NTSB Safety Recommendation P-70-017

NTSB safety recommendation P-70-017.

THE NTSB RECOMMENDS THAT THE NORTHERN INDIANA PUBLIC SERVICE COMPANY TAKE THE FOLLOWING ACTION: INSTALL RELIEF DEVICES ON ALL ITS LOW-PRESSURE DISTRIBUTION SYSTEMS WHICH COULD BE OVER-PRESSURED BY INTERCONNECTED HIGH-PRESSURE GAS. IF RELIEF DEVICES WOULD PRESENT A HAZARD, AN AUTOMATIC SHUTOFF DEVICE SHOULD BE INSTALLED AT EACH UNPROTECTED SOURCE OF HIGH PRESSURE GAS. IT IS NOT INTENDED THAT THIS RECOMMENDATION APPLY TO HIGH-PRESSURE GAS CONNECTED TO A LOW-PRESSURE SYSEM BY MEANS OF A REGULARTOR STATION PROVIDED WITH A SUITABLE DEVICE TO PREVENT ACCIDENTAL OVERPRESSURING.

Priority: CLASS II

Overall Status: Closed--No Longer Applicable

Issued Date: 1969-12-04

Adopted Date: 1969-12-04

Overall Date Closed: 1976-09-10

Synopsis: ON JUNE 3, 1969, A SERIES OF EXPLOSIONS AND FIRES OCCURRED IN THE NATURAL GAS DISTRIBUTION SYSTEM IN THE WESTERN HALF OF THE GLEN PARK RESIDENTIAL SUBDIVISION OF GARY, INDIANA. THERE WERE NO FATALITIES, BUT NINE RESIDENTS AND FIVE FIREMEN WERE INJURED. SEVEN HOUSES WERE DESTROYED, AND 45 OTHERS INCURRED DAMAGE EXTENDING FROM MINOR TO VIRTUAL DESTRUCTION. TOTAL PROPERTY DAMAGE WAS ABOUT $350,000.

Probable Cause: The Board finds that the probable cause of this accident was a combination of personnel error and system inadequacy. Involved were the inadvertent opening of a separation valve by a gas company employee allowing gas at 20 p.s.i.g. to flow into a 1/4 p.s,i,g. system and a system which could not control adequately such an increase in pressure owing to the lack of overpressure protection devices. Thereafter, the increase in pressure caused the failure of a regulator diaphragm which allowed an 80-fold overpressure in the low-pressure system to become continuous for 30 - 45 minutes. Significant contributing causal factors were: 1. The inaccessibility of the shutoff valve for the regulator which failed. 2. The lack of systematic review of the hazards in the conversion operation which could have revealed the hazardous condition in which one human error could produce catastrophe, coupled with the lack of a written plan for conversion. 3. The absence in Code B31.8 of any specification of safeguards to be employed at separation (isolation) valves during pressure conversions. 4. The lack of complete leakage surveys, before and during the pressure increase in the eastern area, which would have probably disclosed and leaking condition of the pipe and avoided the major leaks which occurred on June 3, 1969.

Ntsbnumber: DCA69FP004

Report Number: PAR-UNNUMBERED

Addressee Name: Northern Indiana Public Service Company

Addressee Status: Closed--No Longer Applicable

Addressee Date Closed: 1976-09-10

Addressee Acronym: NIPSCO

Addressee Organization Type: P-Private Industry

Communication Date: 1970-05-04

Communication Type: Official Correspondence

Communication Contents: LETTER FROM SCHROER, EICHHORN AND MORROW, ATTORNEYS FOR NIPSCO: IN CERTAIN SITUATIONS OR LOCATIONS, STRICT COMPLIANCE WITH THIS RECOMMENDATION WOULD BE EXTREMELY DIFFICULT.