERCIAL ANDABS Let’s say the

dimensions of motor cruiser Fluky Flooderare

LOA: 50 ft. (15.2 m)

Waterline: 46 .0 ft. (14 m)

d252=+.16 c(B D) mm+

d1

c(B D)

1,500

=+ in.

+

d251=+.68 L(B D) mm+

d1

L(B D)

2,500

=+ in.

+

PART SIX: PLUMBING SYSTEMS WITH NOTES ON FIRE SUPPRESSION

Formula 18-2.

Formula 18-1.