Parts & Components
Hydraulic Breaker Nitrogen System
Nitrogen pre-charge pressure directly determines impact energy and blow rate. Understanding the gas accumulator system is essential for maintaining full breaker performance.
What Is the Nitrogen System?
The nitrogen system in a hydraulic breaker consists of a gas accumulator (a sealed chamber pre-charged with dry nitrogen gas), a flexible diaphragm or bladder that separates the nitrogen from the hydraulic oil, and a charging valve (typically a Schrader-type valve) for checking and adjusting the nitrogen pressure.
The accumulator acts as an energy storage device. During the piston's upstroke, hydraulic oil pressure compresses the nitrogen gas through the diaphragm, storing energy. During the power stroke (downstroke), the compressed nitrogen expands, pushing the diaphragm back and supplementing the hydraulic pressure driving the piston. This stored energy boost is what allows the breaker to achieve higher impact energy than the hydraulic system alone could provide.
The nitrogen pre-charge pressure — the pressure of the nitrogen gas when the accumulator is not connected to the hydraulic circuit — is a critical parameter that must be maintained within the manufacturer's specified range. Too low or too high, and impact performance is reduced and component damage can occur.
Related: For a detailed explanation of how the accumulator fits into the full impact cycle, see Hydraulic Breaker Accumulator in the Working Principle series.
Effect of Nitrogen Pressure on Performance
Correct pressure
Piston reaches optimal velocity at impact. Maximum energy transfer to chisel. Correct blow rate.
Pressure too low
Piston accelerates too slowly — impact velocity is reduced. Lower impact energy per blow. Breaker feels weak. In extreme cases, the diaphragm may bottom out and be struck by the piston.
Pressure too high
Piston decelerates before reaching the chisel — impact velocity is reduced. Lower impact energy. Increased stress on the piston impact face and chisel shank. Accelerated diaphragm fatigue.
Important: The correct nitrogen pre-charge pressure is specific to each breaker model. Always refer to the manufacturer's service manual for the exact specification. Never estimate or use a value from a different model.
Nitrogen Charging Procedure
Always follow the manufacturer's service manual for model-specific procedures. The steps below represent general best practice.
Safety Warnings
Troubleshooting Nitrogen System Problems
| Symptom | Likely Cause | Action |
|---|---|---|
| Reduced impact energy | Nitrogen pressure too low or too high | Check and adjust nitrogen pressure to specification |
| Erratic blow rate | Partially failed diaphragm, or pressure at the boundary of specification | Check nitrogen pressure; inspect diaphragm if pressure is correct |
| Pressure drops quickly after charging | Failed diaphragm (nitrogen leaking into oil side) or leaking charging valve | Check for oil at charging valve port; replace diaphragm if oil present; replace valve if leaking |
| Oil at charging valve port | Diaphragm failure — oil has entered the gas side | Replace diaphragm immediately; change hydraulic oil |
| Milky or foamy hydraulic oil | Diaphragm failure — nitrogen mixing with oil | Replace diaphragm; change hydraulic oil and filter |
| Pressure reads zero | Diaphragm failure, charging valve leak, or gas has been fully lost | Inspect diaphragm before recharging; do not charge if diaphragm is failed |
Frequently Asked Questions
What gas is used in a hydraulic breaker accumulator?
Dry nitrogen (N₂) is the only gas that should be used. Nitrogen is inert (no fire or explosion risk with hydraulic oil), dry (no moisture to degrade the diaphragm), and readily available. Never use compressed air — it contains moisture and oxygen, both of which are harmful. Never use any other gas.
How often should I check the nitrogen pressure?
Check nitrogen pre-charge pressure at every major service interval — typically every 250–500 operating hours. Also check whenever the breaker shows symptoms of reduced impact energy or erratic blow rate, as these can indicate nitrogen pressure loss. Pressure should be checked with the breaker disconnected from the hydraulic circuit and at a known ambient temperature.
Why does my nitrogen pressure keep dropping?
Nitrogen pressure that drops faster than expected between service intervals indicates a leak. The most common cause is a failed accumulator diaphragm — nitrogen is leaking into the hydraulic oil side. Other causes include a leaking charging valve (Schrader valve) or a cracked accumulator housing. Check for oil at the charging valve port — if oil is present, the diaphragm has failed.
What is the correct nitrogen pressure for my breaker?
Nitrogen pre-charge pressure is specific to each breaker model and is listed in the manufacturer's service manual. Typical ranges are 25–80 bar, but this varies significantly between models and sizes. Never use a generic or estimated value — incorrect pressure reduces impact energy and can damage the diaphragm or piston. Always refer to the model-specific service manual.
Can I use a standard tyre inflator or air compressor to charge the nitrogen?
No. A tyre inflator uses compressed air, which contains moisture and oxygen — both harmful to the breaker. An air compressor also uses compressed air. You must use a dedicated nitrogen supply (nitrogen cylinder with regulator) and a nitrogen charging kit designed for hydraulic accumulators. The charging valve on the breaker is typically a standard Schrader valve, but the pressure range (25–80 bar) requires a proper high-pressure nitrogen regulator.
Does nitrogen pressure change with temperature?
Yes. Nitrogen pressure follows the ideal gas law — pressure increases with temperature and decreases with temperature. A breaker charged to the correct pressure at 20°C will show a higher pressure reading when hot (after operation) and a lower pressure reading when cold (in winter storage). The manufacturer's specified pressure is typically given at 20°C. Account for temperature when checking pressure — a reading that appears low in cold weather may be correct at operating temperature.
What happens if I accidentally use compressed air instead of nitrogen?
Compressed air contains approximately 21% oxygen and significant moisture. The oxygen creates a fire and explosion risk when mixed with hydraulic oil under high pressure — this is a serious safety hazard. The moisture degrades the diaphragm material and promotes corrosion inside the accumulator. If compressed air has been used, the accumulator must be purged, the diaphragm inspected and likely replaced, and the hydraulic oil changed.