Technical Specifications
Engineering reference data covering pressure-temperature ratings, material grades, bolt torque, gasket selection, and flange design fundamentals to support your calculations and selections.
Pressure-Temperature Ratings
Maximum allowable working pressure (MAWP) varies by material and temperature per ASME B16.5 Table 2.
Pressure-temperature ratings vary by class and material group. Refer to ASME B16.5 Table 2 for the certified values. The following gives a sample of Class 300 carbon steel (Group 1.1) per ASME B16.5 Table 2-1.1:
- 100°F = 740 PSI
- 200°F = 675 PSI
- 300°F = 655 PSI
- 400°F = 635 PSI
- 500°F = 600 PSI
- 600°F = 550 PSI
F304 and F316L follow Group 2.2 and Group 2.3 respectively per ASME B16.5 Table 2. F316L ratings are slightly lower than F304 at most temperatures.
Material Grade Comparison
ASTM A105
Carbon Steel
Applications
General purpose, low-temperature
Temp Range
Up to 800°F
Relative Cost
Baseline
Most economical choice; requires corrosion protection
ASTM A182 F304
Austenitic Stainless
Applications
Corrosion resistance, food/beverage
Temp Range
Up to 1200°F
Relative Cost
2-3x A105
Non-magnetic; excellent oxidation resistance
ASTM A182 F316L
Austenitic Stainless (Low-C)
Applications
Chloride/seawater service
Temp Range
Up to 1000°F
Relative Cost
2.5-3.5x A105
Enhanced molybdenum for pitting resistance
ASTM A182 F22
Chromium-Molybdenum
Applications
High-temperature power service
Temp Range
Up to 1100°F
Relative Cost
1.5-2x A105
Creep resistance for sustained loads
ASTM A182 F91
9Cr-1Mo
Applications
Advanced power systems
Temp Range
Up to 1200°F
Relative Cost
2-2.5x A105
Higher strength; reduces wall thickness
Duplex 2205
Duplex Stainless
Applications
Seawater, sour gas service
Temp Range
Up to 800°F
Relative Cost
3-4x A105
Dual-phase; superior stress-corrosion cracking resistance
Bolt Torque Specifications
Recommended torque values for flange bolts. Actual requirements vary by application, gasket, and lubrication.
| Bolt Size | Material | Dry | Machine Oil | Moly (MoS₂) |
|---|---|---|---|---|
| 1/2" x 13 | B7 | 35-40 ft-lbs | 25-30 ft-lbs | 20-25 ft-lbs |
| 5/8" x 11 | B7 | 60-70 ft-lbs | 43-50 ft-lbs | 35-40 ft-lbs |
| 3/4" x 10 | B7 | 105-120 ft-lbs | 75-85 ft-lbs | 60-70 ft-lbs |
| 7/8" x 9 | B7 | 150-170 ft-lbs | 105-120 ft-lbs | 85-100 ft-lbs |
| 1" x 8 | B7 | 220-250 ft-lbs | 155-175 ft-lbs | 125-145 ft-lbs |
| 1/2" x 13 | B8 (Stainless) | 15-20 ft-lbs | 12-15 ft-lbs | 10-12 ft-lbs |
| 3/4" x 10 | B8 (Stainless) | 50-60 ft-lbs | 38-45 ft-lbs | 30-35 ft-lbs |
| 1" x 8 | B8 (Stainless) | 100-120 ft-lbs | 75-90 ft-lbs | 60-75 ft-lbs |
Important: These are general guidelines only. Always follow equipment manufacturer specifications and industry standards (ASME, API, NACE) for critical applications. Bolt preload affects flange integrity; over-torquing causes stress corrosion cracking; under-torquing causes leakage.
Gasket Selection Fundamentals
Spiral Wound
Stainless+Graphite
Uses: General industrial, high-pressure
Service: Oil, gas, steam
Temp: Up to 1000°F
PTFE Envelope
PTFE (Teflon) wrapped
Uses: Corrosive liquids, food-grade
Service: Acids, bases, solvents
Temp: Up to 400°F
Rubber
Elastomer (Neoprene, EPDM)
Uses: Water systems, low-temp
Service: Water, glycol
Temp: -20°F to 250°F
Graphite
Graphite composite
Uses: High-temperature steam
Service: Saturated steam
Temp: Up to 650°F
Compressed Non-Asbestos
Compressed non-asbestos (e.g., Klinger-style)
Uses: General industrial standard
Service: Oil, water, steam
Temp: Up to 400°F
Spiral-Wound
Spiral-wound metal/filler (e.g., Flexitallic-style)
Uses: Extreme pressure/temp
Service: High-pressure systems
Temp: Up to 1500°F
Gasket Selection Rules:
- 1.Match gasket chemistry to fluid being sealed (acids, bases, hydrocarbons)
- 2.Select thickness appropriate for flange face pressure
- 3.Consider temperature extremes (both hot and cold operating)
- 4.Ensure gasket compatibility with bolt materials (stainless vs carbon)
- 5.For critical applications, always test gasket swell and compression set
Flange Design Fundamentals
Bolt Hole Patterns
Flange bolt holes are arranged in a circular pattern (bolt circle, or BC) equidistant from the flange center. The number of bolts varies by flange size and pressure class. Bolt spacing must match both the flange and mating equipment.
Rule of thumb: Count the number of bolts and measure bolt circle diameter before ordering. One mismatched bolt circle requires custom drilling-an expensive rework.
Face Types & Finishes
Raised Face (RF): Gasket seating area protrudes; reduces gasket area; most common industrial standard.
Flat Face (FF): No protrusion; matches equipment flat faces; common in large diameter flanges.
Ring Joint (RJ): Specialized groove for metal ring gaskets; high-pressure and severe service.
Surface Finish: Mating surfaces typically 125-250 µin Ra per ASME B16.5. Rough finishes cause leakage.
Hub Length & Bore Tolerance
Bore diameter must accommodate the pipe size plus clearance for installation and future replacement. Hub length affects welding strength and thermal cycling performance.
Critical: Bore diameter is typically ±1/16" to accommodate various pipe mill tolerances. Verify bore clearance before installing to avoid binding.
Back Bevel & Hub Extensions
Weld neck flanges include a back bevel to accommodate full-penetration welds. Custom hub extensions reduce wall thickness requirements in thick-wall pipe applications. Request certified drawings when custom extensions required.
Installation Guidelines
- 1.Verify bolt hole pattern matches mating equipment (count bolts and measure BC diameter)
- 2.Clean all mating surfaces-rust, paint, debris cause leakage
- 3.Install gasket centered on seating surface
- 4.Insert bolts hand-tight, then tighten in crisscross pattern (never radial)
- 5.Torque bolts in multiple passes to recommended value
- 6.Never exceed recommended torque-over-tightening distorts flange and causes leakage
- 7.Re-check torque after initial operation to account for gasket creep
Questions About Technical Specifications?
Our engineering team can review your application, provide pressure-temperature ratings for your exact material and condition, and discuss installation best practices.
Contact Our Engineers →