Ford Truck Enthusiasts Forums - blast media vs nozzle size

Quote:

Originally Posted by daveengelson

Not an authority, believe compressor output, CFM, will dictate size nozzle and thus determine media size. I am limited to nozzle size because have a small shop compressor rated approx. 6.5 CFM @ 90psi. When I purchased the sandblaster also purchased some of seller's blasting media later found was too large, nozzle kept clogging up. Once I went to smaller media equipment worked great.

dave

Dave is correct in that the compressor CFM will dictate which nozzle size to use, which in turn determines the size of the media. If you use too big of a nozzle on a small compressor the compressor will run all the time and still won't be able to keep up with the blast cabinet. This will eventually kill your compressor, since they are not intended for 100% duty cycle.

From: http://www.tptools.com

Q. What size nozzle and how much air do I need?
A. The nozzle and air jet size determines the air requirements. The air jet fits inside the power gun and controls the amount of air leading to the nozzle. Nozzles and air jets can be changed, depending on your air compressor. If you have a 3 HP compressor (7 cfm), your best choice is probably the small nozzle. If you have a 5 HP compressor (15-20 cfm), use a medium nozzle. For a 10 HP or larger compressor, use a large size nozzle. Remember, nozzles and air jets must be changed in sets (small with small, etc.) and are available in steel, ceramic and carbide.

Characteristics of Abrasives: Most abrasives are graded as to Sieve Size. A sieve is a utensil of wire mesh or closely perforated metal used for straining or sifting, and can be used to separate coarser abrasive from finer abrasive. As the abrasive is poured through the sieve, the larger particles remain. The sieve is rated by the number of openings per square inch, so the higher the number, the finer the mesh. Also, the higher the number, the finer the abrasive. If an abrasive is graded 60-80, it means that it will pass through a grade 60 mesh sieve. Coarser abrasives (lower numbers) normally cut faster and create less dust within the cabinet, however the finish can be so coarse that the surface being blasted is extremely rough. If intending to paint or do further preparation on the metal, it is better to use a finer abrasive, to save prep time later. In summary: higher mesh numbers mean finer finishes and slower cutting action. Lower numbers mean coarse finishes and faster cutting action. Experiment with various types and grades of abrasive until you select your "favorites".

In summary, for satisfactory operation when cabinet blasting or using any air tool requiring large amounts of air, please observe the following recommendations:

1. Change nozzles frequently -- consider going to a smaller size to save air, or using a long-wearing Carbide Nozzle which will maintain its orifice size for a longer period of time.

2. Do not blast continually. Take a break every 5 minutes to allow air compressor to cool.

3. If air compressor tank feels hot (warm is normal), and is running continually, stop operating the cabinet or air tool and allow compressor to cool. Otherwise, compressor will overheat and eventually break down. Compressors are not guaranteed against this condition.

4. Compressor must recycle normally on and off and run no more than 2/3 the time. No air compressor is designed for continual operation. Know the capacity of your compressor and the amount of air required for your air tools, and allow a 50% overload factor for best results. (Example: Tool requires 10 CFM air. You need 15 CFM as an overload factor.)

5. Use a minimum 3/8" ID air hose up to 25 ft, from air compressor to cabinet and remember to consider air pressure drop as illustrated in table below. Example: If using 25 feet of 1/4" ID air hose, at 60 lbs pressure, you will experience a pressure drop of 19 lbs, meaning you actually have 41 lbs working pressure.

<table id="Table2" border="1" cellpadding="3" cellspacing="0" height="189" width="583"> <tbody><tr> <td colspan="8"> Air Pressure Drop with 1/4" or 5/16" ID Air Hose

</td> </tr> <tr> <td colspan="2">. </td> <td colspan="2">Pressure Drop (Loss)

</td> <td colspan="2">. </td> <td colspan="2">Pressure Drop (Loss)

</td> </tr> <tr> <td colspan="2">1/4" ID Air Hose

</td> <td height="23" width="12%">25 feet

</td> <td width="12%">50 feet

</td> <td colspan="2">5/16" ID Air Hose

</td> <td width="13%">25 feet

</td> <td width="13%">50 feet

</td> </tr> <tr> <td colspan="2">At 60 lbs pressure</td> <td height="23" width="12%"> 19 lbs

</td> <td width="12%"> 31 lbs

</td> <td colspan="2">At 60 lbs pressure</td> <td width="13%"> 6 lbs

</td> <td width="13%"> 11 lbs

</td> </tr> <tr> <td colspan="2">At 70 lbs pressure</td> <td height="23" width="12%"> 22 lbs

</td> <td width="12%"> 34 lbs

</td> <td colspan="2">At 70 lbs pressure</td> <td width="13%"> 7 lbs

</td> <td width="13%"> 13 lbs

</td> </tr> <tr> <td colspan="2">At 80 lbs pressure</td> <td height="23" width="12%"> 25 lbs

</td> <td width="12%"> 37 lbs

</td> <td colspan="2">At 80 lbs pressure</td> <td width="13%"> 8 lbs

</td> <td width="13%"> 14 lbs

</td> </tr> <tr> <td colspan="2">At 90 lbs pressure</td> <td height="23" width="12%"> 29 lbs

</td> <td width="12%"> 39 lbs

</td> <td colspan="2">At 90 lbs pressure</td> <td width="13%"> 10 lbs

</td> <td width="13%"> 16 lbs

</td> </tr> <tr> <td colspan="2">At 100 lbs pressure</td> <td height="23" width="12%"> 33 lbs

</td> <td width="12%"> 42 lbs

</td> <td colspan="2">At 100 lbs pressure</td> <td width="13%"> 12 lbs

</td> <td width="13%"> 18 lbs

</td> </tr> </tbody></table> Metal piping is always preferred to air hose, as it allows the moisture-laden air to condense in the piping, where it can be removed later with the water separators.