Barber-Colman AK-51642 Pneumatic Relay Module

The Barber-Colman AK-51642 Pneumatic Relay is a compact two-input pressure selector that automatically routes the lower of two pneumatic pressures to a downstream control point, enabling straightforward, electronics-free logic in pneumatic systems. With a direct-acting actuation design, the unit is rated for a maximum of 30 psi gauge (30 PSIG max) and uses standard 1/4 in. outer diameter plastic tubing for connections, allowing quick, reliable integration into existing Barber Colman or Invensys control networks without special tooling. The AK-51642 is listed as discontinued by the manufacturer, so buyers typically source remaining stock from authorized distributors or secondary marketplaces rather than new production runs. In typical use, it provides a simple means to implement pressure-based decision logic in industrial automation and HVACR applications: two input pressures are evaluated, and the lower signal is sent to a single output to drive a downstream valve, relay, or actuator, supporting sequencing, priority control, and fail-safe strategies in pneumatic control schemes.