Declare @Temp Table(Field VarChar(20))
Insert Into @Temp Values('2013-12-06 01:30:40')
Insert Into @Temp Values('02:00:20')
Insert Into @Temp Values('Fast')
Select Sum(DateDiff(Second, 0, Case When IsDate(Field) = 1 Then Convert(DateTime, Field) - Convert(Int, Convert(DateTime, Field)) End) % 86400 / 60.0)
From @Temp