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Technical Specifications
Quick reference for the technical decisions that drive flange selection. Material grade summary, pressure-temperature highlights, NACE hardness, and impact testing.
Material Grade Quick Reference
| Grade | Type | Min Yield | Min Tensile | Typical Use |
|---|---|---|---|---|
| A105 | Forged carbon | 36 ksi | 70 ksi | General pressure service |
| A350 LF2 | Carbon impact tested | 36 ksi | 70 ksi | Low temp to -50 F |
| A350 LF3 | 3.5 Ni carbon | 37 ksi | 70 ksi | Cryo to -150 F |
| A694 F60 | High-yield carbon | 60 ksi | 75 ksi | Pipeline X60 mate |
| F304L | Austenitic stainless | 25 ksi | 70 ksi | General corrosion |
| F316L | Mo-bearing stainless | 25 ksi | 70 ksi | Chloride resistance |
| F11 | 1.25 Cr 0.5 Mo | 30 ksi | 60 ksi | Moderate elevated temp |
| F22 | 2.25 Cr 1 Mo | 30 ksi | 75 ksi | Hot service to 1100 F |
| F91 | 9 Cr 1 Mo V Nb | 60 ksi | 85 ksi | Power main steam |
| A516-70 | Carbon pressure plate | 38 ksi | 70 ksi | Blind and ring flanges |
| A36 | Structural plate | 36 ksi | 58 ksi | AWWA plate-cut, structural |
NACE MR0175 Hardness Limits
For materials exposed to wet H2S service per NACE MR0175 / ISO 15156, hardness is controlled to prevent sulfide stress cracking. Common limits:
- Carbon and low alloy steels: 22 HRC (about 248 HV) maximum
- F22 and F91 alloy: per supplementary annex, typically 22 HRC max post-PWHT
- F304L and F316L stainless: 22 HRC maximum, plus ferrite content limits
- Duplex 2205 and 2507: 28 HRC maximum, separate annex
Charpy Impact
Charpy V-notch impact testing is required on low-temperature pressure service. Common test temperatures and minimum absorbed energy: A350 LF2 at -50 F, 13 ft-lb min average. A350 LF3 at -150 F, 15 ft-lb min. A694 F60 at -20 F, 20 ft-lb min. Test temperature and acceptance criteria are project-specific and called out on the purchase order.