NTSB Safety Recommendation P-70-030

NTSB safety recommendation P-70-030.

THE NTSB RECOMMENDS THAT THE OFFICE OF PIPELINE SAFETY OF THE DEPARTMENT OF TRANSPORTATION TAKE THE FOLLOWING ACTIONS: AS A PART OF ITS ENFORCEMENT ACTIVITY, STUDY THE REGULATOR DESIGN, MAINTENANCE, AND TESTING PROCEDURES OF THE UTILITIES UNDER ITS DIRECT JURISDICTION, INCLUDING MUNICIPAL OPERATIONS NOT REGULATED BY STATES, TO DETERMINE WHETHER GAS CONSUMERS WILL BE PROPERLY PROTCTED AGAINST OVERPRESSURIZATION IN THE EVENT OF A MALFUNCTION OF A PRIMARY REGULATOR. THIS WOULD INCLUDE SAMPLING OBSERVATIONS TO DETERMINE WHETHER REGULATORS ARE ADJUSTED PROPERLY, MAINTAINED, AND TESTED ON A REGULAR BASIS SO THAT THEY WILL FUNCTION CORRECTLY, AND WHETHER THE CONTROL LINE IS PROTECTED FROM DAMAGE.

Priority: CLASS II

Overall Status: Closed - Acceptable Action

Issued Date: 1970-10-14

Adopted Date: 1970-10-14

Overall Date Closed: 1976-07-20

Synopsis: ON NOVEMBER 6, 1969, DURING A HIGHWAY CONSTRUCTION PROJECT IN BURLINGTON, IOWA, A BULLDOZER WEIGHING 70,000 POUNDS DROVE OVER AND PARTIALLY COLLAPSED THE STEEL COVERS OF A GAS REGULATOR PIT, DAMAGING THE REGULATOR. WHILE THE PRESSURE WAS PARTIALLY CONTROLLED BY A MONITORING OR SAFETY REGULATOR, GAS, REPORTEDLY AT FOUR TO FIVE TIMES THE NORMAL OPERATING PRESSURE, ENTERED THE DISTRIBUTION SYSTEM. GAS CUSTOMERS IN THE AFFECTED AREA STARTED REPORTING HIGH GAS PILOTS AND FIRES TO ISU AND THE FIRE DEPARTMENT. THE HIGH-PRESSURE GAS SOURCE WAS TURNED OFF BUT FIRES CONTINUED TO BE REPORTED, THE FIRES WROUGHT MAJOR DAMAGE TO THE INTERIORS OF 10 HOUSES AND MINOR DAMAGE TO KITCHENS AND APPLIANCES IN 42 OTHERS. PROPERTY DAMAGE WAS ESTIMATED AT $80,000.

Probable Cause: The probable cause of the fires in the houses was the continued overpressure condition of the low-pressure distributions system for an extended period of time, which allowed pressure to build up until high gas flames ignited nearby objects. The initiation of the overpressure was caused by a bulldozer which damaged the largest primary working regulator which, with other regulators, controlled the gas pressure entering the low-pressure systems; and by inadequate performance of the monitoring regulator which failed to operate to limit the gas pressure to a safe level.

Ntsbnumber: DCA70MP001

Report Number: PAR-70-01

Addressee Name: RSPA

Addressee Status: Closed - Acceptable Action

Addressee Date Closed: 1976-07-20