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Welcome to our latest blog post. This time, we focus on common control valve repairing reasons businesses have and why successful ones have chosen to invest in proactive maintenance programs for control valves.

As we dive deeper into the topic, we explore professional advice on the signs of a failing control valve, providing a helpful guide for those invested in and newbies curious about the mechanics and maintenance of control valves.

Let’s discuss why control valve repair matters.

Reason 1: Avoiding a Critical Valve Failure

When a control valve fails, it can result in immediate disruptions to the process it controls. These disruptions may include:

• Flow interruptions – A failed control valve may lead to sudden interruptions in fluid flow, causing downtime and potentially impacting production schedules.
• Pressure fluctuations – Unregulated flow due to a malfunctioning valve can result in pressure fluctuations within the system, jeopardizing equipment integrity and safety.
• Temperature variations – Control valves often regulate the temperature of fluids. A failure in temperature control can affect the quality of the end-product or compromise the integrity of the process.
• Loss of control – The most significant immediate effect is the loss of control over the process variable (e.g., flow rate, pressure, temperature, etc.), leading to instability and potential hazards.

To avoid a critical valve failure, organizations implement proactive maintenance programs to check on their valves and ensure they are not about to fail with solutions, such as those from Emerson’s Valve Reliability Suite:

• Valve Condition Monitoring service offering, in which valve data analysts from Emerson use 10 different trend charts to figure out what issues are happening with the valve. Then, they make direct recommendations to fix the valve and warn the customer if they see a disruption in the valve data, which gives you a better chance to fix the valve before an unplanned outage or shutdown.
• Using a software tool like ValveLink, you or a service provider could use offline scans from the data within a digital valve control (DVC) to determine if the valve has failed. The signature test and the step test would give you the full picture of the valve to warn if the valve is broken.
• Use a dashboard, such as Plantweb Insight Valve Health Application, to display trends of past health, valve problem explanations, recommended actions, and a recommended time frame to take action to avoid a critical valve failure.

Control Valve Repairing with Control Valve Diagnostics

Reason 2: Reducing control valve variability

Control Valve Repairing: Leakage

A digital valve controller with the ValveLink software can show signs that there is a packing leak or a decrease in friction. If the digital valve controller is Performance Diagnostics (PD) tier, you can run a Friction Test when the valve is running to capture friction values and help you to notice if the valve packing is worn out. Alternatively, an offline test from ValveLink, called a Signature Test, could be run to determine friction levels and produce the same kind of friction values.

For external leaks in a globe valve, the leak could be between the body and bonnet gasket area, through the bonnet packing stem area and the bolting area, and even the body itself if there is a crack or hole. The actuator could leak externally through the diaphragm, tubing, or a crack in the diaphragm casing.

You should also keep in mind there could be an internal leak, such as in a global valve. The leak could be between the valve plug and seat ring as a start. It can also leak internally due to worn-out, eroded, or corroded trim parts based on the process application. There could be a leak through the actuator, as well as in its diaphragm, O-ring, or actuator stem bushings. In all these cases, parts can be replaced without replacing the entire valve. The valve can also leak due to the valve not closing properly, which is covered in more detail in the next section.

Control Valve Repairing: Setpoint Issues

It is important to understand if the control valve is not closing and opening properly. If the valve is not meeting its setpoint correctly, it is a telltale sign that something may be wrong. To run an online test to check the valve is meeting its setpoint correctly, it is recommended to use three tests from the ValveLink software:

• ValveLink status monitor
• One Button Swipe
• PD Profile Test

For offline test options from ValveLink, a signature test and a default step test can show that the valve is not closing all the way. If you need help checking and repairing a valve, you can reach out to a service provider.

Do you want to know which valve services companies Emerson recommends for control valve repair? Please visit our Valve Service Provider Locator webpage to find our hand-picked service providers near you. Learn more about our Accredited Service Provider program here.

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