Process and Equipment Reliability - Barringer and Associates, Inc.
Process and Equipment Reliability - Barringer and Associates, Inc.
Process and Equipment Reliability - Barringer and Associates, Inc.
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Knowing MTBF or MTTF Tells<br />
About Maintenance Dem<strong>and</strong>s<br />
• Suppose you have 400 pumps. Half of the pumps are<br />
running at any one time (which means we accumulate<br />
200 years of life annually).<br />
• Suppose your MTBF = 2 years/failure.<br />
• How many pump repairs should you expect<br />
MTBF = ΣLife<br />
= 2 years<br />
= 200 years<br />
X failure<br />
, ∴ X = 100<br />
failures<br />
year<br />
ΣFailures failure<br />
• If your competitor has MTBF = 4 years — who has the<br />
advantage <strong>and</strong> by how much<br />
© <strong>Barringer</strong> & <strong>Associates</strong>, <strong>Inc</strong>. 2004 15<br />
Can We Do Better Than Arithmetic<br />
• Weibull analysis provides specific details about failure<br />
modes <strong>and</strong> allows us to forecast future failures<br />
• We have 5 ages-to-failure data from bearings on a<br />
specific machine at (in rank order): 3900, 6500, 7800,<br />
18100, 32600 hours. We also have 5 bearings in<br />
operation that have not failed (suspensions) at: 4000,<br />
6000, 15000, 25000, <strong>and</strong> 30000 hours will be replaced<br />
with similar bearings when failure occurs.<br />
• What’s the failure mode, when are future failures<br />
predicted for the bearings in continuous service<br />
© <strong>Barringer</strong> & <strong>Associates</strong>, <strong>Inc</strong>. 2004 16<br />
8
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