JIS 5K & 10K Flange Dimensions: A Detailed Specification Guide
This guide provides the key dimensions for JIS (Japanese Industrial Standard) 5K and 10K flanges. These are common pressure ratings for Japanese-standard flanges. Knowing these dimensions is critical for fitting and sourcing the right parts for your project.
Understanding JIS “K” Pressure Ratings
The “K” in 5K or 10K is a pressure class rating, similar to “Class” in ANSI standards. It is not a direct pressure value like kg/cm².
A higher “K” number means a thicker, stronger flange designed for higher pressure at a given temperature. The actual maximum working pressure depends on the flange material and temperature, which you must check from official JIS pressure-temperature tables.
How JIS Compares to Other Standards
JIS flanges follow the metric system. They are not dimensionally interchangeable with ANSI (inch-based) or DIN flanges, even for similar pressure capacities.
| Standard System | Pressure Rating Example | Approximate Equivalent (Pressure Capacity) | Interchangeable? |
| JIS (Japan) | 10K | ANSI Class 150, DIN PN16 | No |
| JIS (Japan) | 20K | ANSI Class 300, DIN PN25/40 | No |
| ANSI (USA) | Class 150 | JIS 10K, DIN PN16 | No |
| DIN (Europe) | PN16 | JIS 10K, ANSI Class 150 | No |
JIS B2220 Flange Dimension Tables (10K & 5K)
All dimensions are in millimeters (mm). These are key reference dimensions for standard sizes. “A” is the flange outside diameter, “B” is the bolt circle diameter, and “n” is the number of bolt holes.
JIS 10K Flange Dimensions (Standard Series)
| Nominal Size (mm) | Outside Diameter (A) | Bolt Circle (B) | # of Bolts (n) | Bolt Hole Dia. |
| 10A | 75 | 50 | 4 | 12 |
| 20A | 90 | 65 | 4 | 12 |
| 40A | 140 | 110 | 4 | 16 |
| 65A | 175 | 145 | 4 | 16 |
| 100A | 225 | 190 | 8 | 19 |
| 150A | 295 | 250 | 8 | 23 |
| 200A | 350 | 300 | 8 | 23 |
| 250A | 415 | 355 | 12 | 23 |
JIS 5K Flange Dimensions (Light Series)
| Nominal Size (mm) | Outside Diameter (A) | Bolt Circle (B) | # of Bolts (n) | Bolt Hole Dia. |
| 10A | 75 | 50 | 4 | 12 |
| 20A | 90 | 65 | 4 | 12 |
| 40A | 130 | 100 | 4 | 16 |
| 65A | 155 | 125 | 4 | 16 |
| 100A | 190 | 160 | 8 | 16 |
| 150A | 250 | 215 | 8 | 19 |
| 200A | 295 | 265 | 8 | 19 |
| 250A | 350 | 320 | 12 | 19 |
Important Notes on Dimensions:
- The “A” size (e.g., 100A) corresponds to the nominal bore. 100A is approximately equivalent to a 4-inch (NPS 4) pipe.
- A 10K flange is thicker and has a larger outer diameter than a 5K flange of the same nominal size.
- For some smaller sizes (10A, 20A), 5K and 10K flanges may share the same outer diameter, but the 10K flange will be thicker.
Frequently Asked Questions
Q: How do I identify a JIS 10K flange?
A: Look for markings stamped on the flange’s outer rim. It should include the standard (JIS B2220 or sometimes JIS B2210), the pressure rating (e.g., 10K), the material, and the size (e.g., 100A). The metric bolt sizes are a clear indicator.
Q: Can I connect a JIS 10K flange to an ANSI Class 150 flange?
A: Not directly. The bolt circle diameters (B) and bolt hole sizes are different. A JIS 100A (10K) flange has a 190 mm bolt circle. An ANSI 4″ Class 150 flange has a 190.5 mm (7.5 inch) bolt circle. The 0.5 mm difference will cause misalignment. You need a special adapter.
Q: What are the common materials for JIS flanges?
A: Common materials include carbon steel (similar to S25C, S35C), and stainless steel (SUS304, SUS316). The material must be suitable for your fluid, pressure, and temperature.
Q: When would I use a 5K flange vs. a 10K flange?
A: Use a 5K flange for lower pressure, non-critical services like water lines or general plant air where weight and cost savings are beneficial. Use a 10K flange for higher pressure process lines, steam, or more demanding services.
Q: What’s the difference between JIS B2220 and JIS B2210?
A: JIS B2220 is the primary standard for steel pipe flanges. JIS B2210 covers the basic dimensions for cast iron pipe flanges. For standard steel flanges, B2220 is the correct reference.
Conclusion
JIS 5K and 10K flanges are designed to precise metric dimensions. You cannot substitute them with ANSI or DIN flanges. For a proper fit, you must use the correct JIS-specified part or a custom adapter. Always verify the pressure rating against your operating temperature using the correct material tables.
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