Definition
Saver Sub — A saver sub is a short, sacrificial threaded sub installed between the kelly or top drive and the drill string that absorbs the make-up and break-out wear of repeated connections, protecting the expensive threads above it.
Also known as: saver sub, kelly saver sub, top drive saver sub
What a saver sub is
A saver sub is a short sub run at the very top of the drill string, between the kelly (or top drive) and the first joint of drill pipe. Every stand added or removed makes up and breaks out a connection at this point, so the threads wear quickly. The saver sub takes that wear instead of the kelly or top-drive shaft, which are far more costly to replace.
When the saver sub’s threads wear, it is simply replaced or recut — a cheap consumable protecting an expensive drive component.
Key points
- Sacrificial — designed to be worn out and replaced periodically.
- Connection matching — bridges the top-drive/kelly connection to the drill pipe connection.
- Kelly cock housing — a lower kelly cock is often fitted just above the saver sub.
Renting saver subs
Saver subs are inexpensive protection for high-value drive equipment and are commonly rented as part of a kelly or top-drive package. Explore kelly equipment and BHA components or contact us for the right saver sub connections.