Definition(s)
Metal-to-Metal Seal
Seal or sealing system that relies on intimate and usually high contact stress of mating metal surfaces to achieve a seal. NOTE The thread compound can affect, both beneficially and detrimentally, the performance of a metal seal.
Source: API RP 5C5, Recommended Practice on Procedures for Testing Casing and Tubing Connections, Third Edition, July 2003 (Reaffirmed August 2010). Global Standards