Hi Stephen,
asset criticality analysis formulae and templates are proprietary for each company or service provider and will not be easy to publish.
you can adopt EPRI approach for asset criticality analysis which is quiet straightforward and robust and filling the gaps found in other approaches especially when considering redundant asset (2*100 or 3*50%)
EPRI report is free to download here, https://www.epri.com/research/products/1025341
if still have some questions please contact.
------------------------------
Kamal Mohamed
Maintenance & reliability
Siemens Energy
Beni Suef
------------------------------