Inspections are a Worksafe requirement where a pressure vessel must be tested and deemed safe for continued operation by a Qualified inspector.
Testing must be carried out as follows

External: required every two (2) years from the date of commissioning.

Internal: required every four (4) years from the date of commissioning.

External inspection scope of work: 

Clean the vessel, record all data information, check all welds/fittings for leaks, operational check of the safety relief valve and pressure gauge, check the auto drain and whether the vessel is bolted down. Record DNT measurements and issue compliance certificate to AS3788-2006.

Internal Inspection scope of work: 

Includes the above External Inspection with addition of isolating and de-pressurising the vessel, removal and replacement or test/certification of the safety relief valve. Access the vessel internally and view internal condition and welds, clean the vessel if necessary and replacement of all gaskets/fittings used to access the vessel. Start the compressor and record operating pressures.  
Contact us to organise an inspection on your air receivers.