Hydraulic Troubleshooting Flashcards
The most widely used circuits in industry
Open loop circuit
This returns fluid from the case drains back to the inlet of the main pump
Charge pump (part of a hydrostatic drive closed loop circuit)
In a hydrostatic drive what should the fluid viscosity stay within
16 to 39 St.
Fluid oxidization rate
Above 60 C the oxidization rate doubles every 5 C
Size of reservoir in hydrostatic drive
3/4 of charge pump capacity
A suction filter should not create a pressure drop of more than this
3 psi
If the broken drive shaft has crystallized grainy appearance at right angles to the shaft axis it is caused by
Coupling misalignment
if it appears twisted off then there is overpressure in the system
Electrical solenoids can be either
AC (120 V, large current inrush, can burn out) or DC (little current inrush, safer, won't burn out, but slower than AC)
The malfunctions you must fix on hydraulic systems are all symptoms of faults of these 3 things
Flow, pressure, and direction of flow
____ affects the speed of the actuator, _______ affects the force
Speed, Force
Two types of flow meters
Float - Tube indicator
Turbine - Electronic device attached
Two types of pressure gauges
Compound - Gives vacuum reading as well as pressure reading
Pressure Gauge
Which pressure gauge is recommended for hydraulic systems
Pressure gauge with venting isolation valve with palm button
The mechanism for protecting a gauge is called
Snubbers
Max temp in a closed loop system
80 C
Device used to detect hot spots for internal leakage
Pyrometers or infrared sensor guns
Device used to check the rotating speed of a motor
Tachometer
A sudden increase in the particle count usually means this
A component is starting to fail
This can be connected to a hydraulic system for continuous monitoring of pressure, flow, and temp
Multi-Function test instrument
The two basic feedback loops in a proportional solenoid valve
Inner loop - Comes from a valve mounted sensor
Outer loop - Comes from an actuator-mounted sensor
These valves operate using a mechanical feedback system and an external feedback loop
Servo Valve (extremely accurate)
The difference between the position signal and the command signal
Error signal
Function of a LVDT
Sense the spool position
The seven steps of troubleshooting
- Talk to the operator Gather information
- Know the system
- Inspect the machine
- List probable causes *Isolate and repairing the trouble
- Test probable causes
- Repair the system
- Check for root causes Preventing future problems
The three root causes for failures in a hydraulic system
Contamination
Heat
Leakage
Why would a seal be swollen
Not compatible with system fluid
How should U and V-packings be installed
Open side or lip facing the system pressure
Types of coolers
Fluid to water
Fluid to air
Used in the system main return line, cannot take much pressure
The most frequent cause of improper operation of a fluid to air cooler
Dirt blocking the flow or air
Filter cart is also known as this
Transfer pump
The two kinds of external filtering
Continuous (system can remain in operation) Batch process (more thorough)
Can you filter oxidized fluid
No, additives and lubricity is gone
What should you use to flush the system
Clean system fluid of the correct type
Where should you read the system temperature
As close to the main return line as possible
What does no resistance indicate in a solenoid
A short circuit
Most sequence circuits require the relief valve setting to be at least ___ psi higher than the sequence valve setting
150 psi
