I remember the "good old days" when non-mag collars really were made
of the material Monel and make up torque was 80% of an equivalent
My opinion is that todays Non-Mag connections are of Stainless
Steels with modified chemistry and in many ways their physical
properties are superior to the AISI4140 bar stock.
Hence the connections should be made up to the same torque as that
stated in API RP7G for the connection.
However, many "Senior DDs" are of a different opinion and almost
obstinate in their 80% belief.
Can someone please point me to somewhere that the Non-Mag Make Up
Torques are stated in an API recommended table.
Then next time there is debate, I can diffuse it before it gets
heated. (Or - have I been wrong all these years...).
Thanks a lot........hendo.
.. We have received the following input from TH Hill ..
"API doesn´t really treat non-mag drill collars differently than
regular drill collars. In fact, the yield strength requirements are
identical, indicating that there is no reason to think that non-mag
is less strong than normal.
However, makeup torque doesn´t just create bulk stresses, it also
creates bearing stresses on the thread and seal surfaces. Non-mag
materials are notoriously prone to galling, and phosphate treatment
won´t work to prevent that (bead blasting does, but not as well as
phosphating on carbon steel). Lowering the makeup torque can lower
the bearing stresses and help prevent galling on these expensive
How low you can go depends on your specific application, but as long
as you check the connection capacities (torque and tension) 80% of
recommended is entirely plausible. We´ve seen service companies
recommend 10% less than API across the board to prevent galling
damage. At the same time, regular API makeup torques could also
work if you are proactive about preventing galling (good doping,
check alignment, no thread damage, etc.).
In short, there´s no reason to require that all non-mag makeup
torques be 80% of the API recommendation, but there´s also no reason
to say that it´s API or nothing. Set the connection´s makeup torque
based on the performance you require, and keep in mind that non-mag
needs a little extra care to prevent galling.
Thanks .. "
Drilling & Completions Project Consultant
TH Hill, Houston
We've received the following input from a Directional Drilling Co-
ordinator in Aberdeen ..
" .... I agree with the contributor to the discussion forum. At
INTEQ we use the same make up torque for Non Mag and steel
connections, and have done so for many years. Suggest you go the
manufactures of Non Mag steel for ”˜Non Mag make up torques´.. "