Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
MEL; Human Factors; Manuals; Procedure
While troubleshooting [an Airbus 320] Yellow [Hydraulic] System accumulator [deferral]; it was found to be not accomplished properly. I then began to test the system per AMM 29-13-42 and at approximately 1;820 PSI; as I was looking at the pressure gauge; something in the system let loose and sprayed me in the face and side. I was able to get out of the area without any damage but could have been much worse. What we ended up finding out; not only was the accumulator damaged due to not doing the MEL procedure properly; it caused damage to the yellow system reservoir; yellow system pump; and check valve.
I was assigned to troubleshoot an aircraft's Yellow Hydraulic System deferral to determine if we needed an accumulator. Since this was MEL item we checked to see if it was complied with. It was not complied with. We proceeded to troubleshoot yellow system and charged yellow accumulator to see if it would hold pressure; while charging to target 1;850 PSI at 1;820 PSI the safety valve let loose approximately 2 gallons skydrol while fellow Mechanic was in the charging bay; he was doused with skydrol as a result. It was clear that the accumulator internal bladder had been previously ruptured resulting in 0 pressure; further troubleshooting resulted in finding the yellow system reservoir had been over serviced; we attempted to relieve head pressure air and approximately 0.5 gallons of skydrol was blowing out of reservoir air pressure vent valve. At this point it was clear that the bladder on the yellow reservoir was also ruptured due to skydrol in the reservoir air system. We informed Management of our findings and removed the yellow system reservoir and that concluded our shift.
The reference A320 Minimum Equipment List procedure called for the high pressure pneumatic line to be disconnected from the reservoir to prevent pressure from acting upon the system.  The technicians reported that this line was found to be connected; which may have caused additional damage.