Etesia HYDRO 124D, Technical Training Manual

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Presence of air
The presence of air in the oil can have serious consequences on the operation of hydraulic installations.
- Compressibility (the system becomes "elastic")
- Oxidation
- Rises in temperature
- Cavitation
- Lorentz effect (destruction of synthetic seals by the Diesel effect).
The abnormal presence of air can have several causes :
- Tank too small with eddy (absence of separation between suction and return)
- Suction and return tubes too close to each other.
- Air intake on suction
- Air intake on ram rod seals or pump shafts and internally drained motors.
- Poor purging on starting.
The hydraulic fluid must for its part have anti-foaming properties and good de-aeration qualities (ability to let the air imprisoned
in the fluid escape).
Application to the l’hydro 124 D
The hydraulic oil recommended for the Hydro 124D is of the HV 46 type.
"46" is the viscosity value (in centistokes or cSt) at 40°C.
At 100°C, the viscosity is 8 cSt.
Using a chart, we can determine the following parameters :
- Optimum operating range of the hydrostatic pump : 13 to 55 cSt
Min. temperature : 35°C
Max. temperature : 80°C
- Usual upper viscosity limit for the pumpability of the pumps : 1000 cSt (beyond that, the fluid is too viscous)
Temperature limit 1 : -15°C
- Lower viscosity limit for good lubrication : 6 cSt (beyond that, the fluid is too liquid)
Temperature limit 2 : 115°C
CONCLUSION :
The maximum service life of the hydraulic components is guaranteed when the operating viscosity of the oil is between 13 and
55 cSt inclusive (35°C and 80°C).
Below –15°C the oil is too viscous to be pumped co rrectly. Moreover, the pressures in the circuit are too high.
Above 115°C the oil is no longer viscous enough to guarantee the correct lubrication of the hydraulic components.