New Holland T8010 Manual page 745

Relief Valve
PRESSURE LINE
PUMP
A relief valve is shown as a nor mally closed symbol
connected between the pressure line and the reservoir. The
flow direction arrow points away from the pressure line port
and toward the reservoir. This shows very graphically how a
rel ief va lve op erat es. Wh en pres sure i n th e s ys tem
overcomes the valve spring, flow is from the pressure line
through the relief valve to the reservoir.
Pressure Reducing Valve
HIGH PRESSURE INLET
PILOT
LINE
REDUCED OUTLET PRESSURE
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 versus inlet
pressure. As the outlet pressure builds, it works against a
predetermined spring force. As the spring force is overcome,
flow through the valve is modulated or shut off.
Section 35 - Hydraulic Systems, 3PT - Chapter 1
RELIEF VALVE
712L8F
DRAIN LINE TO
RESERVOIR
712L8H
35-1-8
Sequence Valve
SUPPLY LINE
RELIEF
VALVE
The normally closed symbol is also used for a sequence
valve. The inlet port is connected to a primary cylinder and
the outlet port to the secondary cylinder line. 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. A s pressure increases, the square and
directional flow arrow moves over, connecting the inlet and
outlet ports allowing fluid to flow to the secondary cylinder.
Directional Control Symbols
Simplified Symbols
One Way Valve
NO FLOW
A simple ball check valve is shown. When oil pressure is
exerted on the left side of the ball, the ball is forced into the V
and no oil can flow past it. When oil pressure is applied to the
right side of the ball, the ball moves away from the V and oil
can flow past it.
By Pass Valve
SPRING
A by pass valve is shown as a one way valve with a spring on
the ball end of the symbol. This shows that a pressurized flow
will be necessary to overcome the spring force and allow flow
around the ball
TO PRIMARY
CYLINDER
PUMP
SEQUENCE
VALVE
TO SECONDARY
CYLINDER
712L8G
FREE FLOW
712L8J
712L8K