So....my blasting cabinet imploded today...

[Swingpress]

I can't believe this happened. It was a genuinely stupid mistake and at least the damage was limited.

So a few months ago I had picked up a harbor freight floor standing sand blasting cabinet to supplement a smaller unit I have. After a couple months of reading and then just plain forgetting about it I decided Togo ahead and put it together. I sealed the whole thing VERY well! Because the last thing I want is dust and media on everything. At least I assume it must have been because i kicked on the light and forgot that my shop vac was also on the same switch. When not in use I use the included plug to seal the unit to prevent moisture from entering. Well bout 2.3 seconds after the shop vac fired up and before I could reach the switch to turn it off the cabinet started to creak and groan then, pop!






This was all after pushing out what I could by hand.
Looks like I have Swingpress work ahead of me.

 

[Swingpress]

I must have sealed it fairly well because even with the breather port open the gloves inflate like balloons!

Vacuum blasting anyone?

 

[469 runner]

Wow, the sheetmetal must be really thin on that cabinet. I have a Dee Blast cabinet that with the vacuum on would **** the gloves out like that, but to deform the cabinet? That is crazy.

 

[Schurkey]

That is crazy.

No, that's Harbor Freight.

 

[bushmechanic]

On the bright side, you clearly have a future in hull repair.

 

[ambenz]

You will not do that again!
Fix and move on...I think in one time or another, we been thru one of those moments!
As they say...."That should buff right out!"

 

[afazz]

Just hook it up to your air compressor and explode it back out

 

[PelicanPines]

Wow... that sucked...

Quietly steps back after realizing what I said.

 

[countryroad82]

Well I don't know how to say it but at least you can give yourself a pat on the back for getting it sealed so well. I'm sure that was one of those 'well fawk' moments lol

 

[Swingpress]

At least the blue point grinder base I was blasting came out ok and painted up nice!

Before


After: hammer matte finish

 

[Swingpress]

Well I don't know how to say it but at least you can give yourself a pat on the back for getting it sealed so well. I'm sure that was one of those 'well fawk' moments lol

 

[tarmy]

You ****...figuratively speaking...

You got a great shop vac though...

 

[LXCam]

Sorry for laughing, but that's fn funny.



Oops!

 

[gnpenning]

Soooo what shop vac are you using???

Pictures

 

[SuperCat]

Gotta see the shopvac from hell .....pix please.

 

[Swingpress]

It's nothing special. 4hp 10gal. But moves 130cfm and will pull 55inches of vacuum. The cfm is why I bought it as I wanted something to handle fumes. (Have played with Aqua regia in the past and clean glass with piranha solution occasionally)

Got it for a good price though.

 

[SuperCat]

Since you have already examined the blast cabinet, can you tell us what you think caused the damage? Is a $50 Shop-Vac that powerful, or is the cabinet sheet metal too thin? Or is the design of the cabinet that inadequate? All of the above? Thanks for posting, I am thinking about buying that same cabinet. Well, I was thinking about it, but now I'm not so sure.

 

[Swingpress]

Since you have already examined the blast cabinet, can you tell us what you think caused the damage? Is a $50 Shop-Vac that powerful, or is the cabinet sheet metal too thin? Or is the design of the cabinet that inadequate? All of the above? Thanks for posting, I am thinking about buying that same cabinet. Well, I was thinking about it, but now I'm not so sure.

Those questions could definitely open a can of worms here lol.

Quite frankly the main cause of damage is just physics at work. I will expand in case some of this isn't fresh in the minds of other readers.

The units we typically measure pressure in are either: Atmospheres (atm), torr., or Pascals (Pa.). Though here in the U.S. everyone is usually accustomed to seeing PSI. At sea level the pressure you experience on your body just walking around is 1atm which is equivalent to the following:

1atm = 760torr = 101325Pa = 14.6959psi.
You see they are all the same!
You never feel any discomfort because, among several other factors, your body is pushing back against this pressure with equal pressure. Hence you live and are none the wiser to what's happening.

When we look at the last unit (psi) what happened to the cabinet starts to make sense. When the shop vac turned on and began evacuating the cabinet of atmosphere the external pressure remained at 14.6959psi pushing against the outside, so no surprise there, what that means though, is that all of a sudden there was nothing inside the cabinet to push outward from inside.

To put this into perspective consider a solid 1 cubic foot chunk of steel just sitting on the ground. The atmospheric pressure pushing on all sides of that cube is (as above) 14.6959psi. But to really get a grip of what that means let's find out how much force there is on it.

Surface area of 1 cubic foot steel = 864 square inches then multiply by our pressure of 14.6959psi. Because Pressure = Force / Area so to find force it would be: Force=Pressure x Area.

864 sq inches (Area) x 14.6959psi (Pressure) = 56480.2N (Force)

So we have 56480.2Newtons of force on our cube just sitting outside. So we convert our value for force to something we might be more familiar with like tons.

56480.2N = 6.3486 TONS of force on the cube.

Now, the surface of the blast cabinet is obviously much larger so that value would go up even higher!
All in all, not surprising why it did what it did.

Now as for design? I think that the HF cabinet is (NOTE: for the money) more than adequate and you are getting a good machine if you pay a little attention to it while assembling it. I used latex, quick drying, caulk on every seam, bolt, nut, glass pane, etc. I have no desire to have a mess in my shop that I didn't directly create. Also, yes there are heavier duty, better made cabinets for sale. But even on a $2000.00 cabinet I would still take the extra hour and seal everything I mentioned above myself. So for those reasons this cabinet was a win in my book. The material is thinner yes, but not so much so that I was afraid of damaging it during assembly. Even a heavier cabinet could not be expected to tolerate what I accidentally subjected mine to.

Also, after spending some time talking to Mike from the Tacoma Company, they build the best upgrade kits for the HF blasters, we both agree that the HF is one of if not the best import economy blasters available. It's biggest flaws (in my opinion) are lighting, hoses, and the gun. So I have made a few mods of my own to solve some feed issues others have complained about. Biggest thing is just don't ask a machine to do something it just can't do. Here, I asked my cabinet to act as a vacuum chamber, hence the crunch.

Disclaimer: I know my math was quick and dirty but it was to convert a less well known measurement to something more easily relatable.

Btw: this is what atmospheric pressure can do!

 

[Strouty]

All I could think of................

You have to go from **** to blow!

 

[joel63]

55 inches of vacuum?

I've never seen a vacuum gauge read that high.

 

[Brian_WK]

55 inches of vacuum?

I've never seen a vacuum gauge read that high.

Probably of H20 not mercury.

Brian

 

[braidmeister]

Behold the power of vacuum

You probably won't do something like that again...but there's always next time

 

[The Tool Tyrant]

It's clearly a case of .02thin" ( oh-too-thin) sheetmetal.

 

[Showkey]

It's not about the thin metal.......it about the negative pressure and lack of make up air venting.
If the gloves "inflate" when the vacuum is turned on there is NOT adequate make up air venting.

 

[finn]

It's clearly a case of .02thin" ( oh-too-thin) sheetmetal.

The material is perfectly adequate for a blast cabinet.

It would make a terrible submarine, though.

 

[sberry]

It's not about the thin metal.......it about the negative pressure and lack of make up air venting.
If the gloves "inflate" when the vacuum is turned on there is NOT adequate make up air venting.

This, too tight and there is no leakage there is no air movement.

 

[CajunJohn]

No, that's Harbor Freight.

Well said


Sent from my iPad using Tapatalk

 

[Showkey]

Well said


Sent from my iPad using Tapatalk

For poor design with no vent..........not for poor material. Although it could be poor material just not the cause of this problem.

Look at any quality cabinet it will have a fresh vent........preferably at the opposite end from the vacuum port. This creates a cross flow to clear the dust.