NPS (inches)	Class 150 (mm)	Class 300 (mm)	Class 600 (mm)
2″	15.9	19.1	25.4
4″	19.1	25.4	38.1
6″	22.2	30.2	47.6

Note: These thicknesses include the raised face, and assume the use of carbon steel materials.

To check EN or DIN blind flange thicknesses, refer to standards like EN 1092-1 Type 05 or DIN 2527. You can also request a technical data sheet from sasaflange to ensure compliance with your required flange type and rating.

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Key Factors Affecting Thickness Calculation

If a custom flange is needed, or if you want to verify a flange beyond standard limits, consider the following factors:

1. Design Pressure (P)

This is the maximum internal pressure the flange will experience. It must be known or specified in bar, MPa, or psi.

2. Nominal Size (NPS or DN)

Larger diameters require thicker flanges due to the increased surface area exposed to pressure.

3. Material Yield Strength (Sy)

Stronger materials like stainless steel 316 or alloy steel can handle more pressure with less thickness.

4. Design Temperature (T)

As temperature increases, material strength generally decreases, requiring more thickness.

5. Corrosion Allowance

In aggressive environments, an extra corrosion allowance (commonly 1.5 to 3 mm) is added.

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General Calculation Formula (Based on ASME VIII Div 1)

The blind flange thickness can be roughly estimated using the formula:

h = (P × D²) / (4 × Sy × E × K)

Where:

• h = minimum thickness (mm)

• P = design pressure (MPa)

• D = flange diameter (mm)

• Sy = allowable material stress at design temperature (MPa)

• E = weld joint efficiency (typically 1 for non-welded flanges)

• K = design factor (usually 1.5 or higher for safety)

Important: This is a simplified approach and should not replace official pressure vessel calculations governed by ASME or EN codes. Always consult a mechanical engineer or refer to certified design software.

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Example Calculation

Let’s say you need a blind flange for a 6-inch carbon steel pipe at 10 bar pressure and 100°C.

• P = 1 MPa (10 bar)

• D = 152 mm

• Sy = 138 MPa (for A105 at 100°C)

• E = 1

• K = 1.5

Plug into the formula:

h = (1 × 152²) / (4 × 138 × 1 × 1.5)
h ≈ 30 mm

So, the blind flange should be at least 30 mm thick for safety.

Alternatively, select a Class 300 flange, which has a standard thickness of 30.2 mm for 6″.

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When to Use Custom Flange Thickness

Custom flange designs may be necessary when:

• The pressure exceeds standard ASME Class 2500

• The pipe system uses non-standard materials

• The application involves vibration, fatigue, or cyclic loading

• Extra corrosion allowance is required

• Local regulations mandate specific thickness values

In such cases, sasaflange can manufacture blind flanges based on your design drawings or technical requirements, including full dimensional inspection and pressure testing.

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Conclusion

Understanding how to calculate blind flange thickness helps ensure system safety, cost-efficiency, and compliance with international standards. For most applications, standard thicknesses defined by ASME, EN, or DIN are sufficient. However, in high-pressure or custom conditions, careful calculation based on material strength and pressure is essential.

For certified blind flanges with accurate thickness and material data, rely on sasaflange. Our engineering team can assist with standard selection or custom designs, providing durable and pressure-rated solutions for all your flange needs.