NTSB Safety Recommendation P-70-021

NTSB safety recommendation P-70-021.

THE NTSB RECOMMENDS THAT THE UNITED STATES OF AMERICA STANDARDS INSTITUTE B31.8 COMMITTEE TAKE THE FOLLOWING ACTION: INCLUDE IN ITS STANDARDS A REQUIREMENT PROVIDING THAT EXISTING REGULATOR STATIONS BE UPGRADED TO COMPLY WITH THE STANDARDS FOR NEWLY CONSTRUCTED REGULATOR STATIONS.

Priority: CLASS II

Overall Status: Closed - Acceptable Action

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: American Society of Mechanical Engineers

Addressee Status: Closed--No Longer Applicable

Addressee Date Closed: 1976-09-10

Addressee Acronym: ASME

Addressee Organization Type: A-Associations

Communication Date: 1970-06-26

Communication Type: Official Correspondence

Communication Contents: LETTER FROM THE CHAIRMAN OF THE COMMITTEE: THE COMMITTEE ACKNOWLEDGES THAT THE RECOMMENDATION IS PERTINENT BUT ONLY INDICATES THAT TO COMPLETELY REBUILD REGULATOR STATIONS BASED ON CURRENT CODE REQUIREMENTS IS UNJUSTIFIED. 9/15/70 - THE FOLLOWING PROPOSAL WAS PROPOSED TO BE INCLUDED IN THE CODE: EVERY EXISTING LOW PRESSURE DISTRIBUTION SYSTEM CONNECTED TO A GAS SOURCE WHERE THE FAILURE OF PRESSURE CONTROL MIGHT RESULT IN A PRESSURE WHICH WOULD EXCEED THE MAXIMUM ALLOWABLE OPERATING PRESSURE OF THE SYSTEM SHALL BE EQUIPPED WITH SUITABLE PRESSURE RELIEVING OR PRESSURE LIMITING DEVICES WHICH WILL CONTROL THE PRESSURE TO THE MAXIMUM ALLOWABLE OPERATING PRESSURE OF THE SYSTEM. 3/73 - THE SECOND EDITION OF THE ASME GUIDE FOR GAS PIPING SYSTEMS WAS PUBLISHED AND INCLUDED THE RECOMMENDED CHANGE. CORRESPONDENCE DOCUMENTATION INCOMPLETE.