The Versatile Stud Bolt with Heavy Nuts-Revolutionizing Applications

A stainless stud bolt with a heavy hex nut — A193 B8M stud and A194 8M (or 8) nut — is the corrosion-resistant bolting for flanged joints that see water, salt, or sour fluid. It keeps the clamp load where a plain carbon steel bolt would rust away. For the sealing face, see our flange gaskets and flange products.

What the B8M Stud and Heavy Nut Is

A193 B8M is 316 stainless, strain-hardened to a controlled hardness (class 2) so it is strong without being brittle, and it resists chloride pitting better than 304. The A194 8M heavy hex nut matches it: thicker and wider than a standard nut, so it spreads load on the flange face and resists rounding under torque. Together they are the stainless answer to the B7 / 2H carbon pair.

Material and Pairing

• A193 B8M stud — 316 stainless, strain-hardened class 2 for strength and toughness.
• A194 8M (or 8) heavy hex nut — stainless, paired by hardness to the stud.
• Heavy hex form — more bearing area than standard hex, less embedment.
• Built-in corrosion resistance, no coating to scratch or wear off.

Stainless Versus Carbon Steel

Why Choose Stainless Bolting

Where the joint is wet, offshore, or carrying sour fluid, carbon steel rusts and the nut can seize or thin until the bolt loses preload. B8M's chromium oxide layer protects the metal without a film that scratches off. For H2S service the class-2 hardness keeps the stud inside the NACE limits, so it will not crack under sulfide stress.

Key Benefits

• Resists rust, pitting, and chloride attack in wet and marine duty.
• Heavy hex nut spreads load and resists rounding at high torque.
• No coating to damage — the protection is in the metal.
• Class-2 hardness suits NACE sour-service limits when specified.

Where They Are Used

B8M stud-and-nut sets go on offshore platforms, coastal and subsea lines, desalination and water treatment, and any flange carrying sour or corrosive fluid. They suit joints that must stay tight through weather and washdown without a fresh coat of paint.

In the Joint

The stud carries the clamp load; the gasket between the faces seals, while the flange body joins the spools. Pick stainless for both stud and nut, and pair them with a gasket that survives the same fluid.

Installation and Care

Use a hardened washer where the standard calls for one, keep the nut and threads clean, and lubricate to the specified friction factor so torque gives the right preload. Do not mix B8M with a carbon steel nut — galvanic and hardness mismatch will cause problems. Inspect at each turnaround; stainless rarely rusts, but check the thread for galling and the nut for freedom.

Frequently Asked Questions

B8M stud with a 2H nut — is that OK?

No. Pair B8M with an A194 8M (or 8) stainless nut. A carbon steel 2H nut over a stainless stud risks galvanic corrosion and wrong hardness.

Class 2 or class 1 for sour service?

For NACE sour service use class 2 (B8M / 8M) at the controlled hardness; class 1 is softer and not the sour-service choice.

Does stainless need anti-seize?

Yes — stainless can gall when run against stainless. Use an approved anti-seize so the nut turns and comes apart at the next shutdown.