Transcript Slide 1

Beginner’s Series
{sounds of throat clearing}
Hydraulic Symbols
HYS102
Part D
Pressure Control Valves
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1. Each
member of the
pressure
control family
starts with a
square
2. Yes,
good job.
The 2
little lines
are the
ports
3. Add an arrow
to indicate the
flow path thru
the valve
4. Add a dashed
line from the inlet
port to the top of
the valve
5. Add a spring,
and while you’re
on a roll, put an
arrow thru the
spring at a 450
angle
1. Excellent!
We have a
relief valve
2. The
flow path
arrow is
not in
alignment
with the
ports
3. Which means
the valve is
normally
closed
4. The spring
holds the valve
closed
5. Until pilot
pressure in the
dashed line is high
enough to
overcome the
spring force
6. Yon 450 arrow
means that the
spring, and
thereby, the
pressure setting of
the valve, is
adjustable
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
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
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
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
1. A brake valve
symbol is the same
as a relief and
includes an
external pilot line
in addition to the
internal pilot line
Internal
pilot
2. Typically, a brake
valve is used to
brake the speed of
a freewheeling
hydraulic motor
Brake Valve
External
pilot
1. An unloading
valve symbol is the
same as a relief,
but it has external
pilot
External
pilot
2. Typically, an
unloading valve is
used to unload a
pump at low
pressure
Unloading Valve
5. This valve, as
well as most of
the others,
comes with an
optional check
valve
1. The pressure
reducing valve is
the only normally
open pressure
control
2. Typically, it’s
used to reduce
the pressure in a
portion of the
system
3. It has internal
pilot, but this silly
thing has it coming
from the outlet
port
Normally open
4. You know
an external
drain when
you see one
Pressure Reducing Valve
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
8. A pressure reducing valve is wierd
the only Normally open pressure control
Pilot pressure sensed from the outlet port
Thanks for hanging with me
Wanna hook all of these valves up? There’s handson training in Birmingham
Close this window and click on the final
module, then you’re done