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Notes

46 C.F.R. §§ 171.065–171.068

4 sections in range

§171.065. Subdivision requirements— Type I.

46 C.F.R. § 171.065

(a)
Except as provided in paragraphs (c) and (f) of this section, the separation between main transverse watertight bulkheads on a vessel, other than one described in paragraph (b) of this section, must not exceed—
(b)
The factor of subdivision used to determine compliance with paragraph (a) of this section must be the smaller of 0.5 or the value determined from Table 171.065(a) if—
(1)
The vessel is 430 feet (131 meters) or more in LBP; and
(2)
The greater of the values of Y as determined by the following equations equals or exceeds the value of X in Table 171.065(b):
(c)
The distance A in Figure 171.065 between main transverse watertight bulkheads may exceed the maximum allowed by paragraphs (a) or (b) of this section if each of the distances B and C between adjacent main transverse watertight bulkheads in Figure 171.065 does not exceed the smaller of the following:
(1)
The floodable length.
(2)
Twice the separation allowed by paragraphs (a) or (b) of this section.
(d)
In each vessel 330 feet (100 meters) or more in LBP, one of the main transverse watertight bulkheads aft of the collision bulkhead must be located at a distance from the forward perpendicular that is not greater than the maximum separation allowed by paragraph (a) or (b) of this section.
(e)
The minimum separation between two adjacent main transverse watertight bulkheads must be at least 10 feet (3.05 meters) plus 3 percent of the LBP of the vessel, or 35 feet (10.7 meters), whichever is less.
(f)
The maximum separation of bulkheads allowed by paragraphs (a) or (b) of this section may be increased by the amount allowed in paragraph (g) of this section if—
(1)
The space between two adjacent main transverse watertight bulkheads contains internal watertight volume; and
(2)
After the assumed side damage specified in paragraph (h) of this section is applied, the internal watertight volume will not be flooded.
(g)
For the purpose of paragraph (f) of this section, the allowable increase in separation is as follows—
(h)
The assumed extents of side damage are as follows—
(1)
The longitudinal extent of damage— must be assumed to extend over a length equal to the minimum spacing of bulkheads specified in paragraph (e) of this section.
(2)
The transverse extent of damage— must be assumed to penetrate a distance from the shell plating equal to one-fifth the maximum beam of the vessel and at right angles to the centerline at the level of the deepest subdivision load line.
(3)
The vertical extent of damage— must be assumed to extend vertically from the baseline to the margin line.
(i)
The maximum separation between the following bulkheads must not exceed the maximum separation between main transverse watertight bulkheads:
(1)
The collision bulkhead and the first main transverse watertight bulkhead aft of the collision bulkhead; and
(2)
The last main transverse watertight bulkhead and the aftermost point on the bulkhead deck.
(j)
The minimum separation between the following bulkheads must not be less than the minimum separation between main transverse watertight bulkheads:
(1)
The collision bulkhead and the first main transverse watertight bulkhead aft of the collision bulkhead; and
(2)
The last main transverse watertight bulkhead and the aftermost point on the bulkhead deck.
Notes, amendments, and revision history

Amendments

[CGD 79-023, 48 FR 51017, Nov. 4, 1983, as amended by USCG-2007-0030, 75 FR 78085, Dec. 14, 2010]

Authority

Authority: 46 U.S.C. 2103, 3306; E.O. 12234, 45 FR 58801, 3 CFR, 1980 Comp., p. 277; Department of Homeland Security Delegation No. 0170.1.

Source

Source: CGD 79-023, 48 FR 51017, Nov. 4, 1983, unless otherwise noted.

Amendments

[CGD 79-023, 48 FR 51017, Nov. 4, 1983, as amended by USCG-2007-0030, 75 FR 78085, Dec. 14, 2010]

§171.066. Calculation of permeability for Type I subdivision.

46 C.F.R. § 171.066

(a)
Except as prescribed in paragraph (b) of this section, the following permeabilities must be used when doing the calculations required to demonstrate compliance with § 171.065(a), (b), and (c):
(1)
When doing calculations required to demonstrate compliance with § 171.065(a) and (b), the uniform average permeability given by the formulas in Table 171.066 must be used.
(2)
When doing calculations required to demonstrate that compartments on opposite sides of a main transverse watertight bulkhead that bounds the machinery space comply with § 171.065(c), the mean of the uniform average permeabilities determined from Table 171.066 for the two compartments must be used.
(b)
If an average permeability can be calculated that is less than that given by the formulas in Table 171.066, the lesser value may be substituted if approved by the Commanding Officer, Marine Safety Center. When determining this lesser value, the following permeabilities must be used:
(1)
95% for passenger, crew, and all other spaces that, in the full load condition, normally contain no cargo, stores, provisions, or mail.
(2)
60% for cargo, stores, provisions, or mail spaces.
(3)
85% for spaces containing machinery.
(4)
Values approved by the Commanding Officer, Marine Safety Center for double bottoms, oil fuel, and other tanks.
(c)
In the case of unusual arrangements, the Commanding Officer, Marine Safety Center may require a detailed calculation of average permeability for the portions of the vessel forward or aft of the machinery spaces. When doing these calculations, the permeabilities specified in paragraph (b) of this section must be used.
(d)
When calculating permeability, the total volume of the ‘tween deck spaces between two adjacent main transverse watertight bulkheads that contains any passenger or crew space must be regarded as passenger space volume, except that the volume of any space that is completely enclosed in steel bulkheads and is not a crew or passenger space may be excluded.
Notes, amendments, and revision history

Amendments

[CGD 79-023, 48 FR 51017, Nov. 4, 1983, as amended by CGD 88-070, 53 FR 34537, Sept. 7, 1988; USCG-2014-0688, 79 FR 58287, Sept. 29, 2014]

Authority

Authority: 46 U.S.C. 2103, 3306; E.O. 12234, 45 FR 58801, 3 CFR, 1980 Comp., p. 277; Department of Homeland Security Delegation No. 0170.1.

Source

Source: CGD 79-023, 48 FR 51017, Nov. 4, 1983, unless otherwise noted.

Amendments

[CGD 79-023, 48 FR 51017, Nov. 4, 1983, as amended by CGD 88-070, 53 FR 34537, Sept. 7, 1988; USCG-2014-0688, 79 FR 58287, Sept. 29, 2014]

§171.067. Treatment of stepped and recessed bulkheads in Type I subdivision.

46 C.F.R. § 171.067

(a)
For the purpose of this section—
(1)
The main transverse watertight bulkhead immediately forward of a stepped bulkhead is referred to as bulkhead 1; and
(2)
The main transverse watertight bulkhead immediately aft of the stepped bulkhead is referred to as bulkhead 3.
(b)
If a main transverse watertight bulkhead is stepped, it and bulkheads 1 and 3 must meet one of the following conditions:
(1)
The separation between bulkheads 1 and 3 must not exceed the following:
(i)
If the factor of subdivision (FS) determined from § 171.065 (a) or (b) is greater than 0.9, the distance between bulkheads 1 and 3 must not exceed the maximum separation calculated to demonstrate compliance with § 171.065.
(ii)
If the factor of subdivision is 0.9 or less, the distance between bulkheads 1 and 3 must not exceed 90% of the floodable length or twice the maximum bulkhead separation calculated to demonstrate compliance with § 171.065, whichever is smaller.
(2)
Additional watertight bulkheads must be located as shown in Figure 171.067(a) so that distances A, B, C, and D, illustrated in Figure 171.067(a), satisfy the following:
(i)
Distances A and B must not exceed the maximum spacing allowed by § 171.065.
(ii)
Distances C and D must not be less than the minimum separation prescribed by § 171.065(e).
(3)
The distance A, illustrated in Figure 171.067(b), must not exceed the maximum length determined in § 171.065 corresponding to a margin line taken 3 inches (7.6 cm) below the step.
(c)
A main transverse bulkhead may not be recessed unless all parts of the recess are inboard from the shell of the vessel a distance A as illustrated in Figure 171.067(c).
(d)
Any part of a recess that lies outside the limits defined in paragraph (c) of this section must be treated as a step in accordance with paragraph (b) of this section.
(e)
The distance between a main transverse watertight bulkhead and the transverse plane passing through the nearest portion of a recessed bulkhead must be greater than the minimum separation specified by § 171.065(e).
(f)
If a main transverse bulkhead is stepped or recessed, equivalent plane bulkheads must be used in the calculations required to demonstrate compliance with § 171.065.
Notes, amendments, and revision history

Authority

Authority: 46 U.S.C. 2103, 3306; E.O. 12234, 45 FR 58801, 3 CFR, 1980 Comp., p. 277; Department of Homeland Security Delegation No. 0170.1.

Source

Source: CGD 79-023, 48 FR 51017, Nov. 4, 1983, unless otherwise noted.

§171.068. Special considerations for Type I subdivision for vessels on short international voyages.

46 C.F.R. § 171.068

(a)
The calculations done to demonstrate compliance with § 171.065 for a vessel that makes short international voyages and is permitted under § 75.10-10 of this chapter to carry a number of persons on board in excess of the lifeboat capacity must—
(1)
Assume the uniform average permeabilities given in Table 171.068 in lieu of those in Table 171.066; and
(2)
Use a factor of subdivision (FS) that is the smaller of the following—
(i)
The value from Table 171.065(a).
(ii)
0.50.
(b)
For a vessel less than 300 feet (91 meters) in length, the Commanding Officer, Marine Safety Center may approve the separation of main transverse watertight bulkheads greater than that permitted by paragraph (a) of this section if—
(1)
The shorter separation is impracticable; and
(2)
The separation is the smallest that is practicable.
(c)
In the case of ships less than 180 feet (55 meters) in length, the Commanding Officer, Marine Safety Center may approve a further relaxation in the bulkhead spacing. However, in no case may the separation be large enough to prevent the vessel from complying with the flooding requirements for Type II subdivision in § 171.070.
Notes, amendments, and revision history

Amendments

[CGD 79-023, 48 FR 51017, Nov. 4, 1983, as amended by CGD 88-070, 53 FR 34537, Sept. 7, 1988]

Authority

Authority: 46 U.S.C. 2103, 3306; E.O. 12234, 45 FR 58801, 3 CFR, 1980 Comp., p. 277; Department of Homeland Security Delegation No. 0170.1.

Source

Source: CGD 79-023, 48 FR 51017, Nov. 4, 1983, unless otherwise noted.

Amendments

[CGD 79-023, 48 FR 51017, Nov. 4, 1983, as amended by CGD 88-070, 53 FR 34537, Sept. 7, 1988]