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.

Case 1: Closes by Itself, Yet "Everything Normal" On Site

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:

1. An automatic-close clause in the DCS logic — the most common cause: once the SCS condition is met the DCS commands the closure; the actuator itself is faultless

2. Command cabling: insulation breakdown, shorted or grounded command wires, water ingress — one engineer complains of construction-era cables "with joints wrapped in adhesive tape"; test the command cable insulation with a megger

3. Stuck interposing relays / solid-state relays (SSR): SSR sticking is an industry classic — one plant swapped contactors for SSRs and slept better, another fitted cheap SSRs and replaced them constantly; note that miniature DC-controlled SSRs are polarized — reversed wiring conducts outright (an engineer was "stunned" by this)

4. DCS cards: one brand's DO card is known to "fire commands erratically" when failing

5. Operator error: check the operation log

6. Cross-brand hint: EMG MOVs have closed themselves when hot air leaking from the stem overheated the control board into thermal protection — overheat protection also "moves things by itself"

Case 2: Local Control Fine, Automatic Close Dead

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:

• Different signal paths: automatic close requires the actuator to receive the condition-transition signal; since single-point control works, the actuator and its receiver are fine — so ask why the signal never arrives. Degrading sensitivity of the card's pulse detection after years of service is one plausible explanation
• The decisive one-minute test: find the cabinet terminals behind that DO point from the engineer station and short them — if the valve moves, the problem is DCS logic; if not, it is the valve head
• Check the DO trend: pulse or holding signal, the historical trend shows instantly whether the DCS ever issued the close command — quite possibly it never did
• Logic blocking: verify that the automatic-open command ever released, and that no other condition is blocking the close
• Voltage adaptation: another valve type on the same card (whose 48VDC relay accepts a wider voltage range) always worked — the card's voltage compatibility across valves is another explanation

The Framework

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.