| Standard | ASTM A194 Grade 2H / ASME B18.2.2 · Grade 2HM / Grade 7 |
|---|---|
| Material | ASTM A194 Grade 2H / 2HM / 7 carbon and alloy steel |
| Strength Grade | Grade 2H / 2HM / 7 |
| Size Range | M12-M64 / 1/2"-4" |
| Surface Treatment | Plain / Black Oxide / PTFE Coated / Zinc Phosphate / HDG |
Product Description
ASTM A194 heavy hex nuts are pressure bolting nuts used with ASTM A193 stud bolts in flanges, valves, pressure piping, heat exchangers and power generation equipment. Grade 2H commonly pairs with A193 B7 studs. Grade 2HM has controlled maximum hardness and commonly pairs with A193 B7M studs. Grade 7 remains available where the project specifies a compatible alloy-steel nut grade.
Grade 2H and 2HM are not interchangeable markings. The selected nut must match the stud grade, proof-load and hardness requirements, thread fit, coating, lubrication and traceability scope. A 2HM marking alone does not prove compliance with NACE MR0175 / ISO 15156 or NACE MR0103 / ISO 17945; the applicable standard, edition and inspection requirements must be invoked by the purchase order.
Plain and black oxide finishes are common for controlled industrial bolting, PTFE coated nuts are used with coated studs for corrosion protection and friction control, zinc phosphate is used in selected machinery or pressure bolting packages, and HDG nuts require nut-fit control after coating. For shutdown or maintenance orders, nuts can be supplied kitted with B7 studs by diameter and length.
| Product type | ASTM A194 heavy hex nuts for pressure bolting |
|---|---|
| Standards | ASTM A194 Grade 2H / Grade 2HM / Grade 7 / ASME B18.2.2 |
| Material | Carbon or alloy steel meeting the specified ASTM A194 grade |
| Strength grade | Grade 2H / Grade 2HM / Grade 7 |
| Grade 2H selection | General pressure bolting nut commonly paired with ASTM A193 Grade B7 studs |
| Grade 2HM selection | Controlled-maximum-hardness nut commonly paired with ASTM A193 Grade B7M studs |
| Sour-service qualification | NACE MR0175 / ISO 15156 or NACE MR0103 / ISO 17945 only when explicitly invoked and verified for the project |
| Size range | M12-M64 / 1/2 in-4 in |
| Common models | M16, M20, M24, M30, 1/2 in, 5/8 in, 3/4 in, 7/8 in, 1 in, 1-1/4 in |
| Thread type | UNC / 8UN / metric thread by stud bolt requirement |
| Surface finish | Plain / Black oxide / PTFE coated / Zinc phosphate / Hot-dip galvanized |
| Matched hardware | A193 B7 with A194 2H; A193 B7M with A194 2HM; Grade 7 only with the specified compatible stud system |
| Documentation | MTC, proof load or hardness report, coating report and CoC on request |
| Parameter | 1 | 1/4 | 1/2 | 1-1/8 | 1-1/4 | 1-3/8 | 1-1/2 | 1-5/8 | 1-3/4 | 1-7/8 | 2 | 2-1/4 | 2-1/2 | 2-3/4 | 3 | 3/8 | 3/4 | 3-1/4 | 3-1/2 | 3-3/4 | 4 | 5/16 | 5/8 | 7/16 | 7/8 | 9/16 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| P | 8|12|20 | 20|28|32 | 13|20|28 | 7|12|18 | 7|12|18 | 6|12|18 | 6|12|18 | 6|12|18 | 5|8|12 | 6 | 4.5 | 4.5 | 4 | 4 | 4 | 16|24|32 | 10|16|20 | 4 | 4 | 4 | 4 | 18|24|32 | 11|18|24 | 14|20|28 | 9|14|20 | 12|18|24 |
| s/min | 1.575 | 0.448 | 0.85 | 1.756 | 1.938 | 2.119 | 2.3 | 2.481 | 2.662 | 2.844 | 3.025 | 3.388 | 3.75 | 4.112 | 4.475 | 0.669 | 1.212 | 4.838 | 5.2 | 5.562 | 5.925 | 0.546 | 1.031 | 0.728 | 1.394 | 0.909 |
| s/max | 1.625 | 0.5 | 0.875 | 1.812 | 2 | 2.188 | 2.375 | 2.562 | 2.75 | 2.938 | 3.125 | 3.5 | 3.875 | 4.25 | 4.625 | 0.688 | 1.25 | 5 | 5.375 | 5.75 | 6.125 | 0.562 | 1.062 | 0.75 | 1.438 | 0.938 |
| e/min | 1.796 | 0.556 | 0.969 | 2.002 | 2.209 | 2.416 | 2.622 | 2.828 | 3.035 | 3.242 | 3.449 | 3.862 | 4.275 | 4.688 | 5.102 | 0.763 | 1.382 | 5.515 | 5.928 | 6.341 | 6.755 | 0.622 | 1.175 | 0.83 | 1.589 | 1.037 |
| e/max | 1.876 | 0.577 | 1.01 | 2.093 | 2.309 | 2.526 | 2.742 | 2.959 | 3.175 | 3.392 | 3.608 | 4.041 | 4.474 | 4.907 | 5.34 | 0.794 | 1.443 | 5.774 | 6.207 | 6.64 | 7.073 | 0.65 | 1.227 | 0.866 | 1.66 | 1.083 |
| k/min | 0.956 | 0.218 | 0.464 | 1.079 | 1.187 | 1.31 | 1.433 | 1.556 | 1.679 | 1.802 | 1.925 | 2.155 | 2.401 | 2.647 | 2.893 | 0.341 | 0.71 | 3.124 | 3.37 | 3.616 | 3.862 | 0.28 | 0.587 | 0.403 | 0.833 | 0.526 |
| k/max | 1.012 | 0.25 | 0.504 | 1.138 | 1.251 | 1.378 | 1.505 | 1.632 | 1.759 | 1.886 | 2.013 | 2.251 | 2.505 | 2.759 | 3.013 | 0.377 | 0.758 | 3.252 | 3.506 | 3.76 | 4.014 | 0.314 | 0.631 | 0.441 | 0.885 | 0.568 |
Selection
A194 Grade 2H nuts are commonly purchased with A193 B7 studs. Controlled-hardness 2HM nuts are commonly paired with B7M studs when specified, together with the applicable project corrosion standard, hardness testing and traceability requirements.
Oil and gas fastenersPressure service nuts support power plant valves, pumps, heat exchangers and turbine auxiliary systems. Confirm grade, finish and certificate requirements for high-temperature or critical service.
Power generation fastenersA194 heavy hex nuts can be packed with B7 studs by line item, size and flange package, reducing assembly sorting time during plant maintenance or project installation.
Industrial equipment fastenersAssembly
Manufacturing
FAQ
Grade 2H heavy hex nuts are commonly used with ASTM A193 Grade B7 studs. Controlled-hardness Grade 2HM nuts are commonly used with ASTM A193 Grade B7M studs.
Grade 2H is the common general pressure-bolting nut grade. Grade 2HM has controlled maximum hardness and grade-specific testing for use with B7M-type systems. A 2HM marking alone does not establish NACE compliance; the applicable sour-service standard and project requirements must be stated separately.
No. ASTM A194 is primarily used for pressure service bolting, while ASTM A563 is used for structural bolt assemblies. The two should not be substituted without engineering approval.
Yes. PTFE coated A194 nuts are often used with PTFE coated studs, but coating thickness, friction assumptions and thread fit should be confirmed.
Send grade, size, thread type, finish, quantity, matching stud bolt grade and certificate requirements. For kits, include the stud diameter and length schedule.
Yes. Grade marking, heat number traceability, MTC, CoC, proof load or hardness reports can be supplied according to order requirements.
Send the A194 grade, size, thread, coating, quantity, matched stud grade and certificate scope. Specify B7 with 2H or B7M with 2HM, plus any applicable NACE / ISO requirement. Grade 7 remains available where specified.
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