[Code of Federal Regulations]
[Title 46, Volume 7]
[Revised as of October 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 46CFR174.255]

[Page 178-179]
 
                           TITLE 46--SHIPPING
 
   CHAPTER I--COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED)
 
PART 174_SPECIAL RULES PERTAINING TO SPECIFIC VESSEL TYPES--Table of 
Contents
 
             Subpart H_Special Rules Pertaining to Liftboats
 
Sec. 174.255  Restricted service.

    This section applies to each liftboat unable to comply with Sec. 
174.250 and limited to restricted service as defined by Sec. 125.160 of 
this chapter.
    (a) Intact stability. (1) Each liftboat must be shown by design 
calculations to meet, under each condition of loading and operation 
afloat, the following requirements:
    (i) Those imposed by Sec. 174.045, given a ``K'' value of at least 
1.4.
    (ii) A range of positive stability of at least 10 degrees extending 
from the angle of the first intercept of the curves of righting moment 
and wind heeling moment, either to the angle of the second intercept of 
those curves or to the angle of heel at which downflooding would occur, 
whichever angle is less.
    (iii) A residual righting energy of at least 0.003 meter radians (5 
foot-degrees) between the angle of the first intercept of the curves of 
righting moment and wind heeling moment, either to the angle of the 
second intercept of those curves or to the angle of heel at which 
downflooding would occur, whichever angle is less.
    (2) For this section, each wind heeling moment must be calculated as 
prescribed by Sec. 174.055 of this part using winds of 60 knots for 
normal conditions of operation afloat and of 70 knots for severe-storm 
conditions of operation afloat.
    (3) For paragraph (a)(1) of this section, the initial metacentric 
height must be at least 300 millimeters (1 foot) for each leg position 
encountered while afloat including the full range of leg positions 
encountered while jacking.
    (b) Damaged stability. (1) Each liftboat must be designed so that, 
while it is in each of its normal operating conditions, its final 
equilibrium waterline will remain below the lowest edge of any opening 
through which additional flooding can occur if the liftboat is subjected 
simultaneously to--
    (i) Damage causing flooding described by paragraph (b)(4) of this 
section; and

[[Page 179]]

    (ii) A wind heeling moment calculated in compliance with Sec. 
174.055(b) using a wind speed of 50 knots.
    (2) Each liftboat must have a means of closing off each pipe, 
ventilation system, and trunk in each compartment described by paragraph 
(b)(4) of this section if any part of the pipe, ventilation system, or 
trunk is within 760 millimeters (30 inches) of the hull.
    (3) For compliance with paragraph (b)(1) of this section, no 
compartment on the liftboat may be ballasted or pumped out to compensate 
for the flooding described by paragraph (b)(4) of this section.
    (4) For compliance with paragraph (b)(1) of this section, each 
compartment within 760 millimeters (30 inches) of the hull, excluding 
the bottom of the liftboat, between two adjacent main watertight 
bulkheads and the uppermost continuous deck or first superstructure deck 
where superstructures are fitted must be assumed subject to simultaneous 
flooding.
    (5) In the calculations required by paragraph (b)(1) of this 
section, the permeability of a floodable space must be as listed by 
Table 174.205(d).
    (c) On-bottom stability. Each liftboat must be shown by design 
calculations to exert a continuous downward force on each footing when 
the vessel is supported on the bottom with footings and is subjected to 
the forces of waves, currents, and winds of 70 knots under normal 
conditions of operation, and winds of 100 knots under severe-storm 
conditions of operation when elevated in a safe place, if this place is 
other than a harbor of safe refuge. The waves and currents must be 
appropriate for the winds and place.