NTSB Safety Recommendation P-98-027

NTSB safety recommendation P-98-027.

THE NTSB RECOMMENDS THAT THE TENNESSEE GAS PIPELINE COMPANY: REVIEW YOUR SUPERVISORY CONTROL & DATA ACQUISITION SYSTEM & MAKE THE MODIFICATIONS NECESSARY TO INCREASE THE LIKELIHOOD THAT ANY CRITICAL EVENT INVOLVING THE COMPANY'S PIPELINES IS QUICKLY & ACCURATELY REPORTED TO PIPELINE CONTROLLERS, ALLOWING THEM TO TAKE TIMELY ACTION TO CORRECT OR LIMIT THE EFFECTS OF ANY FAILURE IN THE PIPELINE SYSTEM.

Priority: CLASS II

Overall Status: Closed - Acceptable Action

Issued Date: 1998-10-16

Adopted Date: 1998-09-28

Overall Date Closed: 1999-04-21

Synopsis: ABOUT 4:50 A.M. CENTRAL DAYLIGHT TIME ON 10/23/96, IN TIGER PASS, LOUISIANA, THE CREW OF THE BEAN HORIZON CORPORATION (BEAN) DREDGE DAVE BLACKBURN DROPPED A STERN SPUD INTO THE BOTTOM OF THE CHANNEL IN PREPARATION FOR CONTINUED DREDGING OPERATIONS. THE SPUD STRUCK & RUPTURED A 12-INCH-DIAMETER SUBMERGED NATURAL GAS STEEL PIPELINE OWNED BY TENNESSEE GAS PIPELINE COMPANY (TENNESSEE GAS). THE PRESSURIZED (ABOUT 930 PSIG) NATURAL GAS RELEASED FROM THE PIPELINE ENVELOPED THE STERN OF THE DREDGE & AN ACCOMPANYING TUG, THE G.C. LINSMIER. WITHIN SECONDS OF REACHING THE SURFACE, THE NATURAL GAS IGNITED. THE RESULTING FIRE DESTROYED THE DREDGE & THE TUG. ALL 28 CREWMEMBERS FROM THE DREDGE & TUG ESCAPED INTO THE WATER OR ONTO NEARBY VESSELS.

Probable Cause: The National Transportation Safety Board determines that the probable cause of this accident was the failure of Tennessee Gas Pipeline Company to accurately locate the company’s pipeline across Tiger Pass before that location was dredged. Contributing to the accident was the revocation by the Research and Special Programs Administration of Federal requirements for all pipeline operators to install and maintain markers to identify the locations at which their pipelines cross navigable waterways.

Ntsbnumber: DCA97FP001

Report Number: PAR-98-01-SUM

Addressee Name: Tennessee Gas Pipeline Company

Addressee Status: Closed - Acceptable Action

Addressee Date Closed: 1999-04-21

Addressee Acronym: TGP

Addressee Organization Type: S-State Government

Communication Date: 1999-03-25

Communication Type: Official Correspondence

Communication Contents: Letter Mail Controlled 3/31/99 4:12:41 PM MC# 990338 TENNESSEE GAS PIPELINE HAS AN EXTENSIVE SUPERVISORY CONTROL AND DATA ACQUISITION SYSTEM (SCADA) IN PLACE WITH OVER 1,900 ELECTRONIC DATA POINTS. THE ELECTRONIC DATA POINTS ALLOW TENNESSEE GAS PIPELINE'S GAS CONTROL CENTER TO MONITOR PRESSURES AND FLOW RATES AND TO SET ALARMS AT CERTAIN FLOW OR PRESSURE CONDITIONS. ALSO, AN ARTIFICIAL INTELLIGENCE SYSTEM IS BEING DEVELOPED TO PROVIDE ALARMS FOR IMPROVED SYSTEM MONITORING BASED ON TRENDS AND TRANSIENT CONDITIONS. TENNESSEE'S SCADA SYSTEM IS CONSTANTLY BEING EXPANDED AND UPGRADED. IN 1998 WE ADDED 68 NEW ELECTRONIC DATA POINTS, INCLUDING THREE ON THE MAIN LATERAL THAT IS CONNECTED TO THE SUBJECT PIPELINE. NOT ONLY ARE WE ADDING DATA POINTS, WE ARE IMPROVING THE SCADA SYSTEM BY UPGRADING THE COMMUNICATIONS NETWORK AND CONVERTING TO A NEW COMMUNICATIONS FORMAT CALLED MODBUS PROTOCOL. BOTH OF THESE IMPROVEMENTS WORK TO REDUCE THE SCAN UPDATE TIMES AND ALLOW DATA TO BE SCANNED FASTER. THESE IMPROVED SCAN UPDATE TIMES WILL ALLOW FOR QUICKER DETECTION OF ABNORMAL CONDITIONS ON THE PIPELINE. TENNESSEE ALSO TAKES QUICK ACTION TO REPAIR ANY COMMUNICATIONS AND ELECTRONIC EQUIPMENT IN ORDER TO MAINTAIN A RELIABLE MONITORING SYSTEM. THIS DEMONSTRATES THAT WE ARE CONSTANTLY WORKING TO IMPROVE OUR CAPABILITIES TO QUICKLY AND ACCURATELY PROVIDE INFORMATION TO THE GAS CONTROLLERS SO THAT CRITICAL EVENTS CAN BE IDENTIFIED AND TIMELY ACTION CAN BE TAKEN TO CORRECT THE SITUATION.

Addressee Acronym: TGP

Addressee Organization Type: S-State Government

Communication Date: 1999-04-21

Communication Type: Official Correspondence

Communication Contents: THE SAFETY BOARD NOTES THAT TENNESSEE GAS PIPELINE HAS AN EXTENSIVE SUPERVISORY CONTROL AND DATA ACQUISITION SYSTEM (SCADA) IN PLACE WITH OVER 1,900 ELECTRONIC DATA POINTS AND THAT THE ELECTRONIC DATA POINTS ALLOW TENNESSEE GAS PIPELINE'S GAS CONTROL CENTER TO MONITOR PRESSURES AND FLOW RATES AND TO SET ALARMS AT CERTAIN FLOW OR PRESSURE CONDITIONS. THE BOARD ALSO UNDERSTANDS THAT TENNESSEE GAS PIPELINE'S SCADA SYSTEM IS CONSTANTLY BEING EXPANDED AND UPGRADED AND THAT 68 NEW ELECTRONIC DATA POINTS, INCLUDING 3 ON THE MAIN LATERAL THAT IS CONNECTED TO THE PIPELINE IN THIS ACCIDENT, WERE ADDED IN 1998. WE ARE PLEASED TO LEARN THAT BOTH IMPROVEMENTS WILL WORK TO REDUCE THE SCAN UPDATE TIMES AND ALLOW DATA TO BE SCANNED FASTER, WHICH WILL RESULT IN IMPROVED SCAN UPDATE TIMES THAT WILL ALLOW FOR QUICKER DETECTION OF ABNORMAL CONDITIONS ON THE PIPELINE. ADDITIONALLY, TENNESSEE GAS PIPELINE REPORTS THAT IT TAKES IMMEDIATE ACTION TO REPAIR ANY COMMUNICATIONS AND ELECTRONIC EQUIPMENT TO MAINTAIN A RELIABLE MONITORING SYSTEM. BECAUSE TENNESSEE GAS PIPELINE HAS TAKEN ACTION TO MAKE THE NEEDED CORRECTIONS AND MODIFICATIONS TO ITS SUPERVISORY CONTROL AND DATA ACQUISITION SYSTEM, P-98-27 HAS BEEN CLASSIFIED "CLOSED--ACCEPTABLE ACTION."