Section 5
Recirculation System
20425595
5-2005/Rev 0
5-2
The recirculation pump pulls oil from the reservoir and sends it to the heat exchanger. The oil-to-
water heat exchanger controls heat build-up in the hydraulic oil. The plate style design allows
cooling water and oil to flow side by side through alternating plates.
The cooled oil then passes through the filter element and returns to the reservoir. The cooling
water either is discharged to the 1/2-inch NPT drain on the bulkhead or is routed to a customer
supplied water chiller.
The hydraulic oil filter assembly consists of the filter head, a filter element, pressure gauge,
bypass relief valve and the oil fill port. The filter element should be changed when the gauge
reads 30 psi (2.1 bar) at normal operating temperature.
If the element is not replaced, and fills with debris, the bypass relief in the filter head will open to
prevent over pressurization. The relief valve opens at 50 psi (3.4 bar). When the valve opens, the
oil bypasses the filter and unfiltered oil is allowed to return to the reservoir.
The temperature/low level switch monitors the oil temperature and level in the reservoir.
NOTE
To conserve water usage it is recommended that the cooling water be shut off at
the end of the day. A sensor bulb from the modulating valve is submerged in the
reservoir. Even when the control power is off, the valve will remain open,
allowing water to flow until the oil is cooled.
5.3 Service and Maintenance Procedures
To ensure the supply of properly conditioned oil to the main hydraulic system, the components
will require routine servicing and maintenance. The procedures for servicing these components
are detailed below.
NOTE
Refer to Section 11, Parts List for a complete listing of replacement parts and part
numbers.
Hydraulic Oil Maintenance
The hydraulic oil should be replaced after 3,000 hours or one year of service, whichever comes
first. The oil should be replaced sooner if a fluid sample indicates contamination that cannot be
rectified by filtering.
An air breather and filter is located on the reservoir. The air breather prevents dirt from being
sucked into the reservoir when the oil level drops, and allows air to escape when the level rises.
The air breather must not be used as a fill point. Oil must only be added at the fill port on the
filter head and removed at the drain valve.
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