API661, Air cooler: the radial clearance between the fan tip and the fan orifice ring

[wodding]

API661, Clause 7.2.3.6: The radial clearance between the fan tip and the fan orifice ring shall be as shown in Table 6. I'm wondering this "radial clearance" is fan ring ID minus fan tip OD or (fan ring ID minus fan tip OD)/2?
can someone shed light on this?...many thanks

 

[wodding]

can anyone share with your opinion?

 

[gr2vessels]

Radial is not diameter, but if you want, then fan ring ID minus Fan tip OD divided by 2 is the clearance you're looking for.
Cheers,
gr2vessels