How It Works: The Hydraulic Hammer


Hydraulic hammers are essential pieces of construction equipment. They are used in both the building and demolition sides of construction. For construction, they can be used to dig a hole, breaking up rocks in the ground or breaking the dirt to dig a hole more easily.

When doing demolition, the hammer can quickly break up concrete, walls, and foundations to bring down structures. Since they can break through hard material so easily, these hammers are great tools for mining too.

These big machines are often mounted or attached to tractors, backhoes, and diggers. These tools are great for building and demolition. The most interesting thing about these hammers though, is how they work.

The Science Behind the Hammer

These hammers use hydraulics to work, which is the reason behind their name, but it is also what sets them apart. Pascal’s law, which is a mechanical principle in mechanics, is the basic function of the hydraulic hammer. By putting pressure on one part of a fluid, it transfers the pressure to all areas of the fluid, which multiplies the force.

Hydraulics use hydraulic oil, which as a fluid cannot be compressed, with pressure stored in a small canister. This hydraulic system supplies the force for hitting. Regular, hand-held hammers don’t even compare to the strike of a hydraulic hammer.

There are two main types of hydraulic hammers, with different valves. One type has an inner valve while the second type has an outer valve. The inner parts are mostly the same, with the necessary cylinder to provide the pressure and a piston to convert the energy into the hammering action. Other similar hydraulic parts include:

  • the side rods: designed for supporting mounted hammer applications
  • a nitrogen chamber: a low-pressure chamber to help supply power
  • the main valve: the only moving part, other than the piston, to help hammer
  • the front cap: keeps the hammer attachment in place during impact

Hydraulic Hammer Classes

Hydraulic hammers come in different sizes, or classes, to fit a variety of jobs. Each one has a recommended usage amount to help users know which class is best for each job. While each hammer will have a different measurement depending on the brand, here are some basic stats on each class that you can see their potential impact on a job:

  • Small class: The impact frequency on this size is anywhere from 400 to 1200 BPM with a 1400 to 2175 PSI
  • Medium class: The impact frequency here is 370-700 BPM with a 2175 to 2610 PSI
  • Large class: This size has an impact frequency 200 to 400 BPM with a 2300 to 2610 PSI

These measurements show the number of times the hammer can hit the target in a minute, along with how much pressure is used. It is important that the right class hammer is used for each job. Using a hammer with too much pressure for a job that requires less can do too much damage.


If you are in the market for a hydraulic hammer and have any questions about what size is right for your project, we are always willing to answer questions.

Posted by RJB Hydraulic Hammers