3. EN 1092-1: The PN (Nominal Pressure) System<\/p>\n
The PN rating system designates pressure in bar. However, like ASME, the actual performance varies by temperature.<\/p>\n
Common Ratings: PN6, PN10, PN16, PN25, PN40, PN63, PN100.<\/p>\n
Designation: Identified by DN (Nominal Diameter) and PN.<\/p>\n
4. The Danger of “Direct Conversion”<\/p>\n
Engineers often mistakenly assume PN16 = Class 150. While they may serve similar pressure ranges, they are physically incompatible for several reasons:<\/p>\n
Dimensional Mismatch: Bolt circle diameters (BCD), bolt hole counts, and flange thicknesses differ. An ASME Class 150 flange will not bolt to an EN PN16 flange.<\/p>\n
Facing Variations: Raised Face (RF) heights and Flat Face (FF) requirements vary between standards, leading to gasket seating failures.<\/p>\n
Material Behavior: Different material groups across standards respond differently to thermal expansion and stress.<\/p>\n
5. Critical Selection Checklist<\/p>\n
To avoid field failures and procurement errors, verify these parameters before ordering:<\/p>\n
Standard System: ASME B16.5, EN 1092-1, or JIS?<\/p>\n
Nominal Size: NPS (inches) or DN (mm)?<\/p>\n
Pressure Rating: Class or PN?<\/p>\n
Material Spec: (e.g., A105, A182 F316L, A350 LF2).<\/p>\n
Design Temp\/Pressure: Consult the specific P-T (Pressure-Temperature) Tables.<\/p>\n
Facing Type: RF (Raised Face), FF (Flat Face), or RTJ (Ring Type Joint).<\/p>\n
Frequently Asked Questions (FAQ)<\/p>\n
Q1: Can ASME Class 150 and EN PN16 flanges be interconnected?<\/p>\n
A: No. While their pressure ratings may be similar at certain temperatures, their physical dimensions are different. The Bolt Circle Diameter (BCD), the number of bolt holes, and the flange thickness do not align. Attempting to force a connection will lead to bolt misalignment and uneven gasket compression, resulting in high leakage risks and potential joint failure.<\/p>\n
Q2: Why isn’t the flange named after its maximum working pressure?<\/p>\n
A: Because a flange’s pressure capacity is a function of temperature. As operating temperatures rise, the yield strength of the metal decreases, lowering the allowable pressure. “Class” or “PN” are designations used to reference Pressure-Temperature (P-T) Rating tables, which engineers use to determine the safe limit for specific operating conditions.<\/p>\n
Q3: Do carbon steel and stainless steel flanges have the same capacity if they are both Class 300?<\/p>\n
A: No. Material properties vary significantly. For instance, at elevated temperatures, the strength of stainless steel (e.g., SS316) degrades at a different rate than carbon steel (e.g., A105). You must always verify the specific Material Group in the standard’s P-T tables to find the correct pressure limit.<\/p>\n
Q4: What is the difference between RF and FF faces, and does it affect the rating?<\/p>\n
A: RF (Raised Face) has a small concentrated surface area to increase sealing pressure, while FF (Flat Face) covers the entire flange surface. While they fall under the same pressure class, they are not always interchangeable. FF faces are typically used when connecting to cast iron equipment (like pumps or valves) to prevent the flange from cracking when the bolts are torqued.<\/p>\n
Q5: What are the essential parameters for ordering or specifying a flange?<\/p>\n
A: To ensure total compatibility, you must confirm these six elements:<\/p>\n
Standard: (e.g., ASME B16.5 or EN 1092-1)<\/p>\n
Nominal Size: (NPS in inches or DN in mm)<\/p>\n
Pressure Rating: (Class or PN)<\/p>\n
Material Grade: (e.g., ASTM A105, A182 F316L)<\/p>\n
Facing Type: (e.g., RF, FF, RTJ)<\/p>\n
Schedule\/Bore: (Required for Weld Neck flanges to match the pipe’s ID, e.g., Sch 40 or Sch 80)<\/p>\n
Technical Support and Supply<\/p>\n
Hunan Tubular Steel Industry Co., Ltd.<\/p>\n
Since 2012, we have provided high-performance piping solutions for oil and gas, mining, and renewable energy projects worldwide. We ensure your components meet strict ASME and EN compliance to prevent installation delays.<\/p>\n
Need technical assistance? Contact our engineering team for customized flange selection and material validation.<\/p>\n
Media Contact<\/span> Selecting the wrong flange pressure rating is a leading cause of piping incompatibility, leakage, and costly downtime. A common industry pitfall is assuming a “Class” or “PN” number represents a fixed pressure limit in psi or bar. In reality, these … Continue reading
Company Name:<\/strong> Hunan Tubular Steel Industry Co., ltd.<\/a>
Email:<\/strong> Send Email<\/a>
Country:<\/strong> China
Website:<\/strong> https:\/\/www.tubularpiles.com\/<\/a><\/p>\n<\/p>\n","protected":false},"excerpt":{"rendered":"