If this is a conventional sand blasting cabinet, the majority of your abrasive media should be falling back into the bottom hopper of the cabinet. The vacuum helps improve visibility by drawing the lighter airborne dust toward the cabinet exit. It also helps reduce the mess around the cabinet by establishing a negative pressure differential to negate the amount of pressurized air being injected into the cabinet from the spray nozzle.
Ideally you will want a primary filter right inside the cabinet to reduce the amount of large particles from getting into the vacuum system. It should be coarse enough that it doesn't foul rapidly.
Your Dust Deputy is a good idea for capturing much of the abrasive media. Keep in mind that a cyclonic separator functions by spinning the heavy particles toward the outer walls of the separator. This may tend to wear out your dust deputy faster than normal.
Similarly, the high speed air flow in your hoses with abrasives will wear your hoses faster than normal. Make sure you are using a collection bag inside your CT26 so you don't abrade the interior of the vacuum canister. The speed of the air inside the canister will be much lower than in the hoses, so there won't be as much abrasion taking place.
By the time your vacuum air reaches the HEPA filter of the CT vac, most of the abrasives will already be removed. The filter will do a good job getting the rest.
By the way, my old sandblasting cabinet (shown on the right below) didn't have an active vacuum system. It worked just fine with a simple air filter on a vent. The drawback was that the positive pressure of the incoming air made dust leak out at all of the joints.
The new cabinet is designed for an active vacuum system, but I still haven't connected it.
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