HET4 Failure/Fluid Analysis Flashcards
Failure and fluid analysis
When doing fluid analysis, you can only analyze oils and coolant?
False, specialty fluids
and Exhaust gases or pneumatic system gases
Describe Failure analysis
Systematic process to determine why their was a mechanical failure
What type of maintenance program can fluid analysis help with?
Predictive maintenance program
Schedule testing of fluid can show what trends?
Wear rates of internal components
Rate of deterioration and additive depletion
Amount/Time of external contamination
What is spot-checking refereed to as?
Random fluid analysis
Should ppm of wear particles be high or low during break-in period?
High
What are the three major areas that a good oil analysis will show?
Deterioration of the oil itself (physical or additive)
Amount in PPM and type of wear particles
Presence of foreign contamination
At what point in the stream should the 4 oz oil sample be taken?
Mid Stream
If dirt/debris falls into the sample will you get an inaccurate sample reading?
Yes, make sure outside area is clean before taking sample
Should oil samples be taken cold or when the oil is warm (recently operated)?
Warm - recently operated (contamination will be suspended)
True or false:
Some metals can be both oil additives and also wear particles
True
What are three ways to take an oil sample?
Live Machine
Hand Pump
Mid Stream
What can cause a Viscosity increase in oil?
Contamination by a higher viscosity fluid
Running high operating temperatures
Extended drain intervals
What can cause a decrease in oil viscosity in an engine?
Fuel dilution
If an oil sample shows plenty of glycol, sodium and boron what is contaminating the oil?
Coolant/anti-freeze
At what temperature does oil boil off water?
100°C
Is a high Tin level on an oil analysis normal during break in?
Yes normal during break in
How many steps can be involved in a failure analysis?
up to 9 steps
What is the FIRST step involved in failure analysis?
Are there any concerns regarding liability?
includes: warranty, cost of repairs, personal/property damaged or other litigation
What is the LAST step involved in failure analysis?
Complete reports and store vital information. (from reports to pictures)
What should you do before “returning to service” and proving repairs are complete?
Test operation compared to manufacture/design specs
When you are doing mechanical failure analysis, what should you keep during the process?
Anything that may be evidence: filters oil samples (fluid samples) relevant materials (i.e bolts, gears, parts) -Store to keep condition as is-
What are three types of metal fractures?
Fatigue, Brittle, Ductile
What are the three classifications of steel?
Low, Medium, High carbon
When does a fatigue fracture usually happen?
Near the normal life expectancy - can be premature
Brittle Fractures occur when?
Usually from shock or impact load
Are fatigue fractures usually have smooth fracture surfaces?
Yes
What does a sudden or brittle fracture produce on the surface?
Rough Fracture Surface
Are ductile breaks(fracture) happen from one high stress?
It can result after being stressed multiple times
What can determine the classifications of metal wear? (3)
Type of stress
Movement of the parts
Damage to the wear surface
What are the types of metal wear? (7)
Visible wear Adhesive wear Abrasive wear Surface fatigue wear Brinelling (true/false) Corrosive wear Erosive wear
What is the general cause of adhesive wear?
Lack of lube
A part shows a build up of material and smearing, what is the wear called?
Adhesive wear (galling)
What type of fracture is caused when there has been repetitive torque stalls?
Ductile Fracture
If an engine is at a high RPM and the clutch is “dropped” engaged, what type of fracture can happen?
Brittle Fracture
Abrasive wear is usually caused by what problem?
Contaimination
Surface fatigue can be a result of?
Normal operation - old age
When exhaust temp is 2500°F or higher what is produced?
NOx (oxides of nitrogen)
Adhesive wear can also be shown as?
Galling (metal transfer)
During a root cause analysis, it has been found to be contamination is the cause of the failure. Is this a good enough answer?
No, you must find wear the contamination can from or its cause
If high CO is found in the exhaust, what could cause this?
Plugged air filter or bad air/fuel mixture
