Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
Monel 400 U-Bolts - Pipe & Frame Clamps, UNS N04400 ASTM F468
Monel 400 U-bolts (also Monel 400 U-clamp, Alloy 400 U-bolts, UNS N04400 U-bolts, Nickel 400 pipe clamp, Werkstoff 2.4360 U-bolt) are U-shaped fasteners threaded on both legs and clamped through a backing plate or saddle with two hex nuts. Shape is set by project drawing; chemistry comes from ASTM B164 annealed rod and the mechanical floor on the threaded legs follows ASTM F468 Class A. The alloy registers as UNS N04400. Used where the clamp sees hydrofluoric acid, flowing seawater, sour gas at NACE MR0175 limits, or a non-magnetic constraint on a naval deck. Monel® is a registered trademark of Special Metals Corporation; TorqBolt is not authorized by, affiliated with or endorsed by Special Metals.
U-Bolt Subtypes Manufactured in Monel 400
Four U-bolt geometries cover the bulk of nickel-copper alloy demand. Each is bent cold from ASTM B164 annealed rod, with thread rolled on both legs after the bend, then re-annealed to relieve bending strain.
- Round U pipe clamp: half-circle bend, inside dimension equal to pipe OD plus 1 to 2 mm clearance. Used on B36.10 carbon pipe, B36.19 stainless pipe and Monel 400 line pipe. Pairs with a flat plate, saddle or cushioned clamp.
- Square U frame clamp: two right-angle bends, used on rectangular hollow section, structural channel and instrument-air manifold supports. Inside width set to section width; throat depth to section height plus backing plate.
- V-bolt: 60 to 90 degree included angle (rather than a U), seats positively on a round bar, wire rope or hose where the clamp must resist axial slip. Common on offshore lift accessories.
- Leaf-spring U-bolt: heavy section (rod 5/8 in upward), square bend, fitted across a chassis spring pack. Used on marine engine sub-frames and minesweeper running gear where non-magnetic and seawater-tolerant clamping is required.
Standard U-Bolt Sizes (Rod Diameter and Inside Dimension)
Stock U-bolts are formed in the rod diameter / inside dimension combinations below; non-standard bends are CNC-formed against a project drawing. Inside dimension is the clearance between the two legs, set 1 to 2 mm above the pipe OD or section width.
| Rod diameter | Metric thread | UNC thread | Inside dim. (in) | Inside dim. (mm) | Pipe NPS covered |
|---|---|---|---|---|---|
| 1/4 in | M6 | 1/4-20 | 0.50 to 2.50 | 13 to 64 | NPS 1/4 to NPS 2 |
| 5/16 in | M8 | 5/16-18 | 0.75 to 3.00 | 19 to 76 | NPS 1/2 to NPS 2-1/2 |
| 3/8 in | M10 | 3/8-16 | 1.00 to 4.50 | 25 to 114 | NPS 3/4 to NPS 4 |
| 1/2 in | M12 | 1/2-13 | 1.50 to 6.625 | 38 to 168 | NPS 1 to NPS 6 |
| 5/8 in | M16 | 5/8-11 | 2.375 to 8.625 | 60 to 219 | NPS 2 to NPS 8 |
| 3/4 in | M20 | 3/4-10 | 3.50 to 10.75 | 89 to 273 | NPS 3 to NPS 10 |
| 7/8 in | M22 | 7/8-9 | 4.50 to 12.75 | 114 to 324 | NPS 4 to NPS 12 |
| 1 in | M24 | 1-8 | 6.625 to 14.00 | 168 to 356 | NPS 6 to NPS 12 |
| 1-1/4 in | M30 | 1-1/4-7 | 8.625 to 16.00 | 219 to 406 | NPS 8 to NPS 14 |
F468 Mechanical Floor on the Threaded Legs
The threaded legs qualify to ASTM F468 Class A (F 468U / F 468U4). F468 caps hardness at 25 HRC across the size range, 10 HRC inside the NACE MR0175 35 HRC sour-service ceiling. Source: ASTM F468/F468M Table 2.
| Marking | Diameter (in) | Hardness | Tensile (ksi) | Tensile (MPa) | Yield min (ksi) | Yield min (MPa) | Elongation |
|---|---|---|---|---|---|---|---|
| F 468U | 0.250 to 0.750 | 75 HRB to 25 HRC | 80 to 130 | 552 to 896 | 40 | 276 | 20% |
| F 468U | 0.875 to 1.500 | 60 HRB to 25 HRC | 70 to 130 | 483 to 896 | 30 | 207 | 20% |
| F 468U4 | 0.875 to 1.500 | 75 HRB to 25 HRC | 80 to 130 | 552 to 896 | 40 | 276 | 20% |
| F 468HF | all | 60 to 95 HRB | 70 to 120 | 483 to 827 | 30 | 207 | 20% |
Manufacture and Traceability
B164 annealed bar is cut to length and cold-bent on a CNC mandrel to the drawing inside dimension. The blank is solution-annealed at 871 to 982 degC to dissolve bending strain; thread is rolled on both legs after anneal so the surface stays in compression. Each lot ships from one heat number with marking on the bend crown. MTC is issued to EN 10204 type 3.1 for process service and to type 3.2 for sour service, NORSOK M-650 and pressure-boundary supply.
Companion Backing Plate, Nuts and Washers
Each U-bolt ships with the matching saddle and clamping hardware from the same B164 / B127 heat where a single-heat assembly is specified. The complete kit is the supply unit.
| Component | Standard | Material | Form | Quantity per U-bolt |
|---|---|---|---|---|
| Backing plate / saddle | Project drawing or MSS SP-69 | Monel 400 plate to ASTM B127 | Flat plate, drilled saddle or cushioned isolator | 1 |
| Hex nut (heavy hex) | ASTM F467 grade Ni-Cu (F 467U) | UNS N04400 | Heavy hex or standard hex | 2 |
| Flat washer | DIN 125 / DIN 9021 fender | UNS N04400 | Plain washer (see washers) | 2 |
| Lock device (optional) | DIN 985 / DIN 982 | UNS N04400 nylon-insert lock nut | Vibration-resistant retention | 2 (replaces hex nuts) |
Sour Service Compliance (NACE MR0175)
The Monel 400 U-bolt clears the NACE MR0175 / ISO 15156-3 hardness gate by design: F468 caps the legs at 25 HRC against a 35 HRC sour-service ceiling. The post-bend anneal restores the annealed condition required by the standard. The companion ASTM F467 nut and the B127 backing plate share the same chemistry, so the clamped joint carries one sour qualification, not three. Verify H2S partial pressure, chloride concentration and temperature against ISO 15156-3 Annex A.4. See sour service applications.
Applications
- HF acid and HF alkylation pipe support: default U-bolt on HF-wetted lines in API RP 751 inspection regimes. The nickel-copper film resists HF attack across the 70 to 95 percent acid band. See HF acid resistance and HF alkylation.
- Marine pipe restraint and seawater service: condenser tube clamps, brackish-water cooler supports, ballast-water piping, sea-chest manifold restraints on FPSO and shipboard. Eliminates bimetallic corrosion against 316L and copper-alloy condenser tube. See marine applications and seawater corrosion.
- Offshore platform tubing: holds seamless tubing to deck cable trays and instrument-air manifolds in NORSOK M-650 supply. The 25 HRC F468 cap satisfies NORSOK sour-service on the same order.
- Naval non-magnetic deck fittings: N04400 permeability is below 1.005 mu_r, qualifying the U-bolt for minesweeper and submarine deck hardware. See magnetic permeability.
Frequently Asked Questions
Q. Is the U-bolt covered directly by ASTM F468?
A. F468 covers straight-shank wrought nonferrous bolts and studs; it does not call out U-bolt geometry. The Monel 400 U-bolt is supplied to F468 chemistry and mechanical floor on the legs, with U-bend per project drawing or MSS SP-69.
Q. Round U pipe clamp vs square U frame clamp?
A. The round U has a half-circle bend sized to pipe OD, used on B36.10 pipe. The square U has two right-angle bends and seats on rectangular hollow section or channel. Both are bent from B164 rod, threaded on both legs, supplied with two hex nuts and a backing plate.
Q. Do Monel 400 U-bolts qualify for NACE MR0175 sour service?
A. Yes. Legs are F468 Class A (25 HRC max), the post-bend anneal restores the annealed condition required by ISO 15156-3, and the EN 10204 type 3.2 MTC carries the NACE compliance statement.
Q. Can the U-bolt ship with a cushioned saddle?
A. Yes. The Monel 400 U-bolt clamps over a TFE or chloroprene cushion seated on a Monel 400 saddle, sized to pipe OD and selected for temperature.
Related Reading
Parent family Monel 400 bolts (ASTM F468); companion line pipe seamless pipe (B165); legs spec ASTM F468. Source bar ASTM B164 / round bar; backing plate ASTM B127 / plate. Companion nut ASTM F467 / heavy hex nuts; washers. Sour-service rationale sour service (NACE MR0175); HF rationale HF acid resistance.
Request a Quote
Send project drawing (or rod diameter, inside dimension, leg length, thread, lock-device preference, quantity) plus marking and MTC requirement to info@torqbolt.com or WhatsApp +91-22-66157017. Ex-Mumbai price and lead time returned within one working day. Domestic India 3 to 7 working days; export through JNPT or Mundra.
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