SKF Flush Ground Bearings Suffix 'G"

[rota2]

Hello All
I am a bit confused about SKF designation "G" on angular contact bearings to indicate it is flush ground for back to back mounting.I am also seeing bearings that do not have the suffix "G" that can be mounted in a back to back arrangement, ex BECBM. What is the difference here? I was of the opinion that only the bearings with the suffix "G" are to be installed as thrust bearings (back to back).
Thanks

 

[Tmoose]

G means universally ground, so that if either pair of ID or OD faces are inline then the desired preload will be achieved (and both faces WILL be inline). This allows rigid mounting either <> or >< as long as ID and OD spacers and shoulders are equal length. Spring loaded arrangement preload is set by spring, not bearing face offset

All that needs to be done with universally ground bearings to make a "matched" set of bearings is get ID and OD with the same size codes.

In previous times the bearings had to be selectively chosen or manufactured to make a matched set.

 

[jmoritz]

A G suffix on SKF angular contact bearings yield a preload after pairing. BECBM bearings are universally ground but have a clearance once paired.

 

[rota2]

Thanks for the info, but tell me what applications would you use which, we have here a double suction boiler feed pump, two stage, that was fitted with skf BECBM bearings in a back to back arrangement, these bearings discoloured the oil within minutes of being put in service, and failed catastrophically soon after,the OEM specified an skf BG bearing.
I take it, from what you said, we need the bearing to be preloaded for this service,but i still can't understand why a bearing with a higher clearance will fail in this service so soon?!