Dresser Gasket — Grade 27 BUNA-S Armored | Armored Gasket for Dresser Style 38, 40, 138 Couplings

Grade 27 SBR Compound | Integral Brass Coil Armor | Electrical Continuity | Cathodic Protection | Natural Gas Service | Up to 212°F

Overview

The Dresser Grade 27 BUNA-S Armored Gasket is identical in rubber compound to the standard Grade 27 BUNA-S gasket, with one critical addition: a brass coil (helix) molded directly into the gasket tip as an integral, inseparable component. The armor is an elastic, virtually indestructible brass coil that becomes part of the gasket sealing lip during the molding process. When the coupling is tightened, the armor "bites" into the pipe surface at both ends, creating a metal-to-metal contact path from pipe to gasket to pipe — allowing electrical current to pass through the coupled joint without interruption.

This matters critically in two service conditions. First, in natural gas distribution, utilities and gas companies commonly require armored gaskets to maintain electrical continuity through service lines and mains that are part of a cathodic protection system — current must flow through the joint, not be blocked by the rubber gasket. Second, in any pipeline where cathodic protection current must cross the joint, the armored gasket is the code-compliant solution. The brass armor does not degrade the sealing performance of the gasket — it is shielded within the gasket lip and does not contact the line content on the pressure side of the seal.

How Dresser Armored Gaskets Work

The armor — a continuous elastic brass coil or helix — is cast directly into the gasket tip material during the rubber molding process. It is not a separate component; it cannot be separated from the gasket body. When the coupling followers are tightened and the gasket is compressed against the pipe OD, the exposed coil end on each face of the gasket lip bites into the pipe surface. This creates two small areas of metal-to-metal contact — one at each pipe end — providing a low-resistance electrical pathway from pipe to pipe across the coupled joint. The rubber compound on either side of the armor continues to seal the joint against fluid leakage. The armor protects the rubber from the line content on the ID side, extending gasket life in applications where the line fluid might otherwise degrade the rubber sealing material at the contact point.

When You Need Armored vs. Plain Gaskets

Use armored gaskets whenever: (1) the pipeline is part of a cathodic protection system and the utility or engineer specifies electrical continuity through joints; (2) the line contains natural gas and local code, utility standard, or DOT regulation requires conductive joints on the service line; (3) you are replacing gaskets in a coupling that originally shipped with armored gaskets. Use plain Grade 27 gaskets when electrical continuity is not a requirement and the line content and temperature are within Grade 27's service range.

Key Features

• Integral Brass Coil Armor — Factory Molded: The brass coil helix is permanently part of the gasket body — not a loose insert. Cannot fall out, misalign, or be lost during installation.
• Metal-to-Metal Electrical Continuity: Armor bites into pipe surface at both ends as coupling is tightened — provides cathodic protection current path through the coupled joint. Critical for natural gas service lines and cathodic protection compliance.
• Sealing Performance Unaffected: The armor is on the ID lip of the gasket and is shielded from the pressure side of the seal by the surrounding rubber compound. Sealing performance is identical to plain Grade 27.
• Grade 27 BUNA-S Base Compound: Same SBR rubber as plain Grade 27 — same temperature rating (212°F), same chemical compatibility, same durometer, same color code (White). Choose armored vs. plain based solely on electrical continuity requirement.
• Standard on Style 65 and Style 90 Fittings: Style 65 and Style 90 compression fittings for gas service ship with Grade 27 Armored as standard. Grade 42 Armored available for oil/condensate service.
• Natural Gas Service Standard: For bolted couplings used on natural gas mains and service lines, armored gaskets are the correct specification in the vast majority of utility standards and DOT-regulated systems.

Specifications

? ARMORED vs. PLAIN — COLOR CODE IS IDENTICAL: Both Grade 27 plain and Grade 27 Armored gaskets have a White mold color code. Always confirm armored vs. plain status from part number or product label before installing — not from color alone. When in doubt, feel the gasket lip for the brass coil.

Questions? Contact us at sales@watermainsupply.com or call 281.664.8000.