Knowledge about the life of the cooling fan

The calculation of the life of the cooling fan product feels more professional knowledge, here is a brief introduction to the relevant knowledge.

u003cbru003eCalculation of product life expectancy MTTF and L10

u003cbru003e1. Product life expectancy MTTF refers to the expected time when 63.2% of the product is defective, or the time when the reliability is 36.8%. Product life expectancy L10 is the expected time when the product is 10% defective

u003cbru003e Time, or the time when the reliability is 90%

u003cbru003e MTTFu003dt1+(t2-t1)*0.632 L10u003dt1+(t2-t1)*0.1

u003cbru003e t1: The shortest time to reach the defective rate value t2: The longest time to reach the defective rate value

u003cbru003e2. There is no standard for the definition of badness requested, such as:

u003cbru003e(1) A batch of products can be used for testing. After 2000, 3000, 5000, 10000, and 18000 hours, test whether the speed and current consumption exceed the specifications as the definition of bad.

u003cbru003e(2) Or use a precision measuring instrument to measure the residual amount of lubricating oil on the axis as a poor definition.

u003cbru003e3. The more samples are tested, the more reliable the data is, at least three.

u003cbru003e4. The test time can be 2000, 3000, 5000, 10000, 18000 hours as standard. That is to say, the test time point i is 1,2,...n, because there are five test points, so nu003d5, Iu003d1,2,3,4,5 total five points.

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u003cbru003e5. Assume that an existing fan product is deemed defective when the shaft oil is consumed to 50%. Because it takes a long time for the oil to reach 50%, the time must be determined by the method of heterodyne.

u003cbru003eIf the fuel loss curve approaches linearity, the fuel consumption formula can be written as Yu003dAx+b

u003cbru003eY: The remaining oil finger after i time

u003cbru003eX: Time (unit: hour)

u003cbru003ea: The slope of the curve. Equal to Σ(Xi-X)*(Yi-Y)/ Σ(Xi-X)2

u003cbru003eb: Constant (unit: %) is equal to Y-[Σ(Xi-X)*(Yi-Y)/ Σ(Xi-X)2]*Xu003dY-Ax

u003cbru003eNote: When calculating, if bu003e100% is calculated as 100%

u003cbru003eX: u003d Average value of each test time point

u003cbru003e u003d(2000+3000+5000+10000+18000)/5u003d7600 hours

u003cbru003eY: The average value of grease residues at each test time point. Suppose there are three samples S1, S2, S3 and their grease residues after i time are as follows:

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u003cbru003eXu003d7600, Yu003d(99.9+99.8+99.6+99.1+98)/5u003d99.28%

u003cbru003eau003d[(2000-7600)(99.9-99.28)+(3000-7600)(99.8-99.28)+(5000-7600)(99.6-99.28)+ (10000-7600)(9931-99.28)+ (18000-7600)(98-99.28)]/[(2000-7600)2+(3000-7600)2+(5000-7600)2+(10000-7600)2+(18000-7600)2]u003d[ (-3472)+(-2392)+(-832)+(-432)+(-13312)]/[(31360000)+(21160000)+(6760000)+(108160000))u003d-20440/167440000u003d- 0.000122

u003cbru003ebu003dY-aXu003d99.28-(-0.000122*7600)u003d99.28+0.927u003d100.2(%), calculated as 100(%) according to the fuel consumption formula Yu003daX+b, knowing the amount of lubricant in the S1 fan (Y) 50% time left X

u003cbru003eXu003d(Y-b)/au003d(50-100)/(-0.000122)u003d-50/(-0.000122)u003d409836 hours

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u003cbru003eXu003d7600, Yu003d(99.5+99.2+97+93+87)/5u003d95.14%

u003cbru003eau003d[(2000-7600)(99.5-95.14)+(3000-7600)(99.2-95.14)+(5000-7600)(97-95.14)+ (10000-7600)(9.-95.14) +(18000-7600)(87-95.14)]/ [(2000-7600)2+(3000-7600)2+(5000-7600)2+(10000-7600)2+(18000-7600)2]u003d [(-24420)+(-18680)+(-4840)+(-5140)+(-84660)]/[(31360000)+(21160000)+(6760000)+(108160000)]u003d-137740/167440000u003d -0.0008226

u003cbru003ebu003dY-aXu003d95.14-(-0.0008226*7600)u003d95.14+6.25u003d101.39(%), calculated as 100%

u003cbru003eAccording to the fuel consumption formula Yu003daX+b, it is known that the time X when the S2 fan has 50% lubricating oil (Y):

u003cbru003eXu003d(Y-b)/au003d(50-100)/(-0.0008226)u003d-50/(-0.0008226)u003d60782 hours

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u003cbru003eXu003d7600, Yu003d(99.5+99.3+98+96+93)/5u003d97.16%

u003cbru003eau003d[(2000-7600)(99.5-97.16)+(3000-7600)(99.3-97.16)+(5000-7600)(98-97.16)+ (10000-7600)(96-97.16)+ (18000-7600)(93-97.16)]/ [(2000-7600)2+(3000-7600)2+(5000-7600)2+(10000-7600)2+(18000-7600)2]u003d[ (-13104)+(-9844)+(-2184)+(-2784)+(-43264)]/[(31360000)+(21160000)+(6760000)+(108160000))u003d-71180/167440000u003d- 0.0004251

u003cbru003ebu003dY-aXu003d0.90-(-0.0004251*7600)u003d97.14+3.23u003d100.37(%), calculated as 100%

u003cbru003eAccording to the fuel consumption formula Yu003daX+b, it is known that the time X when the S3 fan has 50% of the lubricating oil (Y):

u003cbru003eXu003d(Y-b)/au003d(50-100)/(-0.0004251)u003d-50/(-0.0004251)u003d117619 hours

u003cbru003e6. Know from the above three samples:

u003cbru003eThe fan that consumes 50% of the oil first is S2, the time is 60,782 hours, the slowest is S1, the time is 409,836 hours, so we know that t1u003d60782 hours, t2u003d409836 hours

u003cbru003e7.MTTFu003dt1+(t2-t1)*0.632u003d60782+(409836-60782)*0.632u003d60782+220602u003d281384 hours

u003cbru003eL10u003dt1+(t2-t1)*0.1u003d60782+(409836-60782)*0.1u003d60782+34905u003d95687 hours