NTSB Safety Recommendation Letter P-78-034 through P-78-037

Page 1Official PDFNATIONAL TRANSPORTATION SAFETY BOARD WASHINGTON, D.C. M r . G. H. Lawrence President American Gas Association 1515 Wilson Boulevard Arlington, Virginia 22209 SAFETY RECOMMENOAT l O N ( S ) P-78-34 through -37 A t 12:50 a . m . , c . s . t . , on December 15, 1977, a 2-inch p l a s t i c gas main under an a l l e y i n downtown Lawrence, Kansas, pulled out of a compression coupling which joined it t o a steel gas main. Natural gas escaped from t h e main and migrated through the stone foundation w a l l s of two nearby buildings. A t 1:20 a.m., t h e accumulations of gas i n t h e two buildings ignited. The r e s u l t i n g explosion and f i r e destroyed one building, severely damaged the other building, and broke nearby windows. Two persons were k i l l e d and t h r e e persons were injured. I.-/ The 394-foot-long polyethylene p l a s t i c gas main had been i n s e r t e d i n an abandoned 3-inch s t e e l main on June 2, 1975, without being designed o r anchored against pullout. The Safety Board's test on t h i s ,joint indicated t h a t t h e r e w a s an approximate one-third reduction i n t h e p u l l o u t r e s i s t a n c e of the j o i n t a f t e r i t had been i n s t a l l e d f o r 2 112 years. Marks on t h e end of t h e p l a s t i c pipe indicated t h a t it had moved within t h e standard compression coupling by thermal contraction over t h r e e winters. This accident was almost a "carbon copy" of t h e f a i l u r e t h a t occurred i n Fremont, Nebraska, on January 10, 1976. 21 That f a i l u r e indicated t h a t another brand of standard compression coupling with a similar smooth m e t a l s t i f f e n e r used i n s i d e t h e p l a s t i c pipe a l s o weakened w i t h time and pipe movement a l s o had taken place over two winters. - 11 For more d e t a i l e d information read "Pipeline Accident Report -- Kansas Public Service Company, Inc., Explosion and F i r e , Lawrence, Kansas, December 15, 1977," (NTSB-PAR-78-4). - 21 "Pipeline Accident Report -- Nebraska Natural Gas Company, Pathfinder Hotel Explosion and F i r e , Fremont, Nebraska, January 10, 1976," (NTSB-PAR-76-6). 2386#

Page 2- 2 - The Safety Board is concerned that there may be more unanchored plastic pipe insertions moving within their standard compression couplings which may ultimately fail if additional testing is not undertaken to determine which joints are safe. The Safety Board considers this a major safety problem that needs attention. Therefore, the National Transportation Safety Board recommends that the American Gas Association: Conduct tests to determine the effect of time on the pullout resistance of standard compression couplings and polyethylene plastic pipe. (Class 111, Longer Term Action)(P-78-34) Conduct tests on the more common types of mechanical joints used on plastic pipe. Publish the results of these tests to member companies along with the recommendations of the manufacturers regarding whether the joint should be used for gastightness only or also for pullout resistance. (Class 111, Longer Term Action)(P-78-35) Conduct tests on the more common internal stiffeners used to reinforce plastic pipe. Determine what style of compression coupling is compatible with each stiffener. (Class 111, Longer Term Action) (P-78-36) Determine the effect of polymer aging, outdoor exposure, and stacking of coiled plastic pipe on its ultimate use. Specify to the natural gas industry what tests should be conducted on the pipe to prove its integrity if excessive storage is found to be detrimental. (Class 111, Longer Term Action)(P-78-37) KING, Chairman, McAIlAMS, HOGUE, and DRIVER, Members, concurred in the above recommendations.#