raschemmel:
To a certain extent, some of the information can be obtain by simple manual testing.
Example, you have a valve that has a shaft. You clamp a pair of vise grips on the shaft and open and
close the valve by hand. Then you remove the visegrips from the valve and clamp on the motor shaft and turn on the motor and tell it to turn (slowly) one way or the other , then you try to stop that motor from turning by holding onto the vise grips and mentally compare the force needed to turn the valve with the force needed to stop the motor.Additionally there are other more accurate ways to measure the torque, like attaching a pully to the shaft
and having the motor lift a weight, (like a bucket you add or remove water from and then weigh the bucket. ) The converse of this is attach a pulley to the shaft of the valve and measure the weight of the amount of water needed to open and close the valve and then see if the motor can lift that amount of water (or sand, or rocks, or diamonds, or coins etc)
At the end of the day, you don't need to know the torque spec in Nm. All you need to do is find a motor that is capable of performing the required task and then look at the spec sheet for that motor and whatever it is , it exceeds the torque spec for you task.
Fish scale?