Contamination When Sandblasting and/or Painting Big Tanks or Structures

Hello inedesca,

From what I know, sandblasting materials are generally benign - they are not dangerous to the environment. However, throughout the sandblasting operation, particles may break up into smaller particles. This can be an inhalation hazard. Dust or vapor masks will be required for prevention of conditions such as silicosis.

Quantitation of solvents in paints may be required if your usage is high enough and depending on the location of the operation.

The only way to make sure that the solvent vapors do not make it to the environment is to conduct the operation in an enclosed chamber that is ventilated, taking all of the solvent vapors to a treatment process. This treatment can consist of scrubber and/or thermal oxidation technology.

Scrubbers have been around for a long time. They require a substantial amount of maintenance. Of the thermal oxidation technologies, Regenerative Thermal Oxidizers (RTOs)have the cheapest operating cost, provided you can supply a relatively constant stream of Volatile Organic Compounds (VOCs) in sufficient concentration to keep the oxidation chamber "lit", thereby requiring little or no utility natural gas. RTOs require a relatively low amount of maintenance compared with scrubbers.

In order to find out what equipment you will need, you need to estimate the amount of VOCs you will generate:

Mass of VOCs generated = (Mass of coatings used) - (Mass of coatings used) * (solids weight-fraction of coating).

I would contact the environmental agency in your country for guidance.

Mike

Thank you Mikerho, trouble comes with the sizes, we are talking of railroad tanks and bridge structures, no way to enclose them.

Seems to me that there is no solution, if I have to contaminate, sorry, there is nothing that can be done in this case.

Sand blasting now is not permitted in most of the places (silicosis) . We use grits instead of sands, the size ensures that the powders are to minimum.

For painting, try to get the painting process that has maximum transfer ratio, that way you may be able to help the environment maximum (like Electrostatic, HVLP, etc). It is not only the volatiles (that anyway can not be helped) but the airborne paints that have more damage potential to ecology (soil, water, air pollution)

You can use walnut shell as your abrasive which completely brakes down.

In a slightly different situation we used a heavy tarp hanging under neath the with a course filter at the bottom, like at gaint funnel. It was on secured by a rail so you just slid it along.

The funnel let water though into a tank which was filtered again and re-used when done we then treated (sorry can't tell you the chemical we used to treat it) and then just let it go as storm water. I do recall we had to get the water tested before we did this.

The waste collected by a course filter was dump in a truck and taken to a chemical waste dump (who I believe had their own treatment process) most of our waste was old style lead paint and pickling acid though.

The whole set up didn't catch everything but a good 90% it

For most paint application surface preparation you want something like an SA 2.5 surface finish. Walnut shells will not give this to you they are too soft.

Hi Everyone,

Don't handle solvent containing epoxies, use solventless or 100% solid epoxy coatings.

During blasting operation, the dust is the only danger for workers and around. Good protection is necessary and you can continue to clean, Gil.

Containing the paint sounds impossible, airless electrostatic would give best result, with least amount of overspray. As far as the sand blasting is concerned, they make a water blaster in which sand is carried in the water, messy as hell, but no dust. I believe it's called wet blasting. I would use a wet blast, (sand & water), followed by a rust converting primer applied through an airless electrostatic machine, to take care of any minor surface rust that develops.

If you have proper ventilation and air moniters 2 words will suffice DRY ICE From solid to gas in the twinkling of an eye. NEXT

In open ? large structures ?

Yes, bridge components to be assembled in the field.

These might be about 30 feet long x 6 feet wide, weighing some 4 tons each manufactured at our shop and sent by truck to the site, so you understand there is no way to use a blas and a paint booth.

In PA the usually have large "tarps" stretched around the sides and bottoms of where they are sand blasting with vacuums to remove the materials. The big issue for us is that many of our older bridges were painted with lead based paints so the sanding material and paint is considered a hazardous material and has to be treated that way.

SSPC - SP5/NACE No. 1