- 26 -
5.9. Adjusting impact rate – 2-speed selection
For PRB150 and bigger model
1. Speed selection switch
2. Locking button
3. Cylinder
Low speed
(mark
I
)
High speed
(mark
II
)
The PRB150 ~ PRB700 hydraulic hammers have a 2-speed selection valve on the cylinder body to change
the impact rate and the impact energy according to working condition.
Low speed: working with normal impact rate and maximum percussive power
Breaking large rocks embedded under ground, or breaking heavy-reinforced concrete structures requires
strong percussive power rather than high impact rate. When impact energy per blow of hammer is not
sufficient to make breakage on material, however fast impact rate may be, the hammer does not give
expected breaking productivity because the chisel cannot penetrate into the material.
For this kind of work, maximum percussive power, even though low impact rate, is needed.
The speed selection switch is set to the low speed mode (mark I) in the factory when delivered, as shown in
the previous figure.
High speed: working with increased impact rate and reduced percussive power
When breaking small or soft rocks, or when tearing up thin concrete surfaces reduced percussive power is
sufficient, and the impact rate switching system allows the hammer to be operated at a higher impact rate, by
reducing the stroke. The impact energy is thus adapted to the lighter application.
To change impact rate to high speed:
1. Push the locking button (2) with a small size screwdriver.
2. Turn the speed selection switch (1) counter-clockwise by using an 8 mm hex L-wrench so that the locking
button (2), faces toward the high speed mode (mark
II
)
1
2
3
