NTSB Safety Recommendation Letter P-76-003 through P-76-004

Page 1Official PDFNATIONAL TRANSPORTATION SAFETY BOARD WASHINGTON, D.C. Forwarded t o : Mr. O l i v e r Peden P r e s i d e n t Nebraska N a t u r a l Gas Company 340 E a s t M i l i t a r y Fremont, Nebraska 68025 i SAFETY P-76-3 and 4 R E C O M M E N D A T I O N ( S ) A t 9:30 a.m. on .January 10, 1976, t h e s i x - s t o r y P a t h f i n d e r Hotel i n Fremont, Nebraska, exploded and burned. Eighteen persons d i e d and 4 1 persons were h o s p i t a l i z e d ; the h o t e l was d e s t r o y e d and g l a s s was broken i n o t h e r b u i l d i n g s w i t h i n a one-block r a d i u s . The N a t i o n a l T r a n s p o r t a t i o n S a f e t y Board's i n v e s t i g a t i o n d i s c l o s e d t h a t a 2-inch p l a s t i c g a s main had p u l l e d o u t o f its compression c o u p l i n g a t t h e i n t e r s e c t i o n o f S i x t h and Broad S t r e e t s , about 1 5 f e e t from t h e northwest c o r n e r of t h e h o t e l basement. The p i p e had p u l l e d o u t of i t s 6-inch-long compression c o u p l i n g a f t e r t h e p i p e had c o n t r a c t e d i n l e n g t h 2 1 / 2 i n c h e s . N a t u r a l g a s , l e a k i n g from t h e p i p e a t 13-psig p r e s s u r e and capped above by f r o z e n e a r t h and t h e c o n c r e t e road s u r f a c e , seeped i n t o t h e h o t e l basement. The p l a s t i c main had been i n s t a l l e d on J u n e 26, 1974. The 348-foot- long segment was i n s e r t e d i n t o an e x i s t i n g 4-inch s t e e l main and a 5-inch- l o n g , steel i n t e r n a l s t i f f e n e r w a s used i n s i d e t h e p l a s t i c p i p e a t t h e compression c o u p l i n g s . From .June 26, 1974, when i t was i n s t a l l e d , t o January 10, 1976, when i t p u l l e d o u t of i t s c o u p l i n g , t h e p i p e could have 0 c o n t r a c t e d i n l e n g t h from 3 i n c h e s t o 9 1 / 2 i n c h e s , given a 25 F temperature d i f f e r e n t i a l . I n its i n s t a l l a t i o n handbook, t h e manufacturer o f t h e p l a s t i c p i p e s t a t e s : "Since i n s e r t e d p i p e i s n o t r e s t r i c t e d i n l i n e a r movement as i n d i r e c t b u r i a l , t h e e f f e c t of expansion and c o n t r a c t i o n (1 i n c h p e r L O O f e e t f o r 10°F change) must be c o n s i d e r e d when u s i n g compression-type f i t t i n g s . " The manufacturer f u r t h e r states: " I n r e l a t i v e l y s h o r t s e r v i c e r u n s (100 f e e t ) , p r o p e r l y t i g h t e n e d f i t t i n g s w i l l hold over a normal temperature range, however, i n l o n g e r runs p o s i t i v e t r a n s i t i o n f i t t i n g s may be r e q u i r e d t o p r e v e n t p u l l - o u t . "#

Page 2- 2 - The S a f e t y Board l e a r n e d t h a t a t 5 p.m., on t h e evening b e f o r e t h a c c i d e n t , Nebraska N a t u r a l Gas Company responded t o a g a s o d o r complai n e a r t h e h o t e l and d i s c o v e r e d a 2-inch p l a s t i c main t h a t had p u l l e d o f i t s compression coupling. Iwo days a l t e r t h e a c c i d e n t , w S i x t h and Park S t r e e t s t o s h u t o f f observed t h a t t h e 2-inch p l a s t i c p i p e had p u l l e d c o u p l i n g . I h e r e E o r e , t h e N a t i o n a l t h e Nebraska N a t u r a l Gas Company: T r a n s p o r t a t i o n S a f e t y Board r e c o 1. Review i t s e n t i r e system t o see i f p i p e h a s p u l l e d o of i t s c o u p l i n g elsewhere and t o r e c t i f hazardous c o n d i t i o n s found. (P-76-3) Followup) 2 . ConducL tests below t h e f r o s t l e v e l d u r i n g t h i s review of t h e system t o monitor a l l p l a s t i c p i p e j o i n t s made w i t h s h o r t compression c o u p l i n g s where p u l l o u t and r e s u l t a n t gas l e a k s could o c c u r . (P-76-4) (Class I, Urgent Followup) REED, Acting Chairman, McADAMS Members, concurred i n t h e above r e c By: Chairman NATIONAL TRANSPORIAIION SAFETY BOARD WASHINGTON D C 20594 OFFICIAL BUSINESS PENALIY FOR PRIVATE USE. 8300 NdTIONbL T#