[Code of Federal Regulations]
[Title 46, Volume 4]
[Revised as of October 1, 2002]
From the U.S. Government Printing Office via GPO Access
[CITE: 46CFR105.20-3]

[Page 102-103]
 
                           TITLE 46--SHIPPING
 
    CHAPTER I--COAST GUARD, DEPARTMENT OF TRANSPORTATION (CONTINUED)
 
PART 105--COMMERCIAL FISHING VESSELS DISPENSING PETROLEUM PRODUCTS--Table of Contents
 
           Subpart 105.20--Specific Requirements--Cargo Tanks
 
Sec. 105.20-3  Cargo tanks.

    (a) Construction and Materials. (1) The cargo tanks must be 
constructed of iron, steel, copper, nickel alloy, copper alloy; or 
aluminum. The tanks shall be designed to withstand the maximum head to 
which they may be subjected, except that in no case shall the thickness 
of the shell or head be less than that specified in this subparagraph. 
Tanks of over 150 gallons capacity shall have a minimum thickness as 
indicated in Table 105.20-3(a)(1):

                          Table 105.20-3(a)(1)
------------------------------------------------------------------------
                                       A.S.T.M.          Thickness in
            Material                 specification      inches and gage
                                   (latest edition)     number \2\ \3\
------------------------------------------------------------------------
Nickel copper...................  B127, hot rolled    0.107 (USSG 12).
                                   sheet or plate.
Copper nickel \1\...............  B122, Alloy No. 5.  0.128 (AWG 8).
Copper \1\......................  B152, Type ETP....  0.182 (AWG 5).
Copper silicon \1\..............  B97, Alloys A, B,   0.144 (AWG 7).
                                   and C.
Steel or iron...................  ..................  0.179 (MSG 7).
Aluminum \4\....................  B209, Alloy.......  \5\ 5086 0.250
                                                       (USSG 3).
------------------------------------------------------------------------
\1\ Tanks fabricated with these materials shall not be utilized for the
  carriage of diesel oil.
\2\ The gage numbers used in this table may be found in many standard
  engineering reference books. The letters ``USSG'' stand for ``U.S.
  Standard Gage'' which was established by the act of Mar. 3, 1892 (15
  U.S.C. 206) for sheet and plate iron and steel. The letters ``AWG''
  stand for ``American Wire Gage'' (or Brown and Sharpe Gage) for
  nonferrous sheet thicknesses. The letters ``MSG'' stand for
  ``Manufacturers' Standard Gage'' for sheet steel thicknesses.
\3\ Tanks over 400 gallons shall be designed with a factor of safety of
  four on the ultimate strength of the tank material used with a design
  head of not less than 4 feet of liquid above the top of the tank.
\4\ Anodic to most common metals. Avoid dissimila-metal contact with
  tank body unless galvanically compatible.
\5\ And other alloys acceptable to the Commandant.

    (2) All tank joints, connections, and fittings shall be welded or 
brazed. Tanks with flanged-up top edges will not be acceptable.
    (3) All tanks exceeding 30 inches in any horizontal dimension shall 
be fitted with vertical baffle plates of the same material as the tank. 
Limber holes at the bottom and air holes at the top of all baffles shall 
be provided.

[[Page 103]]

Tanks constructed of material of greater thickness than minimum 
requirements and that are reinforced with stiffeners may be accepted 
without baffles.
    (4) An opening fitted with a threaded pipe plug may be used on the 
bottom of the tank for cleaning purposes.
    (b) Supports. (1) Tanks shall be adequately supported and braced to 
prevent movement. The supports and braces shall be insulated from 
contact with the tank surface with a nonabrasive and nonabsorbent 
material.
    (c) Fittings. (1) Filling lines shall be at least 1\1/2\ inches 
standard pipe size and extend to within 1\1/2\-pipe diameters of the 
bottom of the tank.
    (2) Suction lines from diesel oil tanks may be taken from the bottom 
provided a shutoff valve is installed at the tank. Tanks for Grades B 
and C liquids shall have top suctions only.
    (3) Vent lines shall be at least equal in size to the filling lines.
    (4) When a cargo tank contains Grades B or C liquids, the vent lines 
shall be terminated with an approved pressure vacuum relief valve not 
less than 3 feet above the weather deck. When a cargo tank contains 
Grades D or E liquids the vent line may be terminated with a gooseneck 
fitted with flame screen at a reasonable height above the weather deck.
    (d) Hydrostatic tests. All tanks vented to the atmosphere shall be 
hydrostatically tested to a pressure of 5 pounds per square inch or 1\1/
2\ times the maximum head to which they may be subjected in service. A 
standpipe of 11\1/2\ feet in length attached to the tanks may be filled 
with water to accomplish the 5 pounds per square inch test.

[CGFR 69-53, 34 FR 11265, July 4, 1969, as amended by CGD 72-206R, 38 FR 
17229, June 29, 1973; CGD 76-061, 41 FR 23401, June 10, 1976]