# 2.9: Hydraulic Schematics

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A YouTube element has been excluded from this version of the text. You can view it online here: https://openoregon.pressbooks.pub/hydraulics/?p=68

Discuss the advantages and disadvantages of representing hydraulic components using pictorial, cutaway, and schematic symbols

Differentiate between working, pilot, and drain lines and show how these lines are depicted schematically

Differentiate between schematically connected and unconnected fluid conductors

Describe an enclosure and how enclosures are depicted schematically.

Describe which fluid(s) these colors represent in a hydraulic schematic

Red

Blue

Yellow

Orange (2)

Green (2)

Purple

Define the purpose of these general shapes in a hydraulic schematic:

Circle

Square

Diamond

Slanting Arrow

Define a prime mover. Draw the schematic symbol for a motor and internal combustion engine.

Define a pump. Draw the schematic symbol for a fixed displacement pump, variable displacement pump, pressure compensated variable displacement pump, and manual pump. Differentiate between these types of pumps.

Define the purpose of a case drain and draw the schematic symbol.

Define a coupling. Draw the schematic symbol for a shaft linking a prime mover and pump.

Define a reservoir. Draw the schematic symbol for an atmospheric/vented reservoir and pressurized reservoir.

Define a hydraulic motor. Draw the schematic symbol.

Define a hydraulic cylinder. Draw the schematic symbol for a double acting hydraulic cylinder, a hydraulically extended spring retracted single acting cylinder, a spring extended hydraulically retracted single acting cylinder, and single acting ram. Discuss how these cylinders extend and retract. Describe the purpose of a vent port on a single acting cylinder.

Draw the schematic symbol for a double rod cylinder, a tandem/duplex cylinder, a telescoping cylinder, and an intensifier.

Draw the schematic symbol for a double acting cylinders with a fixed cushion on extension, a fixed cushion on retraction, and a fixed cushion on extension and retraction. Do the same for variable cushions.

Identify the purpose of a pressure relief valve and draw the schematic symbol.

Identify the purpose of a burst/rupture disc and draw the schematic symbol. (see the pressure relief valve lecture)

Identify the purpose of a directional control valve. Draw the schematic symbol for the following directional control valves and discuss the uses of these valves:

2 position, 2 way, solenoid actuated directional control valve spring offset into the NC position featuring a manual override

2 position, 3 way, manually actuated directional control valve spring offset into a position that dumps A to T

2 position, 4 way, solenoid actuated directional control valve with detents featuring a cross connect and straight through position

3 position, 4 way, manually actuated directional control valve, spring centered into a closed center position featuring a straight through and cross connect position

Differentiate between closed, tandem, float, and open center positions. Draw the schematic symbols.

Identify the purpose of a check valve, pilot to open check valve, pilot to close check valve, restriction/orifice type check valve, and manual shutoff valve. Draw the schematic symbol for these devices and discuss how these valves operate.

Identify the purpose of a flow control valve and draw the schematic symbol for the following devices: fixed flow control valve, variable flow control valve, variable flow control valve with check valve bypass, pressure compensated variable flow control valve with check valve bypass, pressure and temperature compensated variable flow control valve with check valve bypass. For flow control valves with check valve bypass identify direction of free flow and controlled flow.

Identify the purpose of a pressure control valve and draw the schematic symbol for the following devices: pressure relief valve, sequence valve, pressure reducing valve, counter balance valve, unloading valve.

Discuss how the following characteristics assist in identifying pressure control valves:

Pilot line

Deactivated state

Check valve bypass

Internal vs external drain

Location and perceived function

Identify the purpose and general operation principle of an accumulator and draw the schematic symbol for a gas charged accumulator, spring loaded accumulator, and weighted accumulator. Discuss any safety precautions regarding accumulators.

Identify the purpose and draw the schematic symbol for the following devices: pressure gauge/manometer, quick disconnect inspection ports, pressure switch (hydraulic and electric), pressure sensor, flow meter, limit switch, magnetic proximity switch (hydraulic and electric)

Identify the purpose and draw the schematic symbol for the following devices: filter, filter with check valve bypass, heater, cooler, cooler with liquid heat transfer fluid, cooler with gas heat transfer fluid. Discuss the purpose of counter flow in heat exchangers.

Define a hydraulic power unit (HPU). Identify devices commonly found in an HPU.
Identify the purpose and draw the schematic symbol for a rotary hydraulic coupling.

This page titled 2.9: Hydraulic Schematics is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by Jim Pytel (OpenOregon) via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.