In plants with Japanese pumps, compressors or heat exchangers the equipment side is often JIS flanged. If the piping was designed to ASME, the connection point becomes a compatibility problem.
The differences
| Criterion | ASME B16.5 | JIS B2220 |
|---|---|---|
| Measuring system | Inches, NPS | Metric, A (mm) and B (inch) series |
| Class designation | Class 150, 300… | 5K, 10K, 16K, 20K, 30K, 40K |
| Bolt circle | ASME table | Generally smaller |
| Bolt thread | UNC / 8 UN | Metric ISO |
| Face | RF, FF, RTJ | RF and FF common |
The K value indicates approximate pressure capacity: 10K is roughly 10 kgf/cm², about 10 bar. Class 150 and 10K look close, but the dimensions do not match and they cannot be bolted together.
Where it appears
- Japanese pump and compressor connections
- Shipyard and marine piping
- Boundary connections of imported package units
- Heat exchangers and boilers manufactured in Asia
How to bridge it
- Adapter flange: A purpose made part with a JIS face on one side and ASME on the other
- Spool piece: A short pipe with a different standard flange at each end; the cleanest boundary
- Change the equipment flange: Ask the equipment maker for the project standard, which is the best answer on a new project
Remember that bolt threads change too: metric on the JIS side, imperial on the ASME side. An adapter flange needs a separate stud set for each face.
When ordering
On the JIS side, state the class (10K, 20K and so on), nominal size (A or B series), face form and material. Share the equipment drawing and we will verify dimensions and work out the adapter solution with you: enquiry form.
FAQ
Are 10K and Class 150 the same?
Their pressure capacities are close, but dimensions differ and bolt circles do not match.
What are JIS A and B series?
The A series follows metric pipe sizes, the B series inch based pipe sizes.
What is the cleanest transition?
A spool piece with a different standard flange at each end, which makes the boundary clear and simplifies maintenance.
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