Short answer
A hydraulic breaker is an attachment that turns an excavator’s hydraulic power into repeated blows. Inside it, a piston is driven up by oil pressure, compressed nitrogen in the gas chamber springs that movement back and throws the piston down; the piston strikes the tool shank and the blow passes through the tool into the material. So a breaker takes its force from the hydraulics, its speed from the nitrogen, and does its work through the tool. That trio also explains nearly everything else about breakers: why flow matters, why power falls when nitrogen pressure drops, and why tool choice is half the output.
How the blow is produced
Oil from the machine is routed through the breaker’s valve to the underside of the piston and drives it up. As the piston rises it compresses the nitrogen in the gas chamber, much like winding a spring.
When the piston reaches the top the valve changes position and the pressure beneath it is released. The compressed nitrogen pushes the piston down and oil pressure works in the same direction. The piston accelerates and strikes the top face of the tool shank.
The blow travels along the tool and enters the material. That cycle repeats many times a second; a breaker’s blow rate and blow energy are set by the speed of the cycle and the mass of the piston.
The main parts
- Piston: the part that produces the blow. The heart of the breaker and its most sensitive surface.
- Cylinder: the body the piston moves inside. Its surface quality and cleanliness set piston life directly.
- Valve: the part that builds the cycle by switching oil direction. The rhythm of the blow rate comes from here.
- Gas (nitrogen) chamber and diaphragm: they act as the spring that drives the piston down.
- Front head and bushings: the section that keeps the tool shank on axis and takes lateral load.
- Tool retainer (pin, lock, spring): holds the tool in place but does not carry the blow.
- Tie rods: hold the upper and lower bodies together; their torque value is critical.
- Housing and dampers: keep vibration and noise away from the outer casing.
Why flow and pressure matter so much
A breaker’s cycle runs on oil flow. Too little flow and the cycle slows: the breaker strikes but the blow rate falls and the work takes longer. Too much flow and the cycle speeds up, loading the internals beyond what they were designed for.
Pressure sits on the side that sets blow energy. Too little and the piston cannot accelerate enough; too much and either the relief valve intervenes or parts are strained.
So every breaker has a flow range and a pressure range, and the machine’s auxiliary circuit has to fall inside them. We covered the matching in the tonnage rule guide and in the breaker selector.
Nitrogen pressure is not a power setting
A common mistake on site is raising nitrogen pressure when a breaker hits weakly. Nitrogen acts as a spring, and taken above its designed value the blow does not increase; the cycle is disturbed and parts are strained. The correct value is model specific and given in the manual. The cause of a weak blow is usually on the hydraulic side or in wear.
The tool: half the output
The breaker produces the energy, the tool delivers it into the material. The wrong tool makes the right breaker look inefficient.
There are four basic types. A moil point loads a narrow spot and penetrates hard brittle material. A chisel sets its edge against the direction of the crack and works in layered material. A blunt tool spreads over a wide face and breaks by crushing. A pyramid tool balances penetration against durability.
What each type does in which material is covered on the tools page and in its own guide.
When a breaker is the right tool, and when it is not
- Right: reinforced concrete demolition, rock breaking, secondary breaking, hard ground in foundation excavation, frozen ground.
- Right: mechanical excavation where blasting is prohibited or impractical.
- Not: wide area excavation in massive, very hard rock. A drum cutter or another method may be faster there.
- Not: separating rebar from concrete. That is a pulveriser’s job; a breaker bends rebar rather than separating it.
- Not: cutting work. Cutting section and rebar is a shear’s job.
- Not: lifting, pushing, dragging. A breaker carries load only along its own axis.
Silenced and standard housings
Breakers are built with open (standard) housings and enclosed (silenced) housings. In an enclosed type the internal mechanism sits inside an outer casing on damping buffers.
That brings two benefits: noise radiated outwards falls, and the internal mechanism is protected from external impacts. Which is why enclosed housings are preferred in urban demolition and on sites with noise limits.
In exchange an enclosed housing is heavier and usually more expensive. The choice follows the site’s noise limits and the external impact the attachment is exposed to.