Anti-Rotation for AIFR 1

[KVARM]

How many no of anti rotation devices are using for AIFR and assuming 20 m dia tank then how many no of anti rotation device required?. Is there any calculation for this to arrive the quantity if so kindly share.
Thanks in Advance.

 

[JStephen]

"A guide pole with rollers, or two or more seal centering cables" per API-650-H.5.4.