B737-800
Maintenance Airframe; Maintenance Powerplant
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Manuals; Company Policy; Aircraft; Procedure
Aft drain mast was removed in ZZZ. Was reinspecting tape and realized no blanking plate had been installed. Tape was blown out from inside. Contacted engineering was told the blanking plate was not required because drain mast was going to reinstalled so that step from amm is not necessary. I do not believe that is the proper interpretation of the AMM.
Technician reported that proper procedure was not followed when a drain mast was repaired.