API 610 Bearing Temperature Rise 1

[spartan117]

Hello,

I am designing a bearing calculation sheet and noticed a discrepancy in API 610 (10th Edition) paragraph 6.10.2.4 in regards to the acceptance criteria during testing. According to the paragraph,

"b) for ring-oiled or splash systems, an oil-sump temperature below 82 degrees C (180 degrees F); during shop testing, the sump oil temperature rise shall not exceed 40K or 70R above the ambient temperature in the test cell..."

I understand that Kelvin and Rankin are equal to Celsius and Fahrenheit, respectively, when referring to differential temperatures. However, according the statement above, the temperature rise can either be 40 degrees Celsius or 70 degrees Fahrenheit higher than the ambient temperature in the test cell. This does not match with the conversion from 40 degrees Celsius, which is 104 degrees F. If I ever run the test, I would obviously pick 40 degrees C over the limitation of 70 degrees F. Could anyone explain why you would allow higher temperature rise in one system of measurement?

 

[1gibson]

Add 40*C to get 80*C, convert that to *F and then see what the difference is.

 

[spartan117]

I am not understanding...

I would add 40 degrees C to another 40 degrees C? The conversion is 176 degrees F. How is that relevant to the 40 K (70 R) temperature rise?

40 K does not equal 70 R in differential temperature. How are those values reconciled? Am I missing something?

 

[electricpete]

This does not match with the conversion from 40 degrees Celsius, which is 104 degrees F

That is a "normal" conversion of temperatures:
DegF = DegC * (9/5) + 32

However, it doesn't apply for differential temperatures. For differential temperatures, the reference temperature (32F) is irrelevant (cancels out):
DegF = DegC * (9/5)

For differential temperatures, Rankine is interchangeable with DegF and Kelvin is interchangeable with DegC:
DegR = DegK * (9/5)
70 ~ 40 * (9/5)
it checks out (to within a few degrees)





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(2B)+(2B)' ?

 

[spartan117]

Thank you, electricpete! That answers the question.