Find sum of Datagridview Time column in c#

Question

I have a Time column in datagridview,which value is something like this:

 

1:29:48

1:48:45

 

I have multiple value in this column ,not just two value ,and i am trying to add Time by separating hour,minutes and second

and I am getting value is 18:77:93

 

It should be 3:18:33 ,how i can achieve this.Plz Suggest me something..