Adding HH:MM:SS not working

Hi,
I have a column with hours in the following format HH:MM:SS, that looks like this:

12:16:00
1:35:00
1:35:00
12:47:00
12:46:00
12:51:00
4:33:00
4:05:00
12:54:00
3:19:00
3:19:00


I am trying to add the sum total of all hours, but its not working.
I have my column formatted as time -> 37:30:55

Any suggestions?
Thanks.