16
5.6
The blast pattern
Abrasive leaving the blast wheel blades is not thrown in all
directions. Scatter is restricted to an angle of about 50°.
This is achieved through the use of a control cage which
surrounds the impeller. The position of the window in the
control cage determines the blast pattern.
Correct adjustment of the control cage and thus of the blast
pattern is the most important factor for optimum working
with the blast cleaning machine.
Incorrect adjustment of the control cage results in very high
wear and premature blasting-through of the liners in the
blast wheel housing, as well as reduced blasting
performance, uneven cleaning and a possible loss of the
rebounce energy of the abrasive.
The following 5 factors affect the blast pattern:
The turning direction of the blast wheel must correspond to the instructions on the housing
(arrow indicating the turning direction).
With increased wear of the tune-up kit (impeller, control cage) the blast pattern will change.
The size of the abrasive affects the blast pattern. With every exchange of abrasive, the blast pattern
must be re-adjusted.
The correct adjustment of the control cage is the most important factor to obtain an optimum blast
pattern. Each control cage has a lateral window. The position of the window determines where the abrasive
is fed onto the blast wheel blades and where it hits the surface to be treated.
Different types and hardness of surfaces.
1.7
Adjusting the blast pattern
1)
Move the blast head of the blast machine onto a 5-8 mm thick steel plate and blast for 45 seconds at full
amperage without moving the machine from the spot.
2)
Move the machine from the blast zone and carefully inspect the steel plate.
3)
You will find the hot spot on the blasted surface where the machine has developed the highest blast cleaning
intensity. This spot is normally somewhat lighter than the rest of the blast cleaned area due to the large
amount of heat that is generated.
4)
If the ‘hotspot’ is too much on the right, turn the blastwheel cover a little bit clockwise. Loosen the clamp
lever for cage adjusting (item 13) and hammer on the finger to adjust the position (3-6mm).
Tighten the clamp lever after adjusting.
If the ‘hotspot’ is too much on the left, turn the blastwheel cover a little bit counter-clockwise.
5)
Now the blasting procedure can be started. When a concrete surface is to be blasted, check the blast pattern
again after some meters and re-adjust slightly if necessary.
WARNING! Never loosen the cage clamps lever or try to adjust the blast wheel cover when the
machine is in operation!!
