Choosing the correct carbon steel flange requires understanding both dimensional standards En pressure-temperature ratings. Flange dimensions determine compatibility with the piping system, while the pressure class specifies the maximum allowable working pressure under different operating temperatures.
The most widely used dimensional standards include ASME B16.5 for NPS ½”–24″, ASME B16.47 for NPS 26″–60″, and EN 1092-1 for European piping systems.
Carbon Steel Flange Dimensions
Flange dimensions vary depending on:
- Applicable standard (ASME, EN, JIS, AWWA)
- Nominal Pipe Size (NPS or DN)
- Pressure Class or PN Rating
- Flenstype
- Facing Type (RF, FF, RTJ)
Typical dimensions include:
| Dimensie | Beschrijving |
| Buitendiameter (OD) | Overall flange diameter |
| Boutcirkeldiameter (BCD) | Diameter through the bolt hole centers |
| Aantal boutgaten | Varies by size and pressure class |
| Diameter boutgat | Required bolt clearance |
| Flensdikte (T) | Neemt toe met de drukclassificatie |
| Hub Diameter | Applicable to Weld Neck flanges |
| Bore Diameter | Matches pipe inside diameter |
| Raised Face Height | Typically 1.6 mm (1/16″) for Class 150 & 300; 6.4 mm (1/4″) for Class 600 and above |
Pressure–Temperature Ratings for Carbon Steel
Common Carbon Steel Flange Materials:
| Materiaal | Typical Service |
| ASTM A105 | Standard temperature piping |
| ASTM A105N | Normalized applications requiring improved toughness |
| ASTM A350 LF2 | Low-temperature service |
| ASTM A694 F52/F60/F65/F70 | High-strength pipeline systems |
De ASME B16.5 Pressure–Temperature Rating Chart is one of the most important references for selecting carbon steel flanges. It specifies the maximum allowable working pressure for each pressure class at different operating temperatures based on the flange material.
The chart applies to common carbon steel flange materials such as ASTM A105, ASTM A350 LF2, En ASTM A216 WCB, helping engineers ensure that the selected flange is suitable for the intended service conditions.
How to Read the Chart
The table consists of four key elements:
- Material Group – Identifies the applicable flange material (e.g., ASTM A105 forgings).
- Operating Temperature – Listed in degrees Celsius (or Fahrenheit in other editions).
- Drukklasse – ASME pressure classes including Class 150, 300, 400, 600, 900, 1500, and 2500.
- Maximum Allowable Working Pressure – The maximum pressure (in bar or psi) permitted at each temperature.
ASME Pressure Class Overview
| Drukklasse | Typische toepassingen |
| Klas 150 | Water, HVAC, low-pressure process piping |
| Klas 300 | General industrial service |
| Klas 600 | Refining, petrochemical, higher-pressure systems |
| Klas 900 | High-pressure process plants |
| Klas 1500 | Severe operating conditions |
| Klas 2500 | Extremely high-pressure applications |
Opmerking: Pressure classes are not equal to the maximum allowable pressure. The actual allowable pressure depends on the flange material and operating temperature as defined in ASME B16.5.
Pressure Rating Selection Guide
| Recommended Class | Operating Condition |
| Klas 150 | Low-pressure water systems |
| Klas 300 | Algemene industriële leidingen |
| Klas 600 | Steam and refinery service |
| Klas 900 | High-pressure hydrocarbons |
| Klas 1500 | Critical oil & gas applications |
| Klas 2500 | Extreme pressure process systems |
Factors Affecting Pressure Rating
Several factors influence the allowable working pressure of a carbon steel flange:
- Material grade
- Operating temperature
- Flensafmetingen
- Pressure class
- Gasket type
- Bolt material and preload
- Design code (ASME B16.5, EN 1092-1, etc.)
Always consider the complete flange assembly rather than the flange alone when determining pressure capability.
FAQs About Carbon Steel Flange Dimensions and Pressure Ratings
Refer to the applicable standard, such as ASME B16.5 or EN 1092-1, and identify the nominal pipe size (NPS or DN), pressure class or PN rating, and flange type. Each standard provides detailed dimensional tables for outside diameter, bolt circle, bolt holes, thickness, and bore.
Generally, yes. Higher pressure classes have thicker sections and are designed to withstand higher pressures. However, the allowable working pressure also depends on the material and operating temperature.
In many cases, a Class 300 flange can be used in place of a Class 150 flange if the piping design allows it. However, bolt lengths, gasket selection, mating flanges, and system design should all be verified before substitution.
ASME pressure classes (e.g., Class 150, 300, 600) and EN PN ratings (e.g., PN16, PN40, PN100) are based on different standards and are not directly equivalent. While there are approximate comparisons, flange dimensions, drilling patterns, and pressure-temperature ratings differ, so they should not be interchanged without engineering verification.
As temperature rises, the mechanical strength of carbon steel decreases. ASME B16.5 accounts for this by reducing the maximum allowable working pressure at elevated temperatures to ensure safe operation.
Full-service supplier of Carbon Steel Flange for all your requirements
SSM offers significant product advantages in the manufacture of Carbon Steel Flange. Whether it’s quality or price – we will meet your requirements.
Why Choose SSMALLOYS Carbon Steel Flanges?
SSMALLOYS manufactures and supplies premium forged carbon steel flanges for demanding industrial applications worldwide. Our products comply with international standards and are available in a wide range of sizes, pressure classes, and materials.
Wij bieden:
- ASTM A105, A350 LF2, and A694 forged flanges
- ASME B16.5, ASME B16.47, EN 1092-1, JIS, and AWWA standards
- Weld Neck, Slip-On, Blind, Socket Weld, Threaded, and Lap Joint flanges
- Pressure Classes 150–2500 and PN6–PN400
- EN 10204 3.1 / 3.2 certification
- PMI, UT, MT, PT, and third-party inspection
- OEM manufacturing and custom dimensions
- Fast global delivery with complete export documentation
Whether you require standard piping flanges or custom-engineered forgings, SSMALLOYS provides dependable quality, competitive pricing, and responsive technical support to help keep your project on schedule.
Looking for a trusted carbon steel flange manufacturer?
Whether you need standard ASME flanges, EN 1092-1 flanges, large-diameter forged flanges, or custom-engineered solutions, SSMALLOYS is ready to support your project with high-quality products, competitive pricing, and dependable global delivery.
Contact our sales team today for a fast quotation, technical assistance, or customized manufacturing solutions tailored to your requirements.
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