TM 5-2410-240-23-1
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IMPLEMENT HYDRAULIC SYSTEM CONTINUED
5. Pressure Override Relief (POR) Valve Operation
Oil flows from the drive loop and enters the POR valve through the passages (Figure 19, Items 5 and 6). Since the
pressure of the oil in the passage (Figure 19, Item 5) is greater than the pressure of the oil in the passage
(Figure 19, Item 4), the resolver (Figure 19, Item 6) moves to the left. High-pressure oil from the drive loop flows
through the passage (Figure 19, Item 7). The pressure oil acts against the piston (Figure 19, Item 8).
Under normal operating conditions, oil pressure in the passage (Figure 19, Item 5) is less than the force of the
spring (Figure 19, Item 1). In this case, the pistons (Figure 19, Items 9 and 8) do not move.
When the drive loop encounters a stall, the pressure oil in the passage (Figure 19, Item 7) overcomes the force of
the spring (Figure 19, Item 1). The pressure oil moves the piston (Figure 19, Item 8) to the left, which also moves
the piston (Figure 19, Item 9) to the left. This opens a path from the passage (Figure 19, Item 2) to the passage
(Figure 19, Item 3). Signal oil from the pump stroking actuator in the passage drains to the case drain through the
passage. The piston pump destrokes in order to reduce the flow through the drive loop until the drive loop pressure
decreases to normal operating conditions.
As drive loop pressure decreases, the spring (Figure 19, Item 1) overcomes the pressure that is acting against the
piston (Figure 19, Item 8). The spring moves the spring retainer (Figure 19, Item 10) to the right. As a result, the
piston (Figure 19, Item 9) moves to the right and the piston blocks oil in the passage (Figure 19, Item 2).
Figure 19. Pressure Override Relief (POR) Valve.
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