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December 2 - December 6, 2019

What is best media to use to remove aged epoxy coal tar from a steel tank before re-lining?

Selected Answers

From Lydia Frenzel of Advisory Council on December 7, 2019:
When I first saw this question, my answer was "it's obvious. use water-jetting," as I have spent the last 30 years working on the WJ and Wet Abrasive Blast (WAB) cleaning methods. I didn't respond immediately. It is gratifying that other people also proposed this method. The contractor should select the most efficient combination of pressure and flow, the stand-off distance, and the transverse rate for the removal rate. If possible, vacuum recovery for the solids and water is used. At least, have a pick-up pump suitable for solids and water in the immediate vicinity of the removal so that there is minimal standing water. If it is needed, equipment exists to separate the solids and liquid, remove dissolved components, and get the water back into the system. I have seen separation and recycling since around 1994.

From Aajjay Sunkay of ASSETREIFURB ENGINEERRS on December 6, 2019:
Use of dry ice as the media for blasting  prevents heat generation during removal of coal tar epoxy. One of the important benefits of dry ice for blasting is no dust generation.  But the limitations include no  surface profile generation and the high level of noise generation, which requires  hearing protection. You can also try wet blasting, which contains a mix of chilled iron grit and water as media with high pressure above 35000 psi up to 45000 psi . Care should be taken that no heat is generated during blasting and hence wet slurry blasting will serve the purpose of removal of coal tar epoxy coating from steel tank.

From Paul Tsourous of Jupiter on December 2, 2019:
If performing the work during warm weather, I would suggest removing the coating first with UHP (+40k water pressure), then select the appropriate abrasive to achieve proper surface profile. If you are performing this work during cold temps, the coal tar should become brittle, and could be removed efficiently with medium to large angular abrasives.

From Geir Christianslund of Aker Solutions MMO on December 2, 2019:
Use ultra-high pressure water.

From Larry Muzia of Exceletech Coating & Applications, LLC on November 27, 2019:
Typically, aged coal tar is brittle and with good procedure can be removed without great effort. Crushed glass works well if you are in an area near a distribution center; otherwise, black beauty can do the work as well. As should be noted, use clean air, plenty of cfm and psi for the nozzle size.  Use a sweeping technique   to reduce heat build-up within the layer of coal tar, which can slow down the removal process. If you do not require a deep blast profile, a fine grade will do a nice job.

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Tagged categories: Coating Materials; Paint and coatings removal; Tanks and vessels

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