Our client approached us looking for a solution to a project involving the removal of epoxy coating from steel fuel storage tanks.
Foremost, they wanted to offer a solution to the facility owner, showing a safer blasting method without compromising productivity.
The epoxy coating had an average thickness ranging from 275 microns to 300 microns. Additionally, it was in poor to fair condition.
Previously, the contractor had stripped the tanks on this site using a manual dry abrasive blasting process in which the blasting operator worked from a boom lift. Using the dry blasting, production rates for removal of the old coating were typically in the 15-25 m² per hour range.
VertiDrive Multi Purpose Robots
For this application, we recommended the VertiDrive M4 convertible system. The VertiDrive M4 enables UHP waterjet blasting and can be reconfigured for open abrasive blasting.
The coating is removed rapidly with UHP water jetting. Subsequently followed by abrasive blasting to create the required profile.
In advance, we prepared a section of the tank wall. Secondly, we blasted the wall to a SA 3 white metal finish with a surface profile of 70 microns. Thirdly, we applied an epoxy tank coating to a dry film thickness of 300 to 320 microns.
We trialed two methods with the Vertidrive M4:
1. Captive UHP Waterjet operating at 2800 bar 26 LPM, and
2. Dry Abrasive Blasting using two #8 (1/2`` orifice) blast nozzles at 690 KPA air pressure, and using GMA Speedblast Garnet as the abrasive medium
VertiDrive M4 – UHP Configuration
Initially, we tested the VertiDrive M4 UHP configuration. We used a Vermeer trailer-mounted vacuum system for vacuum extraction.
During UHP usage, we calculated the paint removal rate to be 49 m²/hr on a straight run stripping a 400 mm wide path.
However, maneuvering time for subsequent runs reduced the overall production rate to an average of 41 m²/hr.
The resultant finish of an SSPC SP WJ 1 Waterjet standard flash rust was not noticeable in the 2 hours following the trial.
VertiDrive M4 – Abrasive Blast Configuration
Afterwards, we tested the abrasive blasting configuration of the VertiDrive M4. Previously, we stripped the area using the UHP setting. The test site was then hosed down and left overnight until a medium flash rust had formed on the bare steel.
We calculated the paint removal rate when using the Vertidrive M4 abrasive blasting configuration. This was 69 m²/hr.
The VertiDrive on a straight run stripped a 15m wide path. Instead, the cleaning rate increased to 75 m²/hr.
The resultant finish was to a SA 3 White Metal standard.
In conclusion, we reduced abrasive consumption by 80% by switching to UHP blasting. Additionally, production increased by 20%.
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