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.
5.7
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 15) 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!!
