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Bearing Life in Years by Operating Schedule

Run the Bearing Life in Years by Operating Schedule MicroSim Fullscreen

About This MicroSim

A bearing's L-10 rating is given in hours: the operating hours at which 10 percent of a large group of identical bearings are expected to have failed. The L-50 life, or average life, is five times the L-10 life. A customer needs the rating in years of their own running schedule:

  • Hours per year = hours per day × days per week × 52
  • L-10 years = L-10 hours ÷ hours per year
  • L-50 years = 5 × L-10 hours ÷ hours per year

The bar chart shows five schedules, from around-the-clock service (24 h/day, 7 days/week, 8,736 h per year) down to 2 h/day, 5 days/week (520 h per year). Each schedule has an L-10 bar (solid) and an L-50 bar (light, with a heavy outline), and every bar carries its value. The vertical axis is a log scale, so a 4-year bar and a 900-year bar both stay readable; each gridline is 10 times the one below. Hover over or tap a bar to see the rating, the schedule, the hours per year and both lives.

The sim starts with three challenges, in this order:

# L-10 rating Schedule L-10 life
1 40,000 h 16 h/day, 5 days/week 9.6 years
2 40,000 h 24 h/day, 7 days/week 4.6 years
3 20,000 h 8 h/day, 5 days/week 9.6 years

The bars are hidden until you check your answer. An answer is correct when it is within ±0.1 year of the model value. You get two attempts: a wrong answer shows the calculation, and a second wrong answer shows the model value and the challenge counts as missed. When a challenge is resolved, the chart shows that rating, outlines the matching schedule, and prints the chart value next to your answer. Mastery is 3 of 3 on the first attempt.

After challenge 3, Explore mode unlocks the L-10 rating menu: 20,000, 40,000, 60,000, 80,000 or 100,000 hours. All ten bars update at once. Every bar scales in proportion to the rating, and the 2 h/day bar is always about 17 times (16.8 times) the 24/7 bar. Explore mode is never scored.

How to Use

  1. Read challenge 1, type the L-10 life in years (one decimal is enough) and press Check (or Enter).
  2. A correct answer reads "✓ Correct: 9.6 years." in a solid green box. A wrong one reads "✗ Not quite." with the calculation in a dashed red box; use the second attempt.
  3. Press Next challenge (or Enter) for challenges 2 and 3. "Challenges correct: n of 3" keeps the running score, and the numbered chips show each challenge as ✓, ✗ or current.
  4. After challenge 3, press Start exploring. The summary box shows the first-attempt score and the mastery line. Change the L-10 rating and compare the bars. Start over clears the score.

Keyboard: Enter checks the answer, and Enter again goes to the next challenge. Tab reaches the answer box, the buttons and, after challenge 3, the rating menu; the arrow keys change the rating.

Data label: "Source: FanPedia, page 90 (L-10 and L-50 ratings) · 52-week year · Log scale", below the chart.

Iframe Embed Code

You can add this MicroSim to any web page by adding this to your HTML:

<iframe src="https://moroshek.github.io/FanTASTIC-textbook/sims/ch03-bearing-life-years/main.html"
        height="840px"
        width="100%"
        scrolling="no"></iframe>

Lesson Plan

Learning Objective

The learner will calculate the L-10 and L-50 bearing life in years from a rated L-10 life in hours and an operating schedule, to within 0.1 year (Bloom: Apply, verb: calculate).

Audience

Adult professional development: new application engineers, sales staff, representatives and facilities staff who have read "Bearing Life" in Chapter 3.

Duration

10 minutes

Prerequisites

  • Bearing, L-10 life and L-50 life (Chapter 3)
  • Operating schedule in hours per day and days per week

Activities

  1. Challenges (5 min): Work each challenge with a calculator before pressing Check. Write down the hours per year first, then the years.
  2. Exploration (3 min): At 40,000 h, read the L-50 years for 16 h/day, 5 days/week (48.1 years) and check that it is five times the L-10 bar. Switch to 80,000 h and confirm every bar doubled.
  3. Discussion (2 min): A customer says "40,000-hour bearings last 40,000 hours." Use the chart to explain what L-10 means and why their schedule matters.

Common Misconceptions Addressed

  • L-10 life is the life of every bearing: the chart labels it L-10, and the chapter's wording "by about 9.6 years, roughly 1 in 10 of these bearings will have failed" is the reading to use.
  • L-50 life is twice L-10: the L-50 bar sits five times higher on every schedule.
  • A rating in hours lasts the same number of years for every customer: the same rating spans from a few years to centuries across the five schedules.

Assessment

  • The running line "Challenges correct: n of 3" counts challenges solved on either attempt. At the end the sim shows "First-attempt score: n of 3" and the mastery line; mastery is 3 of 3 within ±0.1 year on the first attempt.
  • Reading the chart in Explore mode is not evidence of mastery. Ask the learner to convert a 60,000-hour rating for a 24 h/day, 5 days/week schedule (9.6 years) without the chart.

References

  1. Rolling-element bearing - Wikipedia article covering bearing life ratings, including L10 life.
  2. FanPedia: The Fan & Blower Encyclopedia - Twin City Fan's reference; page 90 defines L-10 and L-50 life and gives the example values used here.
  3. Bearing (mechanical) - Wikipedia overview of bearing types, including the ball and roller bearings used in fan pillow blocks.