After MI and replaced the second stage nozzle to MS5002B, we are facing problems with the nozzle. The machine starts up normally, reaches completed sequence and TNR for low pressure rotor. Suddenly the nozzle went to 15 degrees after 12 hours operation. We stopped the machine and checked the travel position by AUTOCAL and everything was ok. We started up and after 36 hours the same problem appeared. We replaced servo valve and started up again, but in this time when HP rotor reached 100%, the nozzle started to move and when reached 14.2 degrees it went to 15 degrees. We changed FSR manually for reducing HP speed around 94% and we increased FSR and the machine went to SC.

The machine is MS5002B driving centrifugal compressor with Mark5 TMR.

Thanks in advance.

 

WAC,

What Diagnostic Alarms are being annunciated?

The reference for the second-stage nozzle position is speed (LP speed during starting; HP speed during normal operation). And the feedback is LP speed during starting and HP sped during normal operation. Usually there will be Diagnostic Alarms and/or Process Alarms when there are speed feedback problems.

So, if the nozzles are moving then it's likely there is a problem with speed feedback--or the wiring to the servo-valve (polarity).

Use VIEW2 to gather data on the reference for nozzle control and on the speed feedback signals.

Please write back to let us know what you find.

 

This sounds very interesting, please can you tell us if you`ve already done a mechanical check of the hydraulic cylinder and accumulators. what about process, load sharing, anti surge...

Cordially
INST_FOREMAN