Why does my blast cabinet have glass AND acrylic?

[phil81uk]

Hi! I've just almost assembled my SBC220 blast cabinet. It's a very popular, fairly large, low cost blast cabinet, probably made in the far east. It came with both a glass panel, and an acrylic screen. The instructions say that the acrylic should be on top of the glass, and the bottom of the glass has a protective film.

So the layers are, from top to bottom:

1. Acylic (top layer)
2. Glass
3. Protective film.

Why do I need the glass and the acrylic on top of each other?

 

[brightspark]

generaly just the glass on top and sacrificial protective film under it to stop the glass from being marked and thrown away when there's no visibility

 

[phil81uk]

Thanks. I've skipped installing the acrylic, just put in the glass and protective film.

Also why are there two ports on the cabinet? One is 56mm diameter and is marked exhaust port. I will attach my extractor to it. The second is 90mm diameter and is marked "air inlet" and I can't think what it's for. Air comes in through the gun so why is an inlet needed?

The inlet is connected via a flue like channel:

 

[rtbcomp]

The acrylic on the top will protect you if the glass shatters.

You need more air than the nozzle supplies to scavenge the dust from the cabinet. The shape of the inlet is to stop media getting out of the cabinet.

 

[henry Kadzielski]

Good morning
Once you use this machine you will see what has been said above. The dust builds up as you blast as there is no grit cleaning in these suction blast machines. I also have one of these and have had for many years. What I have done is increase the gun size and nozzels to allow greater air flow. The suction blasters are slower than an equivalent pressure blast machines. That is is you have the available air. I also put a 100mm suction outlet atop the machine and connected it to a stand alone dust extractor. Both the existing air inlets and outlets are now for air in. The dust now clears much faster and you can see what you are doing. I am using about 50cfm of air in this machine and it works good now. I also have a pressure blast cabinet bigger that what you have and the result is much more noticable with pressure blast.
Regardless of what you have a cabinet is still much better that doing without one

 

[T0rnado69]

The acrylic on the top will protect you if the glass shatters.

as rtbcomp has said.

last thing you want is bits of glass flying up at your face while your looking through it.

 

[bletchmonster]

I have a guyson cabinet and have discovered that cling film is brilliant for protecting inside of glass. The vacuum from the extracter sucks it away from the glass so it acts like a bouncy castle for the grit.
Seems to last a few hours before it fugs up and is nearly cheap enough, even for me!

 

[rcx132]

I tried some generic clear film off ebay once on my old home made cabinet, to protect the glass. I don't think it worked well as it distorted the view.

I'm not quite clear on what Henry is saying. I've never seen a pressure blast cabinet. I've seen the pressure blasters but they are just containers.

I've also heard about some sort of driers that are used in blasting, but I'm not sure what they are supposed to dry, the media or the air? I've never seen one, not even on the internet.

 

[brightspark]

I don't even bother with protective screen just the glass sat in some angle and caulked in with silicone it lasts ages and doesn't dust up . when worn just cut round with Stanley knife and stick a new bit in

 

[phil81uk]

So the cabinet is solid and doesn't leak. But the metal tube that sucks media out the collector at the bottom of the cabinet keeps blocking. My media is OLD, it's been sitting in the garage for years. Could it be moist? It's the sealey media that, oops, I've just read Sealey said it's not suitable for use in blast cabinets :/ Boo I've just ordered a fresh bag of it.

 

[brightspark]

don't worry about it it says don't use expendable grit in cabinets but it works ok. if its damp dry it out

 

[henry Kadzielski]

Good morning rcx132.
You asked, so here goes. I use a refrigerated dryer which is coupled to my compressor and dries the air prior to it going out to the shop. This works very well and gives me no trouble with moisture down stream and grit delivery problems. I know that it works, as when it stopped one day the lines and grit got contaminated with moisture and the cabinet didn't work. The drier is the blackish box to the right of the compressor.

Second pic is the old suction cabinet modified with 100mm suction dust extraction. This cabinet I have had for some time and it did spend it's time outside prior to me getting the workshop which it lives in now

The final pic is the new pressure blast cabinet. This is basically a suction blast cabinet with a small pressure pot attached underneath. The cabinet to the left is the integrated dust collection system. This dust collector works very well and clears the cabinet quite quickly. Hope this clears up things

 

[rcx132]

Hi Henry, that's quite a serious setup. I'm a hobbist though and spending £200+ for a drier (seems to be the cheapest they go for) plus fitting it in my tiny workshop is too much.

I've seen the guide on this website says you can get water out by running through long lengths of downwards sloping copper. I'm not even sure if I can do that. I'm going to swap out the media and look at a water separator filter.

Also my compressor pump is on the floor, rubber mounted, and then my tank is hanging fro the ceiling. So the compressed air is being pushed upwards and water will flow towards the pump. I need to check in the pipes if there's water gathering.

I've mixed two usernames in this thread, phil81uk and rcx are both me. I had to change my username because I had some security problems on another forum but my laptop was still logged in with the old username.

 

[henry Kadzielski]

Good morning rcx132.
Anytime you are compressing air there will be moisture in the lines, on question. As the air cools the moisture drops out. The long lengths of copper are to cool the air to allow the moisture to drop out and not travel down the line. You can also run some copper line in a bucket of cold water (like a still), on the out let pipe from the bucket you will need to put some form of trap with a drain (you can get auto drains). Ideally the copper pipe in the 'bucket' would be bigger to slow the air speed down to allow greater cooling and moisture separation. There are many ways to skin a cat, it is up to you what works for you. The biggest advantage of the refrigerated dryer is it's small space related to it's capacity to remove moisture from the compressed air. They are also rated to run continuously at high ambient temps without drama and or requiring supervision. The bucket system will work, however will require the water change depending on the duration of the compressor running.
Hope this helps.