Hello everyone,
Our compressor is experiencing an issue where, while the system is operating normally (32%) , the IGV valve at section 1 suddenly opens fully by itself, then automatically closes back to normal after 10 minutes.
- my compressor: RG 40-5 by MAN Diesel & Turbo SE
I checked the process parameters in the system before the incident occurred, and everything was normal.

 

1st of all , the question is so poor , looks like open end question to ask proper question I advise us to you the 5W and H (what, when, when, where, who, why and How) , which give some detailed about the incident so we can perfom detailed RCA, any how to help you understanding what happened , please read the below , Then let me know if you need extra help to troubleshoot the issue.

Bro, Follow step by step and DON'T JUMP TO CONCLUSIONS with any finding.

Root Cause Analysis (RCA) for Sudden IGV Opening in MAN Diesel & Turbo SE RG 40-5 Compressor

1. Summary of Issue

• Symptoms: IGV section 1 opens fully without operator input, then closes automatically after ~10 minutes.
• Context: Compressor operating at 32% load, parameters normal prior to event (Very poor information).
• Goal: Identify root cause and prevent recurrence.

2. Potential Root Causes
A. Control System Issues

1. Software/Glitch in Controller
   • Possible Cause: Bug in PLC/DCS logic or timer function causing unintended IGV actuation.
   • Check: Review control sequences for IGV modulation. Verify if a timer or failsafe (e.g., over-speed, over-temperature) was triggered.
   • Action: Analyze controller logs for alarms/errors during the event. Compare with manufacturer’s recommended control logic.
2. Signal Interference
   • Possible Cause: Noise in sensor/signaling wires or faulty communication protocols (e.g., 4-20mA loop fault).
   • Check: Inspect wiring for loose connections, corrosion, or EMI. Test sensor outputs (e.g., pressure/temperature) for consistency.

B. Sensor Malfunctions

1. Faulty Inlet Pressure/Temperature Sensor
   • Possible Cause: Spurious low-pressure or high-temperature reading falsely triggering IGV opening (to increase airflow).
   • Check: Compare Section 1 sensor data with adjacent sensors. Perform live calibration verification.
2. Speed Sensor Error
   • Possible Cause: Incorrect rotor speed signal leading to false load calculation.
   • Check: Validate rotor speed (N) against actual operating speed.

C. Actuator or Mechanical Issues

1. IGV Actuator Failure
   • Possible Cause: Hydraulic/pneumatic leak, stuck solenoid, or worn mechanical components causing unintended movement.
   • Check: Test actuator manually. Inspect for leaks or binding.
2. Intermittent Mechanical Wear
   • Possible Cause: Loose bearings or worn gears allowing free movement under certain conditions.
   • Check: Physical inspection of IGV mechanism.

D. Process Disturbances

1. Transient Inlet Conditions
   • Possible Cause: Unrecorded drop in inlet pressure or temperature (e.g., duct leak, filter clogging).
   • Check: Review trends for inlet pressure (P1), temperature (T1), and flow rates.

E. Configuration or Design Flaws

1. Incorrect Control Parameters
   • Possible Cause: Misconfigured IGV opening/closing thresholds or timing.
   • Check: Verify IGV control setpoints (e.g., deadband, rate of change limits).

Important Note: Operating with malfunctioning IGVs can be dangerous and lead to compressor surge or damage. If this symptom recurs, immediate shutdown might be warranted until the root cause is identified and rectified. Avoid enabling modes like IGV Temperature Control until the basic IGV operation is confirmed reliable.

 

@Kahlil Gaser,

A quick Google search (using Google’s AI) yielded this with the question “Does MAN manufacture a combustion turbine?”

“MAN Energy Solutions has recently divested its gas turbine business to CSIC Longjiang GH Gas Turbine, a Chinese company.”

[This appeared at the bottom of the response: “AI responses may include mistakes.”]

Another Google search using the question “MAN RG40-5” yielded this response:

“In essence, the MAN RG40-5 is a powerful and versatile compressor designed for high-performance and demanding industrial applications, especially in the context of carbon capture and utilization.”

Again these quotes are AI-generated. I suppose it’s possible that this compressor was used to compress air for a combustion but it doesn’t seem likely.

I agree that the original poster provided very little in the way of actionable data or information. We don’t know how the IGVS are controlled or by what kind of control system, or even there is a combustion turbine involved at all.

This seems like an unfortunately all too common case of a newbie posting to a technical forum with few details about a problem which may or may not be the actual problem. One would think if this condition were happening there would be alarms of some sort to alert a conscious operator or technician to some kind of problem. We also don’t know when this problem started. Again, more and more people are posting with little information asking for information to solve the problem they perceive rather than posting actionable data and information in the hopes that some expert reading the plea for help will know precisely what to do.

it’s more the norm than the exception these days. And growing worse.

Further I sincerely doubt the original poster searched the forum to see if there were any MAN RG-nn threads for possible information. Probably found a LOT of IGV threads and thought IGVs are IGVs, right?

 

Hey there! We've all been newbies at something, right? I tried to give him some pointers, showing him how to ask questions that'd get good answers from pros like you. AI is everywhere these days; it's used all the time, and teaching others how to use it is pretty cool.

Good day

 

@Kahlil Gaser Reda,

Yes--we were all newbies at one time. I was EXTREMELY fortunate to have several very experienced people take me under their wings, explain things to me more than once, and introduce me to other people who were also experienced and helpful. My network grew and I improved with the help of others.

I also remember when I was very young and the source of information was a library. To use that library required learning to use the card catalog, and learning to use the card catalog was challenging at first. But, it was required learning for a couple of years--and I learned how to think about how to search for information using several different keywords. Sometimes it involved pulling a couple of books out of the library stacks and sitting down and reading to learn other keywords that I could then go to the card catalog and use to get closer to the detail I wanted or required.

I don't hear young people saying that they learned how to use a search engine. They just type in a keyword or term and if the first page of results doesn't yield something totally applicable they just seem to give up. Also, I don't think many young people know how to use an index in a book to look up topics (which, to me, is similar to using Ctrl + F to find specific words in large documents or webpages to drill down to more detailed information without having to read every page).

Of course, this is one of the promised benefits of AI--but, still, one needs to understand where AI gets its information from, AND if the information is freely available and not subject to copyright or paywalls or other restrictive measures meant primarily to monetize the information. Just because something is available in electronic form doesn't mean it's freely available for use or distribution.

But, still, I presume the original poster used their preferred World Wide Web search engine (or aggregator) using "IGV" as the search word or term and it's not a stretch to see that IGV appears in MANY threads multiple times over the last nearly 30 years on Control.com. So, the question was asked here, and possibly one one or more similar forums.

Anyway, I have always tried to remember what it took for me to learn how to ask questions when I was just starting out. I think many equipment operators (the human operators) are unsatisfied with the responses they get from technicians or supervisors about operating maladies--which is usually, "Because that's the way we've always done it," or "There's no time for me to explain it to you right now." So, they turn to the World Wide Web in search of information and assistance using their limited understanding of the equipment and situation they are facing. We can help some of these people, but not all. And, when we ask questions that require data we get few detailed responses. I just hope that some of the questions we ask are helpful in understanding the equipment and operations and troubleshooting and that by discussing it with colleagues it is helpful in resolving the issue. (I just wish more people would respond with feedback about how the problem/issue was resolved and if the information was helpful or not. Just knowing that at least the problem was solved with the help of the information provided--even if we don't know precisely was was most helpful--would be great. Having said that, I still believe that many more people who write to Control.com for help with their problems or understanding do write back to provide feedback than many other similar forums on the World Wide Web. It's one of the things that distinguished Control.com from many of its peers.)

Welcome to Control.com, @Kahil Gaser Reda.

 

@Kahlil Gaser Reda,

Yes--we were all newbies at one time. I was EXTREMELY fortunate to have several very experienced people take me under their wings, explain things to me more than once, and introduce me to other people who were also experienced and helpful. My network grew and I improved with the help of others.

I also remember when I was very young and the source of information was a library. To use that library required learning to use the card catalog, and learning to use the card catalog was challenging at first. But, it was required learning for a couple of years--and I learned how to think about how to search for information using several different keywords. Sometimes it involved pulling a couple of books out of the library stacks and sitting down and reading to learn other keywords that I could then go to the card catalog and use to get closer to the detail I wanted or required.

I don't hear young people saying that they learned how to use a search engine. They just type in a keyword or term and if the first page of results doesn't yield something totally applicable they just seem to give up. Also, I don't think many young people know how to use an index in a book to look up topics (which, to me, is similar to using Ctrl + F to find specific words in large documents or webpages to drill down to more detailed information without having to read every page).

Of course, this is one of the promised benefits of AI--but, still, one needs to understand where AI gets its information from, AND if the information is freely available and not subject to copyright or paywalls or other restrictive measures meant primarily to monetize the information. Just because something is available in electronic form doesn't mean it's freely available for use or distribution.

But, still, I presume the original poster used their preferred World Wide Web search engine (or aggregator) using "IGV" as the search word or term and it's not a stretch to see that IGV appears in MANY threads multiple times over the last nearly 30 years on Control.com. So, the question was asked here, and possibly one one or more similar forums.

Anyway, I have always tried to remember what it took for me to learn how to ask questions when I was just starting out. I think many equipment operators (the human operators) are unsatisfied with the responses they get from technicians or supervisors about operating maladies--which is usually, "Because that's the way we've always done it," or "There's no time for me to explain it to you right now." So, they turn to the World Wide Web in search of information and assistance using their limited understanding of the equipment and situation they are facing. We can help some of these people, but not all. And, when we ask questions that require data we get few detailed responses. I just hope that some of the questions we ask are helpful in understanding the equipment and operations and troubleshooting and that by discussing it with colleagues it is helpful in resolving the issue. (I just wish more people would respond with feedback about how the problem/issue was resolved and if the information was helpful or not. Just knowing that at least the problem was solved with the help of the information provided--even if we don't know precisely was was most helpful--would be great. Having said that, I still believe that many more people who write to Control.com for help with their problems or understanding do write back to provide feedback than many other similar forums on the World Wide Web. It's one of the things that distinguished Control.com from many of its peers.)

Welcome to Control.com, @Kahil Gaser Reda.

Thanks for sharing your thought.

Here's the story: we're moving right along, and the big thing is learning to adapt. These new guys are soaking up tons of info "usually so easy to get" , but it's all kind of thrown at them. as technical trainer my challenge is to guide how to use the information. Convincing them that all this stuff they're learning is useless until they actually use it in a real power plant, control room, or refinery.