4 Types of Pile Driving Hammers
Pile drivers are devices used to drive piles into soil (or in some cases, underwater) to create support for buildings or other structures like retention ponds and dams. The most common driving piles are sheet pile, pipe pile and H-pile, but some types of pile driving hammers are capable of also driving timber and precast concrete piles.
In this post we’ll examine four of the most common types of pile driving hammers: the diesel impact hammer, the vibratory hammer, the air/steam impact hammer, and the hydraulic impact hammer.
Diesel Impact Hammer
Diesel impact pile hammers are a type of drop hammer which utilize a two-stroke, or two-cycle, diesel engine. The lightweight hammers are powered through the ignition of a compressed diesel fuel and air mixture. There are four phases of operation:
- The ram is raised, fuel is injected
- Compression: The ram is released and free-falls. The exhaust port closes, which compresses air and fuel together
- Impact and Combustion: The hammer reaches impact with the pile. The air/fuel mixture heats up due to the compression and combusts, or ignites
- Expansion: The ram is driven upwards as a result of the impact with the pile. The ram’s rising draws in fresh air, beginning the cycle again until the hammer is manually stopped by the working crew, or until its fuel is depleted.
The free-fall hammer can be used to drive all types of steel piling. This type of pile driving hammer is renowned for its reliability. Additionally, diesel hammers are self-contained (no need for an external power supply) and are capable of reaching between 30-50 blows per minute for closed-end hammers, and 70-80 for open-end hammers.
Vibratory pile hammers use a spinning technique, a system of counter-rotating weights which are powered by hydraulic motors, to cut into soil, rather than driving a pile. Vibratory hammers are designed so that the horizontal vibrations of the hammer are canceled out by the vertical vibrations, which are transferred to the pile. This type of pile hammer can also be used up to around 3,300 feet under water.
The hammer is lifted to be positioned over the pile with either an excavator or crane, then secured to the pile with hydraulic clamps. Vibratory pile hammers can be used to both drive piles into and extract piles from the ground. __The most common types of piles extracted are sheet piles from temporary cofferdams and pipe pile from crane access trestle. __
An advantage of using a vibratory hammer over other types of pile driving hammers is that vibratory hammers operate at a much lower noise level than others. They also tend to drive piles quicker than other hammer types.
Air/Steam Impact Hammer
Air/steam impact pile hammers can be classified as either single-acting or double-acting. These external combustion hammers use an external power source such as air compressors or steam boilers to power the ram upward or downward.
Single-acting air/steam hammers allow air or steam to raise the movable portion of the hammer and allows it to free-fall. This type of impact hammer can be readily used in all soil conditions, with an average of 50-60 blows per minute.
Double-acting air/steam hammers allow air or steam to raise the ram of the hammer, and adds additional energy during downstroke for a higher frequency of blows (90-150 per minute). The hammer applies additional air or steam pressure to the top of the piston to enable shorter strokes.
Hydraulic Impact Hammer
Hydraulic impact pile hammers are a modernized version of the diesel impact hammer which use hydraulic power packs as its fuel source. Hydraulic hammers are capable of driving not only steel piles like pipe, sheets, or beams, but also timber and precast concrete piles. Some hydraulic hammers are also capable of reaching up to 80 blows per minute.
In addition to the hydraulic hammer’s ability to drive steel, timber, and precast concrete piles, this type of pile hammer is considered more environmentally-friendly than its diesel hammer counterpart. Not only are there no exhaust fumes released into the air, the noise level from a hydraulic hammer is much lower than that of a diesel hammer.
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