What precautions need to be taken when replacing a non-biodegradable oil by a biodegradable oil?

A biodegradable oil may be selected for a number of reasons: increased respect for the environment, desire to meet the criteria for a particular environmental label, standard (e.g.: ISO 14001) or regulation.  In order to meet the requirements of the ISO 15380 standard and be considered biodegradable, no more than 2% of an oil should be non-biodegradable.  In order to ensure that this very low threshold is not exceeded, the facility has to be systematically flushed when switching over to a biodegradable lubricant. 
The procedure used should remove as much of the old lubricant as possible, depending on the type of equipment in question: gearbox, with or without oil circulation, hydraulic circuit, compressor, etc.

Furthermore, most biodegradable oils are formulated from esters. Although esters are generally compatible with mineral oils and PAO-based synthetic oils, their solvency properties limit their compatibility with elastomers. Depending on which product is selected, its compatibility with the equipment's seals and paintwork should therefore be validated with the manufacturer.