HIGH-PRESSURE WATERBLAST
ACIER
The use of a high-pressure water jet through a nozzle at a pressure of 70 MPa (10,000 psi) or more to prepare a surface for coating or maintenance inspection. High-pressure water provides velocities greater than 340 m/s (1,100 ft/s) at the nozzle outlet. High-pressure wateron steel does not produce a surface profile, unlike sandblasting; it exposes the original profile of the surface if one exists. However, it removes paint, contaminants, rust, salts and much more.
The different standardized degrees of surface preparation used in the industry for preparing steel with high-pressure water are:
- NACE/SSPC WJ-1 – Clean to bare substrate or ISO 8501-4 Sa 3
- NACE/SSPC WJ-2 – Very thorough cleaning or ISO 8501-4 Wa 2.5
- NACE/SSPC WJ-3 – Thorough cleaning or ISO 8501-4 Wa 2
- NACE/SSPC WJ-4 – Light cleaning or ISO 8501-4 Wa 1
CONCRETE
For concrete surface preparation, high-pressure water takes on a whole other importance. Indeed, for concrete, this method will not only remove laitance, efflorescence, grease, oils and other contaminants, but also epoxy and urethane coatings with the appropriate nozzles. It is used on horizontal surfaces as well as on vertical and overhead surfaces. With ultra-high-pressure water, hydrodemolition is also possible.
The NACE No. 6/SSPC-SP 13 standard is generally used for concrete surface preparation, together with the ICRI guides.
As with steel, there are different degrees of surface preparation standardized by the ICRI (International Concrete Repair Institute). Ten degrees of surface preparation are currently recognized, CSP 1 to 10.