A positioner is a tool that uses a control signal to regulate the position of an actuator or valve. It guarantees that the valve or actuator reaches and stays in the intended position, increasing the precision and effectiveness of process control in automated systems, like those used in process industries.

What is the operation of a positioner?

A process controller or controller system sends a control signal to a positioner, which is often a digital signal or 4–20 mA. It makes sure the valve moves to the proper position to manage the flow, pressure, or level by comparing this signal to the valve’s current position and adjusting the actuator accordingly.

What is a positioner used for?

Positioning the valve or actuator accurately to regulate flow, pressure, temperature, or other process variables within a predetermined range is the main function of a positioner. For automatic valves in sectors including power generation, chemicals, water treatment, and oil and gas, it offers precise and responsive control.

Positioner Types

Various Positioner Types

There are two primary categories of positioners:

• Pneumatic Positioners: These regulate the actuator by use of pneumatic signals, or air pressure. Conventional pneumatic valve control systems frequently use them.
• Electro-pneumatic Positioners: These positioners use electrical input signals, such as 4–20 mA, to drive the actuator by converting them into pneumatic output signals.
• Digital (Smart) Positioners: These are sophisticated positioners that use fieldbus protocols (e.g., HART, Profibus) to connect digitally with control systems. They have capabilities like self-calibration, diagnostics, and remote adjustment.

The distinction between electro-pneumatic and pneumatic positioners

• The pneumatic positioner It is utilized in systems with a pneumatic control signal and runs solely on pneumatic pressure.
• Positioner that uses electropneumatics: enables the actuator to be positioned by converting an electrical control signal (4–20 mA) into a pneumatic output. These positioners offer greater flexibility and precision and are utilized in contemporary digital control systems.

Digital (Smart) Positioners: 

These are sophisticated positioners that use fieldbus protocols (e.g., HART, Profibus) to connect digitally with control systems. They have capabilities like self-calibration, diagnostics, and remote adjustment.

The distinction between electro-pneumatic and pneumatic positioners

• The pneumatic positioner It is utilized in systems with a pneumatic control signal and runs solely on pneumatic pressure.
• Positioner that uses electropneumatics: enables the actuator to be positioned by converting an electrical control signal (4–20 mA) into a pneumatic output. These positioners offer greater flexibility and precision and are utilized in contemporary digital control systems.
• Calibration: To make sure the positioner reacts appropriately to control inputs and precisely places the actuator, calibrate it after installation.
• Testing: Send control signals to the positioner to check that the actuator travels smoothly to the desired position.

How a Positioner Is Calibrated

To adjust a positioner’s calibration:

• Set the zero and span: Modify the zero and span settings on the positioner to correspond with the necessary range of valve positions.
• Control signal input: To make sure the actuator is responding appropriately, apply the control signal (4–20 mA or another) and see how it moves.
• Fine-tuning: Make sure the valve achieves the desired position at every signal level by adjusting the calibration.
• Examine the system: Make sure the valve always moves to the appropriate locations over the whole signal range.

Upkeep and Issue Resolution

How a Positioner Is Maintained

In order to keep a positioner:

• Frequent Inspection: Look for indications of damage, wear, or leaks in the positioner.
• Cleanliness: If it’s a pneumatic positioner, make sure the positioner and actuator are kept clear of impurities.
• Calibration: To make sure the positioner is giving precise control, recalibrate on a regular basis.
• Maintenance of the Air Supply (for Pneumatic Positioners): In order to keep moisture and impurities from impairing the positioner’s performance, maintain the air supply with filters and regulators.
• Replace Worn Parts: To maintain the positioner’s optimal operation, replace gaskets, seals, and any other worn parts as needed.

How to Proceed If the Positioner Is Not Giving the Right Answer

Should the positioner’s response be incorrect:

• Verify the control signal: Make sure the control signal, such as 4–20 mA, is connected correctly and falls within the appropriate range.
• Check for leaks: Examine pneumatic positioners for air leaks and electro-pneumatic positioners for wiring problems.
• Check the Calibration: Verify the positioner’s calibration and make any required adjustments.
• Examine the actuator: Make sure the actuator is operating correctly because problems with it may impact how well the positioner performs.

Operation and Performance

To what extent is a positioner accurate?

With a narrow margin of error, positioners often offer precise control over valve locations. Particularly, smart positioners provide remarkable accuracy and are frequently employed in high-precision applications.

Normal Pneumatic Positioner Pressure Range

The usual air supply pressure range for pneumatic positioners is 20–100 psi (1.4-6.9 bar). For optimal performance, make sure the pressure is within the manufacturer’s parameters.

How to Determine Whether the Positioner Is Operating Properly

To confirm the positioner’s effectiveness, you ought to:

• Keep an eye on how the control signals are received.
• Verify that the actuator movement is in line with the desired location.
• Utilize the diagnostics (found in smart positioners) to find mistakes, deviations, or malfunctions.
• Send signals to the valve to see if it reaches the desired settings without any problems or delays.

Tips for Safety and Operation

Can You Use Positioners Without Risk?

Indeed, safety is a priority in the design of positioners, particularly in automated systems. In order to avoid over-travel, under-travel, or system failures, they make sure that valves and actuators move exactly to the right places. When performing maintenance or installation, always adhere to safety procedures.

Is It Safe to Use Positioners in Dangerous Situations?

Yes, positioners can be used in dangerous situations, but choosing one that is rated for such settings is crucial. Use explosion-proof positioners that adhere to the applicable safety certifications (such as ATEX or IECEx) in areas with hazardous or explosive gasses.

How to Make Sure a Positioner Is Properly Sealed

To guarantee that a positioner is properly sealed:

• Regularly examine gaskets and seals for wear or damage.
• Any damaged or worn seals should be replaced right away.
• To prevent any movement that can result in leaks, make sure the positioner is mounted firmly.
• To prevent clogging or seal wear, make sure the air supply for pneumatic positioners is dry and clean.

Choosing and Acquiring

How to Pick Your System’s Proper Positioner

Take into account the following elements while choosing a positioner:

• Control type: Depending on your control system (analog vs. digital), select pneumatic, electro-pneumatic, or smart positioners.
• Use: Align the positioner with the valve and actuator type (e.g., linear or rotary actuators).
• Environmental factors: Choose a positioner that is appropriate for the temperature, humidity, and possible exposure to hazardous circumstances of the operating environment.
• aspects: Take into account aspects including interoperability with current control systems, ease of calibration, and diagnostic capabilities.

Can I Purchase Positioner Replacement Parts?

Indeed, the manufacturer or approved distributors offer replacement parts for internal components, actuators, seals, and sensors. Always confirm that replacement parts are compatible with the positioner’s particular model and manufacturer.

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