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 TM 55-1925-273-10-1
0039 00
HYDRAULIC OPERATION
When the operator powers up one or both hydraulic pumps, power is sent to the electric motor(s) (figure 1, item 2) for the
selected hydraulic pump(s) (figure 1, item 1). Once the hydraulic pump is turning, it draws hydraulic fluid through the
suction strainer (figure 1, item 7) and into the hydraulic pump. The hydraulic pump pressurizes the hydraulic fluid in
response to the amount of restriction on the system. If the restriction is low (no load applied), system pressure is very low.
If the restriction is high (load applied), the system pressure will vary in response to the load. The pressurized hydraulic
fluid exits the hydraulic pump and flows through the supply piping (figure 1, item 13) to the downstream components
(capstan, anchor windlass, deck crane, and tow pins), where the hydraulic pressure and flow are transformed into physical
work. Hydraulic fluid exiting the downstream components returns to the reservoir (figure 1, item 6) through the return
piping (figure 1, item 14) and the return filters (figure 1, item 9).
If the restriction is extraordinarily high due to an overloaded downstream component or a closed cutoff valve (figure 1, item
15), the system relief valve opens at 2700 PSI (186 bar) to vent hydraulic fluid back to the reservoir (figure 1, item 6). This
prevents catastrophic damage to the hydraulic pump, piping, and other hydraulic components.
The return filters (figure 1, item 9) are provided with a bypass valve (figure 1, item 16) and a restriction gauge (figure 1, item
17). If the filter restriction rises above 25 PSI (1.7 bar), the bypass valve opens, permitting hydraulic fluid to bypass the
filters and to return to the reservoir (figure 1, item 6). Because permitting unfiltered hydraulic fluid to return to the reservoir
opens the door to eventual system failure, the restriction gauge is provided to enable timely return filter changes. Performing
regular filter changes helps to ensure that the central hydraulic system and its components enjoy a long service life.
ELECTRICAL OPERATION
When the main disconnect switch (figure 4, item 1) is CLOSED (ON), power is supplied to the control panel (figure 2, item 1).
Power (440 Vac) from the main disconnect switch (figure 4, item 1) flows through a transformer (figure 4, item 2) where it
is converted to a lower voltage for the control circuitry. Leaving the transformer, the power is supplied to the REMOTE/
OFF/ON switch (figure 4, item 3), to the low oil level switch (figure 4, item 4), and to the thermal overload reset switches
(figure 4, item 5).
If the REMOTE/OFF/ON switch (figure 4, item 3) is in the OFF position, the switch is OPEN and no power is
supplied to the low oil level switch's (figure 4, item 4) Normally Closed (NC) contacts. If the switch is in the ON
position, the switch is CLOSED between terminals 13 and 14, supplying power to the low oil level switch's NC
contacts. If the switch is in the REM position, the switch is CLOSED between terminals 21 and 22, supplying power
to the REMOTE/OFF/ON switch (figure 4, item 3) in the EOS console. When the START pushbutton ( f i g u r e 3,
item 1) is pressed, the switch CLOSES, supplying power to the low oil level switch's NC contacts. When the STOP
pushbutton (figure 3, item 2) is pressed, the switch is OPEN, securing power to the low oil level switch's NC con-
tacts.
When power is supplied from the REMOTE/OFF/ON switch (figure 4, item 3), and when the low oil level switch's (figure
4, item 4) NC contacts are CLOSED (hydraulic fluid level is above the low mark), power is supplied to the high temperature
cutoff switch (figure 4, item 6). The high temperature cutoff switch has both NC and Normally Open (NO) contacts. The
NC contacts supply power to the P1/P2/P1&P2 (figure 4, item 7) switch, while the NO contacts supply power to the HIGH
OIL TEMP light (figure 4, item 8).
When the P1/P2/P1&P2 switch (figure 4, item 7) is in the P1 position, the switch is CLOSED between terminals 1
and 2 and OPEN between all other terminals. This supplies power to the pump 1 control relay (figure 4, item 9).
When the pump 1 control relay is powered, it CLOSES between terminals 9 and 5 and OPENS between terminals 9
and 1. This powers the pump 1 starter (figure 4, item 10) and the pump 1 RUNNING light (figure 4, item 11). When
the pump 1 control relay is not powered, it CLOSES between terminals 9 and 1 and OPENS between terminals 9 and
5. This illuminates the number 1 pump READY light (figure 4, item 12) and secures power to the motor by opening
the pump 1 starter.
0039 00-4
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