Haihao Group is your trusted expert in piping systems and ASME pressure vessel fasteners

As a leading expert in the field of piping systems, Haihao Group prides itself on providing top-quality products that meet the rigorous standards of various pipeline engineering projects, including the manufacturing of pressure vessels. One crucial component of these projects is the use of fasteners that comply with ASME standards. Below, we outline the common ASME pressure vessel fastener standards, materials, and grades that we regularly utilize.

Bolts and nuts with Teflon coating

Common Fastener Standards

Fasteners, such as bolts, studs, and nuts, are essential for pressure vessels. The most frequently used ASME standards for these fasteners include:

ASME/ASTM A193: This specification covers alloy and stainless steel bolt materials used in high-temperature or high-pressure service, or other special-purpose applications. Ferritic steels should undergo appropriate heat treatment to suit each grade’s high-temperature properties.

ASME/ASTM A320: This specification includes alloy steel bolting materials and bolting components for low-temperature service pressure vessels, valves, flanges, and fittings.

ASME/ASTM A194: This standard covers various carbon, alloy, martensitic, and austenitic stainless steel nuts. These nuts are used in high-pressure or high-temperature service, or both.

Prefabricated Pipes

Studs and Nuts Combinations

ASME/ASTM B7 Studs and ASME/ASTM 2H Nuts:

Material: B7 stud materials are made of chromium-molybdenum steel, quenched and tempered to achieve the desired tensile strength.

Applications: These studs/bolts are used in pressure vessels where corrosion resistance is not required, stress corrosion cracking is unlikely, and temperatures are generally below 400°C (750°F).

Surface Treatments: B7 studs/bolts can have different surface treatments:

Plain finish

Hot-dip galvanized

Zinc-coated and/or PTFE/Xylan-coated (for corrosion resistance)

Sizes and Strengths:

Yield strength of 720 MPa (105 ksi) for diameters up to M64 (2.5″).

Yield strength of 655 MPa (95 ksi) for diameters from M64 (2.5″) to M100 (4″).

Yield strength of 515 MPa (75 ksi) for diameters from M100 (4″) to M180 (7″).

Nuts: Heavy hex nuts of ASME/ASTM A194 2H grade are typically paired with these studs.

ASME/ASTM A193 B7M Studs:

Material: The chemical composition of B7M studs is similar to B7 grade, but they are quenched and tempered to achieve lower hardness and tensile strength.

Applications: Typically used in environments prone to stress corrosion cracking (SCC) and in floating head heat exchangers.

Nuts: ASME/ASTM A194 2HM grade nuts, similar to 2H grade but recommended for SCC environments.

ASME/ASTM A193 B16 Studs:

Material: Made of chromium-molybdenum-vanadium alloy steel.

Applications: High-temperature applications from 400°C (750°F) to 595°C (1100°F), where maintaining strength and reducing relaxation at high temperatures is critical.

Nuts: Can be paired with Grade 4 and Grade 7 nuts, which are heat-treated chromium-molybdenum steel, suitable for sub-zero conditions and can be used down to -48°C as per ASME VIII-1.

Differences Between ASME/ASTM B8 Class 1 and Class 2 Studs

ASME/ASTM A193 B8 Studs:

Material: Made of 304 austenitic stainless steel and require solution treatment.

Class 1: No strain hardening, with a yield strength of 205 MPa (30 ksi).

Class 2: Strain hardened, with a yield strength of 690 MPa (100 ksi) for sizes M20 (3/4″) to M24 (1″).

Nuts: Paired with ASME/ASTM A194 8 grade nuts.

ASME/ASTM B8M Studs:

Material: Made of 316 austenitic stainless steel, which offers enhanced corrosion resistance.

Classes:

Class 1: Requires solution treatment.

Class 2: Requires strain hardening.

Nuts: Paired with ASME/ASTM A194 8M grade nuts.

ASME/ASTM A320 L7 and L7M Grades

Applications: These grades are typically used in low-temperature environments ranging from -50°F to -150°F.

Nuts: Commonly paired with ASME/ASTM A194 Grade 4 and Grade 7 nuts.

At Haihao Group, we are committed to providing high-quality fasteners that meet these rigorous standards, ensuring the reliability and safety of your pressure vessel applications. Our extensive expertise and dedication to excellence make us your trusted partner in the piping systems industry.