New Holland PL6011, Service Manual

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Hydraulic systems - Hydraulic systems
Relief valve
A relief valve is shown as a normally closed symbol con-
nected between the pressure line
(A) and the reservoir
(B) . The flow direction arrow points away from the pres-
sure line port and toward the reservoir. This graphically
represents how a relief valve operates. When pressure in
the system overcomes the valve spring
(C) , flow is from
the pressure line through the relief valve to the reservoir.
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Pressure reducing valve
A pressure reducing valve is shown as a normally open
symbol in a pressure line. This valve works opposite of
a relief valve, since it senses outlet pressure
(A) versus
inlet pressure (B) . As the outlet pressure builds, it works
against a predetermined spring force. As the spring force
is overcome, flow through the valve is reduced or shut off.
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Sequence valve
The normally closed symbol is also used for a sequence
valve
(A) . The inlet port is connected to a primary cylin-
der (B) and the outlet port to the secondary cylinder line
(C) . When the piston in the primary cylinder reaches the
end of its stroke, the pressure in the supply line increases.
The sequence valve is also connected to the supply line
and also feels the increase in pressure. As pressure in-
creases, the envelope and directional flow arrow move
over, connecting the inlet and outlet ports allowing fluid to
flow to the secondary cylinder.
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Hydraulic systems - Hydraulic symbol - Directional control (35.000)
Hydraulic systems - Hydraulic symbol - Composite (35.000)
Hydraulic systems - Hydraulic symbol - Flow control (35.000) Reference:
Hydraulic systems - Hydraulic symbol - Table of symbols (35.000)
73383738 15/09/2017
35.1 [35.000] / 11