Short answer
A breaker can have two separate gas sections and on site both get called "the nitrogen". The first is the gas chamber: it sits above the piston and acts as the spring that drives it down, and part of the blow energy comes from there. The second is the accumulator: it damps the pressure pulses in the hydraulic circuit and protects both the hose and the machine’s pump. What separates them is their function; what joins them is that they use the same part: the diaphragm. Because the diaphragm is the flexible membrane separating gas from oil, it is the weak link in both sections, and fault symptoms usually start there.
The gas chamber: the spring behind the blow
As the piston is driven up by hydraulic pressure it compresses the nitrogen in the gas chamber. That is like winding a spring. When the piston reaches the top, the compressed nitrogen pushes it down and, together with oil pressure, forms the blow.
So nitrogen pressure relates directly to blow energy; but the relationship is not linear. When pressure falls the blow weakens, while taking pressure above the design value does not increase the blow, it disturbs the cycle and strains parts.
Pressure falling over time is normal and we covered the reasons in the nitrogen pressure guide. A sudden drop is not normal and usually points to the diaphragm.
The accumulator: the damper in the line
The accumulator smooths the pressure pulses the breaker’s cycle leaves in the circuit. Every blow shakes the line; the accumulator absorbs that and reduces what passes into the hose and the machine’s control elements.
So an accumulator fault shows not in the breaker but in the line: hoses start shaking and jumping noticeably. On site that is often taken for a hose problem.
The accumulator’s second function is the smoothness of the cycle. When the damping fails the blow rhythm can become irregular, and that feels like power loss.
The diaphragm: the shared weak link
The diaphragm is the flexible membrane that separates gas from oil. It flexes on every cycle, which makes it the part most exposed to fatigue.
When a diaphragm tears, gas passes to the oil side. The consequence runs both ways: gas pressure falls and that section stops doing its job, while at the same time gas mixes into the hydraulic oil. Oil with gas in it foams, and because foamed oil is more compressible the system runs soft and irregular.
So a diaphragm fault does not give a single symptom: power loss, irregularity and sometimes hose shaking appear together. The number of symptoms makes diagnosis harder, but their appearing together makes the diaphragm a strong suspect.
Charging nitrogen is a measurement job
Charging gas pressure without a gauge is like giving medicine without a diagnosis. And because pressure varies with temperature, measurement is taken with the breaker at working temperature; read cold, the value comes out low and a needless charge follows. The correct value and the measuring conditions are model specific and given in the manual; no gas other than nitrogen is ever used.
Symptoms and how to tell them apart
- Gradual power loss with no leak: this may be a normal fall in gas pressure; measure first, then charge.
- Sudden power loss: a torn diaphragm is the first suspect.
- Pressure falling again soon after charging: a diaphragm or sealing problem; charging again is not a solution.
- Noticeable shaking and jumping in the hoses: the accumulator side. Hose routing can give the same symptom, so the two are separated.
- Foam in the oil: it shows gas has passed to the oil side and points to the diaphragm.
- Irregular blow rhythm: the valve or the accumulator; both give the same symptom and measurement tells them apart.
Do and don’t
Do
- Measure the pressure with a gauge and with the breaker at working temperature.
- Where pressure falls again soon after charging, assess the diaphragm.
- With hose shaking, put the accumulator on the suspect list too; do not look only at the routing.
- Stop work when you see foam in the oil; foamed oil means both power loss and damage.
- When changing a diaphragm, watch the cleanliness of the gas section; debris fatigues the new diaphragm too.
Don't
- Do not use any gas other than nitrogen.
- Do not charge without a gauge.
- Do not attribute a weak blow automatically to low nitrogen; hydraulics and wear give the same symptom.
- Do not try to gain power by taking pressure above the design value.
- Do not carry on working with a torn diaphragm; gas mixes into the oil and the damage spreads.