Power Plant Computer Reliability Survey

DURING THE PERIOD FROM JANUARY 1, 1975 TO JULY 1, 1977 FILURE DATA WAS COLLECTED ON FORTY-THREE (43) POWER PLANT COMPUTER SYSTEMS WITH A TOTAL OF OVER SEVENTY (70) YEARS OF OPERATING HISTORY. FINDINGS WERE: COMPUTERS WHICH ARE WELL MAINTAINED HAVE AVAILABILITY OF OVER 99.5 PERCENT. NINETY-NINE PERCENT PLUS IS A REASONABLE TARGET FOR SINGLE COMPUTER INSTALLATION IN OVERALL PLANNING. FAILURES OF BULK MEMORY HAVE A HIGH MTTR, DUE MAINLY TO THE LACK OF REPLACEMENT PARTS AT THE SITE. THERE IS A SIGNIFICANT NUMBER OF COMPUTERS THAT STOP FREQUENTLY AND ARE RESTARTED WITH NO ATTEMPT TO SOLVE THE PROBLEM. THESE MACHINES REDUCE THE MEAN TIME BETWEEN FAILURES FROM AN ATTAINABLE THIRTY (30) DAYS TO AN AVERAGE FOR THE SURVEY OF TEN (10) DAYS.