The Dresser Style 39 Insulating Coupling provides both a mechanical pipe joint and complete electrical isolation in a single, field-proven assembly. It follows the same basic design and dimensions as the Style 38 coupling — with one critical addition: a full-boot plastic tubular insulator inside the middle ring that electrically separates pipe ends at the joint. The insulating gasket has a skirt that extends under the follower ring to isolate it from the pipe, while the armored gasket on the opposite end bonds the coupling to the pipe and can share cathodic protection currents. One coupling handles both mechanical joining and corrosion protection simultaneously.

Style 39 couplings are specified on lines requiring cathodic protection and wherever dissimilar metals are joined — conditions where uncontrolled galvanic current causes accelerated corrosion. They are widely used across gas distribution, oil transmission, and industrial pipeline applications. Insulating features can be supplied on both ends when the application demands complete end-to-end isolation.