Issue with IGV for siemens turbine SST600

Dear team members,
I need some help with an issue related to IGV . This IGV is installed at expander inlet. Control of this IGV is done using a cylinder with pneumatic circuit consisting of SIPART positioner. IA pressure provided to the cylinder/actuator is 6kg. There are two volume boosters installed on the cylinder/actuator. There is a magnetostrictive sensor to provide position feedback which is connected to the cylinder shaft. IGV movement is from -15deg to 8 deg. Offgas from our process is given to the expander through IGV. Offgas pressure is normally maintained at 1100 kPa and temperature is 145degC. Under no load condition, IGV works great, i.e. 0~100% movement as per the degree of movement. But when we connect it to the process, within a month IGV starts to malfunction. For instance, when the command is 100%, IGV should move up towards 8 deg but sometimes, it goes to -10 deg and gets stuck there. Surprisingly, the position feedback we get is 100% but physically, the IGV is close. This phenomena is very surprising and has been happening very frequently. Also we checked for any IA leakage and did not find any. Just as a precautionary measure, we changed all the IA accessories and cylinder/actuator during our last shutdown
Any help in troubleshooting is much appreciated.
 
Dear team members,
I need some help with an issue related to IGV . This IGV is installed at expander inlet. Control of this IGV is done using a cylinder with pneumatic circuit consisting of SIPART positioner. IA pressure provided to the cylinder/actuator is 6kg. There are two volume boosters installed on the cylinder/actuator. There is a magnetostrictive sensor to provide position feedback which is connected to the cylinder shaft. IGV movement is from -15deg to 8 deg. Offgas from our process is given to the expander through IGV. Offgas pressure is normally maintained at 1100 kPa and temperature is 145degC. Under no load condition, IGV works great, i.e. 0~100% movement as per the degree of movement. But when we connect it to the process, within a month IGV starts to malfunction. For instance, when the command is 100%, IGV should move up towards 8 deg but sometimes, it goes to -10 deg and gets stuck there. Surprisingly, the position feedback we get is 100% but physically, the IGV is close. This phenomena is very surprising and has been happening very frequently. Also we checked for any IA leakage and did not find any. Just as a precautionary measure, we changed all the IA accessories and cylinder/actuator during our last shutdown
Any help in troubleshooting is much appreciated.
Hi Salman Khan ,

I would like to support you if you can tell us :

If Sipart positioner got slot initiator alarm& limit switch module?

As i get a read on OEM manual , My first question is if there is any alarm annunciated .

Thank you for your reply,
Controls Guy25.
 
Hi,
Thanks for your reply. So this positioner does not have any limit switch module or slot annunciation module. Also no alarm is anunciated. There is this magnetostrictive sensor connected with the cylinder shaft which gives the position feedback . So the confusion is that this position sensor is giving a feedback of 100%open but as per IGV degree , it is close. That is what confusing us. I hope this helps.
 
Dear team members,
I need some help with an issue related to IGV . This IGV is installed at expander inlet. Control of this IGV is done using a cylinder with pneumatic circuit consisting of SIPART positioner. IA pressure provided to the cylinder/actuator is 6kg. There are two volume boosters installed on the cylinder/actuator. There is a magnetostrictive sensor to provide position feedback which is connected to the cylinder shaft. IGV movement is from -15deg to 8 deg. Offgas from our process is given to the expander through IGV. Offgas pressure is normally maintained at 1100 kPa and temperature is 145degC. Under no load condition, IGV works great, i.e. 0~100% movement as per the degree of movement. But when we connect it to the process, within a month IGV starts to malfunction. For instance, when the command is 100%, IGV should move up towards 8 deg but sometimes, it goes to -10 deg and gets stuck there. Surprisingly, the position feedback we get is 100% but physically, the IGV is close. This phenomena is very surprising and has been happening very frequently. Also we checked for any IA leakage and did not find any. Just as a precautionary measure, we changed all the IA accessories and cylinder/actuator during our last shutdown
Any help in troubleshooting is much appreciated.

Is it a sipart ps-2?? I hope the settings of your positioner is accurate as sipart positioners are very setting and calibration sensitive. Once set correctly, they work without any hassle but if done incorrectly they become a nightmare.
With sipart positioners, if a 100% command is given, and the positioner mechanical feedback arm does not move to 100% within a stipulated time, it will generate an error (alarm) and the positioner hangs(it does not responds to any further commands) which has to be either reset manually or the command has to fall down to the positioner's current feedback arm travel for it to get reset automatically. So when u face the problem are you seeing any alarm being generated on the positioner's screen??
Also I think that the reason for the IGV staying at -10deg during 100% command might be because the positioner hangs...which might be because the Fce doesn't move within the stipulated time...Also 6kg/cm2 of IA is too much for your positioner as the main actuation work will be done by the inlet supply air pressure to the booster relays. Too much positioner inlet air pressure might lead to relay saturation. Check your volume booster and its setting. Also I'm considering that your IGV is mechanically smooth while in operation.
Is it a problem being faced on a newly installed system???
For the position fb part, check the mA retransmission is according to the position of the IGV when u face the problem....Because IGV if fully closed, the mA retransmitted should be accordingly and so should be the display on the SCADA.
 
Thank you udshrd for the response. Yes the positioner is PS2. IA pressure initially was 4 kg, But since the day we started having this mechanical issue, we increased the pressure to 6 kg. In that way, we thought we will be giving more pressure for IGV movement. Also when the IGV was stuck at -10 deg, we didn't see any error on the positioner. And yes, when we removed the IGV during one of our shutdown, we saw that IGV was mechanically very smooth. We also checked the settings during the shutdown and didn't find any issue with the cylinder movement. But we will make some arrangements to see the mA output on the positioner because present positioner does not have mA output module.
But what about the positin feedback issue. FYI we are getting position feedback via a LVDT which is connected to the actuator shaft. So When IGV gets stuck at -10deg, why do we get a feedback of 100%.
 
Thank you udshrd for the response. Yes the positioner is PS2. IA pressure initially was 4 kg, But since the day we started having this mechanical issue, we increased the pressure to 6 kg. In that way, we thought we will be giving more pressure for IGV movement. Also when the IGV was stuck at -10 deg, we didn't see any error on the positioner. And yes, when we removed the IGV during one of our shutdown, we saw that IGV was mechanically very smooth. We also checked the settings during the shutdown and didn't find any issue with the cylinder movement. But we will make some arrangements to see the mA output on the positioner because present positioner does not have mA output module.
But what about the positin feedback issue. FYI we are getting position feedback via a LVDT which is connected to the actuator shaft. So When IGV gets stuck at -10deg, why do we get a feedback of 100%.
I said about the position feedback...check the current in series and whether it matches or not with the actual actuator position in the field.If not, then there is a problem with your position feedback transmitter. LVDT plunger sometime tends to get stuck. Also they are generally indirectly coupled to the actual equipment , whose movement is to be measured. Check the couplings,screws nut etc. for looseness if you have any.
Also is the sipart positioner calibrated properly ???? What is the voltage at the terminals during 20mA ???
 
Hi udshred, I have attached siemens positioner data with this thread. Please go through with it and let me know your observations. Also regarding your question about positioner calibration, the answer is yes. This positioner was calibrated and checked during last shutdown in Feb 2020. Under no load, we did not find any issue with the IGV. It's only when connected with the process, we are facing the problem. Mechanically also, IGV movement was smooth. Present condition is that IGV is working fine with no issue. I will tell you the problem in detail .
Process value(PV) was 1180 kpa, Set point (SP) was 1180kpa and Manipulate value(MV) was 80%. Deg of IGV was 1.5. Then after a while, PV increased to 1200 kpa and to compensate that SV was increased 1200 kpa. MV at that time was 100% and deg of IGV was -2. This went for another hour and last reading of IGV was -8. Corresponding PV was 1205 kpa, SP was 1210 kpa, MV was 100%. Feedback was also 100%. Then automatically, PV started to reduce and everything went to normal . Hope the scenario is clear to you. In my opinion, even if we remove the IGV from process and check again, we will not find any issue. Please let me know your observations and opinion regarding this. Any suggestion is welcome
 

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Hi udshred, I have attached siemens positioner data with this thread. Please go through with it and let me know your observations. Also regarding your question about positioner calibration, the answer is yes. This positioner was calibrated and checked during last shutdown in Feb 2020. Under no load, we did not find any issue with the IGV. It's only when connected with the process, we are facing the problem. Mechanically also, IGV movement was smooth. Present condition is that IGV is working fine with no issue. I will tell you the problem in detail .
Process value(PV) was 1180 kpa, Set point (SP) was 1180kpa and Manipulate value(MV) was 80%. Deg of IGV was 1.5. Then after a while, PV increased to 1200 kpa and to compensate that SV was increased 1200 kpa. MV at that time was 100% and deg of IGV was -2. This went for another hour and last reading of IGV was -8. Corresponding PV was 1205 kpa, SP was 1210 kpa, MV was 100%. Feedback was also 100%. Then automatically, PV started to reduce and everything went to normal . Hope the scenario is clear to you. In my opinion, even if we remove the IGV from process and check again, we will not find any issue. Please let me know your observations and opinion regarding this. Any suggestion is welcome
No honestly I am unable to understand the situation. I dont understand from where you are getting the 'deg' reading and from where you are getting the 'feedback' reading...??? You said in your earlier post that the feedback is taken from a LVDT position f/b transmitter...so now from where are you getting your 'deg' reading...?? Also settings of positioners are very application specific...I cannot comment on the settings without having a thorough look at your system...sorry with that..
 
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