Connections supplied by different manufacturers are only regarded as “Fully Interchangeable” if the pin and box are identical/within the same tolerance windows. The connections can be mutually substituted without any significant negative changes to the individual manufacturer-provided performance properties or make-up torques (MUT).

The connections are “Compatible” when they can be correctly screwed together and their seal faces engage but certain features of either component are not fully functional. For example, additional seals or torque shoulders, thereby resulting in lower performance characteristics than when they are not used together.

As an example of these definitions, DPM-DS connections are compatible with the equivalent API connections and interchangeable with some manufacturer’s double shouldered API connections.

As DPM-DS are compatible with the equivalent API connections, they can be used in the same string without using a crossover sub. However, the additional torsional strength from the feature of a double shouldered connection is not present, therefore it is important to use the lower MUT of the 2 connections when making up in a mixed string.