The FOXBORO 43AP-FA46C/PA-CC is a specific configuration of the highly regarded Foxboro 43AP Pneumatic Indicating Controller. This model is designed for direct measurement and control of pressure, featuring a Proportional plus Integral plus Derivative (PID) control action, making it suitable for complex process dynamics. It directly measures process pressure using a helical pressure element with a specific range.
Product Overview
The FOXBORO 43AP-FA46C/PA-CC is a Model 43AP Pneumatic Indicating Controller from Foxboro (now part of Schneider Electric). It is a classic, robust, and highly dependable analog instrument that continuously measures process pressure, compares it to a set point, and produces a proportional pneumatic (air pressure) output signal to control a final control element, typically a control valve.
Let’s dissect the full model code:
- 43AP: Designates the basic model as 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.
- -A4: Specifies the control action as Proportional plus Integral (Reset). This is a common and effective control mode (P+I or PI) that provides a response proportional to the control error and also eliminates any steady-state offset (the difference between the setpoint and the actual process variable). The integral (reset) range is typically adjustable from 0.01 to 50 minutes per repeat.
- Note: While the prompt indicated A4, it’s worth noting that “A6” is a standard Foxboro code often used for Proportional-Plus-Integral-Plus-Derivative (PID) when a separate derivative unit is included or specifically enabled. Given the common usage of “A4” for PI, if this is a typo in the provided string, and “A6” was intended, the PID capabilities would be the key feature. Assuming the A4 is correct as stated, the control is P+I. If A6 was intended for PID, that would be a significant feature. For the purpose of this response, we’ll proceed with A4 (P+I) as specified, but acknowledge that A6 is a PID option.
- -6: Refers to the Output Signal and Gauge: This typically means an output signal of 0.2 to 1.0 bar or kg/cm², and a local gauge indicating 0 to 2 bar or kg/cm². This is an alternative to the more common 3-15 psi output.
- -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.
- /PA: This signifies that the controller is equipped with a Pressure (Helical) Measuring Element for its input. This means the controller directly senses the process pressure via a robust helical mechanism. Helical elements are typically used for higher pressure ranges compared to bellows.
- -CC: This specific suffix after “/PA” denotes the pressure range of the helical element. Based on common Foxboro configurations and vendor listings, “-CC” typically corresponds to a high-pressure range, often 0 to 14 MPa (0 to 2000 psi, or 0 to 140 bar/kg/cm²). Other “Px” suffixes (like “AA”, “BB”, “DD”) would indicate different helical ranges.
This particular configuration makes it highly suitable for direct measurement and control of process pressures within the 0-2000 psi range, offering a local, intrinsically safe, and reliable control solution with P+I action and a bar/kg/cm² output.
Technical Specifications
Main Features and Advantages
The FOXBORO 43AP-FA46C/PA-CC offers a compelling set of features and advantages, particularly due to its direct high-pressure measurement capability and robust pneumatic design:
Direct High Process Pressure Measurement (/PA-CC): This is a defining characteristic. The controller directly senses and indicates high process pressures via its internal helical element, specifically calibrated for the 0-2000 psi range. This eliminates the need for a separate pressure transmitter, simplifying the control loop, potentially reducing components, and offering faster response for pressure control applications. Helical elements are inherently strong and suited for higher pressures.
Inherent Safety and Robustness: As a purely pneumatic instrument, it is fundamentally intrinsically safe and immune to electrical noise, electromagnetic interference (EMI), and radio frequency interference (RFI). This makes it exceptionally well-suited for hazardous (explosion-proof) environments (e.g., in oil & gas, chemical plants) without requiring costly additional safety barriers or specialized enclosures. Its mechanical design also contributes to its durability in harsh industrial conditions.
Proven Reliability and Longevity: The Foxboro 43AP series has an extensive track record of reliable and continuous operation in demanding industrial environments. Their mechanical nature often means a longer operational life and simpler troubleshooting compared to some early electronic systems.
Proportional plus Integral (Reset) Control (A4): The “A4” control action provides the essential combination of proportional response (to the magnitude of the error) and integral action (to eliminate any steady-state offset). This ensures precise and stable control, allowing the process pressure to accurately reach and maintain its setpoint over time.
Bumpless Auto/Manual Transfer (“C” option): This is a critical operational feature, allowing operators to seamlessly switch between automatic and manual control modes without introducing sudden changes or disturbances to the pneumatic output, and thus to the process. This significantly enhances operational stability and minimizes process upsets during mode changes.
Local Indication: The controller provides a direct, mechanical indication of the measured process pressure, the set point, and the output control signal. This allows operators to quickly monitor and assess the process status directly in the field, independent of a central control system.
Field Mountable (“-F”): Designed for mounting directly on a pipe or yoke, typically close to the pressure tap or control valve. This simplifies pneumatic piping and can enhance control loop responsiveness due to shorter signal lines.
Metric Output (6): The 0.2 to 1.0 bar or kg/cm² output signal and gauge provides a metric-friendly indication, which is preferred in many international applications.
Application Field
The FOXBORO 43AP-FA46C/PA-CC is primarily utilized in process industries that rely on pneumatic instrumentation for direct, robust, and reliable pressure control, especially within its specified high-pressure range of 0-2000 psi. Its main application fields include:
Oil and Gas Industry:
- Pipeline Pressure Control: Regulating high pressures in natural gas or crude oil transmission pipelines.
- Wellhead Control: Managing tubing or casing pressures on high-pressure wells.
- Separator Pressure Control: Maintaining stable pressures in high-pressure oil/gas/water separators.
- Refineries and Petrochemical Plants: Controlling pressures in high-pressure vessels, reactors, and headers where the intrinsic safety of pneumatic devices is a key benefit.
Chemical Processing:
- Controlling high-pressure reaction vessel pressures or solvent recovery systems.
- Managing pressure in chemical storage or blending tanks where high pressures are involved.
Power Generation (Traditional Plants):
- Controlling steam pressures, boiler drum pressures, or other high-pressure utility lines within conventional power plants.
Industrial Manufacturing:
- Applications involving high-pressure hydraulic or pneumatic systems, or control of processes using high-pressure gases.
In essence, the 43AP-FA46C/PA-CC is employed wherever a direct, continuous, closed-loop control of high process pressure (0-2000 psi range) is needed, and the inherent safety, reliability, and local indication capabilities of a pneumatic controller are highly valued.
Related Products
The FOXBORO 43AP-FA46C/PA-CC functions as a self-contained pressure controller within a pneumatic control loop. Its related products primarily involve the final control element and the necessary instrument air supply system.
Primary Connecting Instruments:
- Pneumatic Control Valves: These are the final control elements that receive the 0.2-1.0 bar/kg/cm² output signal from the 43AP-FA46C/PA-CC to manipulate the process pressure. They typically consist of:
- A valve body (e.g., globe valve, ball valve) suitable for high-pressure service and pressure control applications.
- A pneumatic actuator (diaphragm or piston type) that converts the air signal into mechanical force to move the valve stem.
- Often, a pneumatic valve positioner (e.g., Foxboro 69P or 69F) mounted on the valve. While the 43AP-FA46C/PA-CC provides a direct output, a positioner helps improve control valve accuracy, linearity, and overcomes friction, especially in high-pressure applications.
