Double-acting hammers use steam or air to raise the striking parts and also to impart energy during the downstroke in addition to that supplied by gravity. The basic
design was developed out of a desire on the part of engineers for a greater number of
blows per minute. The double-acting hammers in common use today operate in a range
of 100 to 250 blows per minute.
To provide higher frequencies double-acting hammers are usually designed with
light rams. A large percentage of the energy rating of the hammer is due to steam force.
These hammers are, therefore, extremely sensitive to system pressure.
