Flotsam and Jetsam

In Mid-May, 2008, I got two separate inquiries about “how much metal will UHP WJ remove compared to dry Blasting?

In each case, the owner was looking at corroded areas and didn’t have a protocol or specification for UHP WJ for corrosion removal.

The question of material removal of metals has been studied for several years. This subject has been looked at in depth by the companies like Thiokol who use UHP WJ to remove corrosion, and the aircraft engine manufacturers (Delta, Lufthansa, KLM, United, General Electric) who use UHP WJ to remove hard coatings where they previously used chemical stripping or very fine grit. These companies have very intricate parts and cannot stand loss of metal.

1991 Metallurgy Report on Surface Stress of Steel after Cleaning with 36,000 psi waterjet.

There is a metallurgy report dated 1991 from Materials Evaluation Lab who looked at this for Jet Edge who was doing some work for a Global Oil Production Company.  The oil company engineers wanted and analysis of stress on steel after cleaning with 36-40,000 psi waterjetting.  The UHP WJ equipment was an intensifier system- this means it had low flow volume.

These are the engineer’s conclusions:

1. Pressurized water effectively removed rust and other corrosion products from metal surfaces. This was done with minimal disturbance of microstructural features.

2. Methods using abrasive particles were necessary for the removal of adherent mill scale. Those techniques cause severe distortion of the metal surface.

3. The pressurized water method was considered the best preparatory cleaning for non-destructive inspection. It offered a more “authentic” representation of the surface than the other methods evaluated.