NTSB Safety Recommendation P-77-031

NTSB safety recommendation P-77-031.

INVESTIGATE MORE DEPENDABLE ITEMS OF CONTROL EQUIPMENT AND REPLACE EXISTING SOLENOID AND 4-WAY VALVES AT FIRE GATE VALVES WITH THIS EQUIPMENT.

Priority: CLASS II

Overall Status: Closed - Acceptable Action

Issued Date: 1977-10-31

Adopted Date: 1977-10-13

Overall Date Closed: 1979-01-05

Synopsis: ON DECEMBER 7, 1976, A NATURAL GAS COMPRESSOR FAILED AND THEN EXPLODED AND BURNED AT AN EXXON GAS SYSTEM, INC., STATION NEAR ROBSTOWN, TEXAS. AN EMERGENCY SHUTDOWN SYSTEM WAS ACTIVATED, BUT FOUR AUTOMATED FIRE GATE VALVES DID NOT CLOSE. ANOTHER EMERGENCY CONTROL SYSTEM ALSO FAILED TO AUTOMATICALLY CLOSE THE SHUTOFF VALVES, LEADING TO TWO OF THE FIVE COMPRESSORS IN THE STATION. A SECOND EXPLOSION OCCURRED WITHIN THE BURNING BUILDING. THE FIRE KILLED ONE PERSON, INJURED TWO PERSONS, AND DESTROYED THREE ENGINE-DRIVEN COMPRESSORS AND THE COMPRESSOR BUILDING.

Ntsbnumber: DCA77MP005

Report Number: PAR-77-03

Addressee Name: ExxonMobil Corporation

Addressee Status: Closed--No Longer Applicable

Addressee Date Closed: 1979-01-05

Addressee Organization Type: P-Private Industry

Communication Date: 1977-12-20

Communication Type: Official Correspondence

Communication Contents: EXXON GAS SYSTEM LTR: THE STATION 1 EMERGENCY SHUTDOWN SYSTEM HAS BEEN REDESIGNED IN 2 PHASES: (1) IMPROVED SOLENOID TO ELIMINATE ONE INTERMEDIATE DEVICE STILL HAS 4-WAY VALVES; IMPROVED BY NEW LUBRICATION SYSTEM AND PERIODIC TESTING AND INSPECTION; AND (2) HIGH PRESSURE, HIGH VOLUME SOLENOID VALVE TO ELIMINATE 4-WAY VALVES. NUMBER 2 IS PREFERABLE BUT UNTESTED. TESTS ON THIS SYSTEM WILL BEGIN WITH DELIVERY OF UNITS IN MID-JANUARY 1978. 5/12/78 - EXXON RESPONSE TO NTSB LETTER OF 4-27-78: EXXON TESTING HAS CONFIRMED THE USE OF THE HIGH PRESSURE, HIGH VOLUME SOLENOID VALVE TO ELIMINATE THE 4-WAY VALVE AS A NECESSARY COMPONENT IN THE PRIMARY EMERGENCY SHUTDOWN SYSTEM. THE STATION 1 SYSTEM USING THIS NEWLY DEVELOPED SOLENOID VALVE HAS BEEN OPERATIONAL SINCE MARCH 20, 1978. BASED ON THE SATISFACTORY EXPERIENCE, STATIONS 2,3,4,6,6A, AND 7A HAVE BEEN SCHEDULED FOR CONVERSION WORK TO BE COMPLETED BEFORE END OF 1978. THE EMERGENCY SHUTDOWN SYSTEMS AT STATIONS 5,7, AND 8 UTILIZE HYDRAULICALLY ACTUATED FIRE GATE VALVES WHICH ARE CONSIDERABLY DIFFERENT IN DESIGN. EXXON IS REVIEWING CONTROL SYSTEM DESIGN IMPROVEMENTS WITH VALVE MANUFACTURER AND ESTIMATES THAT CHANGES CONSISTENT WITH RECOMMENDATION P-77-31 WILL BE IMPLEMENTED BY LATE DECEMBER 1978. 7/31/78 - EXXON LETTER: STATIONS 1,2,3,4,6,6A AND 7A HAVE BEEN SCHEDULED FOR CORRECTION AS PER LETTER OF 5-12-78. STATIONS 5,7 AND 8 HAVE BEEN INVESTIGATED AND IT WAS FOUND A PILOT VALVE AND 3 POSITION GAS OPERATED VALVE CAN BE ELIMINATED BY USING AN ELECTRICALLY ACTIVATED SOLENOID VALVE IN THE FIRE GATE VALVE CONTROL SYSTEM. IT WAS ALSO FOUND THAT THE MANUALAUXILARY PUMP ON THE HYDRAULIC SYSTEM SHOULD BE AUTOMATED. BY THESE MODIFICATIONS, THE RELIABLITY OF THE EMERGENCY SHUT-DOWN SYSTEMS ON STATIONS 5,7 AND 8 WILL BE ENHANCED CONSISTANT WITH THE RECOMMENDATION. THESE MODIFICATIONS ARE SCHEDULED FOR YEAR END 1978.

Addressee Organization Type: P-Private Industry

Communication Date: 1979-01-05

Communication Type: Official Correspondence