Vault to be accessible by one or more large man-holes, which, when not in use, are to be kept locked by a large padlock of three or more tumblers, key to be held by some responsible party.
A trough must run from one end of the vault to the other, directly under each tank, and in the same direction as the tank or tanks.
Tank to be of boiler iron or steel, at least 3⁄16 inch in thickness, to be cold riveted, rivets to be not less than 3⁄8 inch in diameter and not over 1 inch apart between centres; the entire outer surface of tank to have two good coats of coal tar or mineral paint before the tank is placed in position.
No tank shall be over 8 feet in diameter by 25 in length, nor shall any vault have over two tanks.
When tank is set, the bottom of the tank must be 3 inches above the concrete floor of the vault, and must be in saddles of masonry not less than twelve inches in thickness, built from the concrete floor of the vault, said saddles not to be more than 3 feet apart between centres, and laid in hydraulic cement, with an opening through centre for drainage.
Tank must incline 1 inch per 10 feet in length toward the end from which it is to be tapped, said incline of the tank to be opposite to the incline at the bottom of the vault.
The filling pipe, man-hole, telltale or indicator, pump supply connection, steam connection, overflow pipe and ventilating pipes, where they connect with tank, must be made petroleum tight by the use of litharge and glycerine cement.
Flanges to make tank 3⁄4 inch in thickness to be riveted on the inside so as to furnish a satisfactory joint where connections are made, must be used.
Filling pipe connection must have gas-tight valve between the tank and hose coupling, which must be kept closed and locked unless the tank is being filled. Each tank must have ventilating pipes at least 11⁄2 inches in diameter, one of which must connect with one end of the top of the tank and must be in the form of an inverted J, a union to be placed in pipe just below the bend, within which shall be placed a diaphragm of fine wire gauze; the other ventilating pipe must be at the other end of the top of the tank and must be conducted to the inside of the smoke stack or into the open air at least 10 feet above the surface, so that all the gases that form in the tank will be constantly changed.
Tank must have indicator to show height of oil in tank at all times, said indicator to be so arranged as to allow no escapement of gases from tank. All pipes leading from the tank to the pump or place of burning, must incline toward the tank, and have a fall of at least 2 feet from bottom of stand pipe to top of storage tank, and must be so constructed that the feed pipe from stand pipe to burners shall be entirely above burners, so that no pockets of oil can be formed in any one of the pipes between the main tank, stand pipe, oil pump or place of burning.