B757-200
Maintenance Powerplant; Maintenance Airframe
Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Aircraft; Airport; Human Factors; Manuals
I had to replace the Crew Oxygen (O2) bottle on a B757-200 aircraft.  Maintenance Manual (MM) 12-15-08 requires the airplane to be 'grounded correctly' per MM 20-41-00.  MM 20-41-00 states 'the airplane must be statically grounded to a common; approved; identified ground.' The [static] grounds at the ZZZ Maintenance Hangar are clearly marked and dated.  However; the grounds at company terminal are devoid of markings. This leads one to question the validity of these grounds for aircraft maintenance.  Facility Maintenance tested a sole ground on Gate X (where the B757 resided); using the values found in the Servicing Manual. After it was determined this ground was indeed 'approved;' the O2 bottle was replaced. There isn't a uniform marking system for the aircraft grounds at ZZZ Hangar and terminal areas. [Recommend] the Terminal grounding points on all gates be inspected for [static] resistance then marked as 'approved' grounds.
A Line Mechanic reports about the lack of a uniform marking system for aircraft static grounds at their company terminal gates.  The Aircraft Maintenance Manual (AMM) required the static 'grounding' of a B757-200 aircraft prior to removing and replacing the Crew Oxygen (O2) bottle.