NTSB Safety Recommendation Letter P-78-050 through P-78-051

Page 1Official PDFNATIONAL TRANSPORTATION SAFETY BOARD WASHINGTON, D.C. Forwarded to: \ M r . L. D. Santman i Director \ SAFETY RELOMMENDATION(S) Materials TransDortation Bureau Department of Transportation P-78-50 and -51 Nashington, D. C. 20590 ------------_---“.___I___________________- A t 2 p.m., e.d.t., on May 1 7 , 1978, a Columbia Gas of Ohio, Inc., (gas company) construction crew, mistaking an 8-inch, low-pressure steel g a s main f o r an 8-inch, high-pressure steel gas main, d r i l l e d a small p i l o t b i t hole through t h e w a l l of t h e low-pressure gas main and began t o c u t i n t o the pipe w a l l with a large diameter b i t . The construction crew w a s making a “hot tap“ t o complete the f i n a l tie-in of an &-inch, replacement g a s main t o t h e e x i s t i n g high-pressure system on the north s i d e of Glessner S t r e e t i n Mansfield, Ohio. The hot t a p w a s t o b e made using a 3-way tapping tee which had i t s s i d e o u t l e t welded t o the 7, live,“ high-pressure replacement gas main and its bottom o u t l e t mistakenly welded t o t h e low-pressure gas main. When the 1-inch p i l o t b i t on t h e Williamson tapping machine attached t o t h e top o u t l e t of the tee penetrated t h e wall of t h e low-pressure gas main, gas a t 42 psig pressure from the high-pressure gas system entered t h e 14-inch water column (w.c.) (approx- imately 1 / 2 psig pressure), low-pressure g a s main and rapidly increased t h e pressure i n the low-pressure system i n a 4.8-square-mile area of Mansf i e l d . Shortly a f t e r 2 p-m., t h e Mansfield F i r e Department began receiving r e p o r t s of f i r e s caused by excessively high appliance flames on gas appliances. A r e s i d e n t who l i v e d near t h e construction s i t e ran t o t h e gas company crew and t o l d them t h a t t h e p i l o t l i g h t on her gas range had f l a r e d 2 f e e t and then had blown out. The gas company crew immediately s h u t off a nearby valve on the high-pressure gas system, which stopped t h e flow of gas from the high-pressure system t o the low-pressure system. A t 2:06 p.m., the gas company dispatcher received a report t h a t a l a r g e volume of gas w a s being vented from a building t h a t housed a d i s t r i c t regulator s t a t i o n , which w a s 3/4 mile from t h e construction site. The man dispatched t o the s t a t i o n reported t h a t t h e pressure had exceeded t h e low-pressure recording gauge which recorded pressures up t o 30 inches W.C. ( s l i g h t l y over 1 psig). An o i l seal pressure r e l i e f valve t h a t had been set f o r 32 inches W . C . a l s o had been overpressured 2414#

Page 2and w a s venting gas t o the atmosphere through its 4-inch vent pipe. Seven other o i l s e a l r e l i e f valves on d i s t r i c t regulators within the 4.8-square-mile area a l s o had been overpressured. By 2:20 p.m., a f t e r being overpressured f o r 20 minutes, the low- pressure d i s t r i b u t i o n system returned t o its normal pressure of 14 inches W . C . Gas was physically shut off at approximately 2,000 meters or services out of t h e 12,300 meters i n the 4.8-square-mile area. The shutoffs were made by firemen, police, gasmen, emergency response personnel, and residents. There were no f a t a l i t i e s o r i n j u r i e s requiring h o s p i t a l i z a t i o n because of t h i s accident. Property damage t o 16 houses resulted from the i g n i t i o n of nearby combustibles by high p i l o t flames; 5 of these houses were extensively damaged. On A p r i l 28, 1978, the gas company construction crew had abandoned and capped an old main a t its connection t o the 8-inch, high-pressure gas main on t h e north s i d e of Glessner Avenue, on the e a s t s i d e of Arthur S t r e e t . A t t h a t excavation there were two 8 5/8-inch outside diameter ( O . D . ) , coated, wrapped, and welded s t e e l gas mains, which were i d e n t i c a l i n appearance. The high-pressure gas main was 3 f e e t north of and about 1 0 inches higher than the low-pressure gas main. Before completing the f i n a l tie-in of the new replacement gas main t o the e x i s t i n g 8-inch, high-pressure gas main on the west s i d e of Arthur S t r e e t , the gas main a t l a s w a s consulted t o v e r i f y the locations of the two gas mains. The a t l a s showed the %inch, high-pressure and low-pressure mains traversing Arthur S t r e e t p a r a l l e l t o each other. The small-scale--1 inch t o 200 feet--gas main a t l a s did not i n d i c a t e the depths of the mains or t h e i r locations from the l o t l i n e , nor did it show the mains crossing each other. However, investigations a f t e r the accident showed t h a t the two mains crossed i n the Arthur S t r e e t i n t e r - section. I n the excavation f o r the f i n a l tie-in west of Arthur S t r e e t , approximately 75 f e e t from the f i r s t excavation, the mains appeared t o be i n the same r e l a t i v e position ( 3 f e e t a p a r t ) , but the north main w a s 4 inches lower than t h e south main, which made the tie-in more d i f f i c u l t . The construction crew welded an 8-inch, 3-way tapping tee t o the top of t h e north main, which they presumed was the high-pressure main, and welded the s i d e o u t l e t of the t e e t o the newly i n s t a l l e d high-pressure gas main. Next they pressure-tested the t e e and new main successfully and then f i l l e d them with gas a t 42 p s i g from the high-pressure system. This w a s done so that the pressure between the newly i n s t a l l e d main would be the same a s t h a t i n the main t o be tapped so the s t e e l chips from the pipe-tapping operation would not blow up i n t o the tapping and plugging apparatus and clog it.#

Page 3- 3 - The gas company procedure manual acknowledges t h a t it is important t o recognize that operating maps may not be correct. The gas company's procedure f o r "By-Passing and Stopping Gas Flow " recommends t h a t pressure gauges be i n s t a l l e d t o insure against l o s i n g pressure and customer outages. However, the tapping section of the procedure does not contain pressure gauge requirements and does not mention the p o s s i b i l i t y of overpressuring a low-pressure system. G a s company procedures f o r "Main Tie-Ins" state t h a t t h e s p e c i f i c tie-in plan, which includes the tapping operations, can be e i t h e r written o r o r a l . In t h i s accident, t h e workmen were t o follow an o r a l plan and d i d not consider t h a t t h e high- and low-pressure gas mains could cross each other i n Arthur S t r e e t between the two excavations. Consequently, a pressure gauge w a s not used t o determine which l i n e w a s the high- pressure gas main. After t h e accident the f i r s t excavation east of Arthur S t r e e t w a s re-opened and a pipe l o c a t o r w a s connected d i r e c t l y t o the high-pressure main. This main w a s touching another pipe i n Arthur S t r e e t and could not be traced e l e c t r o n i c a l l y . The two pipes were excavated where they were touching and were e l e c t r i c a l l y short-circuited; they were then separated. When traced with t h e pipe locator again, t h e high-pressure gas main w a s found to have crossed the low-pressure gas main with two 45" elbows i n t h e Arthur Street i n t e r s e c t i o n . The gas company records d i d not contain f i e l d measurements of where these l i n e s crossed and, consequently, the gas main atlases d i d not show this crossing. T i t l e 49 CFR 192.627 requires t h a t "Each tap made on a pipeline under pressure must be performed by a crew qualified t o make hot taps." The 1976 ASME Guide covering this Federal code suggests t h a t : "When t h e pipeline i s exposed, it should be thoroughly examined t o (a) v e r i f y the i d e n t i t y of t h e pipeline t o b e tapped by location, size, kind, type of coating, etc." In t h i s accident, t h e crew w a s qualified t o make hot taps, but i t w a s d i f f i c u l t t o i d e n t i f y the correct pipeline because the two l i n e s were i d e n t i c a l . However, t h e Safety Board concludes t h a t because of the s i m i l a r i t y of t h e two gas mains, a pressure gauge tap should have been made t o determine t h e exact location of t h e high-pressure main. I f the construction crew had not immediately shut off the valve on the high- pressure gas main, and if the low-pressure system had not had the eight o i l seal relief valves t o relieve the high pressure, a catastrophic accident could have occurred. The National Transportation Safety Board investigated and issued s a f e t y recommendations (P-74-24 and -25) on a similar accident i n Greenwich, Connecticut, on May 25, 1977. In t h a t accident, a gas company crew tapped a 3-inch casing pipe thinking it w a s t h e gas main, and severed the 2-inch gas main i n s i d e causing a massive gas escape.#

Page 4- 4 - I The leaking gas entered a building where it exploded and then burned, destroying three buildings, damaging one building, and injuring 10 persons. A s i n t h i s accident, the gas company crew did not have accurate gas main a t l a s e s , and they did not p o s i t i v e l y i d e n t i f y the type, s i z e , and pressure of the gas main t o b e worked on. Therefore, the National Transportation Safety Board recommends t h a t the Materials Transportation Bureau of the U.S. Department of Transportation: Revise 49 CFR 192 t o require t h a t gas company system maps and records be maintained accurately t o i d e n t i f y the location, s i z e , and operating pressure of a l l of t h e i r pipelines. (Class 111, Longer Term Action) (P-78-50) Revise 49 CFR 192 t o require t h a t gas system operators v e r i f y through pressure monitoring o r other means the i d e n t i t y of a l l pipelines before performing hot taps. (Class 111, Longer Term Act ion) (P- 78- 5 1) i n K I N G , Chairman, McADAMS, HOGUE, the above recommendations. and DRIVER, Members, concurred hairman#