The cobalt case against Victorian trainers Mark Kavanagh and Danny O'Brien could drag on into this year's spring carnival.

The Victorian Civil and Administrative Tribunal has provisionally set August 1 for the start of their appeal for administering cobalt to affect the performance of a horse in a race.

One of the trainers' arguments is that the labs which conducted the cobalt tests were not accredited at the time, although VCAT on Monday heard Racing Victoria disagrees.

O'Brien was disqualified for four years by the Racing Appeals and Disciplinary Board after four horses returned high cobalt readings and Kavanagh was banned for three years over one horse's cobalt level, also recorded during the 2014 spring carnival.

The Kavanagh and O'Brien appeal is expected to go for 10-15 days, with an initial nine-day hearing likely from August 1.