CEMP-E
EI 02G001
01 July 1997
Table 3-1 (continued)
Hammer
Type
Description
Advantages
Disadvantages
External Combustion Hammers (Continued)
Differential
Variation of
Frequency of blows approaches
Rebound effects make
Acting Air/
double-acting
that of double acting hammer
hammer energy output
Steam
hammer with
while the effective stroke is
variable
Hammers
different valve
the same as for single-acting
arrangement.
hammers.
Can be used in horizontal
position.
Works best in sandy soil, but
can be used in any soil.
Hydraulic
Use hydraulic
Efficient both in power pack
Expensive to rent or purchase.
Impact
fluid to raise
energy conversion and
Hammers
the ram; some
generally with impact force
units have
transfer. More difficult to maintain
assisted fall
than other impact hammers.
as well.
May be used underwater.
Some units have sound
attenuation features.
Internal Combustion Hammers
Single-Acting
Self-contained
Independent of outside power
Cannot be inverted and
Diesel Hammers
unit which uses
sources (boiler, compressor,
used as pile extractor.
ignition of fuel to
hydraulic power pack, Etc.)
impart additional
In soft driving, may stall due to
energy during
inadequate rebound.
downstroke to
drive pile upward.
Long stroke of ram
Light weight and easily portable.
may cause tension
cracking in concrete piles.
Low operating cost.
On hammers with
Ease of operation in cold weather.
atomized fuel system,
fuel system is complicated.
.
Low-frequency (40-60 blows per
minute) blow rate.
3-11
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