Stud Bolts
Giriraj Impex is a manufacturer, stockist, supplier and exporter of stud bolts for flanged joints – fully threaded studs to ASTM A193 Grade B7, B7M, B16, B8 and B8M (Class 1 and 2), and ASTM A320 Grade L7 and L43, supplied with ASTM A194 heavy hex nuts. We manufacture stud bolts in imperial and metric sizes, cut to the lengths needed for ASME B16.5 and B16.47 flanges, plain, zinc plated, galvanised or PTFE coated, with mill test certificates.
Stud bolts with two nuts are the standard bolting for pipe flanges, valves, pressure vessels and heat exchangers in refineries, petrochemical plants, power stations and oil and gas facilities.
Stud bolt grades
| Stud | Nut | Material | Typical service |
|---|---|---|---|
| A193 B7 | A194 2H | Cr-Mo alloy steel | General flanges, ambient to elevated temperature |
| A193 B7M | A194 2HM | Cr-Mo, controlled hardness | Sour service |
| A193 B16 | A194 4 or 7 | Cr-Mo-V alloy steel | High temperature |
| A320 L7 | A194 4 or 7 | Cr-Mo, impact tested | Low temperature |
| A193 B8 (304) | A194 8 | Stainless steel | Corrosion resistance, cryogenic |
| A193 B8M (316) | A194 8M | Stainless steel | Corrosion resistance, chlorides |
Class 1 B8 and B8M studs are solution treated; Class 2 studs are strain hardened for higher strength. Duplex, super duplex and nickel alloy studs are on our duplex and super duplex fasteners, Inconel fasteners and Hastelloy fasteners pages.
Stud bolts per flange
| NPS | Class 150 | Class 300 |
|---|---|---|
| ½ | 4 × ½" | 4 × ½" |
| ¾ | 4 × ½" | 4 × ⅝" |
| 1 | 4 × ½" | 4 × ⅝" |
| 1¼ | 4 × ½" | 4 × ⅝" |
| 1½ | 4 × ½" | 4 × ¾" |
| 2 | 4 × ⅝" | 8 × ⅝" |
| 2½ | 4 × ⅝" | 8 × ¾" |
| 3 | 4 × ⅝" | 8 × ¾" |
| 4 | 8 × ⅝" | 8 × ¾" |
| 5 | 8 × ¾" | 8 × ¾" |
| 6 | 8 × ¾" | 12 × ¾" |
| 8 | 8 × ¾" | 12 × ⅞" |
| 10 | 12 × ⅞" | 16 × 1" |
| 12 | 12 × ⅞" | 16 × 1⅛" |
| 14 | 12 × 1" | 20 × 1⅛" |
| 16 | 16 × 1" | 20 × 1¼" |
| 18 | 16 × 1⅛" | 24 × 1¼" |
| 20 | 20 × 1⅛" | 24 × 1¼" |
| 24 | 20 × 1¼" | 24 × 1½" |
The number and diameter of bolts are set by ASME B16.5 for each size and class. For larger sizes and other classes, see the flange dimensions chart.
Stud bolt length
Stud length depends on the flange thickness, the facing (raised face or RTJ), the gasket thickness and the nut height, plus an allowance so that the stud projects beyond each nut. ASME B16.5 lists recommended stud lengths for raised-face and RTJ flanges in each class, and many piping specifications add their own rules – for example, extra length for hydraulic bolt tensioning. Send us the flange size, class, facing and gasket type and we will calculate the stud lengths for your bolting list.
For critical joints, bolting is tightened with calibrated torque wrenches or hydraulic tensioners to a target bolt stress, rather than by feel. The target stress depends on the stud material, gasket type and flange class, and the joint is tightened in a cross pattern in several passes so that the gasket is compressed evenly. Coated or lubricated studs need lower torque than plain studs for the same bolt load.
Specifications
| Item | Details |
|---|---|
| Standards | ASTM A193, A320, A194; ASME B18.31.2 (studs), B18.2.2 (heavy hex nuts) |
| Threads | UNC up to 1", 8UN above 1"; ISO metric |
| Sizes | ½" to 4" diameter, and metric equivalents; lengths to order |
| Finish | Plain, black oxide, zinc plated, hot-dip galvanised, PTFE (xylan) coated |
| Options | NACE MR0175 / ISO 15156 (B7M/2HM), impact test |
| Documents | Mill test certificate (MTC); third-party inspection on request |
Materials
- Carbon steel fasteners – B7 studs with 2H nuts, A307 bolts.
- Alloy steel fasteners – B7, B16, L7, L43 studs.
- Stainless steel fasteners – B8, B8M studs with 8 and 8M nuts.
- Duplex and super duplex fasteners, Inconel and Hastelloy fasteners for corrosive service.
All fastener materials are on the fasteners page.
How we manufacture stud bolts
Stud bolts are made from certified bar, heat treated to the grade's requirements, cut to length and threaded by rolling or cutting, with chamfered ends. Each lot is hardness tested and, as the standard requires, tensile and impact tested. Studs are marked with the grade symbol and manufacturer's identification, and nuts are marked with their grade.
Ordering stud bolts
Please give the stud and nut grades, diameter, length (or flange details for us to calculate), number of nuts per stud, coating, quantity and any NACE MR0175 / ISO 15156, impact or inspection requirement.
Frequently Asked Questions
A stud bolt is a fully threaded rod used with two heavy hex nuts to bolt flanged joints.
ASTM A194 Grade 2H heavy hex nuts are the standard nuts for A193 B7 studs.
Under ASME B16.5, a 4" Class 150 flange uses eight ⅝" stud bolts.
From the flange thickness, facing, gasket thickness and nut height, plus projection beyond the nuts. ASME B16.5 lists recommended lengths.
Class 1 studs are solution treated; Class 2 studs are strain hardened for higher strength.
Yes. Stud bolts and nuts can be supplied PTFE coated, zinc plated or hot-dip galvanised.
Request a Quote for Stud Bolts
Tell us the product, grade, size, standard, quantity and delivery location, and our sales team will reply with a quotation.
Inconel® are trademarks of Special Metals Corporation; Hastelloy® of Haynes International.