CLS Case Analysis & Practical Application 3

Question 1

A lube tech is sampling oil from a turbine that operates at 65°C. The sample is taken when the unit is shut down and the oil temperature has dropped to 25°C. What is the main concern with this sampling approach?

Accepted Answer

Contaminants and wear particles settle when oil is cold, making the sample unrepresentative

Answer

Particles settle rapidly in cool, static oil, so a cold-oil sample will under-report contamination and wear compared to a sample taken at operating temperature.

Question 2

A centrifugal pump handling a corrosive chemical slurry has its bearing housing redesigned to use sealed-for-life bearings pre-packed with grease. Six months later failures begin. What is the most probable cause?

Accepted Answer

Heat and vibration have degraded the factory grease charge faster than anticipated

Answer

Sealed-for-life bearings rely on a fixed grease charge that can degrade under elevated temperatures and vibration, causing premature failure when the grease life is shorter than the intended service interval.

Question 3

A maintenance team is troubleshooting a hydraulic cylinder that drifts under load. Oil analysis shows the fluid is clean and within viscosity specification. What lubrication-related cause should be ruled out next?

Accepted Answer

Cylinder seal wear allowing internal bypass between piston faces

Answer

A drifting hydraulic cylinder with acceptable fluid condition points to internal seal bypass, allowing fluid to pass from the high-pressure side to the low-pressure side of the piston.

Question 4

A plant is considering extending oil drain intervals in its diesel-powered lift trucks from 250 hours to 500 hours. Which approach best supports this decision?

Accepted Answer

Using used oil analysis (UOA) data over multiple samples to validate oil condition at 500 hours

Answer

Used oil analysis over multiple drain cycles provides empirical evidence of remaining oil life, making the drain interval extension scientifically defensible.

Question 5

After a bearing failure, inspection reveals a fluted (washboard) pattern on the outer race. Which root cause does this pattern indicate?

Accepted Answer

Electrical current passing through the bearing and creating arc damage

Answer

Fluting on bearing races is the classic signature of electrical current discharge (EDM), which occurs when stray current arcs through the bearing contact zone.

(CLS) Certified Lubrication Specialist Practice Test

(CLS) Certified Lubrication Specialist Practice Test

CLS Case Analysis & Practical Application 3