Attention! Error in API 617 ?? 1

[jurry]

From: jurryb@themail.com

Standard API 617 it. 2.9.5.5. wrote: "During the shop test of the machine - assembled with the balanced rotor, operating at its maximum continuous speed range - the peak -to-peak amplitude of unfiltered vibration in any plane , measured on the shaft adjacent and relative to each radial bearing, shall not exceed the value in Equation 5 or 25 micrometers, whichever is less:"( ? peak-to-peak? 25 mk peak-to-peak - this is very small and Equation 5 not working) Is this right or not and why?
Any information would be greatly appreciated. Regards, Jurry.

 

[Franko]

The equation is as intended. A recent draft reverted back to the older version: Square Root (12000 /rpm), but the API gurus wouldn't listen to reason (some customers will). Thus a centrifugal compressor running at 3000 rpm with perhaps 15 mil clearance bearings will have the same one mil limit as a 12000 rpm unit with perhaps 4 mil clearance bearings. The equation works as API intended - all units below 12000 rpm must meet one mil; those above 12000 are to meet Sqrt (12000/rpm). We agree with the limit for the high speed unit - the limit for the one at 3000 rpm is ridiculous. The relative dynamic bearing loads and encroachment on bearing and seal clearances are much different. In quotations to land jobs we often have to avoid taking exceptions. With much care in rotor assembly and bearing design along with our at-speed balance facility, the task of meeting the spec is a lot easier.