I have been in touch with suppliers of actuators for subsea valves. They have mentioned their solutions are available for no matter the valve size, as long as the interface is API 17D class 2, 4 or 7.
During my search, I could barely find any mention of these classes, even in the API 17D itself.
What are the API classes for torque tools? Do they depend on size? Is there a rule of thumb to "convert" class to valve size?