What was found
DURING CLIMBOUT FROM DTW, THE ALTITUDE WARNING HORN ACTIVATED AT 23,500 MSL. THE CREW INITIATED A DESCENT AND COMPLIED WITH EMERGENCY, AND COM CHECKLISTS. RETURNED TO POINT OF ORIGIN (DTW). REMOVED AND REPLACED THE RIGHT SAFETY VALVE, OPERATIONAL CHECK NOT REQUIRED DUE TO PART IS AN OVERHAULED PART.