(a) General requirements for fuel oil tanks. All tanks shall be designed and installed in accordance with the provisions for steel work in subchapter ten of this chapter or in accordance with the provisions of this subchapter.
(1) All fuel oil storage tanks shall be built of steel plates or sheets, made by the open hearth or basic oxygen process. Such steel shall be free from physical imperfections, and shall be new, in good condition, and free from rust.
(2) Tanks shall be welded, riveted and caulked, or riveted and welded. Flanges or other pipe connections may be welded. All caulking shall be placed with round nose tools and without damage to the plates. Filler of any kind between plates shall be prohibited.
(3) Tanks to be buried shall be cleaned and then coated on the outside with two coats of red lead, or equivalent. They shall be further protected by a coating of hot tar, asphalt, or equivalent rust resistive material, applied at the work site. Tanks installed inside buildings above ground shall be coated with one coat of red lead, or equivalent.
(4) All buried storage tanks shall be constructed of at least one-quarter inch thick metal and shall be designed to withstand any external loads to which the tank may be subjected.
(5) At the time of installation all storage tanks shall bear a permanently-fixed plate, spot welded or equivalent, bearing the name of the tank manufacturer, the gauge of the material, and capacity of the tank. Shop fabricated storage tanks shall be installed without structural alteration.
(6) All openings shall be through the top of the storage tank, except that storage tanks of two hundred seventy-five gallon capacity or less, located above ground but below the lowest story, may be provided with a three-quarter inch opening for gravity discharge and a one inch opening in the bottom for cleaning and protection against corrosion.
(7) Tanks for no. 1, no. 2, no. 3 and no. 4 commercial grade oils need not have manholes. However, if manholes are used for such oils, the manhole covers shall be bolted and made gastight. Tanks for no. 5 and no. 6 commercial grade oils shall have manhole covers bolted or otherwise secured to the tanks and kept hydrostatically tight at all times.
(8) Tanks outside of buildings shall be electrically grounded in accordance with the requirements for equipment grounding of the electrical code of the city of New York.
(9) Tanks shall be located at least seven feet, measured in the most direct manner, from any source of exposed flame unless protected as provided in paragraph two or three of subdivision (a) of section 27-829 of this article and at least two feet from any surface where the temperature exceeds one hundred sixty-five degrees Fahrenheit.
(b) Construction requirements, cylindrical tanks, except vertical tanks above ground outside of buildings, more than two hundred seventy-five gallon capacity.
(1) The thickness of cylindrical tanks, including oval, elongated oval, or obround tanks of more than two hundred seventy-five gallon capacity shall be subject to the following requirements:
a. Tanks thirty-six inches in diameter and less – at least 1/4 in. shell and 1/4 in. heads.
b. Tanks thirty-seven to seventy-two inches in diameter – at least 1/4 in. shell and 5/16 in. heads.
c. Tanks seventy-three to one hundred twenty inches in diameter – at least 5/16 in. shell and 3/8 in. heads.
d. Tanks over one hundred twenty inches in diameter shall be of at least 3/8 in. steel and shall be stiffened by angle rings or equivalent members so as to retain their cylindrical form.
(2) Dished heads for such tanks shall have a curvature the radius of which is not greater than the diameter of the tank. Dished heads shall be formed with an adequate cylindrical extension rim to provide a welding or riveting surface. If flat heads are used, they shall be braced in the same manner as described for the bracing of flat sides of rectangular tanks.
(3) Riveting in single lap seams shall not exceed a pitch as follows:
a. Shell 1/4 in. thick 5/8 in. diameter rivets, 2 1/4 in. pitch.
b. Shell 5/16 in. thick 5/8 in. diameter rivets, 2 3/8 in. pitch.
c. Shell 3/8 in. thick 3/4 in. in diameter rivets, 2 1/2 in. pitch.
(c) Rectangular tanks, of more than two hundred seventy-five gallon capacity.
(1) Plates for rectangular tanks of more than two hundred seventy-five gallon capacity shall be at least 5/16 in. thick.
(2) Corners may be made up by bending the plates or by using angles.
(3) Minimum rivet diameter in seams shall be 5/8 in., and rivets shall be spaced not more than 2 1/4 in. center-to-center.
(4) All flat surfaces of rectangular tanks shall be braced by structural members or rods.
(5) When structural members are used, the rivet pitch shall not exceed six inches.
(6) All structural members shall be designed in accordance with the requirements of subchapter ten of this chapter.
(7) Connections between bracing members and the sides of the tank shall be designed so that the connection will not fail before the member will fail.
(d) All tanks except vertical tanks above ground, two hundred seventy-five gallon or less capacity.
(1) All oil storage tanks of two hundred seventy-five gallon capacity or less that are not buried shall have a minimum thickness of shell and head plates of no. 10 manufacturer's standard gauge steel plate. Storage tanks of sixty gallon capacity or less shall be similarly constructed but need not be thicker than No. 14 manufacturer's standard gauge.
(e) Vertical storage tanks over one thousand gallon capacity located outside of building above ground.
(1) Vertical tanks located outside of buildings above ground shall be built of steel plates of the quality required for cylindrical tanks.
(2) The minimum thickness of shell or bottom plates shall be one quarter of an inch, and the minimum thickness of roof plates one-eighth of an inch. The thickness of shell plates shall be determined in accordance with the following formula:
t = P × R × F
T × E
T × E
where: t = thickness of shell plate in inches.
P = head pressure at bottom of ring under consideration in psi.
R = radius of shell, in inches.
F = factor of safety (taken as five).
T = tensile strength of plate, in psi as verified by mill test certificate.
E = efficiency of vertical joint in ring under consideration. E shall in no case be taken greater than one.
(3) Roof plates shall have single lap-riveted or welded watertight seams, and the roof shall be built to shed water. Bottom plates shall have single lap riveted or welded seams. Shell plate seams shall be designed to develop the full strength of the plate.
(f) Storage containers of six gallons or less.
(1) Oil storage containers used with burners or oil burning heaters and having a capacity of six gallons or less used in connection with burners or oil-burning heaters shall be designed so as to withstand a hydrostatic pressure test of at least five psi without permanent deformation, rupture, or leakage, and shall be approved.
(2) All storage containers used with burners or oil burning heaters shall be installed with rigid metal fasteners for wall, floor, or stand type installations, and shall be protected against mechanical damage.
(3) Portable containers may be filled by a pump mounted on a storage tank, provided that the pump is approved.