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National
United States Regulations
46 CFR PART 171—SPECIAL RULES PERTAINING TO VESSELS CARRYING PASSENGERS
Title 46: Shipping
PART 171—SPECIAL RULES PERTAINING TO VESSELS CARRYING PASSENGERS
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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: CGD 79–023, 48 FR 51017, Nov. 4, 1983, unless otherwise noted.
Subpart A—General
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§ 171.001 Applicability.
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(a) This part applies to passenger vessels inspected under subchapter K or H of this chapter.
(b) Specific sections of this part also apply to nautical school ships, sailing school vessels and oceanographic vessels. The applicable sections are listed in subparts C and D of part 173 of this chapter.
[CGD 79–023, 48 FR 51017, Nov. 4, 1983, as amended by CGD 83–005, 51 FR 923, Jan. 9, 1986; CGD 95–012, 60 FR 48052, Sept. 18, 1995; 60 FR 50120, Sept. 28, 1995; CGD 85–080, 61 FR 944, Jan. 10, 1996]
§ 171.010 Definitions.
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(a) Cockpit means an exposed recess in the weather deck extending no more than one-half of the vessel's length over deck (LOD) measured over the weather deck.
(b) Deepest subdivision load line means the waterline that corresponds to the deepest draft permitted by the applicable subdivision requirements in this part.
(c) Equivalent plane bulkhead means a bulkhead that is—
(1) Used in lieu of a recessed or stepped bulkhead when doing the subdivision calculations required in this part; and
(2) Located as shown in Figure 171.010(a).
(d) Ferry means a vessel that—
(1) Operates in other than ocean or coastwise service;
(2) Has provisions only for deck passengers or vehicles, or both;
(3) Operates on a short run on a frequent schedule between two points over the most direct water route;
(4) Offers a public service of a type normally attributed to a bridge or tunnel.
(e) Freeing port means any direct opening through the vessel's bulwark or hull to quickly drain overboard water which has been shipped on exposed decks.
(f) Floodable length means the length of a shell to shell segment of the vessel that, when flooded, will sink and trim the vessel until the margin line is tangent to the waterline.
(g) Flush deck means a continuous weather deck located at the uppermost sheer line of the hull.
(h) International voyage has the same meaning provided for the term in §70.05–10 of this chapter.
(i) Machinery space means, unless otherwise prescribed by the Commandant for unusual arrangements, the space extending from the molded base line to the margin line and between the main transverse watertight bulkheads bounding the following spaces:
(1) Each space containing main and auxiliary propelling machinery.
(2) Each space containing propulsion boilers.
(3) Each space containing permanent coal bunkers.
(j) Open boat means a vessel not protected from entry of water by means of a complete deck, or by a combination of a partial weather deck and superstructure which is seaworthy for the waters upon which the vessel operates.
(k) Passenger space means a space which is provided for the accommodation and use of passengers, other than a baggage, store, provision or mail room.
(l) Recessed bulkhead means a bulkhead that is recessed as shown by bulkhead B in Figure 171.010(b).
(m) Small passenger vessel means a vessel of less than 100 gross tons—
(1) Carrying more than 6 passengers, including at least one passenger for hire;
(2) That is chartered with the crew provided or specified by the owner or owner's representative and carrying more than 6 passengers;
(3) That is chartered with no crew provided or specified by the owner or owner's representative and carrying more than 12 passengers; or
(4) That is a submersible vessel carrying at least one passenger for hire.
(n) Short international voyage means an international voyage where—
(1) A vessel is not more than 200 nautical miles (370 kilometers) from a port or place in which the passengers and crew could be placed in safety; and
(2) The total distance between the last port of call in the country in which the voyage began and the final port of destination does not exceed 600 nautical miles (1111 kilometers).
(o) Scupper means a pipe or tube of at least 30 millimeters (1.25 inches) in diameter leading down from a deck or sole and through the hull to drain water overboard.
(p) Stepped bulkhead means a bulkhead that is stepped as shown by bulkhead A in Figure 171.010(b).
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(q) Well deck means a weather deck fitted with solid bulwarks that impede the drainage of water over the sides or an exposed recess in the weather deck extending one-half or more of the length of the vessel (LOD) measured over the weather deck.
[CGD 79–023, 48 FR 51017, Nov. 4, 1983, as amended by CGD 85–080, 61 FR 944, Jan. 10, 1996]
§ 171.015 Location of margin line.
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(a) A vessel with a continuous bulkhead deck and sufficient sheer. If the average value of the sheer at the forward perpendicular (FP) and the after perpendicular (AP) is at least 12 inches (30.5 cm), the margin line must be located no less than 3 inches (7.6 cm) below the upper surface of the bulkhead deck at side as illustrated in Figure 171.015(a).
Table 171.015
------------------------------------------------------------------------
Required position of
Average value of sheer at FP and AP in inches margin line below top of
(cm) deck amidships in inches
(cm)
------------------------------------------------------------------------
12 (30.5)..................................... 3 (7.6)
6 (15.2)...................................... 6 (15.2)
0............................................. 9 (22.8)
------------------------------------------------------------------------
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(b) A vessel with a continuous bulkhead deck and insufficient sheer. If the average value of the sheer at the forward perpendicular (FP) and the after perpendicular (AP) is less than 12 inches (30.5 cm), the margin line must be a parabolic curve with the following characteristics:
(1) The parabolic curve must be at least 3 inches (7.6 cm) below the upper surface of the bulkhead deck at the FP and AP.
(2) The parabolic curve must be at least the distance given in Table 171.015 below the surface of the bulkhead deck amidships.
(3) Intermediate values not shown in Table 171.015 must be interpolated.
(4) Figure 171.015(b) illustrates a margin line drawn in this manner.
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(c) A vessel with a discontinuous bulkhead deck. A continuous margin line must be drawn that is no more than 3 inches (7.6 cm) below the upper surface of the bulkhead deck at side as illustrated in Figure 171.015(c).
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(d) A vessel with a discontinuous bulkhead deck where the side shell is carried watertight to a higher deck. A continuous margin line must be drawn as illustrated in Figure 171.015(d).
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§ 171.017 One and two compartment standards of flooding.
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(a) One compartment standard of flooding. A vessel is designed to a one compartment standard of flooding if the margin line is not submerged when the total buoyancy between each set of two adjacent main transverse watertight bulkheads is lost.
(b) Two compartment standard of flooding. A vessel is designed to a two compartment standard of flooding if the margin line is not submerged when the total buoyancy between each set of three adjacent main transverse watertight bulkheads is lost.
Subpart B [Reserved]
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Subpart C—Large Vessels
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§ 171.045 Specific applicability.
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This subpart applies to each vessel that fits into any one of the following categories:
(a) Greater than 100 gross tons.
(b) Greater than 65 feet (19.8 meters) in length.
(c) Carries more than 12 passengers on an international voyage.
(d) Carries more than 150 passengers.
(e) The stability of which is questioned by the OCMI.
§ 171.050 Intact stability requirements for a mechanically propelled or a nonself-propelled vessel.
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Each vessel must be shown by design calculations to have a metacentric height (GM) in feet (meters) in each condition of loading and operation, that is not less than the value given by the following equation:
where—
N=number of passengers.
W=displacement of the vessel in long (metric) tons.
T=14 degrees or the angle of heel at which the deck edge is first submerged, whichever is less.
b=distance in feet (meters) from the centerline of the vessel to the geometric center of the passenger deck on one side of the centerline.
K=24 passengers/long ton (23.6 passengers/metric ton).
§ 171.055 Intact stability requirements for a monohull sailing vessel or a monohull auxiliary sailing vessel.
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(a) Except as specified in paragraph (b) of this section, each monohull sailing vessel and auxiliary sailing vessel must be shown by design calculations to meet the stability requirements in this section.
(b) Additional or different stability requirements may be needed for a vessel of unusual form, proportion, or rig. The additional requirements, if needed, will be prescribed by the Commandant.
(c) Each vessel must have positive righting arms in each condition of loading and operation from—
(1) 0 to at least 70 degrees of heel for service on protected or partially protected waters; and
(2) 0 to at least 90 degrees of heel for service on exposed waters.
(d) Each vessel must be designed to satisfy the following equations:
(1) For a vessel in service on protected or partially protected waters—
where—
X=1.0 long tons/sq. ft. (10.9 metric tons/sq. meter).
Y=1.1 long tons/sq. ft. (12.0 metric tons/sq. meter).
Z=1.25 long tons/sq. ft. (13.7 metric tons/sq. meter).
(2) For a vessel on exposed waters—
where—
HZA, HZB, and HZC are calculated in the manner specified in paragraph (e) or (f) of this section.
X=1.5 long tons/sq. ft. (16.4 metric tons/sq. meter).
Y=1.7 long tons/sq. ft. (18.6 metric tons/sq. meter).
Z=1.9 long tons/sq. ft. (20.8 metric tons/sq. meter).
A=the projected lateral area or silhouette in square feet (meters) of the portion of the vessel above the waterline computed with all sail set and trimmed flat. Sail overlap areas need not be included except parachute type spinnakers which are to be added regardless of overlap.
H=the vertical distance in feet (meters) from the center of A to the center of the underwater lateral area or approximately to the one-half draft point.
W=the displacement of the vessel in long (metric) tons.
(e) Except as provided in paragraph (f) of this section, HZA, HZB, and HZC must be determined as follows for each condition of loading and operation:
(1) Plot the righting arm curve on Graphs 171.055 (b), (c), and (d) or (e).
(2) If the angle at which the maximum righting arm occurs is less than 35 degrees, the righting arm curve must be truncated as shown on Graph 171.055(a).
(3) Plot an assumed heeling arm curve on Graph 171.055(b) that satisfies the following conditions:
(i) The assumed heeling arm curve must be defined by the equation—
HZ=HZA cos2 (T)
where—
HZ=heeling arm.
HZA=heeling arm at 0 degrees of heel.
T=angle of heel.
(ii) The first intercept shown on Graph 171.055(b) must occur at the angle of heel corresponding to the angle at which deck edge immersion first occurs.
(4) Plot an assumed heeling arm curve on Graph 171.055(c) that satisfies the following conditions:
(i) The assumed heeling arm curve must be defined by the equation—
HZ=HZB cos2 (T)
where—
HZ=heeling arm.
HZB=heeling arm at 0 degrees of heel.
T=angle of heel.
(ii) The area under the assumed heeling arm curve between 0 degrees and the downflooding angle or 60 degrees, whichever is less, must be equal to the area under the righting arm curve between the same limiting angles.
(5) Plot an assumed heeling arm curve on Graph 171.055 (d) or (e) that satisfies the following conditions:
(i) The assumed heeling arm curve must be defined by—
>HZ=HZC cos2 (T)
where—
HZ=heeling arm.
HZC=heeling arm at 0 degrees of heel.
T=angle of heel.
(ii) The area under the assumed heeling arm curve between the angles of 0 and 90 degrees must be equal to the area under the righting arm curve between 0 degrees and—
(A) 90 degrees if the righting arms are positive to an angle less than or equal to 90 degrees; or
(B) The largest angle corresponding to a positive righting arm but no more than 120 degrees if the righting arms are positive to an angle greater than 90 degrees.
(6) The values of HZA, HZB, and HZC are read directly from Graphs 171.055 (b), (c), and (d) or (e).
(f) For the purpose of this section, the downflooding angle means the static angle from the intersection of the vessel's centerline and waterline in calm water to the first opening that cannot be rapidly closed watertight.
(g) HZB and, if the righting arms are positive to an angle of 90 degrees or greater, HZC may be computed from the following equation:
where—
I=the area under the righting arm curve to—
(1) the downflooding angle or 60 degrees, whichever is less, when computing HZB; or
(2) the largest angle corresponding to a positive righting arm or 90 degrees, whichever is greater, but no greater than 120 degrees when computing HZC.
T=the downflooding angle or 60 degrees, whichever is less, when computing HZB or 90 degrees when computing HZC.
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[CGD 79–023, 48 FR 51017, Nov. 4, 1983, as amended by CGD 83–005, 51, FR 924, Jan. 9, 1986]
§ 171.057 Intact stability requirements for a sailing catamaran.
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(a) A sailing vessel that operates on protected waters must be designed to satisfy the following equation:
Where—
B=the distance between hull centerlines in meters (feet).
As=the maximum sail area in square meters (square feet).
Hc=the height of the center of effort of the sail area above the deck, in meters (feet).
W=the total displacement of the vessel, in kilograms (pounds).
X=4.88 kilograms/square meter (1.0 pounds/square foot).
(b) A sailing vessel that operates on partially protected or exposed waters must be designed to satisfy the following equation:
Where—
B=the distance between hull centerlines in meters (feet).
As=the maximum sail area in square meters (square feet).
Hc=the height of the center of effort of the sail area above the deck, in meters (feet).
W=the total displacement of the vessel, in kilograms (pounds).
X=7.32 kilograms/square meter (1.5 pounds/square foot).
[CGD 79–023, 48 FR 51017, Nov. 4, 1983, as amended by CGD 83–005, 51 FR 924, Jan. 9, 1986; CGD 85–080, 61 FR 944, Jan. 10, 1996]
§ 171.060 Watertight subdivision: General.
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(a) Each of the following vessels must be shown by design calculations to comply with the requirements in §§171.065 through 171.068 for Type I subdivision or §171.075 for Type III subdivision:
(1) Each vessel 100 gross tons or more on an international voyage: and
(2) Each vessel 150 gross tons or more in ocean service.
(b) Each vessel not described in paragraph (a) of this section must be shown by design calculations to comply with the requirements in §§171.070 to 171.073 for Type II subdivision.
(c) Except as allowed in §171.070(c), each vessel must have a collision bulkhead.
(d) Each double-ended ferry that is required by paragraph (c) of this section to have a collision bulkhead must also have a second collision bulkhead. One collision bulkhead must be located in each end of the vessel.
§ 171.065 Subdivision requirements— Type I.
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(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—
(floodable length)×(factor of subdivision)
where—
the factor of subdivision is listed under FS in Table 171.065(a).
(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):
or
where—
M, V, and P have the same value as listed in Table 171.065(a); and
P1=the smaller of the following:
(i) 0.6LN (0.056LN) where—
N=the total number of passengers; and L=LBP in feet (meters).
(ii) The greater of the following:
(A) 0.4LN (0.037LN). (B) The sum of P and the total volume of passenger spaces above the margin line.
(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:
where—
“total volume of allowed local subdivision” is determined by calculating the unflooded volume on each side of the centerline and multiplying the smaller volume by two.
(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.
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Table 171.065(a) (English units)
------------------------------------------------------------------------
Vessel length (LBP) Criterion numeral (CN) FS
------------------------------------------------------------------------
CN less than or equal A
to 23.
Vessel length greater than 392 feet CN greater than 23 and F1
less than 123.
CN greater than or B
equal to 123.
------------------------------------------------------------------------
CN less than or equal 1
to S.
Vessel length greater than or equal CN greater than S and F2
to 200 feet and less than or equal less than 123.
to 392 feet.
CN greater than or B
equal to 123.
------------------------------------------------------------------------
Vessel length less than 200 feet... ...................... 1
------------------------------------------------------------------------
Where_
FS=the factor of subdivision.
CN=60((M+2P)/V)+30000(N/L\2\)
A=(190/(L-160))+0.18
B=(94/(L-85))+0.18
F1=A-((A-B)(CN-23)/100)
S=(10904-25L)/48
F2=1-((1-B)(CN-S)/(123-S))
L=the length of the vessel (LBP) in feet.
M=the sum of the volume of the machinery space and the volumes of any
fuel tanks which are located above the inner bottom forward or aft of
the machinery space in cubic feet.
P=the volume of passenger spaces below the margin line.
V=the volume of the vessel below the margin line.
N=the number of passengers that the vessel is to be certificated to
carry.
Table 171.065(a) (Metric Units)
------------------------------------------------------------------------
Vessel length (LBP) Criterion numeral (CN) FS
------------------------------------------------------------------------
CN lesthan or equal to A
23.
Vessel length greater than 120 CN greater than 23 and F1
meters. less than 123.
CN greater than or B
equal to 123.
------------------------------------------------------------------------
CN less than or equal 1
to S.
Vessel length greater than or equal CN greater than S and F2
to 61 meters and less than or less than 123.
equal to 120 meters.
CN greater than or B
equal to 123.
------------------------------------------------------------------------
Vessel length less than 61 meters.. ...................... 1
------------------------------------------------------------------------
Where_
FS=the factor of subdivision.
CN=60((M+2P)/V)+2787(N/L\2\)
A=(58/(L-49))+0.18
B=(29/(L-26))+0.18
F1=A-((A-B)(CN-23)/100)
S=(3323.5-25L)/14.6
F2=1-((1-B)(CN-S)/(123-S))
L=the length of the vessel (LBP) in meters.
M=the sum of the volume of the machinery space and the volumes of any
fuel tanks which are located above the inner bottom forward or aft of
the machinery space in cubic meters.
P=the volume of passenger spaces below the margin line.
V=the volume of the vessel below the margin line.
N=the number of passengers that the vessel is to be certificated to
carry.
Table 171.065(b)_Table of X
------------------------------------------------------------------------
Vessel LBP in feet (meters) X \1\
------------------------------------------------------------------------
430 (131)...................................................... 1.336
440 (134)...................................................... 1.285
450 (137)...................................................... 1.230
460 (140)...................................................... 1.174
470 (143)...................................................... 1.117
480 (146)...................................................... 1.060
490 (149)...................................................... 1.002
500 (152)...................................................... 0.944
510 (155)...................................................... 0.885
520 (158)...................................................... 0.826
530 (162)...................................................... 0.766
540 (165)...................................................... 0.706
550 (168)...................................................... 0.645
554 (169) and up............................................... 0.625
------------------------------------------------------------------------
1 Interpolate for intermediate values.
§ 171.066 Calculation of permeability for Type I subdivision.
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(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 buldheads and is not a crew or passenger space may be excluded.
Table 171.066_Table of Uniform Average Permeabilities
------------------------------------------------------------------------
Location Uniform average permeability
------------------------------------------------------------------------
10 (a-c)
Machinery space........................... 85+_____
v
------------------------------------------------------------------------
35(a)
Volume forward of machinery space......... 63+___
v
------------------------------------------------------------------------
35(a)
Volume aft of machinery space............. 63+___
v
------------------------------------------------------------------------
For each location specified in this table_
a=volume below the margin line of all spaces that, in the full load
condition, normally contain no cargo, baggage, stores, provisions, or
mail.
c=volume below the margin line of the cargo, stores, provisions, or mail
spaces within the limits of the machinery space.
v=total volume below the margin line.
[CGD 79–023, 48 FR 51017, Nov. 4, 1983, as amended by CGD 88–070, 53 FR 34537, Sept. 7, 1988]
§ 171.067 Treatment of stepped and recessed bulkheads in Type I subdivision.
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(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.
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§ 171.068 Special considerations for Type I subdivision for vessels on short international voyages.
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(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.
Table 171.068_Table of Uniform Average Permeabilities
------------------------------------------------------------------------
Location Uniform average permeability
------------------------------------------------------------------------
10 (a-c)
Machinery Space.......................... 85+____
v
------------------------------------------------------------------------
35(b)
Volume Forward of Machinery Space........ 95-__
v
------------------------------------------------------------------------
35(b)
Volume Aft of Machinery Space............ 95-___
v
------------------------------------------------------------------------
For each location specified in this table_
a=volume below the margin line of all spaces that, in the full load
condition, normally contain no cargo, baggage, stores, provisions, or
mail.
b=volume below the margin line and above the tops of floors, inner
bottoms, or peak tanks of coal or oil fuel bunkers, chain lockers,
fresh water tanks, and of all spaces that, in the full load condition,
normally contain stores, baggage, mail, cargo, or provisions. If cargo
holds are not occupied by cargo, no part of the cargo space is to be
included in this volume.
c=volume below the margin line of the cargo, stores, provisions, or mail
spaces within the limits of the machinery space.
v=total volume below the margin line.
[CGD 79–023, 48 FR 51017, Nov. 4, 1983, as amended by CGD 88–070, 53 FR 34537, Sept. 7, 1988]
§ 171.070 Subdivision requirements—Type II.
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(a) Each vessel, except a ferry vessel, must be designed so that, while in each condition of loading and operation, it complies with the standard of flooding specified in Table 171.070(a).
(b) Except as provided in paragraph (c), each ferry vessel must be designed so that, while in each condition of loading and operation, it meets the standard of flooding specified in Table 171.070(b).
(c) A ferry vessel described in paragraph (d) of this section need not meet the standard of flooding specified in Table 171.070(b), except that a ferry vessel in Great Lakes service must at least have a collision bulkhead.
(d) Paragraph (c) of this section applies to a ferry vessel that—
(1) Is 150 feet (46 meters) or less in length; and
(2) Has sufficient air tankage, or other internal buoyancy to float the vessel with no part of the margin line submerged when the vessel is completely flooded. If foam is used to comply with this paragraph, it must be installed in accordance with the requirements in §170.245 of this subchapter.
(e) Except as specified in paragraph (f) of this section, each main transverse watertight bulkhead must be spaced as follows:
(1) If the LBP of the vessel is 143 feet (43.5 meters) or more, each main transverse watertight bulkhead must be at least 10 feet (3 meters) plus 3 percent of the vessel's LBP from—
(i) Every other main transverse watertight bulkhead;
(ii) The collision bulkhead; and
(iii) The aftermost point on the bulkhead deck.
(2) If the LBP of the vessel is less than 143 feet (43.5 meters) and the vessel does not make international voyages, each main transverse watertight bulkhead must be no less than 10 percent of the vessel's LBP or 6 feet (1.8 meters), whichever is greater, from—
(i) Every other main transverse watertight bulkhead;
(ii) The collision bulkhead; and
(iii) The aftermost point on the bulkhead deck.
(f) If a vessel is required by §171.060 to have a collision bulkhead in each end of the vessel, then each main transverse watertight bulkhead must be no less than the distance specified in paragraph (e) of this section from—
(1) Every other main transverse watertight bulkhead; and
(2) Each collision bulkhead.
Table 171.070(a)_Standard of Flooding
------------------------------------------------------------------------
Standard of
Passengers carried Part of vessel flooding
(compartments)
------------------------------------------------------------------------
400 or less................. All....................... 1
------------------------------------------------------------------------
401 to 600.................. All of the vessel forward 2
of the first MTWB aft of
the collision bulkhead..
All remaining portions of 1
the vessel.
------------------------------------------------------------------------
601 to 800.................. All of the vessel forward 2
of the first MTWB that is
aft of a point 40% of the
vessel's LBP aft of the
forward perpendicular.
All remaining portions of 1
the vessel.
------------------------------------------------------------------------
801 to 1000................. All of the vessel forward 2
of the first MTWB that is
aft of a point 60% of the
vessel's LBP aft of the
forward prependicular..
All remaining portions of 1
the vessel.
------------------------------------------------------------------------
More than 1000.............. All....................... 2
------------------------------------------------------------------------
Where for this table-
``MTWB'' means main transverse watertight bulkhead; and ``Standard of
Flooding`` is explained in § 171.017 of this subchapter.
Table 171.070(b)_Standard of Flooding for Ferry Vessels
------------------------------------------------------------------------
Standard of
Vessel length Part of vessel flooding
(compartments)
------------------------------------------------------------------------
150 feet (46 meters) or less.. All..................... 1
------------------------------------------------------------------------
All of the vessel 2
forward of the first
MTWB aft of the
collision bulkhead.
Greater than 150 feet (46 All of the vessel aft of 2
meters) and less than or the first MTWB forward
equal to 200 feet (61 meters). of the aft peak
bulkhead.
All remaining portions 1
of the vessel.
------------------------------------------------------------------------
Greater than 200 feet (61 All..................... 2
meters).
------------------------------------------------------------------------
Where for this table_
``MTWB'' means main transverse watertight bulkhead; and ``Standard of
Flooding'' is explained in § 171.017 of this subchapter.
§ 171.072 Calculation of permeability for Type II subdivision.
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When doing calcualtions to show compliance with §171.070, the following uniform average permeabilities must be assumed:
(a) 85 percent in the machinery space.
(b) 60 percent in the following spaces:
(1) Tanks that are normally filled when the vessel is in the full load condition.
(2) Chain lockers.
(3) Cargo spaces.
(4) Stores spaces.
(5) Mail or baggage spaces.
(c) 95 percent in all other spaces.
§ 171.073 Treatment of stepped and recessed bulkheads in Type II subdivision.
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(a) A main transverse watertight bulkhead may not be stepped unless additional watertight bulkheads are located as shown in Figure 171.067(a) so that the distances A, B, C, and D illustrated in Figure 171.067(a) comply with the following:
(1) A and B must not exceed the maximum bulkhead spacing that permits compliance with §171.070; and
(2) C and D must not be less than the minimum spacing specified in §171.070(e).
(b) A main transverse watertight bulkhead may not be recessed unless all parts of the recess are inboard from the shell of the vessel as illustrated in Figure 171.067(c).
(c) If a main transverse watertight bulkhead is recessed or stepped, an equivalent plane bulkhead must be used in the calculations required by §171.070.
§ 171.075 Subdivision requirements—Type III.
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(a) Each vessel must be shown by design calculations to comply with the requirements of Regulations 1, 2, 3, 4, 6, and 7 of the Annex to Resolution A.265 (VIII) of the International Maritime Organization (IMO).
(b) International Maritime Organization Resolution A.265 (VIII) is incorporated by reference into this part.
(c) As used in IMO Resolution A.265 (VIII), “Administration” means the Commandant, U.S. Coast Guard.
§ 171.080 Damage stability standards for vessels with Type I or Type II subdivision.
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(a) Calculations. Each vessel with Type I or Type II subdivision must be shown by design calculations to meet the survival conditions in paragraph (e), (f), or (g) of this section in each condition of loading and operation assuming the extent and character of damage specified in paragraph (b) of this section.
(b) Extent and character of damage. For the purpose of paragraph (a) of this section, design calculations must assume that the damage—
(1) Has the character specified in Table 171.080(a); and
(2) Consists of a penetration having the dimensions specified in Table 171.080(a) except that, if the most disabling penetration would be less than the penetration described in the table, the smaller penetration must be assumed.
(c) Permeability. When doing the calculations required in paragraph (a) of this section, the permeability of each space must be calculated in a manner approved by the Commanding Officer, Marine Safety Center or be taken from Table 171.080(c).
(d) Definitions. For the purposes of paragraphs (e) and (f) of this section, the following definitions apply:
(1) New vessel means a vessel—
(i) For which a building contract is placed on or after April 15, 1996;
(ii) In the absence of a building contract, the keel of which is laid, or which is at a similar stage of construction, on or after April 15, 1996;
(iii) The delivery of which occurs on or after January 1, 1997;
(iv) Application for the reflagging of which is made on or after January 1, 1997; or
(v) That has undergone—
(A) A major conversion for which the conversion contract is placed on or after April 15, 1996;
(B) In the absence of a contract, a major conversion begun on or after April 15, 1996; or
(C) A major conversion completed on or after January 1, 1997.
(2) Existing vessel means other than a new vessel.
(3) Watertight means capable of preventing the passage of water through the structure in any direction under a head of water for which the surrounding structure is designed.
(4) Weathertight means capable of preventing the penetration of water, even boarding seas, into the vessel in any sea condition.
(e) Damage survival for all existing vessels except those vessels authorized to carry more than 12 passengers on an international voyage requiring a SOLAS Passenger Ship Safety Certificate. An existing vessel is presumed to survive assumed damage if it meets the following conditions in the final stage of flooding:
(1) On a vessel required to survive assumed damage with a longitudinal extent of 10 feet (3 meters) plus 0.03L, the final angle of equilibrium must not exceed 7 degrees after equalization, except that the final angle may be as large as 15 degrees if—
(i) The vessel is not equipped with equalization or is equipped with fully automatic equalization; and
(ii) The Commanding Officer, Marine Safety Center approves the vessel's range of stability in the damaged condition.
(2) On a vessel required to survive assumed damage with a longitudinal extent of 20 feet (6.1 meters) plus 0.04L, the angle of equilibrium must not exceed 15 degrees after equalization.
(3) The margin line may not be submerged at any point.
(4) The vessel's metacentric height (GM) must be at least 2 inches (5 cm) when the vessel is in the upright position.
(f) Damage survival for all new vessels except those vessels authorized to carry more than 12 passengers on an international voyage requiring a SOLAS Passenger Ship Safety Certificate. A new vessel is presumed to survive assumed damage if it is shown by calculations to meet the conditions set forth in paragraphs (f) (1) through (7) of this section in the final stage of flooding and to meet the conditions set forth in paragraphs (f) (8) and (9) of this section in each intermediate stage of flooding. For the purposes of establishing boundaries to determine compliance with the requirements in paragraphs (f) (1) through (9), openings that are fitted with weathertight closures and that are not submerged during any stage of flooding will not be considered downflooding points.
(1) Each vessel must have positive righting arms for a minimum range beyond the angle of equilibrium as follows:
------------------------------------------------------------------------
Required
Vessel service range
(degrees)
------------------------------------------------------------------------
Exposed waters, oceans, or Great Lakes winter................ 15
Partially protected waters or Great Lakes summer............. 10
Protected waters............................................. 5
------------------------------------------------------------------------
(2) No vessel may have any opening through which downflooding can occur within the minimum range specified by paragraph (f)(1) of this section.
(3) Each vessel must have an area under each righting-arm curve of at least 0.015 meter-radians, measured from the angle of equilibrium to the smaller of the following angles:
(i) The angle at which downflooding occurs.
(ii) The angle of vanishing stability.
(4) Except as provided by paragraph (f)(5) of this section, each vessel must have within the positive range the greater of a righting arm (GZ) equal to or greater than 0.10 meter or a GZ as calculated using the formula:
where—
C=1.00 for vessels on exposed waters, oceans, or Great Lakes winter;
C=0.75 for vessels on partially protected waters or Great Lakes summer;
C=0.50 for vessels on protected waters;
?=intact displacement; and
Heeling moment=greatest of the heeling moments as calculated in paragraphs (f)(4) (i) through (iv) of this section.
(i) The passenger heeling moment is calculated using the formula:
Passenger Heeling Moment=0.5 (n w b)
where—
n=number of passengers;
w=passenger weight = 75 kilograms; and
b=distance from the centerline of the vessel to the geometric center on one side of the centerline of the passenger deck used to leave the vessel in case of flooding.
(ii) The heeling moment due to asymmetric escape routes for passengers, if the vessel has asymmetric escape routes for passengers, is calculated assuming that—
(A) Each passenger weighs 75 kilograms;
(B) Each passenger occupies 0.25 square meter of deck area; and
(C) All passengers are distributed, on available deck areas unoccupied by permanently affixed objects, toward one side of the vessel on the decks where passengers would move to escape from the vessel in case of flooding, so that they produce the most adverse heeling moment.
(iii) The heeling moment due to the launching of survival craft is calculated assuming that—
(A) All survival craft, including davit-launched liferafts and rescue boats, fitted on the side to which the vessel heels after sustained damage, are swung out if necessary, fully loaded and ready for lowering;
(B) Persons not in the survival craft swung out and ready for lowering are distributed about the centerline of the vessel so that they do not provide additional heeling or righting moments; and
(C) Survival craft on the side of the vessel opposite that to which the vessel heels remain stowed.
(iv) The heeling moment due to wind pressure is calculated assuming that—
(A) The wind exerts a pressure of 120 Newtons per square meter;
(B) The wind acts on an area equal to the projected lateral area of the vessel above the waterline corresponding to the intact condition; and
(C) The lever arm of the wind is the vertical distance from a point at one-half the mean draft, or the center of area below the waterline, to the center of the lateral area.
(5) Each vessel whose arrangements do not generally allow port or starboard egress may be exempted, by the Commanding Officer, Marine Safety Center, from the transverse passenger heeling moment required by paragraph (f)(4)(i) of this section. Each vessel exempted must have sufficient longitudinal stability to prevent immersion of the deck edge during forward or aft egress.
(6) Each vessel must have an angle of equilibrium that does not exceed—
(i) 7 degrees for flooding of one compartment;
(ii) 12 degrees for flooding of two compartments; or (continued)
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