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

source： date：2026-09-29

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