Having Problems? Here’s Why Your Power Actuator Isn’t Working

A process valve that won’t open or close means a process that stops moving. When it comes to
troubleshooting your power actuator, there are almost as many possible causes as there are actuator
types.

Before you get overwhelmed with all of those possibilities, taking an old-school approach to your
troubleshooting may save you a lot of time. Here we will take a methodical look at the most
common issues we see with valves and actuators.

Is it a Valve or Actuator Problem?

As you know, a valve and actuator combo are exactly that – a combination of a physical valve, and
the power actuator that moves the valve to a different position.

The first step in a methodical approach to troubleshooting is to find out if the valve is stuck due to
something physical or mechanical, or if it is the actuator failing to move the valve.

Usually, the quickest way to find out is to remove the actuator and attempt to move the valve stem
by hand. While the actuator is removed, you should also attempt to activate it without the load of
the valve itself.

Once you’ve determined if the problem lies in the valve or the actuator, half the problem is solved.
We will look at some common issues for both in a moment.

Power Actuator Types

There are three main types of power actuators: electric, pneumatic (air operated), and fluid
(hydraulic operated). Each type has its own set of troubleshooting protocols that differ from the
others.

Matters can get complicated even further because there are several varieties of each, depending on
the size and type of valve it’s trying to move.

Common Issues

To get your process moving again, start with the simple and most common causes of failure. In an
industrial setting, look at environmental factors before you begin dissecting an actuator. Do you
have extremes of temperature, moisture, or a corrosive environment?

The process itself can also be an environmental factor. What type of material are you moving
through the valve? Is it something that needs to remain at a higher temperature, but thickens when
cooled?

Any of these physical process or environmental factors can be a gremlin in the system, wreaking
havoc on equipment.

If you have eliminated those factors and determined that the problem is within the actuator itself,
take a look first at these most common culprits:

 Worn valve stem: if the valve is free and the actuator moves, check the connection to the
valve stem – most likely a drive nut. If the valve stem is worn or gear is stripped, the
actuator can’t physically grip the stem to turn it. Be sure to keep your valve lubricated.
 Check for contaminants in pneumatic actuators, like water in the airline, or a plugged filter.
Also, be sure to make sure that you have adequate air pressure.
 Check all the seals in pneumatic and hydraulic actuators to be sure you don’t have fluid or
air escaping where it shouldn’t, causing a lack of motive pressure.
 Check for proper operation of solenoids that control the fluid or air that operate the
actuator.
 Be sure the starting and ending positions are still correct in electrical rotary actuators. If
you have had prior slippage or other mechanical issues, you may be hitting a travel limit too
soon.
 If you can, force operation by controls or PLC on electrical actuators. That will quickly
eliminate problems like failed stepper motors, thermal overloads, fuses, etc.

Be Simple-Minded

There are literally hundreds of possible causes of valve/actuator failure. Keep your thought process
simple by looking for the obvious environmental and process conditions first. Power actuators
rarely fail all by themselves or due to a manufacturing defect.

This simple-minded troubleshooting approach will often be a big timesaver in getting your process
back up and running quickly. And time is money.

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