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Installation, Operation and Maintenance Manual
MAN 564 Rev. 6
June 2020
Maintenance
Section 5: Maintenance
B) Settings of relief valves (see the attached sectional drawings)
The relief valve (item Ra of operating diagram MAN562-A) is set at Biffi factory at a proper
value and there is no reason to change the setting on the field.
The relief valve (item Ra of operating diagram MAN562-A) is set at Biffi factory at a
pressure value at least 20% higher than the pressure required into the hydraulic cylinder,
during the manual operation by the handpump, to ovrcome the valve required torque, in
opening and in closing, along all the valve angular stroke.
At the same time the set value is at least 10% lower than the pressure required into the
hydraulic cylinder to perform the maximum allowable torque of the actuator and of
the valve.
If a setting of the relief valve has to be performed, proceed as follows:
•
Unscrew the cap nut (item2) from the setting screw (item 44).
•
Loosen the lock nut (item 30).
•
By a male hexagonal wrench rotate clockwise the setting screw (item 44) to
increase the pressure setting value; rotate counterclockwise to decrease the
pressure set value.
•
Check that the pressure set value is the required one.
•
Tighten the lock nut (item 30). During this operation keep the setting screw
(item 44) still with an hexagonal male wrench.
•
Screw the cap nut (item 2) on the setting screw end and tighten so to assure
the tightness.
