Fairchild M90 Pneumatic Selector Relay

Feature & Principle

It is a pneumatic low pressure selector relay manufactured by Fairchild. It receives two independent pneumatic signal inputs, automatically compares the two pressures and outputs the smaller pressure signal to downstream pneumatic instruments. It adopts soft sealing structure for tight shut-off, low switching differential and fast response speed. It is widely used in safety interlock, split range control and redundant signal selection of valve positioners and pneumatic actuators in petrochemical process loops.

Specifications

Model: M90 Brand: Fairchild Function: Select lower pressure from two input signals Supply signal: Pneumatic instrument air Max working pressure: 150 psi Housing material: Anodized aluminum Working temperature: -20℃ ~ +80℃ Port size: 1/4 NPT Mounting: Panel or bracket mounting Certification: CE

Components & Diagnostics

Internal comparison diaphragm assembly, soft seat valve, air passage body, threaded air ports, metal housing. Common faults: air leakage from sealing seat, switching failure, output pressure unstable, diaphragm aging.

Product Brief

Fairchild M90 pneumatic selector relay, pneumatic instrument spare widely used for chemical and oil & gas control valve pneumatic circuit overhaul and replacement.