Marine Stud Bolt & Thread Rod
Marine Stud Bolt & Thread Rod | ASTM A193 B7 Flange Fastener
ASTM A193 B7 alloy steel marine stud bolts and ASTM F568M / ISO 4730 thread rods for ship piping flange connections, heat exchangers, pump assemblies, and valve bonnets. Available in M12–M64 / 1/2"–2"with matched heavy hex nuts per ASTM A194 Gr.2H. Manufactured per ASME B18.31.5 dimensional requirements with full material traceability.
What Is a Marine Stud Bolt and Thread Rod?
Amarine stud bolt is a headless threaded rod that requires two nuts — one on each end — to create a clamped joint. Unlike standard hex bolts, stud bolts are the default fastener for flanged connections in ship piping systems because they provide uniform clamping force across the flange gasket face and allow precise torque control using the nut-turn method. The stud bolt geometry also simplifies inspection: each end can be verified independently for thread engagement and nut projection.
Athread rod (also called all-thread or fully threaded rod) is a continuous full-length threaded bar supplied in 1-meter or 3-meter standard lengths. In marine piping installations, thread rods serve as field-adjustable pipe hanger rods, support bracket fasteners, and U-bolt extensions where the exact length is determined during onboard fitting.
The practical difference: marine stud bolts are precision-cut to a calculated length per ASME B16.5 with chamfered ends and are used in flange joints. Thread rods are cut to length on-site for miscellaneous fastening. Both product types share the same metric and imperial thread standards and are stocked by sinofastener in parallel.
Marine Applications
Note: The following applications are based on typical industry practice for ASTM A193 B7 and A320 L7 stud bolts in marine piping and flange systems.
| Application | Typical Service | Recommended Grade |
|---|---|---|
| Flange bolts — main engine cooling water | Seawater piping, 40–80 deg C | A193 B7 + B16.5 Class 150/300 |
| Heat exchanger cover bolts | Shell-side seawater / freshwater | A320 L7 (low-temp) or B7M |
| Pump casing flange connection | Bilge, ballast, FW cooling | A193 B7 + A194 2H nuts |
| Valve bonnet stud bolts | Steam, feedwater, main discharge | A193 B7 (up to 400 deg C) |
| Exhaust gas boiler flange | High-temp exhaust, 300–450 deg C | A193 B7 / B16 alloy steel |
| Pipe hanger rod / support bracket | Overhead piping support | F568M Class 4.6 / 8.8 thread rod |
| Deck machinery foundation bolts | Winch, crane base plate | A193 B7 cast-in-place studs |
Specifications & Materials
| Parameter | Range | Standard Reference |
|---|---|---|
| Product Type | Stud Bolt (double-end) / Thread Rod (full-thread) | ASME B18.31.5 |
| Diameter Range | M12–M64 / 1/2"–2" | ASME B16.5 (stud) / ISO 4730 (rod) |
| Length Range | 80–3000 mm (stud bolts cut to flange spec) | Per flange thickness + nut + 2–3P exposure |
| Material — High Temp | ASTM A193 Grade B7 (Cr-Mo alloy steel) | ASTM A193 Table 1 |
| Material — Low Temp | ASTM A320 Grade L7 (Ni-Cr-Mo alloy steel) | ASTM A320 Table 1 |
| Material — Metric General | ASTM F568M Class 8.8 / 10.9 | ASTM F568M Table 3 |
| Material — Stainless | ASTM A193 Gr.B8 / B8M (304 / 316 SS) | ASTM A193 Table 2 |
| Tensile Strength (B7) | min 860 MPa (125 ksi) | ASTM A193 Table 2 |
| Tensile Strength (L7) | min 860 MPa, Charpy impact at -101 deg C | ASTM A320 Table 2 |
| Matched Nuts | ASTM A194 Gr.2H / 7 / 7M | ASME B18.2.2 |
| Thread Form | UNC / UNF / Metric Coarse | ASME B1.1 / ISO 261 |
| Surface Treatment | Hot-dip galvanized / PTFE coated / Xylan / Plain | Per purchaser specification |
Why Choose sinofastener for Marine Stud Bolts?
- Flange-spec stud bolt cutting: Each stud bolt is cut to match your flange thickness per ASME B16.5 bolt length table — thread exposure 2–3 pitches beyond the nut face, verified before shipment.
- Grade traceability: Full heat number marking on each stud end, with EN 10204 3.1 material certificates. Chemical composition and mechanical test results provided per lot.
- Mixed-length packing: Different stud bolt lengths for the same piping system are individually tagged and packed by line number to prevent on-site confusion during installation.
- Annual capacity 50,000 tons: Covering ASTM A193 B7, A320 L7, F568M, and A193 B8/B8M stainless in M12–M64. Ready stock for standard flange bolt kits.
Standards Reference
- ASTM A193 — Alloy-Steel and Stainless Steel Bolting for High Temperature or High Pressure Service
- ASTM A320 — Alloy-Steel Bolting for Low-Temperature Service
- ASTM F568M — Carbon and Alloy Steel Externally Threaded Metric Fasteners
- ASTM A194 — Carbon and Alloy Steel Nuts for High Pressure or High Temperature Service
- ASME B16.5 — Pipe Flanges and Flanged Fittings (bolt length determination)
- ASME B18.31.5 — Metric Hex Bolts and Studs
- ISO 4730 — Threaded rods for general purposes
FAQ
What is the difference between a stud bolt and a thread rod?
Amarine stud bolt is precision-cut to a specific length with chamfered ends and is designed for flanged connections using two nuts. A thread rod is a full-length threaded bar supplied in 1 m or 3 m lengths that is cut on-site for pipe hangers, supports, and miscellaneous fastening. Stud bolts are engineered components per ASME B16.5; thread rods are general-purpose per ISO 4730.
How do I determine the correct stud bolt length for a flange?
Per ASME B16.5, the minimum stud bolt length equals: flange thickness x 2 + washer thickness (if used) + nut thickness + 2–3 thread pitches of exposure beyond the nut face. For example, a 150# Class 150 NPS 4 flange requires approximately 165 mm stud bolt length with 3/4"-10 UNC threading. We provide bolt length calculation per your flange specification.
When should I use A320 L7 instead of A193 B7?
ASTM A320 L7 is specified for low-temperature service below -29 deg C (-20 deg F) because it requires Charpy V-notch impact testing at -101 deg C. Typical marine applications include LNG carrier piping, refrigerated cargo systems, and cold seawater circuits. For ambient and high-temperature service above -29 deg C, A193 B7 is the standard choice.
Can you supply stud bolts with PTFE coating for seawater service?
Yes. PTFE (Xylan) coated stud bolts are commonly used in marine seawater piping to provide additional corrosion protection beyond the base alloy steel. The coating is applied after threading to protect both the shank and thread form. We supply PTFE-coated A193 B7 stud bolts in all standard flange sizes.
Contact Us
Email: sales@sinofastener.com
Website: www.zlfastener.com | www.sinofastener.com (Main)
