Among "uncommanded movement" faults, AUMA motor-operated valves feature prominently. This article merges two popular AUMA threads (21 and 15 replies): one where the valve closes by itself yet tests perfectly on site, and one where everything works except the automatic-close function. Together they form a complete troubleshooting framework for uncommanded motion.
Bottom line: for “self-operating” AUMA motor-operated valves, troubleshoot in three layers — DCS logic → relays & cabling → actuator interface card. Most cases end at an auto-close clause in the DCS configuration or a command-cable/relay defect; one short-circuit test at the terminal block settles whether the fault is on the DCS side (valve moves) or the actuator side (valve stays).
Symptom: an AUMA MOV (controller AM 01.1) closes by itself during operation; on arrival, remote and local operation both behave — the fault will not reproduce.
Directions from the replies, by likelihood:
| # | Suspect (by likelihood) | Key points |
|---|---|---|
| 1 | An automatic-close clause in the DCS logic | Most common: once the SCS condition is met the DCS issues the close command — the actuator itself is fault-free |
| 2 | Command cabling | Insulation breakdown, shorted or grounded cores, water ingress; megger the command cores |
| 3 | Stuck interposing relays / SSRs | An industry-wide ailment; miniature SSRs are polarity-sensitive on DC controlled signals — reversed wiring conducts directly |
| 4 | DCS cards | One brand’s DO card is known to “fire commands erratically” when failing |
| 5 | Operator error | Check the operation log |
| 6 | Actuator thermal protection (cross-brand hint) | EMG MOVs have closed themselves when hot air leaking from the stem overheated the control board — “self-operation” includes this layer |
Symptom: a high-pressure-heater drain valve (AUMA — opens automatically on steam extraction, closes automatically above 20% load) would not close automatically, though single-point and local control worked. Replacing the interface card (Z 027 072/01, 48VDC) fixed it — yet the removed card still works on other valves.
The question: why does single-point control work while automatic close does not — does the card use different detection elements for the two signals?
The analysis:
| Analysis | Details |
|---|---|
| Different signal paths | Auto-close relies on a “condition-met” converted signal; local control working means the actuator and its input are fine — why does the signal never arrive? (declining pulse-detection sensitivity of an ageing interface card is one explanation) |
| The decisive test: short the terminal | Find the DO point’s cabinet terminal at the engineering station and short it — valve moves: DCS logic; valve stays: actuator side |
| Check the DO trend | Whether the DCS actually issued the DO is plain from the historical trend — quite possibly it never did |
| Logic interlock | Check whether an outstanding auto-open command blocks the auto-close, or another condition holds it down |
| Voltage fit | Another valve type on the same card (48 VDC relay, wide fitting range) always works — voltage-fitting differences are also a plausible explanation |
For uncommanded-motion troubles walk the three layers — logic → relays & cabling → actuator interface card: first DCS logic and DO historical trends (no dismantling needed), then megger the cables and swap interposing relays, and only then touch the actuator side, using the terminal-short-circuit test to draw the line. Complements our general framework article on self-operating valves.
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