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

Grade 27 SBR Compound | Standard Pipeline Gasket | Up to 212°F | Water, Gas, Air, Acids | Wedge-Section Coupling Seal

Overview

The Dresser Grade 27 BUNA-S Plain Gasket is the standard sealing element used in Dresser Style 38, Style 40, Style 138, and related bolted couplings across virtually all water distribution, gas distribution, industrial, and pipeline applications worldwide. It is the most widely specified Dresser gasket compound by a substantial margin — and the compound that ships as standard in the majority of Dresser bolted couplings unless a specific application calls for a different formulation.

Grade 27 is a Styrene-Butadiene Rubber (SBR) compound, Dresser's designation for what is commonly called BUNA-S in the industry. The compound was developed specifically for the demands of pipeline coupling service: maintaining its sealing pressure over long periods under compression, resisting the temperature cycles and pressure fluctuations of active distribution mains, and remaining chemically compatible with the broadest possible range of pipeline fluids. It has been used successfully in every segment of the pipeline industry for over 130 years.

Applications — Grade 27 BUNA-S Is Recommended For

• Potable water distribution mains — fresh water and salt water lines
• Natural gas and other dry gas distribution and transmission
• Compressed air and inert gas pipelines
• Most acids, alkaline solutions, and chemical solutions at ambient temperature
• Sugar solutions, brine, and food-grade fluids
• Some refrigerants
• General utility pipeline service where line content is water-based or gas

Grade 27 is not recommended for: oils, hydrocarbons, solvents, aromatic compounds, or petroleum products — use Grade 42 BUNA-N (Nitrile) for those services.

Key Features

• Industry Standard Compound: Grade 27 BUNA-S ships as the default gasket in the majority of Dresser bolted couplings from the factory — the universal baseline for Dresser coupling service.
• Wedge-Section Profile: The tapered wedge profile is compressed into the space formed by the conical flare of the middle ring and the pipe OD as followers are tightened — producing a self-energizing seal that tightens further as pressure increases.
• Broad Chemical Compatibility: Compatible with water (potable, salt, and reclaimed), dry gases, air, most acids, and alkaline solutions — covers the vast majority of municipal water, wastewater, and gas distribution service conditions.
• High Resilience / Low Compression Set: Formulated to maintain its spring-back force over long service periods under sustained compression — resisting the compression set that causes gasket seal degradation over time.
• Absorbs Pipe Movement: Resilient SBR construction allows the coupling to flex, deflect, and accommodate thermal expansion and contraction at every joint without cracking or losing sealing force.
• Available in Armored Version: Grade 27 BUNA-S Armored (see separate listing) adds a brass coil to the gasket tip for electrical continuity applications — natural gas, cathodic protection systems, and conductive pipeline applications.
• 212°F Maximum Operating Temperature: Suitable for the full range of normal pipeline operating temperatures in water and gas distribution service.

Specifications

Full Gasket Grade Comparison

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