Hydraulic Fluid; Maintenance - YUKEN KOGYO ELDFG-01EH 10 Series Instruction Manual

6.3 Hydraulic fluid

6.3.1 Fluid type
Petroleum base oil: Use a fluid equivalent to ISO VG32 or 46.
Synthetic fluid: Use a phosphate ester or polyol ester fluid.
(Note) For use with hydraulic fluids other than those listed above, consult us
separately.
6.3.2 Fluid viscosity and temperature
Meet the following requirements for fluid viscosity and temperature during operation.
- Viscosity: 15 to 400 mm
- Fluid temperature: - 15 to 60 ºC
Note that the recommended fluid temperature ranges from 40 to 50 ºC.
6.3.3 Control of contamination
Contamination of hydraulic fluid with foreign matter often affects the proper operation of
the valve. Keep hydraulic fluid clean and use a line filter. To ensure a longer service
life of the valve, improving hydraulic fluid cleanliness is recommended.
Contamination Level
NAS 1638 Class 10
ISO 4406 21/19/15
CAUTION

7. Maintenance

● The service life of the O-rings is about two or three years depending on the condition of
valve operation. Please keep spare O-rings handy for replacement in the event of fluid
leakage.
● The components and performance of the valve deteriorate as the duration of service
increases or depending on the operating conditions. To keep the valve in working order
and prevent unexpected failure of hydraulic equipment, inspecting the valve regularly is
recommended. The recommended inspection interval is at least two to three years. The
valve deterioration conditions depend on the operating conditions of hydraulic equipment
and the fluid contamination level. Thus, performing regular inspection depending on the
situation is recommended. For periodic maintenance, contact our customer support.
● Contamination of hydraulic fluid with foreign matter often affects the proper operation of the
valve. It may cause failure or shorten the valve's service life. Keep hydraulic fluid clean
(contamination level: NAS class 10/ISO 4406 21/19/15 or better). Also, use a line filter and
inspect/clean it regularly.
● Petroleum base oil containing water shortens the valve's service life. To avoid this situation,
inspect the fluid regularly.
● Air entry into the circuit may impair the proper operation of the valve. Bleed air completely
from the circuit.
When phosphate ester fluids are used, prefix "F-" to the model number
because the special seals (fluororubber) are required to be used.
2
/s
Never use contaminated fluid.
Doing so may result in malfunction or failure of the valve.
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