[Code of Federal Regulations]
[Title 46, Volume 1]
[Revised as of Octobery 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 46CFR38.05-3]

[Page 488-489]
 
                           TITLE 46--SHIPPING
 
         CHAPTER I--COAST GUARD, DEPARTMENT OF HOMELAND SECURITY
 
PART 38_LIQUEFIED FLAMMABLE GASES--Table of Contents
 
                  Subpart 38.05_Design and Installation
 
Sec. 38.05-3  Design and construction of pressure vessel type cargo 
tanks--TB/ALL.

    (a) Cargo tanks of pressure vessel configuration (e.g. cylindrical, 
spherical, etc.) shall be designed, fabricated, inspected, and tested in 
accordance with the applicable requirements of part 54 of subchapter F 
(Marine Engineering) of this chapter, except as otherwise provided for 
in this part.
    (b) The requirements of this section anticipate that cargo tanks 
constructed as pressure vessels will, by themselves, constitute the 
cargo containment system and usually will not require a secondary 
barrier.
    (c) In the design of the tank, consideration shall be given to the 
possibility of the tank being subjected to external loads. Consideration 
shall also be given to excessive loads that can be imposed on the tanks 
by their support due to static and dynamic forces under operating 
conditions or during testing. The design shall show the manner in which 
the tanks are to be installed, supported, and secured, and shall be 
approved prior to tank installation.
    (d) Tanks with a service temperature of minus 20[deg] F. or lower 
and fabricated of ferritic materials shall be stress relieved.
    (e) Unlagged cargo tanks, where the cargo is transported, at or near 
ambient temperatures, shall be designed for the vapor pressure of the 
gas at 115[deg] F. The design shall also be based on the minimum 
internal pressure (maximum vacuum), plus the maximum external static 
head to which the tank may be subjected. Whenever surrounding cargo is 
at a greater temperature than the maximum allowable temperature of the 
liquefied flammable gas tanks, the liquefied flammable gas cargo is to 
be such that the design pressure of the liquefied flammable gas tank is 
not exceeded.
    (f) Where cargo tanks, in which the cargo is transported at or near 
ambient temperature, are lagged with an insulation material of a 
thickness to provide a thermal conductance of not more than 0.075 B.t.u. 
per square foot per degree Fahrenheit differential in temperature per 
hour, the tanks shall be designed for a pressure of not less than the 
vapor pressure of the gas at 105[deg] F. The insulation material shall 
conform to the requirements of Sec. 38.05-20. The design shall also be 
based on the minimum internal pressure (maximum vacuum) plus the maximum 
external static head to which the tank may be subjected.
    (g) Cargo tanks in which the temperature is maintained below the 
normal atmospheric temperature by refrigeration or other acceptable 
means shall be designed for a pressure of not less than 110 percent of 
the vapor pressure corresponding to the temperature of the liquid at 
which the system is maintained, or the pressure corresponding to the 
greatest dynamic and static loads expected to be encountered either in 
service or during testing. For mechanically stress relieved cargo tanks, 
additional factors relating design pressure and maximum allowable 
pressure shall be as specified by the Commandant. The material of the 
tank shall satisfy the requirements of subchapter F (Marine Engineering) 
of

[[Page 489]]

this chapter for the service temperature, and this temperature shall be 
permanently marked on the tank as prescribed in Sec. 38.05-5.
    (h) Where applicable, the design shall investigate the thermal 
stresses induced in the cargo tank at the service temperature.
    (i) The shell and head thickness of liquefied gas cargo tanks shall 
not be less than five-sixteenths inch.

[CGFR 66-33, 31 FR 15269, Dec. 6, 1966, as amended by CGFR 68-82, 33 FR 
18806, Dec. 18, 1968]