Hydraulic Symbols

1
Beginners Series
sounds of throat clearing
Hydraulic Symbols HYS102 Part D Pressure Control
Valves
Please advance each slide at the tone.
2
1. Each member of the pressure control family
starts with a square
4. Add a dashed line from the inlet port to the
top of the valve
2. Yes, good job. The 2 little lines are the ports
5. Add a spring, and while youre on a roll, put
an arrow thru the spring at a 450 angle
3. Add an arrow to indicate the flow path thru
the valve
3
1. Excellent! We have a relief valve
5. Until pilot pressure in the dashed line is
high enough to overcome the spring force
2. The flow path arrow is not in alignment with
the ports

1. Which means the valve is normally closed

6. Yon 450 arrow means that the spring, and
thereby, the pressure setting of the valve, is
adjustable
4. The spring holds the valve closed
4
What have we learned so far?
1. A relief is one member of the pressure
control family
2. The valve is held in its normally closed
state by the spring until the pilot pressure
exceeds the spring setting
3. The arrow thru the spring shows that the
spring is adjustable
5
1. A sequence valve symbol is the same as a
relief with the addition of an external drain
2. Typically, a sequence valve is used to cause
one cylinder or motor to start moving before
another cylinder or motor
Sequence Valve
6
1. the counterbalance valve symbol is the same
as a relief
2. Typically, a counterbalance valve is used to
hold a load from falling
Counterbalance Valve
7
What have we learned so far?
4. A Sequence valve has an external drain
5. A counterbalance valve symbol is the same as
a relief valve
8
1. A brake valve symbol is the same as a relief
and includes an external pilot line in addition
to the internal pilot line
2. Typically, a brake valve is used to brake the
speed of a freewheeling hydraulic motor
Brake Valve
9
1. An unloading valve symbol is the same as a
relief, but it has external pilot
2. Typically, an unloading valve is used to
unload a pump at low pressure
Unloading Valve
10
1. The pressure reducing valve is the only
normally open pressure control
2. Typically, its used to reduce the pressure in
a portion of the system
4. You know an external drain when you see one
3. It has internal pilot, but this silly thing
has it coming from the outlet port
Pressure Reducing Valve
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What else have we learned?
6. A brake valve has both internal and external
pilot lines
7. An unloading valve is like a relief except it
has an external pilot line

• A pressure reducing valve is wierd
• the only Normally open pressure control
• Pilot pressure sensed from the outlet port

12
Thanks for hanging with me
Wanna hook all of these valves up? Theres
hands-on training in Birmingham
Close this window and click on the final module,
then youre done