NTSB Safety Recommendation Letter P-79-027

Page 1Official PDFAL T WASHINGTON, D.C. ISSUED: September 6 , 1979 ----"_-______-------___________________I- Forwarded to: Honorable Howard Dugoff Administrator Research and Special Programs Administration Department of Transportation P-79-27 Washington, D.C. 20590 SAFETY RECOMMENDAT I O N (S) A t 1 : l O a.m., c.s.t., on January 19, 1979, i n North Richland H i l l s , Texas, an accumulation of n a t u r a l gas i n a house was i g n i t e d by an unknown source. The r e s u l t i n g explosion and f i r e destroyed t h e house. One r e s i d e n t w a s k i l l e d and another was c r i t i c a l l y injured. The houses i n t h e accident a r e a were connected t o a 6-inch Lone Star Gas Company gas main by 1 1/4-inch service l i n e s . The service connection w a s made with two 90-degree elbows t o allow f o r both hori- z o n t a l and v e r t i c a l movement of t h e l i n e a s t h e s o i l moved. This "swing connection" d i d not prevent t h e f r a c t u r e of t h e pipe. I n v e s t i g a t o r s have determined that gas escaped from a circumferential f r a c t u r e a t the threads of a 1 1/4-inch n i p p l e above t h e s e r v i c e tap on t h e main. The w e t c l a y s o i l a t t h e accident s i t e retarded t h e upward movement of t h e leaking gas. The gas moved l a t e r a l l y along t h e pipe; through t h e d r i e r , more permeable clay; and i n t o t h e house. On November 27, 1978, a l e a k occurred on t h e Lone S t a r system i n Arlington, Texas. This l e a k was a l s o a t the threaded s e c t i o n of a main/service l i n e connection. The l e a k r e s u l t e d i n an explosion i n which one person was k i l l e d . The conditions at t h e January 1 9 , 1979, accident were a l s o similar t o those which existed on October 4 , 1971, when a connection f a i l e d i n North Richland H i l l s . 11 I n a l l t h r e e cases, t h e p i p e l i n e s were located i n dense clay s o i l that swells when i t i s w e t . The movement of t h e s o i l applied f o r c e t o t h e pipes which i n turn induced stresses which concentrated a t t h e threaded connections of the 1 1/4-inch n i p p l e at the service tap. The continued stress eventually caused t h e threaded a r e a s t o crack. In t h e 1971 accident, t h e e f f e c t s of the stress were heightened because Df b r i t t l e n e s s caused by the hydrogenation of t h e galvanized p i p e used a t that connection. I n v e s t i - g a t o r s determined t h a t t h e 1978 l e a k was a l s o induced by a combination of stress and corrosion. - 1/ For more d e t a i l e d information read "Pipeline Accident Report-- Lone S t a r Gas Company, North Richland H i l l s , Texas, October 4 , 197 1" (NTSB-PAR-7 2-.3) . 2718#

Page 2- 2 - The p i p e involved i n t h e January 19, 1979, accident w i l l b e t e s t e d e t a l l u r g i c a l Consultants, l n c . , of Houston, Texas. The type of steel or galvanized steel--has n o t y e t been determined. The equested t h a t the t e s t i n g b e expedited. A s a r e s u l t of its i n v e s t i g a t i o n of t h e 1971 accident, t h e Safety recommended that Lone S t a r make random inspections of its main/ c e l i n e connections t o determine conditions and initiate c o r r e c t i v e a c t i o n as necessary. Lone S t a r r e p l i e d t h a t t h e leak w a s due t o t h e corrosion a c t i o n on t h e galvanized pipe r a t h e r than stress. Lone S t a r s t a t e d t h a t its construction standards "have never permitted the u s e of alvanized pipe underground. Galvanized pipe has been u t i l i z e d i n t h e ast f o r above ground connections. Construction records on work i n t h i s area i n d i c a t e that black steel pipe was used. Any u s e of galvanized pipe was inadvertent and unusual. Since t h e d a t e of t h i s occurrence, a l l of our warehouses have been purged of galvanized pipe of any type. Its u s e has been prohibited. Since t h e d a t e of t h i s accident, w e have followed c l o s e l y a l l r e p a i r s on our system. Excavations number i n excess of 1,000 a month i n t h e F o r t Worth system of which North Richland H i l l s is a p a r t . These excavations have f a i l e d to reveal a s i n g l e similar i n s t a l l a t i o n . I n addition, immediately following t h e accident s e v e r a l services were dug up i n t h e immediate area. These were n o t etermined t o be galvanized pipe." F a i l u r e of p i p e a t the main/service l i n e connection with threaded couplings on the Lone S t a r system appears t o be a recurring problem. After t h e 1971 accident, Lone S t a r only addressed t h e galvanized pipe- hydrogenation corrosion problem and n o t t h e stress problem. The s h o r t time between t h e November 1978 and t h e January 1979 accidents has caused the Safety Board concern as to the s a f e t y of t h e e n t i r e Lone S t a r system. Therefore, t h e National Transportation Safety Board recommends that t h e Research and Special Programs Administration: I n conjunction with t h e Texas Railroad Commission, determine i f t h e type of main/service l i n e con- n e c t i o n with threaded couplings i n s t a l l e d by t h e Lone S t a r Gas Co. c o n s t i t u t e s a hazard t o l i f e and property, and take appropriate a c t i o n under Section 3(b) of t h e Natural Gas P i p e l i n e Safety A c t of 1968. (Class I, Urgent Action) (P-79-27) KING, Chairman, DRIVER, Vice Chairman, MCADAMS, GOLDMAN, and BURSLEY, Members, concurred i n this recommendation.#