The problem comes down to the distinction between a datetime (which represents a particular point in time) and a number which represents a duration. You certainly can treat a number as a duration and you can format it so that it displays in HH:MM:SS format with a bit of trickery. Essentially for display formatting you need Tableau to think it represents that duration after the start of it's time system.
Essentially you want to express the cycle time as a number expressed in fractional days, and then set a custom number format as hh:mm:ss.
Depending on your data source and how are the cycle times are represented there that may require some calculated fields. If you can post a small sample workbook I'll show you what you need to do.