What Is ASTM A194?

ASTM A194 defines the material, chemical, and mechanical requirements for
carbon steel, alloy steel, and stainless steel nuts used in high-pressure and
high-temperature service. In oil and gas systems, crews most often use it for
heavy hex nuts that pair with high-strength studs in critical bolted joints.

Who Sets This Specification?

ASTM International sets and maintains ASTM A194. This organization develops
technical standards through a consensus process that includes manufacturers,
engineers, end users, and industry experts. No single company controls the
standard, and committees review and update it based on real-world performance
and industry needs.

What It Covers

ASTM A194 includes several nut grades designed for different service conditions:

• Grade 2H: High-strength carbon steel heavy hex nuts
• Grade 2HM: Improved performance at elevated temperatures
• Grade 7: Alloy steel nuts for higher temperature service
• Grades 8 and 8M: Stainless steel nuts for corrosion resistance

How It Is Used

Manufacturers produce ASTM A194 nuts to work with studs such as ASTM A193 B7.
Technicians install the nuts onto threaded studs and tighten them to generate
preload. That preload compresses gaskets and helps create a pressure-tight seal
in flange joints.

Common Applications

• Oil and gas pipeline flanges
• Refinery and petrochemical equipment
• Pressure vessels and heat exchangers
• Valves and high-pressure equipment connections
• Wellhead and production systems

Why It Matters

ASTM A194 creates a consistent global requirement for nut performance. Because
manufacturers build to the same specification, operators can source compatible
hardware across suppliers while maintaining predictable performance in critical
bolted joints.

Summary

ASTM A194 is a consensus-driven standard published by ASTM International. It
defines high-pressure nut grades used in industrial bolting systems, ensuring
consistent performance in oil and gas, petrochemical, and pressure-containing
applications.