Nous disposons d'une turbine GE PGT10 équipée d'un système de contrôle Mark VIe. Un problème est survenu au niveau des IGV (Inlet Guide Vanes). Leur plage de fonctionnement normal est comprise entre -42° et +3°. Nous avons constaté des vibrations au niveau du vérin dans la plage allant de -42° à -15°. Au-delà de cette plage, le fonctionnement redevient stable, sans vibrations.
Pour résoudre le problème, nous avons remplacé le vérin par un modèle réparé, changé le LVDT ainsi que la servovalve (MOOG), et nous avons également testé les câbles.

 

Hello,

This is an english only site.
Here is the google translation:
We have a GE PGT10 turbine equipped with a Mark VIe control system. A problem occurred with the IGVs (Inlet Guide Vanes). Their normal operating range is between -42° and +3°. We noticed vibrations in the actuator in the range of -42° to -15°. Beyond this range, operation returns to stable, vibration-free operation.
To resolve the problem, we replaced the actuator with a repaired model, changed the LVDT and the servovalve (MOOG), and also tested the cables.

Please reply in english.

Bertus

 

Thank you, @bertus!

I don't have any personal experience with PGT10s but I can offer some things to investigate. But, first I have a few questions for clarification. It seems you replaced 'some things' related to the movement of the IGVs, and that one (or more) LVDT(s) was also replaced, and the MOOG servovalve was replaced.

And the issues still persists, is that correct?

Was all the replacing done at the same time? If not, was there any noticeable difference after each component was replaced?

Does the PGT10 actuator use one or more LVDTs?

Have you used the Trender function of ToolboxST to record any data to observe the IGV feedback and the IGV output signal to try to determine if the problem originates in the Mark* VIe or outside the Mark* VIe? If so, what have you determined?

Have you observed the hydraulic pressure to see if it is normal and stable when the IGVs are exhibiting the vibration problem? If the hydraulic pressure is not normal or stable, why not?

When did this problem start? After a maintenance outage? After a turbine trip while running?

And last BUT NOT LEAST--are there any Process Alarms annunciated when the IGV vibration is occurring? AND--what Diagnostic Alarms are annunciated when the IGV vibration is occurring?

With all of the above, and presuming the checks you've done don't point to the devices external to the Mark* VIe, then you need to use ToolboxST to examine and analyze if the Mark* VIe output to the IGV servo. OR, the feedback from the LVDT(s).

 

je vous remercie pour réponse et voici mes réponses à vos questions :

Je n'ai aucune expérience personnelle avec les PGT10, mais je peux vous proposer quelques pistes de recherche. J'ai d'abord quelques questions pour clarifier les choses. Il semble que vous ayez remplacé « certains éléments » liés au mouvement des IGV, et qu'un ou plusieurs LVDT (dispositifs de régulation de vitesse) et la servovalve MOOG ont également été remplacés.

Et le problème persiste, est-ce exact ?
Réponse : Exactement ! La servovalve MOOG, le LVDT ainsi que le vérin ont été remplacés

Tous les remplacements ont-ils été effectués en même temps ? Sinon, y a-t-il une différence notable après chaque remplacement ?
Réponse: Oui, le remplacement a été effectué en même temps

L'actionneur PGT10 utilise-t-il un ou plusieurs LVDT ?
Réponse: une seule (1) LVDT

Avez-vous utilisé la fonction Trender de ToolboxST pour enregistrer des données afin d'observer le retour et le signal de sortie de l'IGV et déterminer si le problème provient du Mark* VIe ou de l'extérieur ? Si oui, qu'avez-vous déterminé ?
Réponse: Les tendances révèlent des oscillations

Avez-vous observé la pression hydraulique pour vérifier si elle est normale et stable lorsque les IGV présentent le problème de vibration ? Si la pression hydraulique n'est pas normale ou stable, pourquoi ?
Réponse: la pression de l'huile hydraulique est stable

Quand ce problème a-t-il commencé ? Après un arrêt pour maintenance ? Après un déclenchement de la turbine en fonctionnement ?
Réponse: Le problème apparaît lors du fonctionnement de la machine, et non après un arrêt pour maintenance ni après un déclenchement de la turbine
Et enfin, et surtout, des alarmes de processus sont-elles déclenchées lorsque la vanne d'injection de gaz (IGV) vibre ? Et quelles alarmes de diagnostic se déclenchent lorsque la vanne d'injection de gaz (IGV) vibre ?
Réponse: pas d'alarmes
Compte tenu de tout ce qui précède, et en supposant que les vérifications effectuées ne concernent pas les périphériques externes au Mark* VIe, vous devez utiliser ToolboxST pour examinateur et analyseur si la sortie du Mark* VIe est dirigée vers le servomoteur IGV ou si elle est transmise par le ou les LVDT.
Est-ce que la modification des paramètres du régulateur des IGV pourrait contribuer à atténuer les fluctuations ? Si oui, lesquels précisément?

 

When should we change the null bias value?

What is the suitable null bias value we can use for the IGV?

How can I find the gain of the IGV regulator?

 

Hello,

AGAIN, this is an english only site.
Google translation:
Thank you for your reply, and here are my answers to your questions:

I have no personal experience with the PGT10, but I can offer you some avenues of research. First, I have a few questions to clarify things. It seems you replaced "some components" related to the IGV movement, and that one or more LVDTs (speed control devices) and the MOOG servovalve were also replaced.

And the problem persists, is that correct?
Answer: Exactly! The MOOG servovalve, the LVDT, and the actuator were replaced.

Were all the replacements performed at the same time? If not, is there a noticeable difference after each replacement?
Answer: Yes, the replacement was performed at the same time.

Does the PGT10 actuator use one or more LVDTs? Answer: One (1) LVDT

Have you used the Trender function in ToolboxST to record data to observe the IGV feedback and output signal to determine if the problem is coming from the Mark* VIe or externally? If so, what did you determine?
Answer: The trends reveal oscillations

Have you observed the hydraulic pressure to verify if it is normal and stable when the IGVs exhibit the vibration problem? If the hydraulic pressure is not normal or stable, why?
Answer: The hydraulic oil pressure is stable

When did this problem begin? After a maintenance shutdown? After a turbine trip during operation?
Answer: The problem occurs during machine operation, not after a maintenance shutdown or after a turbine trip
And last but not least, are process alarms triggered when the IGV vibrates? And what diagnostic alarms are triggered when the Induction Gas Valve (IGV) vibrates?
Answer: No alarms.
Given all of the above, and assuming the checks performed do not involve devices external to the Mark* VIe, you should use ToolboxST to examine and analyze whether the Mark* VIe's output is routed to the IGV servomotor or is transmitted by the LVDT(s).
Could changing the IGV controller settings help mitigate the fluctuations? If so, which ones specifically?

Please keep the conversations in english

Bertus

 

@bertus,

Thank you again for the translations (and the admonitions).

Look, changing regulator gains and the like can lead to even more problems and instability. GE does a magnificent job of specifying equipment and knowing the operating characteristics of the equipment and using that information to calculate electro-hydraulic servo settings so that they don't require guessing and trial-and-error. Anyone will find that by using the servo settings for each servo-operated device as listed in the Control Specifications provided with the machine will yield optimal results 99.997% of the time. No guesswork or trial-and-error involved.

Changing servo-valves requires checking the servo-valve current polarity to be sure it's correct for ALL servo outputs/coils of the device. GE uses bipolar servos (much to the dislike of just about everyone) so the polarity of the current being applied is critical.

From the information provided it doesn't seem the problem(s) are on the outside of the turbine control system--but it could be that the servo regulator settings (gain) could be wrong to begin with and don't match the specified values in the Control Specification for the machine.

You keep referring to IGVs--which to my mind are axial compressor inlet guide vanes. BUT, you mentioned the normal operating range of these variable guide vanes is-42 DGA to +3 DGA which suggests to me they are actually the variable second-stage turbine inlet guide vanes, not axial compressor inlet guide vanes. Again, I'm not personally familiar with PGT10 machines so I'm not sure if they even have variable second-stage inlet guide vanes or even what their normal operating range is.

Most PGT10s, from my limited understanding, are used for mechanical drive machines--driving some kind of centrifugal compressor or pump, the flow and pressure of the compressor being the main control parameters which are a function of the speed of the output shaft of the PGT10. What is happening to the PGT10 output shaft speed when these variable guide vane fluctuations are occurring?

What control system is being used to control the centrifugal compressor/pump? Is it the Mark* turbine control system or a third-party control system (say, CCC or some other manufacturer's control system)?