How to Buy a Used Vibratory Hammer
Vibratory hammers drive and extract sheet piles, tubes and beams by shaking them into the ground rather than striking them, which makes them faster and quieter than impact driving in the right ground. They are also mechanically demanding machines: the bearings and the clamp take enormous punishment, and both are expensive.
This guide covers the specifications that determine what a vibro can drive, the condition questions that determine what it will cost you, and the compatibility checks that decide whether you can use it at all.
Eccentric moment, frequency and amplitude
Eccentric moment is the primary size figure and describes the mass and offset of the rotating weights. It sets how much pile the hammer can move. Frequency describes how fast it shakes, and amplitude follows from the moment divided by the mass of the vibrating assembly plus the pile.
High frequency and low amplitude suits driving near existing structures, where you want to limit ground vibration. Higher amplitude drives faster in dense ground but transmits more energy into the surroundings, which may be exactly what a nearby building owner objects to.
If the machine will work in urban environments, ask specifically whether it is a variable-moment unit. Variable moment lets the hammer start and stop without passing through the resonant frequencies that cause the worst ground vibration, and on some sites this is a requirement rather than a preference.
The clamp is the wear item that ends jobs
Clamp condition matters more than almost anything else. A clamp that slips wastes time, damages pile heads and eventually drops piles. Inspect the jaws for wear and rounding, and ask when they were last replaced.
Confirm the clamp suits the sections you drive. Sheet pile clamps, tube clamps and beam clamps are not interchangeable, and a hammer sold with the wrong clamp is a hammer you will be re-equipping before it earns anything.
Check the clamping pressure the system generates and whether it holds. A clamp that bleeds pressure over a few minutes is telling you about its seals.
Bearings, suspension and hours
Bearings are the defining maintenance cost on a vibratory hammer and they are consumed steadily. Ask for the hours since the last bearing change and the service records that support the figure. A hammer approaching a bearing change is not necessarily a bad buy, but the cost belongs in the price.
Listen to the machine running off-pile at low speed and again at working speed. Roughness or a change in note through the range is worth investigating before anything else.
Check the suspension or damper unit that isolates the carrier from the vibration. Perished elastomer mounts are cheap relative to the machine, but a failed suspension transmits the vibration into whatever is holding the hammer, which is expensive.
Carrier and power pack compatibility
Establish how the hammer is intended to be carried: crane-suspended, excavator-mounted or leader-mounted. Excavator mounts in particular need checking against your machine’s weight class and hydraulic capability, not just its coupler.
As with impact hammers, confirm the flow and pressure required at full output against what your pack actually delivers. Under-supplying a vibro shows up as a machine that will not reach frequency under load.
Inspection checklist
- Eccentric moment and frequency matched to your pile sections and ground
- Variable moment confirmed if working near existing structures
- Clamp type confirmed for the sections you drive, and jaw wear inspected
- Clamping pressure checked and held under observation
- Hours since last bearing change established and supported by records
- Machine run through its speed range and listened to off-pile
- Suspension or damper elements inspected
- Carrier weight class and hydraulic capability confirmed
- Power pack flow and pressure confirmed at working temperature
Frequently asked questions
What is a variable moment vibratory hammer, and do I need one?
A variable moment hammer can change the offset of its eccentric weights while running, so it can start and stop without passing through the resonant frequencies that cause the worst ground vibration. Near existing structures this is often a site requirement rather than a preference. On open sites a fixed moment machine is usually sufficient and cheaper.
How long do the bearings last?
It depends on duty and maintenance, and manufacturers publish expected intervals for their own machines. What matters when buying is the hours since the last change and whether records support that figure. Price an approaching bearing change into the offer rather than treating it as a surprise.
Can I mount a vibratory hammer on any excavator?
No. The excavator has to be in the right weight class and able to supply the flow and pressure the hammer needs. Fitting a hammer to an undersized carrier is unsafe as well as ineffective, and the coupler fitting is the least of the compatibility questions.
Browse vibratory hammers on Piling Broker or read the other buyer’s guides.