How To Get The Best Valve Actuator Performance

ATTA doesn’t compromise accuracy or speed when it comes to valve actuators – learn how in this article.

Goldilocks would be overwhelmed with the wide variety of pumps that must be tested on a single valve. Some pumps will have test points that are too high. Some pumps will have test points that are too low. Some pumps have a flow coefficient that is just right for the valve.

It would be unreasonable for Goldilocks to have a valve that is just right  for every pump test. The valve can’t be too large, the valve shouldn’t operate at less than 10%, and the valve transitioning from a high flow to a low flow pump takes way too long.

How do manufacturers manage such specifications? One of the popular

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technologies is an AC motor with a 4-20 mA position control. This design allows high performance for positioning speed, but compromises accuracy during the industry’s common practice of pushing the valve to its limits.

This limitation is often overcome by another method – taking an existing actuator and replacing the AC motor with a stepper motor. Using this with gear reduction allows for very precise positioning capabilities. The compromise here is speed. A stepper system can take up to 2 minutes just to turn 90°! Another limitation of stepper motors is all of its torque is at lower speeds, so it can be a struggle at higher pressures.

How is ATTA different? We choose to use servo motors to compliment our exclusive control algorithms for automatic valve control. Why servo motors, you ask? Because that’s how we can push the limits of a valve’s performance. With a positioning resolution up to 524,288 steps per revolution, this means we can detect a movement as small as .00068°. So yes, our servo systems run with accuracy, even when the valves are at their limits. Curious about speed and torque? The beauty of servo systems is they have most of their torque available at full speed, so they won’t peter out at higher pressures. They comfortably outperform the standard 4-20 mA positioners with speeds up to .35 seconds per 90°, with control of slowing down.

A servo motor is a proven technology with years of utility in the manufacturing industry. If you have any CNC machines, you probably have plenty of servo motors you haven’t even noticed because you can count on them to work.

ATTA’s expertise harnesses the complexity of using servo motors. We are already working with multiple valve manufacturers to tune our system for the highest automatic performance for your test systems.

Does this mean you have to use our servo valve systems when you use our test systems? Fortunately not. We can easily add automatic valve control to 4-20 mA positioners or stepper motor based positioners to improve your test systems performance. At ATTA we want everything to be just right.

Do you have any thoughts on valve performance? Feel free to leave a comment below.

 

One thought on “How To Get The Best Valve Actuator Performance”

  1. The speed issue for constant speed AC or DC motors and steppers is about the same. Variable speed controls for these motors are different, as are the torque and efficiency vs. speed curves. Adding these features can raise the cost to the realm of servo motors, and I agree servos have significant advantages performance-wise. And accuracy requirements will drive the performance specification.

    For example, a control valve with a conventional 4-20 mA signal-driven actuator may have 1% accuracy, and a quarter of that, or more, is due to the actuator. The valve must have high inherent accuracy (minimized friction, compliance and deformation), which makes difficult, and costly demands on valve design. A servo actuator equipped control valve removes most of the actuator-influenced accuracy error, allowing the system to be as good as the valve component can be.

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