The FOXBORO 43AP-FA42C-PC (often seen as 43AP-FA42C/PC or 43AP-FA42C-PC-00) refers to a specific configuration of the classic Foxboro 43AP Pneumatic Indicating Controller. This instrument is designed to control industrial processes using air pressure signals, and the “PC” suffix is particularly important as it indicates the type of input measurement.
Product Overview
The FOXBORO 43AP-FA42C-PC is a Model 43AP Pneumatic Indicating Controller from Foxboro (now part of Schneider Electric). This is a legacy, yet highly reliable, analog instrument that measures a process variable, compares it to a set point, and produces a proportional pneumatic output signal (air pressure) to control a final control element, typically a pneumatic control valve.
Breaking down the model number:
- 43AP: Denotes the basic model, a Pneumatic Indicating Controller.
- -F: Indicates Field Mounting, meaning it’s designed for mounting on a pipe or yoke, often directly in the plant environment.
- -A4: Specifies the control action as Proportional plus Integral (Reset). This combination (P+I or PI control) provides a proportional response to the error and also eliminates steady-state offset (the difference between the setpoint and the actual process variable). The integral (reset) range is typically 0.01 to 50 minutes per repeat.
- -2: Refers to the Output Signal and Gauge: a standard 3 to 15 psi (pounds per square inch) output air signal, with a local 0 to 30 psi output gauge for visual feedback.
- -C: Designates the Automatic Manual Internal Transfer Switching as “Bumpless”. This feature includes a 2-position switch, a balance gauge, and a regulator, allowing for smooth, bumpless transfer between automatic and manual control modes without disturbing the process.
- -PC: This is the crucial part. 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-FA42C-PC controller.
This configuration is very common in pneumatic control systems, allowing the controller to receive inputs from a variety of pneumatic transmitters to control different process variables.
Technical Specifications
Main Features and Advantages
The FOXBORO 43AP-FA42C-PC brings together the robust characteristics of the 43AP series with the flexibility of a pneumatic receiver input:
Pneumatic Receiver Input (/PC): This is a core feature. The controller accepts a standardized pneumatic signal (typically 3-15 psi) from a remote transmitter. This allows for diverse applications, as any process variable (temperature, flow, level, differential pressure, etc.) can be controlled as long as it’s first converted to a pneumatic signal by a suitable transmitter. This also allows for 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 without the need for additional safety barriers or specialized enclosures, a major advantage over electronic counterparts in certain applications.
Proven Reliability: The 43AP series has a long and established history of reliable operation in harsh industrial conditions. Its mechanical design contributes to its durability and resistance to environmental factors like temperature extremes and vibration.
Proportional plus Integral (Reset) Control: The “A4” control action provides the essential combination of proportional response (reacting to the error) and integral action (eliminating steady-state offset), ensuring precise and stable control of the process variable at the setpoint over time.
Bumpless Auto/Manual Transfer (“C” option): This is a critical operational feature that enables operators to switch smoothly between automatic and manual control modes without introducing sudden changes or disturbances to the process output. This enhances operational stability and minimizes process upsets.
Local Indication: The controller provides a direct, mechanical indication of the process variable (as represented by the input pneumatic signal), the set point, and the output control signal. This allows operators to quickly monitor and assess the process status directly in the field.
Field Mountable (“-F”): Designed for mounting directly on a pipe or yoke, typically close to the control valve or process area. This simplifies pneumatic piping and reduces potential signal lag associated with longer pneumatic lines.
Simpler Maintenance (for trained personnel): Compared to complex electronic systems, pneumatic instruments often have fewer delicate electronic components. While requiring regular calibration and clean air, troubleshooting and repair can sometimes be more straightforward for technicians familiar with pneumatic principles.
Application Field
The FOXBORO 43AP-FA42C-PC is widely used in process industries that rely on pneumatic instrumentation for robust and reliable control, especially where the process variable is transmitted pneumatically. Its primary application fields include:
Chemical and Petrochemical Processing:
- Controlling parameters in distillation columns, heat exchangers, and reactors, where a pneumatic transmitter measures the process (e.g., temperature, flow, level) and sends a 3-15 psi signal to the controller.
- In hazardous areas, where the intrinsic safety of pneumatic devices is preferred or mandated for handling flammable or explosive materials.
Oil and Gas Industry:
- Used for critical control loops in refineries, offshore platforms, and natural gas processing plants, managing pressure, flow, and level, often integrating with pneumatic differential pressure or pressure transmitters.
Power Generation (Legacy Plants):
- Boiler control systems, including steam drum level control (from a pneumatic level transmitter), fuel-air ratio control, and steam pressure regulation in older conventional power plants.
Pulp and Paper Industry:
- Controlling flow rates, levels, and pressures in various stages of pulp digestion, chemical recovery, and paper machine operation, with pneumatic inputs from flow or level transmitters.
Water and Wastewater Treatment:
- Regulating flows, levels, and pressures in different treatment stages, such as filtration, sedimentation, and pumping stations, based on pneumatic signals from field transmitters.
Food and Beverage Production:
- Used in processes requiring precise temperature, pressure, or flow control (e.g., pasteurization, fermentation) where pneumatic control is suitable, receiving inputs from hygienic pneumatic transmitters.
In essence, this specific controller is suitable for any industrial process that uses a pneumatic transmitter to convert a process variable into a standard 3-15 psi signal, and then requires robust, reliable, and often intrinsically safe control via a pneumatic output to a control valve.
Related Products
The FOXBORO 43AP-FA42C-PC operates as part of a pneumatic control loop. Its related products are primarily other Foxboro pneumatic devices that connect to it, as well as essential auxiliary equipment.
Primary Connecting Instruments:
- Foxboro Pneumatic Transmitters: These devices are crucial as they provide the 3-15 psi input signal to the 43AP-FA42C-PC. Examples include:
- Foxboro 13A Series Differential Pressure Transmitters: Used for measuring flow, level, or differential pressure.
- Foxboro 12A Series Force Balance Transmitters: Used for various measurements like pressure, temperature (with filled thermal systems), or other variables.
- Pneumatic Control Valves: These are the final control elements that receive the 3-15 psi output signal from the 43AP-FA42C-PC to manipulate the process. They typically consist of a valve body, a pneumatic actuator (diaphragm or piston), and often a pneumatic valve positioner (e.g., Foxboro 69P or 69F) for accurate valve positioning.
Pneumatic Infrastructure and Accessories:
- Instrument Air Supply System: Essential for clean, dry, and regulated air. This includes:
- Air Filters and Dryers: To remove moisture, oil, and particulates from the compressed air.
- Air Regulators: To reduce the plant air pressure (e.g., 80-100 psi) to the required 20 psi for the controller. The 43AP-FA42C-PC often has an integral air supply set, but external regulation is also common.
- Pneumatic Tubing and Fittings: For connecting the controller to the air supply, the input transmitter, and the output control valve.
- Pneumatic Relays and Boosters: Used to amplify the pneumatic signal or increase its speed of transmission, particularly for large or fast-acting valve actuators.
