Grit Blasting

[Riz]

Dear friends,

I want to calculate how much grit is required for grit blasting on shell (if shell material EN10025-2 S355j2+N/EN10025-3 S355 NL-Z25, shell dia is 4m and height is 80m) with following specs?

Abrasive blasting to Sa 2½ with a sharp-edged surface profile corresponding to Rugotest No. 3,BN9a, Keane-Tator Comparator, 2.0 G/S, 2 S, or ISO Comparator, Medium (G). Also kindly share following information with your SUPPLIER as per Nordex Specifications.
The surface shall be cleaned by grit-blasting (EN ISO 8504-2) to Sa 2½ (ISO 8501-1). The blasting abrasive must be free from dust, salt and other contaminants.Surface roughness should be between 50 and 70 µm (roughness ‘medium (G)’ EN ISO 8503-2).

Regards,

Riz

[loriolo]

I do not understand what you mean, because the grit blast machine usually recycle the grit, so a little part of it is lost, and you must change the grit after many application, if you mean the time necessary, it depend of the grit blasting machine do you use.

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I do not understand what you mean, because the grit blast machine usually recycle the grit, so a little part of it is lost, and you must change the grit after many application, if you mean the time necessary, it depend of the grit blasting machine do you use.

[Riz]

I mean to say that how i can calculate the required quantity of grit according to above mention specifications?

Regards,

Riz

[MichiganMan]

4m dia, 80m height... Probably don't want/need to use a recycler for this job. Disposable media. Probably something like boiler slag or crushed glass. I too lazy today to look up the string of letters you used to identify the alloy, but if it is something really hard, then coarser black beauty and higher air pressure to get the job done. If it is a softer alloy, then lower air pressure will get the job done.

I would estimate 24000-40000 lbs (11000-18000 kg)of abrasive (6-10 cu.yds.) depending on what density material you choose to use.

[Riz]

Thank you Michigan Man for your reply.

Actually i am first time calculating grits so i want to know, what a formula/method to calculate grits for Rugotest No. 3, N9a between Surface roughness 50 and 70 µm (roughness ‘medium (G)’ EN ISO 8503-2)?

Regards,

Riz

[MichiganMan]

Unfortunately there isn't really a good formula for grit consumption. Experience is the best teacher and there are too many variables to consider a true formula to be a viable option. Most abrasive blast equipment manufacturers publish a grit consumption chart that gives you flow rates based on the size nozzle and pressure in your system. That is at least a good starting point. Test blasting a small area (as small as 2 sq.ft. to the desired condition can even give you a pretty good idea where you'll wind up.