|
|
|
| ||
 |
Transportation Curriculum Coordination Council |
There are a variety of pile driving hammers for the Contractor to choose from. Each has its own inherent advantages and disadvantages and the Contractor's selection is often dependent upon the project needs and what they have available or can readily get economically.
Hammers advance piles with two different techniques, impact or vibration.
Impact Hammers are hammers that advance the pile through "hitting" it with a ram, hence the name impact.
Vibratory Hammers advance the pile through vibration.
The most common hammers in use are:
 |
These are perhaps the most commonly used hammers in Florida mainly due to their availability and simplicity. The term "open end" comes from the top of the hammer being open, therefore you can actually observe the ram going up and coming down as it delivers the blow. These are impact hammers and the recording of blow counts is the general method of inspection.
Fuel is introduced into the cylinder, the ram drops (gravity) setting off an explosion, which thrusts the ram up and the process is repeated over and over.
These hammers must be equipped with at least three fuel settings that permit ram height adjustment, which in turn, permits adjustment of the hammer energy used during driving.
Advantages
This picture shows some of the parts of the open end diesel hammer.
 |
These impact hammers operate differently from the open end in that the top is enclosed and the pressure build up in the bounce pressure chamber literally throws the ram back down.
A gauge is attached to the bounce chamber to enable recording of the chamber pressure for inspection purposes, as the ram is not visible for determining stroke height.
These are losing popularity due to their low efficiency rating and the difficulties in spotting operation problems.
Advantages
 |
Air hammers are the second most common hammers used in Florida. Steam hammers have all but disappeared from use. Both are impact hammers and unlike the diesel hammers, much cleaner while operating. However, while cleaner than diesel, it requires support equipment, such as a compressor to produce the air pressure. They are comparatively much heavier than the diesel hammers.
The air hammer is equipped with a slide bar, which provides for adjusting to either of two settings, full stroke or half stroke. Once set, the hammer delivers a constant stroke height on each blow, unlike the open end diesel.
Advantages
 |
The hydraulic hammers are probably the third most common used in Florida and are impact hammers. The hammer energy on these can be controlled with precise pressure settings. In fact, rather than recording stroke height during driving, the Inspector records the pressure introduced on pressure gauges, on the hydraulic pump. The Inspector can also record stroke height by marking increments on the slide bar.
Like the air/steam hammers, these also require support equipment. A big drawback to these hammers is the need for a dedicated person to operate the hydraulic power unit and the need for experts when repairs are required.
Advantages
 |
Unlike the other hammers, these operate by vibrating piling into the ground. There is no requirement in the specifications relating to the inspection of these hammers. However, these hammers are typically used to install sheet piles.
In the case of steel piles, the final 15 feet of driving for bearing must be performed with an impact hammer.
| << Previous | Table of Contents | Next >> |
