Product Overview
The FOXBORO 43AP-FA42C is a Model 43AP Pneumatic Indicating Controller from Foxboro (now part of Schneider Electric). It is a robust and highly dependable analog instrument that continuously measures a process variable, compares it to a set point, and produces a corresponding pneumatic (air pressure) output signal to control a final control element, such as a control valve.
The “FA42C” in the model number provides specific configuration details:
- 43AP: Denotes the basic model, a Pneumatic Indicating Controller.
- -F: Indicates Field Mounting (designed to be mounted on a pipe or yoke, rather than panel mounted).
- -A4: Specifies the control action as Proportional plus Integral (Reset), with an integral (reset) range of 0.01 to 50 minutes per repeat. This combination of control modes allows for stable control and the elimination of offset errors.
- -2: Refers to the Output Signal and Gauge: a 3 to 15 psi (pounds per square inch) output air signal, with a 30 psi output gauge.
- -C: Designates the Automatic Manual Internal Transfer Switching as “Bumpless” with a 2-position switch, balance gauge, and regulator. This allows for smooth transfer between automatic and manual control modes without upsetting the process.
These controllers are known for their mechanical reliability, accuracy, and suitability for hazardous environments where electronic instruments might pose a risk.
Technical Specifications
Main Features and Advantages
The FOXBORO 43AP-FA42C Pneumatic Indicating Controller, despite being an older technology, offers several key features and advantages that contributed to its widespread use and continued presence in some industrial settings:
Robust and Reliable Pneumatic Operation: Unlike electronic controllers, pneumatic controllers are inherently immune to electrical noise, electromagnetic interference (EMI), and radio frequency interference (RFI). This makes them ideal for use in electrically noisy environments or hazardous (explosion-proof) areas without the need for intrinsic safety barriers or special enclosures.
Proven Field Performance: The 43AP series has a long history of reliable operation in harsh industrial environments. Their mechanical nature often makes them very robust and less susceptible to the effects of extreme temperatures or vibrations compared to some early electronic counterparts.
Proportional plus Integral (Reset) Control: The “A4” control action provides both proportional and integral control. Proportional control reacts directly to the error, while integral action eliminates offset (the difference between setpoint and process variable), ensuring the process reaches and maintains the setpoint accurately over time.
Bumpless Auto/Manual Transfer: The “C” option for transfer switching is a significant advantage. It allows operators to switch between automatic and manual control modes without causing a sudden bump or disturbance in the process output. This enhances operational stability and reduces process upsets during mode changes.
Direct Indication: As an “indicating” controller, it provides a direct, local visual indication of the process measurement, set point, and output signal. This allows operators to quickly assess process status directly at the instrument.
Field Mountable: The “F” mounting option means it’s designed for direct mounting near the process or control valve, which can simplify piping and reduce signal transmission lag compared to panel-mounted controllers with long pneumatic lines.
Low Maintenance Requirements: While periodic calibration and cleaning are necessary, pneumatic instruments generally have fewer delicate electronic components that can fail, leading to simpler troubleshooting and repair compared to complex electronic systems.
Application Field
The FOXBORO 43AP-FA42C Pneumatic Indicating Controller was widely applied in process industries for continuous control where reliability, intrinsic safety, and robustness were paramount. While modern installations often use electronic or digital controllers, these pneumatic controllers are still found in:
Oil and Gas Industry:
- Refineries and Petrochemical Plants: For controlling distillation columns, heat exchangers, and reactors, especially in hazardous areas where intrinsically safe control is preferred or mandated.
- Pipeline Compressor Stations: Regulating gas flow and pressure.
Chemical Processing:
- Controlling reaction temperatures, pressures, and flow rates in chemical synthesis processes.
- Managing levels in tanks and vessels containing various chemicals.
Pulp and Paper Industry:
- Controlling steam pressure, flow, and level in boilers and recovery systems.
- Managing consistency and flow in pulp processing.
Power Generation (Traditional Plants):
- Boiler controls, including drum level, fuel-air ratio, and steam pressure regulation, particularly in older plants.
- Turbine auxiliary controls.
Water and Wastewater Treatment:
- Regulating flow rates, levels, and pressures in various treatment stages.
Food and Beverage Processing:
- Controlling temperatures in pasteurization, sterilization, and cooking processes.
- Managing flow and pressure in liquid handling systems.
Essentially, the 43AP-FA42C is used in any process requiring continuous, closed-loop control of a process variable where a pneumatic output signal is required, or where the inherent safety and reliability of pneumatic instrumentation are highly valued.
Related Products
The FOXBORO 43AP-FA42C is part of a larger ecosystem of pneumatic instrumentation. Related products would include other Foxboro 43AP series variations, pneumatic control accessories, and the broader range of Foxboro’s historical process control equipment.
Other Foxboro 43AP Controller Configurations:
- Different Control Modes: Other 43AP models offered On-Off (A1), Proportional (A2), Proportional plus Derivative (A3), Proportional plus Integral plus Derivative (A5), Differential Gap (A7), and Automatic Shutdown (A8).
- Different Output Signals: Models with 20 to 100 kPa or 0.2 to 1.0 bar output signals.
- Panel Mount Versions: The 43AP also came in panel-mounted (-P) versions.
- Different Measurement Elements: The “C” at the end of the full ordering code (e.g., 43AP-FA42C/PC) would specify the directly connected measuring element, such as pressure elements (e.g., spiral, helical, bellows), temperature elements (filled thermal systems), or differential pressure elements.
Foxboro Pneumatic Transmitters:
- These devices measure process variables (e.g., pressure, flow, level, temperature) and convert them into a standard pneumatic signal (e.g., 3-15 psi) that serves as the input to the 43AP controller. Examples include the Foxboro 13A Series Differential Pressure Transmitters or 12A Series Force Balance Transmitters.
