They will have to repeat the feat when they visit Thomond Park on Saturday if they are to take their place in the Kingspan Stadium Final on May 30.
But Tandy is confident his ever-improving crop of young Ospreys can maintain their charge for a record fifth PRO12 crown.
"It's always good to have those sorts of rivalries," he said. "It's two good clubs going head to head and I think it brings out something extra from the spectators and the players.
"There is definitely an edge around the game and we are excited to go to Thomond Park on Saturday.
"It is an advantage to have that home semi-final and Munster can strangle teams, in fairness to them. They are a pretty well-rounded team, there is a good balance to their tight play as well as their width - they are definitely a well-coached team.
"The young group that we have got have come through and been through some lows this season but there have been plenty of highs around it.
"They have experienced different things, the training weeks are getting better and they are gaining more experience."
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