VMAC 100
Thank you for asking, yes I did have a great holiday, although busy. It’s good to get back to the grind. My own schedule is looking busier every day with upcoming projects.
I have a few questions before I begin to address each of your points. First,
1. Do you have an experienced Component Level Assessment Engineer to perform the A, B, and C inspections on the engine components or will you use the manufacturers representative?
2. Will you be using the time-based replacement of components without the use of an experienced component Assessment Engineer to perform engine performance analysis and root cause analysis?
3. What is the best time of year for you to perform your required maintenance? Spring, Summer, Fall, Winter?
4. Will you want to stagger the maintenance outages on these engines (usually a good idea depending on operational schedule) or perform all outages in series?
5. What are the normal operating modes of these engines? Base load continuous? Peak load? Backup / Fast Response?
6. Are all of these engines required to run all the time as primary power sources? Are any used as backup engines?
7. Where are these engines operated? (Geographical location, average climate, weather etc.)
I ask these questions because there are 2 practical ways you can go with this maintenance schedule depending on operating mode.
1. You can become a parts changer at regular intervals as specified by the manufacturer which can be much simplified (if setup and controlled properly) when compared to a completely performance based versus cost benefit schedule. This approach will make your parts, tooling and labor costs predictable but could be rather costly when replacing parts which are fully capable of running until the next scheduled outage or if your required maintenance schedule runs into your most critical operational periods (if any?). Remember we are talking about reliability and dependability therefore accurate scheduling and outage execution is the primary focus.
2. You can setup a condition based maintenance schedule with some of the parts changer schedule included provided you focus very closely on component condition, life cycle, and operating schedule. This scientific approach is what finely tunes the cost benefit of preventive and predictive maintenance on any equipment. This scientific approach is also what all power plant owners aspire to achieve because it provides the greatest of all worlds including the efficiency, predictability, greatest cost benefit, reliability, and availability. Let us not kid ourselves, it is these numbers that pay out your yearly pay raise and bonuses. When trying to schedule A, B, and C inspections based solely on operating hours without component assessment you will find that your operating hour scheduled maintenance inspections will eventually run into your most critical demand periods (if any?) as stated above. This is the not the time you will want to perform these outages and definitely not the time you need an engine component failure. You will also find that the various engine components will have very different lifetime cycles that will help to confuse the scheduling of parts replacement even further. Thus the need for experienced component condition assessment.
Now to address each of your points:
“What I plan to implement is A,A,B,A,A,C.”
This is a good plan if starting with new engines or starting from scratch with engines that need a lot of work. However this could be costly to perform a complete rebuild of numerous engines where a complete rebuild is not necessary. Thus an experienced component assessment would be more cost efficient for getting your maintenance program started down the right path.
“However, we shall start counting the run-hrs from zero, after overhaul. The cost of the tools and the manpower required I have ascertained for each stage.”
Same answer as above. This is a good plan if starting with new engines or starting from scratch with engines that need a lot of work. However this could be costly to perform a complete rebuild of numerous engines where a complete rebuild is not necessary. Thus an experienced component assessment would be more cost efficient for getting your maintenance program started down the right path. Knowing the cost is great however costs will change. Further, performing complete outages on engines that run the same amount of operating hours at the same time will virtually guarantee that all engine component life cycles will expire at the same time causing large loses in efficiency, reliability, and availability not to mention multiplied costs in labor, tools, and parts at the same intervals.
“What I want to add to this maintenance program is condition monitoring. I will propose the recording of the following operating data:”
1.ambient temperature.
2.compressor discharge temperature.
3.exhaust temperature.
4.lube oil supply temperature.
5.lube oil return temperature.
6.inlet air pressure (downstream of filters).
7.compressor discharge pressure.
8.exhaust pressure.
9.fuel pressure (before and after start).
10.lube oil pressure (before and after filter).
11.fuel consumption.
12.lube oil consumption.
13.governor rack or metering position.
14.lube oil analysis results especially for trace metals.
All of these are very good data points and can be used to trend numerous engine component life cycle predictions and optimum operating parameters when trended against the corresponding data.
“I plan on proposing the collection of these data every 100hrs under the same load and operating conditions starting from when the turbines start running after overhaul. I the will plot the same data against the engine run-hrs”
I will assume you mean complete overhaul. Data collection frequency is good however actual run hours will not directly correlate with EOH (Equivalent Operating Hours) therefore a calculation of predicted life cycle will be required for engine components. Unless you replace everything internally I would not start all parts at zero. I would keep all of the old data and make an educated hypothesis as to remaining life cycle in some components. Thus an experienced component assessment would be beneficial.
“Now what would happen is that if there is any changes in the operation data/operating behavior over long periods then the next time-based maintenance activity, be it A, B, or C, would be carried out. The operating data would the be taken again for another 1000hrs and if there are still deviations, we apply the next maintenance activity etc.”
I would not necessarily agree with this approach primarily because it sounds like you are becoming a parts changer. This method would also allow you to miss the root cause of problems that could be simply predicted, repaired, or eliminated on your normal outage schedule. The focus here would be trending and paying attention to all parameters. Experience with engines can really pay off here in predicting failures and conditions not specifically addressed in you’re A, B, and C inspection criteria.
“Finally, apart from the checks involved in those class of maintenance activities also would propose some extra checks that would be carried out on1hr, 8hrs, weekly, 250hrs, 500hrs, 1000hrs, 2000hrs, 4000hrs and 8000hrs depending on whether the engine is on operating or standby mode.”
What other specific checks would be performed?
“I also would go to the plant and carry out a study on the failure mode and frequency of the components of the turbines and try to analyze the trend that is component in terms of component failure and how long it works before it fails. Once I can get the average service time would propose that such components be changed before that time is reached to mitigate against their failure which can affect the other components.”
This data is extremely difficult to ascertain by anyone other than an Assessment Engineer, Component Life Cycle Engineer, or a Mechanical Engineer that specializes in Gas Turbine / Jet Engine technologies. I have numerous databases, spreadsheets, life cycle calculations, experience reports and analysis inspection procedures and approaches that address these very issues that I use every day. It has taken me 21 years of study in the manufacturing, installation, startup, commissioning, assessment and component design of these engines to understand as much as I do and I still learn something new on every engine. This will take up all of your free time and creative computer design capabilities to make sense of all the data you can collect. Component life cycle / failure prediction depend on the understanding of many factors including different types of corrosion, creep, fatigue, crack propagation, Thermal Barrier Coatings and spallation, Low Cycle Fatigue, High Cycle Fatigue, Temperature Transients, Component Cooling schemes, materials etc.
“As for the burner, I still have not ascertained the real problem. But I suspect that the diesel fuel quality is low. A purifier unit I will suggest to be used.”
A fuel purifier will be very beneficial if your storage tanks are clean, the purifier is used regularly, the fuel filters are maintained properly, and you have your fuel quality tested regularly. A couple of cents per gallon more for a better quality of fuel can save much. The burner problem could also be a simple problem of fuel valve timing, operating procedures or improper set-points in the turbine control. Burner fouling can also be a fuel rich operating condition. Your trend data should help you with this.
As a final input it would probably behoove you to include in your trending data the addition of a few data measurement points if possible:
1. Weather data including temperature, relative humidity at the times of your data collection.
2. Fuel regulator and / or fuel valve response times to loading /unloading inputs.
3. Governor position and response times versus input and weather data.
4. Starting, Loading, Unloading, and Shutdown cycles and times versus fuel valve/regulator position and timing.
5. Vibration monitoring and trending analysis.
Sorry for being so lengthy with a response but this is my job every day. Sounds like you have quite a project to keep you busy. I hope all of this helps.
Good luck
Romefu12
