FOXBORO 43AP-PA42C-PB-AA PNEUMATIC CONTROLLER 0-6000 KPA HELICAL

• 43AP PA42C PB AA
• DISCONTINUED BY MANUFACTURER
• PNEUMATIC CONTROLLER
• PROPORTIONAL + RESET
• 0-6000 KPA RANGE
• BUMPLESS AUTO/MANUAL SWITCH
• SS GAUGE PRESSURE ELEMENT CALIBRATED

The Foxboro 43AP is a self-contained, pneumatic motion-balance controller designed for direct installation in the field, close to the process measurement point. The specific model 43AP-PA42C-PB-AA is configured for very high pressure applications, using a helical Bourdon tube as its sensing element. It provides a proportional (P) and automatic reset (integral, I) control output to a pneumatic final control element, such as a control valve or damper actuator.

Detailed Model Number Breakdown (Nomenclature)

Foxboro model numbers are highly descriptive. Here’s what each segment means:

• 43AP: The base model number for this series of pneumatic controllers.

• P: Process Connection. P specifies a 0.25″ NPT (F) female connection.

• A: Case Option. A specifies a general-purpose, weatherproof (but not explosion-proof) case.

• 42: Control Action. 42 specifies Direct-Acting, Proportional plus Automatic Reset (PI) control.

  • Direct-Acting: The output pressure increases as the measured process variable increases.

  • Proportional (P): The output change is proportional to the deviation from the setpoint.

  • Automatic Reset (I): Automatically eliminates droop (offset) by continually adjusting the output over time as long as an error exists.

• C: Measured Variable / Sensor Type. C specifies a Helical Bourdon Tube. This is a coiled, hollow tube that untwists as internal pressure increases. It is specifically chosen for this model’s 0-6000 KPA range, as it is ideal for very high pressures.

• P: Setpoint Adjustment. P specifies a Local, Rack & Pinion setpoint adjustment knob located on the front of the controller.

• B: Control Pressure Range. B specifies a 3-15 PSI (0.2-1.0 bar) standard pneumatic output signal.

• AA: Accessories / Specials. AA typically indicates no special accessories or a standard factory configuration.

Key Features & Operational Description

1. Helical Bourdon Tube Sensor (PA42C):

   • The core sensing element is a helical (spirally wound) tube.

   • Process pressure (0-6000 KPA) entering the tube causes it to partially uncoil.

   • This rotary motion is mechanically linked to the controller’s balancing mechanism.

   • Advantage: Excellent for high pressure, provides good sensitivity and a long, durable stroke.

2. Pneumatic PI Control (42):

   • This is a motion-balance system. The mechanism balances the motion from the measurement element against the motion from the setpoint and feedback bellows.

   • It generates a standard 3-15 PSI output signal based on the difference (error) between the process variable and the local setpoint.

   • The Proportional Band (gain) and Reset Rate (integral time) are adjustable via internal screws or knobs, allowing the control response to be tuned for the specific process.

3. Field-Mounted Design:

   • Built for harsh environments. The case is weatherproof, protecting the internal mechanism from dust and rain.

   • Mounts directly on the process line or a nearby stanchion, eliminating the need for long impulse lines and reducing measurement lag.

4. Local Indication & Setpoint:

   • Features a local pointer and scale to show the current process pressure.

   • The setpoint is adjusted locally via a knob, with its own pointer and scale.

Typical Applications

This controller is designed for high-pressure industrial processes, such as:

• Boiler Steam Header Pressure Control

• High-Pressure Natural Gas Line Regulation

• Chemical Process Reactors

• Hydrostatic Testing Pressures

• Water & Wastewater High-Pressure Pump Discharge