Dry ice blasting concern on carbon steel 1

[compit]

Hi All,

I have a client’s supplier who is proposing to to use dry ice blasting to remove a leaded epoxy paint from the internal side of a mild (0.3%) carbon steel vertical above ground storage tank.

I have yet to come across dry ice blasting. My initial concern is that the process is quoted as being effective when the area being blasted is temporarily brought well below the Charpy impact test value for the steel. (

https://info.coldjet.com/the-definitive-guide-to-dry-ice-blasting)

The figures I see quoted where the process is effect is -109°F / -78.9°C.
This localised low temperature coupled with impacts from dry ice pellet kinetic energy & impact thermal kinetic effect " "micro-explosions" make me worry that localised embrittlement / cracking or stress raisers may be born out of the process.

Would anyone have any experience with dry ice blasting on mild carbon steel, or would anyone know of any standards that might address this topic?

Many thanks

 

[Gr8blu]

compit: I happen to be in a facility that uses dry-ice blasting on a regular (if not quite every day) basis. We apply it to all kinds of surfaces and materials, in all kinds of conditions (we repair rotating electrical machines, both AC and DC, over a pretty wide range of power/speed/voltage). Our "impacted" materials range from carbon steel (both hot- and cold-rolled, both coated and uncoated), copper and aluminum, epoxy- and solvent-based resins, insulating materials, and of course paints and varnishes. No appreciable damage to the metallic surfaces - and no resulting special preparations for re-coating. In fact, the dry ice process is so forgiving that we (usually) don't have to even go back and turn a commutator - unless it was already damaged in some other fashion. and the copper is much more susceptible to damage than a comparable steel surface would be. The trick to keeping it enough to do the job without damaging the part is two-fold: the size of the particles, and the pressure used to "blast" them at the desired surface. Things usually work best when the particle size is kept small and the pressure low.

Converting energy to motion for more than half a century

 

[compit]

Gr8blu Thanks for sharing, your comment on procedures to follow, particle size etc exactly highlights the need for proper procedures to be in place, which to me is where peer reviewed research or standards come into play to define what limits may apply. Unfortunately this dry ice blasting is a one off for me being proposed by clients supplier so there won't be any studies or research carried out and I'll be advising using grit blasting or UHP or the likes instead.

 

[chicopee]

Regardless on the type of blasting, just remember to follow the OSHA safety guidelines when personnel is under lead exposures.

 

[IFRs]

From the Shell report:

It should be recognised that Dry Ice Blasting cannot replace grit blasting for new equipment. It is
strictly meant for maintenance purposes. In addition, Dry Ice Blasting is not recommended for
large areas like large tanks where grit blasting will show more productivity. But for relatively
smaller pieces of equipment, such as piping, pipelines, valves & fittings, Dry Ice Blasting can be
used to prepare the steel surface for maintenance painting

 

[TugboatEng]

If waste generation is a concern, ultra high pressure water blasting is also an option. Even with leaded paints, basic filtration is all that is required for sewer disposal.

 

[compit]

@IFRs, thanks, I didn't miss that, my clients contractor has quoted weeks as opposed to what would be few days by conventional methods. The client may have been sold on the potential lower cost of waste disposal without the added weight of lead contaminated grit.
@tugboateng, thanks, I've already suggested UHP as one of the alternatives.

Someone else experienced using dry ice also let me know of the risk of carbonic acid creation where CO2 dissolves in water to form carbonic acid, with carbonic acid be so corrosive to carbon steel I must recommend that that dry ice (CO2) is not used inside a tank as existing corrosion will be damp and may then becomes damp with carbonic acid.

 

[chicopee]

I would drive around for contractors involved in removing leaded paint from bridges before such bridges are painted. These contractors could have useful information.