Hodge Clemco portable blast cleaning machines are designed to project abrasive media to remove contaminants from surfaces, when connected to a suitable sized air compressor and fitted with blast hose and nozzle. They range in cubic capacity from 25 litres to 200 litres. When filled with JBlast expendable abrasive these equate to the following:-
| Model | Cubic capacity (litres) | Practical approx. weight of expendable abrasive |
|---|---|---|
| 1028NC | 20 | 25 |
| 1440NC | 50 | 75 |
| 2040NC | 100 | 150 |
| 2452NC | 200 | 300 |
By law they have to comply with current European Pressure Vessel Directive (PED) 97/23/EC.
System Setup
The most important part of a blast cleaning set-up is the compressor. It should be capable of delivering large volumes of air which is free from oil at a constant pressure. Rotary screw compressors are the best type for blast cleaning. Electric or diesel are both suitable. Cleaning of steel is normally carried out at 90 – 100 psi (6.2 – 6.9 bar). Stone cleaning is carried out from 25 psi (1.7 bar) upwards depending on the type of stone and the degree of contamination.
Air delivery hoses must be as large as possible. When nozzles using 200 cfm (94 l/sec) and above are used, the air delivery hose should be 1½” (38mm) i.d. or larger.
The blast machine should be fitted with a water separator to remove any moisture present in the compressed air supply. It should also be fitted with a remote control valve to enable the operator to turn the machine on and off from a deadman handle placed just behind the nozzle.
An abrasive metering valve at the base of the machine will enable the operator to precisely control the volume of abrasive to achieve maximum economy.
Choice of blast hose is equally important. Larger nozzles with ⅜” (10mm) bore and above are best fed with 1¼” (32mm) i.d. blast hose. Medium sized machines like the 1440NC normally take a 1” (25mm) i.d. blast hose. ¾” (19mm) i.d. hose is often used as a whip end on 1¼” blast hose to facilitate bending the hose into hard to get areas.
The 1028NC machine uses ½” (13mm) i.d. blast hose.
Only externally fitted hose couplings and nozzle holders should be used. Internally fitted couplings and holders cause turbulence and rapid wear on the internals of the blast hose. This may cause it to burst suddenly with dangerous consequences.
Selection of the proper nozzle is an important factor in an efficient blasting operation. They are made in a variety of sizes and material and can be either straight bore or venture. The size of the nozzle must match with the output capacity of the compressor. The following table shows the volume of air required by each nozzle at a given pressure. Work done is proportional to the volume of air pushed through the nozzle, so always choose the largest nozzle that your compressor will run.
AIR CONSUMPTION CHART (Imperial)
Nozzle pressure in psi
| Nozzle Number | Nozzle orifice | 20 | 30 | 40 | 50 | 60 | 70 | 80 | 90 | 100 | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| No. 1 | 1/8” | 6 | 8 | 10 | 11 | 13 | 15 | 17 | 18.5 | 20 | Air (cfm) |
| No. 2 | 3/16” | 14 | 18 | 22 | 26 | 30 | 33 | 38 | 41 | 45 | “ |
| No. 3 | ¼” | 28 | 34 | 41 | 47 | 54 | 61 | 68 | 74 | 81 | “ |
| No. 4 | 5/16” | 41 | 53 | 65 | 77 | 89 | 101 | 113 | 126 | 137 | “ |
| No. 5 | 3/8” | 57 | 74 | 91 | 108 | 126 | 143 | 161 | 173 | 196 | “ |
| No. 6 | 7/16” | 83 | 105 | 124 | 147 | 170 | 194 | 217 | 240 | 254 | “ |
| No. 7 | ½” | 110 | 137 | 165 | 195 | 224 | 252 | 280 | 309 | 338 | “ |
AIR CONSUMPTION CHART (Metric)
Nozzle pressure in bar
| Nozzle Number | Nozzle orifice | 1.4 | 2.0 | 2.8 | 3.4 | 4.0 | 4.8 | 5.5 | 6.2 | 7.0 | Air (cu.m/min) |
|---|---|---|---|---|---|---|---|---|---|---|---|
| No. 2 | 3mm | 0.17 | 0.23 | 0.28 | 0.31 | 0.37 | 0.43 | 0.48 | 0.51 | 0.57 | |
| No. 3 | 5mm | 0.40 | 0.51 | 0.62 | 0.73 | 0.84 | 0.92 | 1.06 | 1.15 | 1.26 | |
| No. 4 | 6.5mm | 0.79 | 0.96 | 1.16 | 1.31 | 1.51 | 1.71 | 1.90 | 2.08 | 2.27 | |
| No. 5 | 8mm | 1.16 | 1.50 | 1.84 | 2.16 | 2.50 | 2.83 | 3.16 | 3.53 | 3.84 | |
| No. 6 | 9.5mm | 1.61 | 2.10 | 2.58 | 3.02 | 3.53 | 4.00 | 4.50 | 4.85 | 5.50 | |
| No. 7 | 11mm | 2.35 | 2.97 | 3.51 | 4.12 | 4.76 | 5.44 | 6.09 | 6.73 | 7.11 | |
| No. 8 | 12.5mm | 3.12 | 3.88 | 4.67 | 5.46 | 6.28 | 7.06 | 7.85 | 8.65 | 9.46 |
Also, see our Air Consumption Calculator
To complete an efficient blast cleaning set-up a full set of personal protective clothing is required. This should include an air fed helmet, designed specifically for blast cleaning, such as the Apollo, a breathing air filter to remove particulate from the breathing air. If there is any doubt about air quality then a test kit should be available to test the air for harmful contaminants such as carbon monoxide, carbon di-oxide, nitrous fume and hydrocarbons.
Having completed the set-up for an efficient blasting operation the only remaining item is the choice of abrasive. This is a wide and varied topic so please consult the Selection Guide in the Abrasives Section of our web site www.hodgeclemco.co.uk