Product Overview

The FOXBORO 43AP-FA45C/PC-00 is a Model 43AP Pneumatic Indicating Controller from Foxboro (now part of Schneider Electric). It is a robust and highly dependable analog instrument designed to continuously measure a process variable (via a pneumatic signal input), compare it to a set point, and produce a corresponding pneumatic (air pressure) output signal to control a final control element, typically a control valve.

Let’s break down the full model number:

• 43AP: Denotes the basic model, a Pneumatic Indicating Controller.
• -F: Indicates Field Mounting, meaning it’s designed to be mounted on a pipe or yoke, usually close to the process equipment.
• -A5: This is a key differentiator. It specifies the control action as Proportional plus Integral plus Derivative (PID) control. This is the most comprehensive and powerful control algorithm, combining:
  • Proportional (P): Responds to the current error.
  • Integral (I): Eliminates steady-state offset (the difference between the setpoint and the actual process variable).
  • Derivative (D): Responds to the rate of change of the error, providing anticipatory action to improve system stability and speed of response, especially useful for processes with lag. The ranges for these actions are typically adjustable (e.g., proportional band 0.05 to 500%, integral 0.01 to 50 minutes per repeat, derivative 0.01 to 10 minutes).
• -2: Refers to the Output Signal and Gauge: a standard 3 to 15 psi (pounds per square inch) pneumatic output air signal. The controller also includes a local 0 to 30 psi output gauge for visual indication of the output pressure.
• -C: Designates the Automatic Manual Internal Transfer Switching as “Bumpless”. This feature incorporates a 2-position switch, a balance gauge, and a regulator, enabling smooth and “bumpless” transfers between automatic and manual control modes without disturbing the process.
• /PC: This is crucial. It indicates that the controller is equipped with a Pressure Receiver (Bellows) measuring element. This means the controller does not directly measure a process variable like temperature or pressure. Instead, its input is a standard pneumatic pressure signal (e.g., 3-15 psi) from a separate, remote pneumatic transmitter. This transmitter measures the actual process variable (like flow, level, temperature, or differential pressure) and converts it into a pneumatic signal, which then becomes the input to the 43AP-FA45C/PC controller.
• -00: This suffix typically denotes no additional standard optional features beyond those specified in the main model code and the /PC element.

This specific configuration makes it a highly versatile and precise pneumatic controller, capable of handling more complex and dynamic process control applications due to its full PID capability, while receiving its input from a remote pneumatic transmitter.

Technical Specifications

Main Features and Advantages

The FOXBORO 43AP-FA45C/PC-00 stands out with its full PID control capability combined with the inherent benefits of pneumatic instrumentation:

Full Proportional plus Integral plus Derivative (PID) Control (A5): This is the most significant feature. PID control provides comprehensive and precise control for a wide range of process dynamics, including those with significant lags or oscillations. The derivative action (rate control) anticipates changes, improving stability and speeding up the response to disturbances. This makes it suitable for more challenging control loops than simpler PI or P-only controllers.

Pneumatic Receiver Input (/PC): This feature allows the controller to accept a standardized pneumatic signal (e.g., 3-15 psi) from a remote pneumatic transmitter. This provides great flexibility, enabling the control of various process variables (flow, level, temperature, differential pressure, etc.) that are first converted into a pneumatic signal. This also allows the controller to be located at a convenient, accessible point away from the primary measurement.

Inherent Safety and Robustness: As a purely pneumatic instrument, it is intrinsically safe and immune to electrical noise, electromagnetic interference (EMI), and radio frequency interference (RFI). This makes it highly suitable for hazardous (explosion-proof) environments (e.g., oil & gas, chemical plants) without the need for complex electrical barriers or specialized enclosures. Its mechanical design provides exceptional durability in harsh industrial conditions.

Proven Reliability and Longevity: The Foxboro 43AP series has a long and established history of dependable operation in demanding industrial conditions, known for its robustness and long operational life.

Bumpless Auto/Manual Transfer (“C” option): This crucial operational feature allows operators to seamlessly switch between automatic and manual control modes without introducing sudden changes or disturbances to the pneumatic output, thereby enhancing operational stability and minimizing process upsets.

Local Indication: The controller provides a direct, mechanical indication of the process variable (derived from the input pneumatic signal), the set point, and the output control signal. This allows operators to quickly monitor process status directly in the field, independent of a central control system.

Field Mountable (“-F”): Designed for direct mounting on a pipe or yoke near the process or control valve, which simplifies pneumatic piping and potentially reduces signal lag.

Adjustable PID Tuning Parameters: The ability to adjust proportional band, integral (reset), and derivative rates allows for optimal tuning of the control loop to match specific process dynamics, ensuring stable and efficient control.

Application Field

The FOXBORO 43AP-FA45C/PC-00 is particularly well-suited for a wide range of continuous process control applications within industries that rely on pneumatic instrumentation, especially those with more complex dynamics benefiting from full PID control.

Chemical and Petrochemical Plants:

• Controlling critical parameters in distillation columns (e.g., overhead temperature, reflux flow), reactors (e.g., reaction temperature, pressure with significant lag), and heat exchangers where precise and stable control is crucial.
• Ideal for hazardous areas where intrinsic safety is a primary concern.

Oil and Gas Production and Refining:

• Advanced control of processes like fractionators, crude units, and gas processing facilities where dynamics might be complex.
• Controlling flow, level, temperature, and pressure loops that require precise tuning to prevent oscillations or manage lags, based on signals from remote pneumatic transmitters.

Power Generation (Traditional Plants):

• More complex boiler control loops, such as steam temperature control, feedwater control for large boilers, and fuel-air ratio control, where PID action provides stability and responsiveness.
• Controlling other auxiliary systems with demanding control requirements.

Pulp and Paper Mills:

• Controlling complex variables in pulp digestion, chemical recovery, and papermaking processes where maintaining tight control is critical for product quality and efficiency.

Water and Wastewater Treatment:

• Advanced flow, level, or pressure control in large-scale treatment plants, especially where rapid changes or high accuracy are needed to prevent upsets.

In essence, this controller is chosen when the process dynamics are challenging, and precise, stable, and anticipatory control is required, all within the robust and intrinsically safe framework of pneumatic instrumentation.

Related Products

The FOXBORO 43AP-FA45C/PC-00 operates as a central component within a pneumatic control loop. Its related products primarily include other Foxboro pneumatic devices that interact with it, along with essential infrastructure components.