Stud bolts, nuts and fasteners for flanged joints
Stud bolts and heavy hex nuts: B7 / 2H, B7M, B8M, L7, plain, galvanized and PTFE coated.
Overview
Flange bolting carries the entire load of the joint. We supply stud bolts and heavy hex nuts in the grades and coatings specified by Pakistani refineries, gas plants and fertilizer complexes, sized to ASME B16.5 / B16.47 flange tables so the correct length and quantity ships with each flange or valve.
ASTM A193 B7 studs with A194 2H nuts cover general hydrocarbon and steam service; B7M and 2HM, hardness controlled, meet NACE MR0175 for sour gas. A320 L7 and A194 Grade 4 or 7 are supplied for low-temperature service, and A193 B8 and B8M Class 1 and 2 with A194 8 and 8M nuts for stainless and corrosive duty.
Coatings include plain black, hot-dip galvanized, zinc plated and PTFE fluoropolymer (Xylan / Takecoat) for offshore and coastal plants where bolts must be removed after years in service. Washers, machine bolts, hex bolts and anchor bolts are available with the same certification.
Typical applications
- Flanged joints in refineries, gas plants and pipelines
- Sour-service bolting (B7M / 2HM)
- Low-temperature LPG and cryogenic flanges (L7)
- Stainless and duplex piping (B8M)
- Coastal and offshore plants (PTFE coated)
- Turnaround and gasket-and-bolt kits
Specified in refineries, oil & gas fields, fertilizer plants, power & heavy industry.
Specifications
| Stud bolts | ASTM A193 B7 · B7M · B16 · B8 / B8M Cl. 1 & 2 · A320 L7 · L7M · B8 · A453 Gr. 660 |
|---|---|
| Nuts | ASTM A194 2H · 2HM · 4 · 7 · 7M · 8 · 8M · heavy hex to ASME B18.2.2 |
| Sizes | ½" – 4" diameter UNC / 8UN; M12 – M100 metric |
| Thread | ASME B1.1 UNC Class 2A/2B · 8UN above 1" · ISO metric |
| Coatings | Plain · hot-dip galvanized · zinc plated · PTFE (Xylan 1070 / 1424) · cadmium alternatives |
| Standards | ASME B18.2.1 · ASME B16.5 bolting tables · NACE MR0175 (B7M / L7M) |
| Testing | Tensile · hardness · impact (L7) · 3.1 certification · PMI for stainless |
| Also available | Hex bolts · machine bolts · washers · anchor bolts · tie rods |
Sizes, classes and materials listed are typical of our stock and supply programme. Other combinations are quoted against your specification. See what is usually ex-stock.
Specifying the right stud bolt
A stud bolt set is specified by the flange, the temperature and the environment. ASTM A193 Grade B7 studs with A194 Grade 2H heavy hex nuts are the standard for carbon and alloy steel flanges from −29 °C to about 400 °C. For sour service, B7M and 2HM are the controlled-hardness grades required by NACE MR0175. Below −29 °C, A320 L7 studs with A194 Grade 4 or 7 nuts keep their toughness. For stainless flanges and corrosive service, A193 B8 (304) or B8M (316) Class 1 or Class 2 (strain hardened, higher strength) with A194 Grade 8 or 8M nuts. Above 400 °C, A193 B16 chrome-moly-vanadium studs with A194 Grade 4 or 7 nuts.
Stud length is read from the ASME B16.5 or B16.47 bolting tables for the flange size, class and gasket type, with an allowance for lined or spectacle-blind joints. Coating protects the joint and the assembly: PTFE-based coatings (Xylan, Teflon) give a low, consistent friction factor and corrosion resistance on refinery and offshore flanges; hot-dip galvanising suits structural and utility bolting; plain or phosphate finish is used where the specification requires it. State the thread (UNC to ASME B1.1, or metric), the length, the coating and whether the set includes two nuts and washers. Each stud and nut is marked with grade and the heat number, and ships with the EN 10204 3.1 certificate.
What to send us for a fast quote
- Stud and nut grades (e.g. A193 B7 / A194 2H)
- Diameter, thread and length (or flange size, class and gasket)
- Coating: PTFE, hot-dip galvanised, plain
- Nuts per stud and washers
- NACE or low-temperature requirement
- Quantity and documents required
Why tenders get rejected, and how we avoid it
Bolting is rejected in Pakistani tenders when the grade marking, the heat number or the hardness certificate is missing, and sour-service lines are rejected when B7 is offered against a B7M requirement. We quote the exact grade pair per line, with the manufacturer's certificate and the hardness and impact values where the grade requires them. More on API licences, authorisation letters and certificates.
Documentation supplied
EN 10204 3.1 material test certificate traceable to heat number, mill test certificate and dimensional report, certificate of origin and manufacturer's certificate of conformity, with NACE, fire-safe, 3.2 and third-party inspection documents where the order requires them. What every document in our package covers.
Frequently asked questions
B7 or B7M?
B7M is the same alloy as B7 but tempered to a maximum hardness of 22 HRC, which makes it resistant to sulphide stress cracking. Specify B7M with 2HM nuts for sour (H2S) service per NACE MR0175.
How do I work out stud bolt length?
Stud length depends on flange size, class, facing and gasket type. Send us the flange details and we supply studs to the ASME B16.5 bolting tables, or confirm against your bolt chart.
Why PTFE-coated bolts?
The fluoropolymer coating prevents corrosion and galling, keeps the tightening torque consistent and allows bolts to be removed without cutting after long service in humid or marine environments.
B7 or B7M?
B7 for general service. B7M (and 2HM nuts) where the specification calls for NACE MR0175 / ISO 15156 sour service: the same steel, tempered to a maximum hardness of 22 HRC and 100 % hardness tested, so it will not crack in H₂S.
Why PTFE-coated studs?
The coating gives a known, low friction factor so the bolt load from a given torque is predictable (ASME PCC-1), and it prevents the stud and nut from seizing in a corrosive atmosphere, which makes the joint easier to open at the next turnaround.
Related products
Stud bolts complete the flanged joint with the flanges and gaskets on their own pages; send us the flange list for a full joint quotation.
Flanges
Weld neck, slip-on, blind, socket weld, threaded and lap joint, Class 150 to 2500, RF and RTJ.
Sizes, classes and brands
Gaskets
Spiral wound, ring joint, kammprofile and non-asbestos sheet gaskets to ASME B16.20 and B16.21.
Sizes, classes and brands
Pipe fittings
Butt-weld elbows, tees and reducers to B16.9; forged socket-weld and threaded fittings to B16.11.
Sizes, classes and brands
Pipes & tubes
Seamless and welded, carbon to super duplex, ⅛" to 120" NPS, with 3.1 certificates.
Sizes, classes and brandsRequest a quotation for stud bolts & fasteners
Send size, class, material, quantity and required documents on WhatsApp or through the form. We reply within one working day with availability and lead time.