You helped a fair bit Jim, Thank you.
You make a good point about immersed surfaces. Surface boats have it bad enough, and were adding a lot more pressure on top of that. Are painting flaws can't hide for long.
I usually blast wood surfaces for furniture, and a fair bit of the hard woods I use are dark in color and have small checks in the surface that the white silica sand gets into and stands out visually. Then I have to pick it out with a dental tool, which can take hours. So that was the main reason I started to use the black copper slag. Then I discovered it cut faster then silica, which cut way down on the hours of blasting I or my employees need to blast a particular product.
It's a pretty cheap product as well. It's the same stuff they throw onto urethane coated surfaces like Rhino linner coatings for traction on floors, stairs, and walkways. I plan to do that on the little standing platform I'll install infront of my conning tower and the little aluminum platforms above my inflatable pontoons.
Regards,
Brent H
From: kocpnt@tds.net
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Copper Slag Blasting Media
Date: Tue, 12 Aug 2008 19:54:58 -0500
Hi Brent,
In almost all cases, when alternative blast medias are used it is as a result of regulation of silica dust, which can and will kill you if you do not use proper remediation methods.
This does not usually mean that the new and/or alternative method is better, only that it meats someones criteria for an alternative.
The main reason that silica was the only main media in use for many years are as follows:
1. Quartz is cheap
2. It provides a nice crisp angular profile if the media is properly graded.
3. If purchased from a good supplier, it will have less than 3/10 of one percent of contaminants.
4. It will generally contain less than 1/10 of 1 percent of moisture.
I have never had failures with copper slag media, since I have never used it. All impurities in blast media will to some extent become imbeded in the base metal.
You might be fine using copper slag, but from my experiance as a contractor, any risk is too much when it comes to possible warranty costs.
An immersion service will disbond many coatings that will last almost forever above water and pressure.
I hope this helps you in some way. There are many way to solve the problem and we all are budget constrained at some point so there may be more than one correct answer.
Best Regards,
Jim K
----- Original Message -----
Sent: Tuesday, August 12, 2008 1:37 PM
Subject: RE: [PSUBS-MAILIST] Copper Slag Blasting Media
Hello Jim,
Thank you for your input. It got me to go ask some more questions and search for more reading materials. What type of coatings have you had trouble applying over a copper slag blasted metal surface, and how did you prep the bare surface after blasting. Where copper slag is derived is also important.
I have found that copper slag blasting media removes, old paint, rust, and other materials about three times faster then silica quartz sand media. Also the metal surface is much rougher, which allows my coatings to adhere better, mechanically speaking.
I talked with three different metal fab guys that use copper slag commercially in my area, and they don't recall having any trouble with coatings not adhering properly to a copper slag blasted metal surface. I do however plan to use a metal prep cleaner, etcher regardless.
One of the guys I spoke to used to work in a Washington state metal fab company, and he said that Washington state OSHA rules wouldn't allow them to use silica sand as a blasting media at all. Idaho rules appear to allow commercial businesses to use silica sand blasting media. But they still have safety regulations regarding it's use.
http://www.osha.gov/SLTC/etools/silica/protect_against/protect_against.html
http://www.osha-safety.org/osha_crystalline_silica.asp
If one uses Copper slag blasting media they still of course should use good safety equipment.
Abstract
"This research investigates occupational exposure to metal and total particulate aerosols during abrasive blasting operations using one substitute abrasive, copper slag. Airborne exposures to metal (As, Be, Pb, Cr, Cd, V, and Ti) and total particulate aerosols from two copper slag sources are evaluated by the collection and analysis of personal breathing zone samples during abrasive blasting operations in both indoor and outdoor settings. Results from this research indicate that abrasive blasting operations using copper slag abrasive can generate, in a relatively short time, total particulate, lead, arsenic, and chromium exposures that exceed permissible exposure limits (PELs) set by the Occupational Safety and Health Administration (OSHA). Results also show statistically significant differences in exposure concentrations between slag sources. A correlation between total particulate concentrations and metal concentrations is indicated in both slag sources and in both indoor and outdoor settings. Results of this research allow occupational health and safety professionals to make a more informed determination of the degree of health risk posed to workers during abrasive blasting operations using commercially obtained copper slag abrasive. " |
Regards,
Brent Hartwig
From: kocpnt@tds.net
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] The Ugly Duckling Submarine
Date: Sun, 3 Aug 2008 15:15:32 -0500
Hi Brent,
It's up to you, but blasting with copper slag will contaminate the surface of the sub if you are doing serious blasting. The copper does inhibite many types of coatings from bonding as well as they are capable of. I do this stuff for a living, and while it is messy, it's really hard to beat a good clean quartz sand blast. Be sure to use respirators and other controls to minimize exposure to silica dust.
Best Regards,
Jim K
----- Original Message -----
Sent: Tuesday, July 29, 2008 9:27 PM
Subject: [PSUBS-MAILIST] The Ugly Duckling Submarine
Hello SMMOM's, (Submadman Organization Members)
Well my sub has come off it's high horse, It doesn't look so high and might now that it's off it's pedestal and trailer. It looks and feels a lot different now.
Just so you all know I haven't been completely goofing off of late, here are some new photos of my K-250 taken apart in preparation for copper slag blasting. I started a new blog page that I can add photos to. So let me know if it works ok.
http://k-250-submarine-refit.spaces.live.com/photos/cns!5085D10EB6AFE47C!124/
No worries, I took plenty of pictures and notes as I took it apart. I'll share that data at a pace.
So now as George would say, it's Full Bore Boggy submarine building.
Regards,
Brent Hartwig
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