Main Features and Advantages

The FOXBORO 43AP-FA42C/PB-BA offers a compelling set of features and advantages, particularly due to its direct pressure measurement capability and robust pneumatic design:

Direct Process Pressure Measurement (/PB-BA): This is the defining characteristic. The controller directly senses and indicates process pressure via its internal bellows element, specifically calibrated for the 0-60 psig range. This simplifies the control loop by eliminating the need for a separate pressure transmitter, potentially reducing components and signal lag for faster response in pressure control applications.

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: The “A4” control action provides the essential combination of proportional response (to the magnitude of the error) and integral action (to eliminate 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.

Simpler Maintenance (for trained personnel): While requiring regular calibration and a clean air supply, pneumatic instruments generally have fewer delicate electronic components. This often leads to more straightforward troubleshooting and repair compared to complex electronic systems, provided technicians are familiar with pneumatic principles.

Application Field

The FOXBORO 43AP-FA42C/PB-BA is primarily utilized in process industries that rely on pneumatic instrumentation for direct, robust, and reliable pressure control, especially within its specified range of 0-60 psig. Its main application fields include:

Oil and Gas Industry:

• Wellhead Control: Managing casing or tubing pressures, or other low to medium pressure applications.
• Gas Pipeline Regulation: Maintaining specific pressures in segments of natural gas distribution or collection lines.
• Vessel Pressure Control: Regulating pressure in smaller separators, storage tanks, or utility vessels.
• Refineries and Petrochemical Plants: Controlling pressures in various process vessels, headers, and utility lines where the intrinsic safety of pneumatic devices is a key benefit.

Chemical Processing:

• Controlling reaction vessel pressures for specific low-pressure reactions.
• Managing pressure in chemical storage or blending tanks.

Power Generation (Traditional Plants):

• Controlling instrument air headers, low-pressure steam lines, or various utility pressures within conventional power plants.

Water and Wastewater Treatment:

• Regulating pressure in specific treatment stages, water distribution lines, or filter backwash systems.

In essence, the 43AP-FA42C/PB-BA is employed wherever a direct, continuous, closed-loop control of process pressure in the 0-60 psig range is needed, and the inherent safety, reliability, and local indication capabilities of a pneumatic controller are highly valued.

 

Related Products

The FOXBORO 43AP-FA42C/PB-BA 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 3-15 psi output signal from the 43AP-FA42C/PB-BA to manipulate the process pressure. They typically consist of:
  • A valve body (e.g., globe valve, butterfly valve) suitable for 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-FA42C/PB-BA provides a direct 3-15 psi output, a positioner helps improve control valve accuracy, linearity, and overcomes friction.

Pneumatic Infrastructure and Accessories:

• Instrument Air Supply System: Essential for providing clean, dry, and regulated air to the controller:
  • Air Filters and Dryers: Crucial for removing moisture, oil, and particulates from the compressed air, preventing internal clogging and corrosion of the controller’s delicate pneumatic components.
  • Air Regulators: To reduce the plant air supply pressure (e.g., 80-100 psi) to the required 20 psi for the controller. The 43AP-FA42C/PB-BA often incorporates an integral air supply set, but external regulation might also be present in the overall system.
• Pneumatic Tubing and Fittings: For routing the instrument air supply and the output signal to the control valve. High-quality, leak-free tubing is vital for pneumatic system performance.
• Pneumatic Relays and Boosters: If the control valve is large or needs to actuate very quickly, a pneumatic relay or volume booster might be used to amplify the 3-15 psi signal from the controller and provide a higher air volume to the actuator, speeding up valve response.

Other Foxboro 43AP Variations:

• While this model has a direct pressure (bellows) input for 0-60 psig, other 43AP models feature different internal measuring elements for direct connection, such as helical or spiral elements for higher pressure ranges (e.g., for 0-2000 psi or higher), or filled thermal systems for direct temperature measurement.
• Models with different control modes (e.g., Proportional only, Proportional + Derivative, On-Off).

Calibration and Test Equipment:

• Pneumatic Calibrators: Used to generate and measure precise pneumatic pressures for calibrating the controller’s input (process pressure) and output (3-15 psi signal).
• Test Pressure Gauges and Manometers: For verifying applied process pressures and output signals, as well as detecting leaks during maintenance.

Installation and Maintenance

Pre-installation preparation: Installing the FOXBORO 43AP-FA42C/PB-BA requires strict adherence to safety protocols, careful mechanical mounting, and precise pneumatic connections, especially since it directly measures process pressure.

1. Safety Procedures: Crucially, before any work, ensure the process line from which the pressure will be measured is completely isolated, depressurized, and locked out following site-specific Lockout/Tagout (LOTO) procedures. Also, ensure the instrument air supply line is shut off and depressurized.
2. Mounting: The “-F” in the model code indicates field mounting (on a 2-inch vertical pipe or element yoke). Mount the controller securely, ensuring it is level and stable to prevent vibration from affecting accuracy. While its NEMA 3 rating indicates weatherproof capability, providing protection from direct, severe weather (e.g., a sunshade or small enclosure) can prolong its life.
3. Instrument Air Supply Connection: Connect a clean, dry, regulated 20 psi (140 kPa) instrument air supply to the controller’s supply port. Verify that the air quality meets Foxboro’s specifications to prevent clogging of internal nozzles and restrictors. Check that the integral air supply set (if present) is functioning correctly and its filter is clear.
4. Process Pressure Connection: Connect the process pressure line directly to the designated input port of the controller’s internal pressure (bellows) measuring element. Ensure all fittings are tight and leak-free. Verify the process pressure range does not exceed the 0-60 psig rating of the /PB-BA element.
5. Pneumatic Output Connection: Connect the controller’s 3-15 psi output line to the pneumatic actuator of the control valve, or to a pneumatic valve positioner if one is used. Ensure these connections are also secure and leak-free.
6. Initial Power-up and Calibration: After all connections are made and verified, slowly pressurize the process line (if safe to do so) and instrument air supply. Refer to the official Foxboro 43AP instruction manual (e.g., MI 011-477 or later revisions, often available from Schneider Electric or automation service providers) for detailed procedures on initial pointer alignment, zero and span calibration of the pressure element, and calibration of the output. This typically involves applying known process pressures and adjusting mechanical linkages. Foxboro also provides technical training videos on 43AP calibration.

Maintenance recommendations: Regular and systematic maintenance is vital for the long-term reliability and accuracy of the 43AP-FA42C/PB-BA.

• Clean and Dry Air Supply: This is the most critical factor. Routinely check and drain instrument air filters (including any integral ones). Contaminated air (moisture, oil, particulates) is the leading cause of issues like nozzle clogging, restrictor blockage, and corrosion of internal components.
• Visual Inspection: Periodically inspect the controller’s exterior for any signs of physical damage, corrosion, loose connections, or deterioration of pneumatic tubing. Check the integrity of the weatherproof enclosure seals.
• Leak Checks: Conduct regular leak checks on all pneumatic connections (supply, process input, output, internal tubing) using a soapy water solution. Even minor leaks can degrade control performance and lead to excessive air consumption.
• Calibration Verification: Regularly verify the controller’s calibration. This involves applying known process pressures (from a test pressure source connected to the input) and checking the accuracy of the indicator pointer and the linearity and range of the output signal. Adjustments should be made according to the manual.
• Mechanical Components: Inspect internal linkages, pivots, and springs for wear, looseness, or friction. Ensure the critical nozzle and flapper components are clean and free from obstructions. The manual will provide specific cleaning instructions (often involving a fine wire for the restrictor/nozzle).
• Gauges: Confirm that the output gauge and any other internal gauges are functioning correctly and are not sticky or damaged.
• Auto/Manual Transfer Check: Test the bumpless transfer switch regularly to ensure it operates smoothly and correctly transfers control without process bumps.
• Process Element Integrity: For the /PB bellows element, visually inspect for any signs of fatigue or leakage, though this usually requires opening the case.
• Documentation: Maintain detailed records of all maintenance activities, calibration results, and any replaced components for historical tracking and troubleshooting.

As a legacy product, finding new replacement parts can be challenging; many users rely on reconditioned units and specialized instrument service companies for repairs and calibration.

Product Guarantee

The FOXBORO 43AP-FA42C/PB-BA is a legacy pneumatic controller. As such, it is no longer manufactured as a new product by Foxboro (which is now part of Schneider Electric). Therefore, a new factory warranty from Schneider Electric is not applicable for this specific model.

However, when purchasing this model from the aftermarket (e.g., industrial surplus dealers, reconditioners, or “new old stock” suppliers), the following types of guarantees are typically available:

• Seller’s Warranty (Used/Remanufactured): This is the most common form of guarantee for legacy industrial equipment. Reputable industrial automation surplus and reconditioning companies (like Automation Service, Valves Depot, or Electrical.com) typically offer their own warranty on refurbished or “new old stock” units. This warranty usually ranges from 1 to 2 years and covers the functionality of the unit, ensuring it has been tested and performs according to its original specifications (including the specific 0-60 psig range for the /PB-BA element). It generally covers defects in materials and workmanship.
• “New Old Stock” Warranty: If a supplier sells a unit as “New – Open box” or “Unused surplus,” they may provide a similar 1-2 year warranty, as the original manufacturer’s warranty would have likely expired due to the product’s age.
• No Warranty (As-Is): Some very old, untested, or explicitly flawed units might be sold “as-is” with no warranty. Buyers should exercise extreme caution with such purchases.

Key aspects of typical aftermarket guarantees for the 43AP-FA42C/PB-BA generally include:

• Coverage: A guarantee that the controller has been tested, calibrated, and is fully functional according to its published specifications for the stated warranty period. This includes the proper operation of the direct pressure (bellows) measuring element within its 0-60 psig range.
• Remedy: The supplier will typically offer to repair or replace the unit if it fails due to covered defects within the warranty timeframe.
• Limitations: These warranties usually do not cover damage resulting from improper installation, misuse, contaminated air supply, physical abuse, unauthorized modifications, or acts of nature. Normal wear and tear, especially for mechanical elements like bellows over extended use, might also be excluded depending on the specific terms.
• Traceability/Certification: Some reconditioners may provide documentation of testing and calibration, ensuring the unit’s performance has been verified.

It is absolutely critical for buyers to explicitly confirm the specific warranty terms with the vendor before purchasing any legacy industrial control equipment like the FOXBORO 43AP-FA42C/PB-BA.