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signal level from the PLC meant to open the valve halfway could fully open the valve. Now that we’ve covered common issues, let’s look at potential troubleshooting.

Control Valve Troubleshooting

Keeping control valves in healthy condition extends the valve’s working life and, more importantly, keeps the process safe. Some standard troubleshooting techniques for control valves include preventive maintenance, moisture removal, and calibration.

Preventive Maintenance

Preventive maintenance can prevent potential faults by identifying a problem's source and eliminating it before it causes trouble.

Some important areas to look at during preventive maintenance for valves include the following.

• Visual inspection for degradation and corrosion. • Smooth movement of the mechanical assembly (free from vibration and jerk). • Tightly inserted pneumatic tubing to its connectors. • Pneumatic tubing leakage, bending, or discoloration. • Proper replacement components.

Moisture Removal

It is common for moisture to be contained in compressed air, which may contact the control valve. The moisture penetrates the valve in different components and affects the valve body (i.e., corrosion). Air systems contain a filter for collecting moisture to prevent adverse effects. These moisture collectors must be discharged frequently to remove the moisture. Otherwise, they can penetrate the valve and cause damage to the valve body.

Positioner Calibration

The positioner valve must be routinely calibrated with the I/P converter output to correctly translate the incoming signal from the PLC. If not calibrated correctly, it can wrongly translate the incoming signal, resulting in incorrect process parameters. Control valves are widespread within the industry and control all sorts of fluids and gases. As you consider their functions, like any device, they have issues and may need troubleshooting. The above may not be an inclusive list, but as you continue to grow your predictive and preventive maintenance plan, you’ll learn more troubleshooting techniques.

Control Automation, info@control.com, www.control.com

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