EE HAD CARRIED APPROX 35 LB OF TOOLS AND EQUIPMENT UP SEVERAL FLIGHTS OF STAIRS TO WORK ON THE KILN EXIT ANALYZER. WHEN HE CAME IN FOR LUNCH HE REPORTED HIS BACK HURT BUT DID NOT REPORT IT AS WORK RELATED. THE EE HAD SURGERY SEVERAL DAYS LATER FOR A RUPTURED DISK. HE REPORTED THE INCIDENT AS WORK REALTED ON 5-9-01.