Back-pressure clappet valve (KOS) is designed to prevent reverse fluid flowing into coil tubing (CT) during run-in-hole operation.
The valves are manufactured with 38, 42, 45 and 54 mm diameters.
Basic parameters and dimensions:
| Parametr | Value | |||
| Designation | KOS-38 | KOS-42 | KOS-45 | KOS-54 |
| Rated string size, tubing string, mm | 60; 73; 89 | 60; 73; 89 | 60; 73; 89 | 73; 89 |
| Pressure differential, MPa, to | 25 | 25 | 25 | 25 |
| Bore minimum diameter, d, mm | 14 | 14 | 20 | 22 |
| Length, L, mm | 405 | 405 | 415 | 510 |
| Diameter, D, mm | 39 | 42 | 45 | 54 |
| Weight, kg, not greater than | 1,9 | 2,4 | 3,2 | 5,9 |
| Working fluid | Drilling fluid, oil, water | |||
| Fluid temperature, °С, not greater than | 100 | |||
| Connecting thread dimensions per GOST 24705-81, 8724-81, 9150-81 | M 30 х 2 | M 42 х 2 | ||