Case Analysis & Practical Application Flashcards

A lube technician samples a circulating oil system by opening a petcock downstream of a filter. Oil analysis results consistently show lower particle counts than expected. What is the likely error?

Answer: Sampling downstream of a filter captures cleaned oil, masking actual system contamination levels

Sampling downstream of a filter gives a misleadingly clean result; representative system samples should be taken upstream of filters or from a turbulent zone in the main flow.

A high-pressure hydraulic press (5000 psi) experiences frequent servo valve stiction and sticking. Oil analysis shows ISO cleanliness at 17/15/12 and water content at 0.03%. What is the most targeted corrective action?

Answer: Improve filtration to achieve ISO 15/13/10 or better, as servo valves require very clean fluid

Servo valves have very tight clearances (1–5 microns) and require ISO 15/13/10 or cleaner fluid; improving filtration to meet this standard directly addresses valve stiction.

A plant transitions its paper machine from a circulating oil system to grease-lubricated bearings on felt-roll positions. Six months later, bearing failures increase. The most likely cause is:

Answer: Grease re-lubrication intervals were set identical to the previous oil change intervals without recalculation

Grease re-lubrication intervals must be calculated based on bearing speed, size, temperature, and load—they cannot simply be copied from oil change schedules.

A lube route audit reveals that a technician is greasing 12 identical 6205 deep-groove ball bearings in electric motors running at 1750 RPM with the same interval and quantity used for much larger, slower bearings. Which consequence is most likely?

Answer: The small, high-speed bearings will be over-greased, causing heat and premature failure

Small, high-speed bearings require significantly less grease than large, slow bearings; applying excess grease causes churning, heat, and seal damage leading to early failure.

An oil mist lubrication system on a bank of rolling mill bearings shows evidence of rancid or acidic odor from the mist header. Oil analysis of the reservoir shows TAN has increased from 0.1 to 1.8 mg KOH/g in four months. What is the root cause to investigate?

Answer: Elevated operating temperatures or aeration in the reservoir are accelerating oil oxidation

A rapid TAN increase in an oil mist reservoir indicates accelerated oxidation driven by heat, aeration, or contamination, all of which expose large oil surface areas to oxygen in a mist system.

During a root-cause analysis of a gearbox failure, the investigation team finds heavy adhesive (scuffing) wear on gear tooth flanks. The oil was the correct ISO VG grade. Which factor is most likely responsible?

Answer: The lubricant lacked adequate extreme-pressure (EP) additives for the applied tooth load

Adhesive/scuffing wear on gear flanks is a classic indicator of EP additive deficiency under high contact stress, where metal-to-metal contact occurs and material transfers between surfaces.

A CLS is reviewing a lube program for a remote mining site where lubricants are stored outdoors for up to 18 months before use. Which storage practice is most critical to prevent in-service lubricant failures?

Answer: Store drums horizontally under shelter with bungs at the 3 and 9 o'clock positions to prevent water ingress through thermal cycling

Horizontal drum storage with bungs at the 3 and 9 o'clock positions prevents the bung seal from being alternately immersed in water and dried, which causes pumping of water into the drum through thermal cycling.