Hydraulic Breaker Nitrogen Charging — Complete Guide
The nitrogen gas charge in a hydraulic breaker's accumulator is critical to its performance. Nitrogen acts as a spring and energy storage medium — it absorbs the return stroke energy and releases it to accelerate the piston on the power stroke. Incorrect nitrogen pressure (too high or too low) directly reduces impact energy, increases component wear, and can cause premature failure. This guide covers how to check, interpret, and recharge nitrogen pressure correctly.
Safety Precautions
- NEVER use oxygen, compressed air, or any gas other than pure dry nitrogen. Oxygen mixed with hydraulic oil is explosive.
- Always wear safety glasses when working with pressurized nitrogen.
- Check nitrogen pressure only when the breaker is cold (ambient temperature) — hot breakers give false high readings.
- Do not exceed the maximum nitrogen pressure specified on the breaker nameplate.
- Nitrogen cylinders must be secured upright and handled by trained personnel.
The Role of Nitrogen in a Hydraulic Breaker
Most hydraulic breakers use a gas-hydraulic percussion system where nitrogen gas in the accumulator works in conjunction with hydraulic oil to drive the piston. The nitrogen charge serves two functions:
Energy storage: During the return stroke, the piston compresses the nitrogen gas, storing energy. This stored energy is released on the power stroke, supplementing the hydraulic oil pressure to accelerate the piston.
Impact frequency control: The nitrogen pressure influences the timing of the piston's return stroke. Correct pressure ensures the piston returns at the right speed for optimal impact frequency.
Without the correct nitrogen charge, the breaker relies entirely on hydraulic pressure for both strokes, resulting in reduced impact energy, lower frequency, and increased thermal load on the hydraulic system.
Correct Nitrogen Pressure Values
Nitrogen pressure specifications vary by breaker model and size. Always refer to the nameplate on your specific breaker for the exact specification. General guidelines by class:
Mini class (SB10, SB20)
Typical cold nitrogen pressure: 5–8 bar (72–116 psi). Check the nameplate for your specific model.
Light class (SB30, SB40)
Typical cold nitrogen pressure: 8–12 bar (116–174 psi).
Medium class (SB43, SB50)
Typical cold nitrogen pressure: 10–15 bar (145–218 psi).
Heavy class (SB81)
Typical cold nitrogen pressure: 15–20 bar (218–290 psi).
These are general ranges only. Always use the pressure specified on your breaker's nameplate — it is the authoritative source for your specific unit.
How to Check Nitrogen Pressure
Allow the breaker to cool
Nitrogen pressure increases with temperature. Always check pressure when the breaker is at ambient temperature — ideally before the first operation of the day. A breaker that has been operating for 2+ hours may show pressure 2–5 bar higher than the cold specification.
Locate the nitrogen charging valve
The nitrogen charging valve is typically located on the back cap or upper body of the breaker. It is usually protected by a threaded cap. Remove the cap and inspect the valve for damage or contamination.
Connect the pressure gauge
Attach the nitrogen pressure gauge to the charging valve. Use only a gauge designed for this purpose — standard tire pressure gauges are not suitable. Read the pressure and compare to the nameplate specification.
If the gauge reads zero, the nitrogen charge has been completely lost. Inspect the charging valve and accumulator diaphragm before recharging.
Interpret the reading
If pressure is within ±1 bar of the specification, no action is needed. If pressure is more than 1 bar below specification, recharge. If pressure is above specification, release gas carefully until the correct pressure is reached.
Nitrogen Charging Procedure
Prepare the nitrogen cylinder
Ensure the nitrogen cylinder contains pure dry nitrogen (99.9% purity minimum). Connect the regulator and charging hose. Set the regulator to slightly above the target pressure.
Connect the charging hose
Connect the charging hose to the breaker's nitrogen charging valve. Ensure the connection is secure and there are no leaks at the fitting.
Charge to specification
Slowly open the nitrogen cylinder valve. Watch the pressure gauge and stop when the target pressure is reached. Close the cylinder valve.
Add nitrogen slowly — rapid charging can cause the accumulator diaphragm to move violently, potentially damaging it.
Check for leaks
Apply soapy water to the charging valve connection. If bubbles appear, the valve is leaking. Replace the valve core or the entire valve assembly.
Disconnect and cap
Disconnect the charging hose. Reinstall the protective cap on the charging valve. Record the date and pressure in the maintenance log.
Effects of Incorrect Nitrogen Pressure
Understanding what happens with wrong nitrogen pressure helps diagnose performance issues:
Low nitrogen pressure: Reduced impact energy (the piston is not accelerated as effectively), lower impact frequency, increased hydraulic oil temperature (the system works harder), and potential for the piston to "float" rather than strike cleanly. In severe cases, the piston can contact the back cap, causing catastrophic damage.
High nitrogen pressure: The piston return stroke is too fast, reducing the time for hydraulic oil to fill the chamber. This results in cavitation, reduced impact energy, and increased wear on the piston and cylinder bore. High pressure also increases stress on the accumulator diaphragm.
Zero nitrogen pressure: The breaker will operate in a degraded mode — some models will still fire but with significantly reduced performance. Others may not operate at all. Operating with zero nitrogen pressure causes rapid wear and should be avoided.
Frequently Asked Questions
Related Articles
Applies to These Models
This guide is especially relevant for the following hydraulic breaker models.
4–8 ton excavators
The SB30 is a light-class hydraulic breaker for 4–8 ton excavators, delivering strong performance for road breaking, foundation work, and medium rock excavation.
View All6–12 ton excavators
The SB40 is a medium-class hydraulic breaker for 6–12 ton excavators, offering high impact energy for general construction, rock breaking, and concrete demolition.
View All20–35 ton excavators
The SB81 is an extra-heavy hydraulic breaker for 20–35 ton excavators, delivering 2000–3000 J of impact energy for quarrying, mining, and major demolition projects.
View All