Main Features and Advantages

The FOXBORO 43AP-PA42N/TA-3B offers a distinct set of features and advantages, primarily stemming from its direct temperature measurement capability and pneumatic design:

Direct Process Temperature Measurement (/TA-3B): This is the defining feature. The controller directly senses process temperature via its integral filled thermal system, which includes a remote bulb placed in the process, connected by capillary tubing to the internal measuring element. This eliminates the need for a separate temperature transmitter, simplifying the control loop, reducing components, and often providing a direct, fast response for temperature control. The “3B” suffix designates a specific, usually common, temperature range.

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 exceptionally well-suited for hazardous (explosion-proof) environments (e.g., oil & gas, chemical plants) without requiring costly additional safety barriers or specialized enclosures.

Proven Reliability: The Foxboro 43AP series has an extensive track record of robust and dependable operation in harsh industrial conditions. Its mechanical design contributes to its durability and resistance to environmental factors like vibration and temperature variations.

Proportional plus Integral (Reset) Control (A4): This control action provides both 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 temperature to accurately reach and maintain its setpoint over time.

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, and thus to the process. This significantly enhances operational stability and minimizes process upsets.

Local Indication: The controller provides a direct, mechanical indication of the measured process temperature, 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 (Assuming -PA is similar to -FA): Designed for mounting directly on a pipe or yoke, typically close to the process or control valve. This simplifies pneumatic piping and can enhance control loop responsiveness due to shorter signal lines.

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

Application Field

The FOXBORO 43AP-PA42N/TA-3B is specifically designed for applications requiring direct, robust, and reliable pneumatic control of temperature. Its primary application fields are in process industries that utilize pneumatic instrumentation:

Chemical Processing:

• Controlling reaction temperatures in smaller reactors or batch processes.
• Maintaining temperatures in heat exchangers, distillation column reboilers/condensers, or storage tanks.

Oil and Gas Industry:

• Controlling temperatures in heaters, treaters, or reboilers at well sites, gathering stations, or smaller processing units.
• Controlling utility fluid temperatures in various auxiliary systems.

Power Generation (Traditional Plants):

• Controlling temperatures in feedwater heaters, fuel oil heaters, or other auxiliary systems within conventional power plants.

Pulp and Paper Industry:

• Controlling temperatures in digesters, dryers, or other process equipment where direct temperature control is needed.

Food and Beverage Industry:

• Applications like pasteurization, cooking, or chilling where direct temperature control is required and the intrinsic safety or simplicity of pneumatic control is desired.

In essence, the 43AP-PA42N/TA-3B is employed wherever a direct, continuous, closed-loop control of temperature within its specific range is needed, and the inherent safety, reliability, and local indication capabilities of a pneumatic controller are highly valued.

 

Related Products

The FOXBORO 43AP-PA42N/TA-3B operates as a standalone temperature controller within a pneumatic control loop. Its related products primarily involve the final control element and the necessary air supply system, along with the thermal system components.

Primary Connecting Instruments:

• Thermal System Components: The /TA-3B implies a complete filled thermal system:
  • Remote Temperature Bulb: Placed directly in the process to sense temperature.
  • Capillary Tubing: Connects the bulb to the measuring element within the controller. This tubing must be protected and routed carefully.
• Pneumatic Control Valves: These are the final control elements that receive the 3-15 psi output signal from the 43AP-PA42N/TA-3B to manipulate the process. They typically consist of:
  • A valve body (e.g., globe valve) suited for temperature control (e.g., steam, cooling water).
  • A pneumatic actuator (diaphragm or piston type) that converts the air signal into mechanical force to move the valve.
  • Often, a pneumatic valve positioner (e.g., Foxboro 69P or 69F) mounted on the valve. While the 43AP-PA42N/TA-3B provides a direct 3-15 psi output, a positioner improves control valve accuracy 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.
  • Air Regulators: To reduce the plant air supply pressure (e.g., 80-100 psi) to the required 20 psi for the controller. The 43AP-PA42N/TA-3B often incorporates an integral air supply set, but external regulation might also be present.
• Pneumatic Tubing and Fittings: For routing the instrument air supply and the output signal to the control valve.

Other Foxboro 43AP Variations:

• While this model has a direct temperature (filled thermal system) input, other 43AP models have different internal measuring elements for direct connection, such as bellows or helical elements for direct pressure measurement, or pressure receivers for pneumatic signal inputs.

Calibration and Test Equipment:

• Temperature Baths/Calibrators: Used to generate precise temperatures for calibrating the thermal system and controller.
• Pneumatic Calibrators: Used to generate and measure precise pneumatic pressures for calibrating the output signal.
• Test Gauges: For verifying output pressures during calibration.