Oil and gas
Fasteners for refineries and oil and gas
Stud bolts with heavy hex nuts for flanged joints, and structural and anchor bolting for plant steelwork. TUFF® stud bolts are made to ASTM A193 and ASTM A320 in Gr. B7, L7 / L7M, B8, B8M and Gr. 660 (A-286), with heavy hex nuts in Gr. 2H / 2HM and 7 / 7M. Sizes M8 – M100 and ½″ – 4″.
TUFF products for this work
Stud / Threaded RodASTM A193, ASTM A320, DIN 975 · M8 – M100, ½″ – 4″
Heavy Hex NutIS 6623, ASTM A194, ASTM A563 · M12 – M100, ¼″ – 4″
Heavy Hex BoltIS 3757, EN 14399-3, EN 14399-4 · M12 – M36, ½″ – 1½″
Foundation BoltIS 5624, DIN 529, ASTM F1554 · M8 – M72
U BoltDIN 3570, ASME B18.31.5 · M10 – M24
Plain WasherDIN 125, ISO 7089, ISO 7090 · M8 – M160
Testing and inspection
Every lot is tested before dispatch to the applicable standard and the order's inspection plan, in our in-house laboratory accredited by NABL to ISO/IEC 17025:2017 for the tests in its scope. Lots have been inspected on customer orders by agencies including TÜV SÜD, TÜV NORD, Lloyd's Register, DNV, SGS, BVQI, RITES and EIL.
In an independent test by Element Materials Technology, Singapore (report T24-56832R, November 2024), one TUFF M22 class 10.9 HSFG bolt reached 1,221 MPa tensile strength against the ISO 898-1 minimum of 1,040 MPa. This is one sample; results vary by size, grade and lot, and the test certificate of each supplied lot governs. Read the test summary.
Test certificates
We issue test certificates with every lot. State the certificate type your order needs, for example EN 10204 3.1 or 3.2, in the enquiry.
Shipping terms
FOB, CIF or other terms, as agreed for the order.
Send an enquiry
Send the standard, grade, size, quantity, finish and the certificate type your order needs. Open the enquiry form or write to sales@tuffbolt.com.
Where TUFF fasteners have been used
- RefineryFasteners for the construction of the world's largest refinery (as of November 2026).
Questions
What is the NACE MR0175 requirement for stud bolts in sour service?
NACE MR0175 / ISO 15156 limits the maximum hardness of carbon and low-alloy steel fasteners used in hydrogen sulphide (H2S) environments to Rockwell C 22 maximum. ASTM A193 Gr. B7M and ASTM A320 Gr. L7M (max 235 HB / 99 HRB) with ASTM A194 Gr. 2HM nuts are specified for sour service.
What is the difference between ASTM A193 B7 and B7M?
B7M is a lower-strength, controlled-hardness version of B7: minimum tensile strength 100 ksi and maximum hardness 235 HBW, with every piece hardness tested. B7 has a minimum tensile strength of 125 ksi up to 2½ in diameter and a maximum hardness of 35 HRC. B7M is used for sour service under NACE MR0175 with A194 2HM nuts; B7 pairs with A194 2H.
What ASTM A194 grade is paired with ASTM A193 B7 stud bolts?
ASTM A194 Grade 2H heavy hex nut is the standard specified pairing for A193 B7 studs in pressure vessel and high-temperature piping applications per ASME codes. Grade 2H provides a minimum proof load stress of 175,000 PSI (1207 MPa).
About the maker
- Fasteners since 1996Pioneer Nuts & Bolts Pvt. Ltd., brand TUFF®. Forging, heat treatment, machining and finishing in-house.
- 50 yearsMetallurgy and heat treatment, since 1976.
- IATF 16949:2016Certified quality management system.
- NABL labIn-house laboratory accredited by NABL to ISO/IEC 17025:2017 for the tests in its scope. Lots tested to the applicable standard.
- Japanese collaborationTechnical collaboration with Japanese fastener companies.
- 150+ testimonialsMore than 150 customer testimonials.