What was found
DEN - PILOT REPORTED CABIN PRESSURE SAFETY VALVE OPEN ABOVE 37,000 FEET IN CRUISE. MANUAL PRESSURE MODE OPERATED NORMALLY PER (ECAM) ELECTRONIC CENTRALIZED AIRCRAFT MONITORING. EXCESSIVE CABIN DELTA P CAUSED ECAM. DESCENDED TO 36,000 FT AND ENGAGED AUTO PRESSURE MODE. BOTH AUTO PRESSURE SYSTEMS FAILED TO MAINTAIN NORMAL DELTA P AND CABIN ALTITUDE. MAINTENANCE REMOVED AND REPLACED THE NR 1 SAFETY VALVE AND PERFORMED OPERATIONAL CHECK, REFERENCE AMM 21-31-52 PB 401 AND AMM 21-31-00-710-006. MAINTENANCE ALSO PERFORMED OPERATIONAL TEST OF THE PRESSURE CONTROL AND MONITORING, REFERENCE AMM 21-31-00-710-002.