What is the the type of sensor? Is the sensor directly actuating the solenoid? Is there a relay? Are you using two wire or 3 wire control? Was power maintained for the duration of the event?

What is the sensor measuring, can the level change dynamically (wave/slosh motion), does noise on the sensor line affect the device controlling the solenoid?

It is s Latching Solenoid and a Three wire type. It an that is that trips when it gets signal from a Level switch Low. what do you think?

The dry vapor leg of the LSL may have flooded with condensate thus causing the trip when level is still good. This can happen when vessel vapor temp is higher than minimum ambient. If so, the vapor leg should be remote sealed to prevent saturated vapor from getting into the vapor leg of the LT-LSL. Ask your plant instrument engineer to raise a work request for this remote seal.

Thanks for your solid analysis. I am the plant EE and prior to this time. I had three pathways.Power, plugged impulse lines and flipping of the LS. I have earlier worked on the impulse lines and power and they are good. I just found out that someone had flipped the LSH which triggered a shutdown.I like your breakdown and let’s keep in touch. I have learnt so much from this forum and appreciate all the feedbacks I received from ya’ll.I look forward to give back when need be.Thanks bro!

Did you intend to use a latching solenoid, that requires manual resetting, or did you want the solenoid to resupply air to the valve when the level returns to normal?