Rotork Motor-Stall Alarm: Valve Opens but Won't Close — Causes and Fix

The outlet damper of a desulfurization system at one plant is driven by a Rotork electric actuator. The valve could be opened but would not close, with a "Motor Stall" alarm on the display. This article summarizes the mechanism analysis and the field troubleshooting of this symptom.

Symptom

• Open command executes normally; the valve does not move on close
• "Motor Stall" fault on the display; no other alarms

What a Stall Alarm Means

The stall alarm logic is: the controller has output the command, but the feedback module does not detect actual movement within the set time — "command present, no motion" equals stall. Troubleshooting must therefore cover three links: does the command arrive, does the motor energize and turn, and is the drive train or valve jammed.

Troubleshooting and Fix

• Check for other valve alarms first to separate electrical from mechanical causes
• Measure the three-phase supply and circuit: phase loss makes the motor hum without turning — a common root cause of stall alarms
• Check mechanical resistance in the closing direction: dust-packed damper guides cause closing-direction stall (opening works because resistance is smaller)
• Field experience: several Rotork stall alarms were cured by replacing the power board (its solid-state relay section) — a degrading SSR gives phase-loss-like output, showing up as one-direction failure

In this case the fault was traced to the power board and cleared by replacement.

Takeaways

• "Stall" does not mean a burnt motor: it is a command-versus-motion mismatch; the root cause may be supply, motor or mechanical jam
• For Rotork actuators, one-direction failure points first to the power board's solid-state relays and phase loss; when one direction works and the other does not, the electrical cause is more likely than symmetric mechanical resistance
• For critical dampers, measure output-side phase balance during overhauls to catch SSR degradation early

Related reading: Rotork IQ Series: Terminal Wiring, Infrared Setter Commissioning & Troubleshooting; Rotork 2nd-Gen IQ/IQT: Menu Terminology Annotated & Common Fault Analysis