A B767-300 PRESSURE DOME ENGINEERING CHANGE ORDER WAS ACCOMPLISHED INCORRECTLY. THE WRONG WASHERS WERE INCLUDED IN THE ACCOMPLISHMENT KIT AND WERE INSTALLED

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MAINT TECHNICIAN AND I COMPLETED THE TASK OF PRESSURE DOME BOLT; NUT; AND WASHER REPLACEMENT. I NOW REALIZE THAT WE INSTALLED THE WRONG WASHERS (FLAT WASHERS) UNDER THE HEAD OF THE BOLTS INSTEAD OF THE CONICAL WASHER THAT SHOULD HAVE BEEN INSTALLED. I REALIZED THIS MISTAKE AFTER BEING ASSIGNED THE SAME TASK ON ACFT. CALLBACK CONVERSATION WITH THE RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE WRONG WASHERS WERE INSTALLED IN THE PRESSURE DOME AT EVERY HOLE BETWEEN THE STRINGERS ON THE UNPRESSURIZED SIDE. THE RPTR SAID; 'THIS WAS THE FIRST TIME MY PARTNER AND I WORKED THIS ENGINEERING CHANGE ORDER.' THE RPTR STATED THE KIT OF PARTS LOOKED OK BUT FAILED TO NOTICE THE WASHERS WERE FLAT NOT CONICAL AS REQUIRED. THE RPTR SAID THE JOB WAS COMPLETED AND INSPECTED. THE RPTR SAID THE AIRPLANE WAS RELEASED FOR SVC. THE RPTR STATED THE NEXT NIGHT WE WERE ASSIGNED TO ANOTHER AIRPLANE TO WORK THE PRESSURE DOME AND THE ERROR WAS DISCOVERED. THE RPTR SAID ENGINEERING WAS ALERTED AND THE AIRPLANE WAS SET UP TO RETURN AND HAVE THE CONICAL WASHERS INSTALLED.