L1 : for ISO, DIN tubes
L2 : for SMS tubes
| DN | 8 | 10 | 15 | 20 | 25 | 32 | 40 | 50 |
|---|---|---|---|---|---|---|---|---|
| L1 (mm) | 90 | 117 | 127 | 137 | 177 | 196 | 211 | 240 |
| L2 (mm) | 90 | 150 | 182 | 226 |
| State | Way of facturing | Ra (μm) | Aspect | Grain |
|---|---|---|---|---|
| 1 | Rough | 3,2 | Satin | 60 |
| 2 | Mechanical polishing inside body | 1,6 | Half-brillant | 120 |
| 3 | Mechanical polishing inside body | 0,4 | Fine-brillant | 280-380 |
| 4 | State 1 + electropolishing internal and external | 2 | Brillant | 120 |
| 5 | State 1 + electropolishing internal and external | 0,8 | Brillant polish |
180-320 |
| 6 | State 1 + electropolishing internal and external | 0,4 | Mirror polish |
300-500 |
The equivalence between Ra and the grain size is only for information. Stainless steel bonnets may be electropolishing.
Electropolishing is an electro-chemical method of removing metal from a surface. The piece to be treated is immerged in a tank filled up with an electrolyte and connected to the positive pole of a current potential. The negative pole is connected to the cathode. The current drives with a high potential the peaks and with a low potential the cavities.