The steam, or pneumatic, hammer has basically
gravity only. In a DOUBLE-ACTION hammer, the
replaced the drop hammer. This hammer (fig. 8-18)
ram is both lifted and driven downward by the power
consists of a cylinder that contains a steam-driven or
drive. A double-action hammer weighs from 5,000 to
air-driven RAM. The ram consists of a PISTON
14,000 pounds and a single-action hammer weighs
equipped with a STRIKING HEAD. The hammer is
about 10,000 pounds.
rested on the butt or head of the pile for driving.
The blow of the double-action hammer is lighter,
but more rapid than that of the single-action hammer.
With a SINGLE-ACTION steam, or pneumatic,
The double-action hammer generally drives lightweight
hammer, the power drive serves only to lift the ram; the
downward blow of the ram results from the force of
or average weight piles into soils of average density; its
rapid blows tend to keep the pile in motion and thereby
Figure 8-18.Steam, or pneumatic, pile hammers.
reduces the resistance of inertia and friction. For heavy
piles in hard or dense soil, however, the resistance from
inertia and friction, together with the rapid,
high-velocity blows of the double-action hammer, tend
to damage the butt or head of the pile.
The single-action hammer generally drives heavy
piles into hard or dense soil; its heavy ram, striking at
lower velocity, allows more energy to be transferred
into the motion of the pile, reducing impact and damage
to the butt or head of the pile.
The diesel pile hammer shown in figure 8-19 is the
most common hammer used in the NCF. This hammer
Figure 8-19.Diesel pile hammer.