NTSB Safety Recommendation Letter P-76-009A, P-76-010, P-76-011

Page 1Official PDFFOR RELEASE: 6:30 A,M,, E , s , T , , APRIL 19, 1976 (202) 426-8787 ISSUED: April 19, 1976 Secretary Department of Transportation Washington, D. C . 20590 \ SAFETY RECOMMENDAT I O N ( s ) I-- P-76-9 through P-76-11 A t 6:57 a . m . on A p r i l 2 2 , 1974, a massive, low-order explosion demolished the west wall of a 25-story commercial building a t 305 E a s t 45th S t r e e t i n New York, New York. The s t r u c t u r e of the adjacent building was damaged and g l a s s was broken i n other buildings i n t h e area. Glass fragments and s l i v e r s were blown i n t o 46th S t r e e t , where they l a y 1 inch deep i n places. No persons were k i l l e d , b u t more than 70 persons were injured. The National Transportation Safety Board's investigation showed t h a t a 6-inch service l i n e located i n the basement of the building had been struck from below and severed by a ruptured hydropneumatic pressure tank i n s t a l l e d d i r e c t l y underneath. G a s a t 7 inches of water column flowed a t 54,000 cubic f e e t per hour from the open end of the separated service l i n e . Gas leakage continued f o r about 1 / 2 hour. Gas odors f i n a l l y were noticed by a building occupant, but the building exploded before any mitigative e f f o r t s took place. Excess flow valves which can be i n s t a l l e d i n a service l i n e and which w i l l close automatically when an excessive amount of gas (a predetermined increased rate of flow) begins t o move through the pipe a r e manufactured currently. This type of valve remains open under normal gas flow conditions, b u t i f t h e l i n e should be severed and a l a r g e volume of gas begins t o flow through t h e rupture, the excess flow valve would close automatically. Most valves of t h i s type a r e f o r use i n high-pressure gas d i s t r i b u t i o n systems of 3 psig o r more, but research i s being done on similar valves capable of operating a t only a few inches of water column. 1745#

Page 2- 2 - The 6-inch gas service line in the basement was considered by the Office of Pipeline Safety to be a gas distribution main and therefore the Federal regulation 49 CFR 192.3. The New York State Public Servic Commission's regulation, 16 NYCRR 255.1855, maintains that the pipeline operator's jurisdiction ends at the first fitting inside the wall of a customer's structure. This is based on the impracticability of a pipe1 operator's trying to operate and maintain thousands of feet of gas pipin inside the walls and ceilings of thousands of buildings within the stat Therefore, the National Transportation Safety Board recommends that the Office of Pipeline Safety Operations of the Department of Transportatio (1) Determine the availability, the practicability, and the state-of-the-art in the manufacture of excess flow valves for use on low-pressure gas distribution systems. Based the results of these findings, amend 49 CFR 192 to incorpora the use of these valves in commercial buildings. (Recomm dation P-76-9 (Class 11, Priority Followup) 4 ( 2 ) Amend 49 CFR 192 to define more realistically an operator responsibility for gas piping inside buildings. (Recomme tion P-76-10] (Class TI, Priority Followup) ( 3 ) Expedite its review of the study of "Rapid Shutd Failed Pipeline Systems and Limiting of Pressure to Pre Pipeline Failure Due to Overpressure" and determine what regulatory action is necessary concerning the use of excss flow valves. (Recommendation P-76-11) (Class 11, Priori Followup) TODD, Chairman, MCADAMS, THAYER, BU in the above recommendations. By: Chairman THIS DOCUMENT WILL BE RELEASED TO THE PUBLIC ON THE DATE S PUBLIC DISSEMINATION OF THIS DOCUMENT SHOULD BE MADE BEFORE FHA#