Hydraulic Principles Flashcards
(43 cards)
Describe pascals law
PRESSURE applied on a confined FLUID is transmitted UNDIMINISHED in all directions and acts with equal FORCE on equal AREAS at RIGHT angles to them
Describe Bernoullis principle
In a system with a CONSTANT FLOW RATE, the ENERGY is transformed from one form to another each time the pipe CROSS-SECTIONAL AREA changes
When is turbulent flow used
When FLUSHING the system
How is flow measured
Measured in velocity and flow rate
Why is water not used as a hydraulic fluid? (2)
Lack of lubricating
Corrosive
What is the definition of viscosity
Measure of a fluids resistance to flow
What is viscosity measured in?
Centistokes
What are the two types of pumps
Hydrodynamic (non-positive)
Hydrostatic (positive)
What are the characteristics of multi cylinder pumps? (4)
Highly efficient
Wide range of capacities
Variable output
Large HP applications
What are the 3 basic types of actuators?
Linear
Rotary
Semi-rotary
What is the Procedure for the motor leakage test
Isolate RETURN LINE
Break system on the DRAIN LINE
Supply oil to the actuator by operating the DIRECTIONAL CONTROL VALVE
Collect oil from the DRAIN LINE and time how long it takes to collect 1 PINT
Take TEMPERATURE of the oil and repeat on opposite RETURN LINE
What conditions mandate a oil change?
Degregation of base oil
Depletion of additives
Identify malpractices in RN hydraulic pumps and motors
Changing filters
Running too hot
Using incorrect oil
Wrong filter locations
Not self priming
What four positions are on a flushing valve?
Normal
Flush return
Flush drain
Test
Describe the operation of a flushing valve
Depressurise hydraulic system
Remove locking piece
Slacken back gland but to avoid damage to disc valves
Move valve to required position
Retighten gland but
Replace locking pieces
Re-pressurise system
Describe how a hydraulic bypass valve works
At a preset pressure a relief valve opens allowing a control signal to the unloading valve, opening the valve
What are the 3 contaminants?
Air
Water
Particulate
What effects would air in the system cause?
Air entrainment
Heat
Dieseling
What effects would particulates in the system cause?
Scoring
Wear
Blocked filters
Blocked valve port
What effect would water in the system cause
Erosion
Corrosion
Emulsification
How are Swagelok fittings installed?
Insert the pipe into the fitting so the pipe rests firmly on the shoulder of the body
Scribe the nut at the 12:00 position
Hold the body in a vice
Tighten the nut 1 1/4 turns
When must the Hydraulic seating unit be used?
When the fitting is over 25 mm
(1 inch)
What are the Methods of fault finding
Hit and miss approach
Shutting down hydraulic machines
Line maintenance
Fault finding procedure
What do I check?
What do I check with?
Where do I check?
What do I expect to read?
What do I check?
