DOB Findings and Recommendations for WTC, Feb 2003

NYC 9/11 Public Portal Document

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( The size of fuel oil tanks ("day tanks") above the lowest level of a building is currently limited to a I capacity of 275 gallons by the Building Code. In some instances, 12-inch diameter fuel oil transfer piping has been installed to provide reservoir capacity in excess.of the 275 gallon limitation. Because this size piping can quickly introduce an increased amount of fuel over multiple floors fuel oil transfer piping to day tanks should be limited in diameter.

In most cases, individual tenants install dedicated emergency generating plants consisting of multiple engine/generator sets. These electrical generating plants are necessarily located in proximity to the tenant space they serve. Re-circulating fuel oil systems are used to pump oil from a tank on the lowest level of the building to a header that allows each of the engines/generators to take the needed amount of fuel oil with the rest returning to the tank. Currently, nothing in the Building Code regulates the assembly and use of these systems. As with day tanks, the Building Code should strike a balance between the amount of fuel oil that can safely circulate through a building and that needed for appropriate emergency energy generation. It is recommended that when fuel oil re-circulating systems are used to provide fuel oil to emergency generators on upper floors, fuel oil headers not exceed 12 inches. Such headers shall be limited to the length required for the specific emergency generator installation, with diameter limits placed on the header and the supply and return lines to and from the fuel tank. Additionally, pipe material, connection location, emergency shut off valve, and joint welding specifications have been made. In some instances oversized piping is used for distribution of oil to emergency generators. Modern equipment design often relies on the recirculation of fuel oil in these distribution pipes for cooling making them necessary for emergency generation. The following standards are proposed where piping is utilized as a means of distributing fuel oil to equipment, without the use of a day tank (to be inserted into Article 17 27-829(b) "exceptions."): ( ! • All piping shall be suitably supported so as to not allow overstressing of piping and shall be suitably isolated from rotating equipment. • All piping shall be schedule 40 steel. • Connections to main header (supply or return) shall be via the top of the pipe. • All fittings to header pipe and equipment shall be welded. • Fittings for immediate shut off valves to equipment shall be screwed or flanged. • Where air vents or vacuum breakers are required they shall be designed for the required use. • All air vents and vacuum breakers shall be hard piped to a local 55 gallon drum, with a leak sensor alarm tied into a central alarm monitoring location.

Recommendation 15. Limit diameter of fuel oil transfer piping in systems using day tanks.

16. Implement standards for piping that is utilized to distribute fuel oil to equipment without the use of a day tank.

L February 2003 WTC Building Code Task Force Page 25 Findings and Recommendations

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