Danfoss ICAD (1200) Valve stalling.

[Grizzly]

Hi Guys!
A site (Un manned by Engineers) has a large surge drum on Ammonia. With it's liquid level being metered by a ICAD /ICM Valve.
Said valve has started to randomly shut closed and the surge drum gradually empties.
Causing the plant to cycle off on it's suction Pressure control. (No Alarms generated).

Resulting in long shutdowns before anyone on-site notices the chill room temps rising.

As anyone will appreciate once emptied getting a large Ammonia plant away again is, Shall we say
"Is a right Pain in the butt, Particularly if the plant room is on the ground floor and the control room is 1st floor!

Once onsite the valve opening is shown as 100% open but is actually closed.

Because the refrigerant level in the receiver is high and opening the Liquid Line bypass.
Allows the refrigerant to flood into the surge drum.
Well at least until the standing pressures have equalised then you have to create a HP /LP differential to further fill the drum.

So no power cuts, ICAD shows 100% but is actually closed?
Any ideas?
Grizzly