What the XMLBL35R2S12EX actually does on a skid
The XMLBL35R2S12EX sits in the Square D XMLB pressure-switch family and is specified as a pressure switch rather than a transmitter — its job is a clean discrete trip or alarm contact at a setpoint, not a 4–20 mA signal back to a controller. On a boiler-feed or compressor skid that distinction matters: a transmitter watches a trend, the switch holds the unit on the grid by interlocking a pump, fan, or trip solenoid the moment the process crosses the setpoint — provided the deadband and proof pressure on the nameplate match the protected equipment.
Sourcing posture for an active pressure switch
For a maintenance-spares purchase that means writing the XMLBL35R2S12EX into the storeroom min/max the same way as any other current Square D switch, with the lead-time conversation handled at the RFQ stage so the safety stock calculation reflects the real schedule.