My buttterfly valves are air or hand operated not motor driven.
I tried a 2Nm Belimo actuator on my 2" Definox brand butterflies, did not close completely.
The Belimo high speed actuator part #LMQ24A 24VDC.
Ebay is a good source for Belimos.
Purchased three slow Belimos a month ago...
You can purchase the 1/2" SS 9-24 VDC 3-wire valves for $26.00 shipped.
I am currently modefining two for an additional $ 3.00 to meet my needs.
My pneumatic valves I can move in less than 1 second.
The butterflies I have don't require more than 4 Nm torque.
This hobby can drive you...