Diesel engine can not give more than half load 10

[ViCH]

Hi everyone. I am electrical technician, and I have problem with Emergency Diesel Generators at site. Full Power Capacity is 2.7MW, but we get speed unstable starting from 1.3 MW, if we want to give more power then engine looks like can not accelerate and frequency start to drop until under-frequency trip. We already check all fuel injection pumps, fuel pressures condition of valves, fuel filters.. Check electronic controls and all auxiliaries, but did not find any major problems.
By trending I found fuel demand is adequately changes with load requested. But I also mentioned that manifold air pressure is maintain 14.2 PSI before start, and 14 PSI +-0.3 fluctuating during and after start. Is it OK? Could it be problem with turbocharger, or wastegate control?
Engine: GE 16V228.
Turbocharger: 7S1716 compressor end. E-40811A

Viktor
Electrical Technician II

 

[gruntguru]

If the turbo spins freely by hand you probably have a blockage somewhere. I haven't seen a response to CatServ's suggestion to test the aftercooler -is the pressure before and after the aftercooler the same?

Exhaust system is another area you should check for blockage. A pressure gauge at the turbine outlet should read less than 2 psi under load. The pressure before the turbine should be similar to the intake manifold pressure. Check your manual.

Can you set yourself up to do some testing under load? Connect some high power loads from around the plant? Build a simple load bank (tank of brine with plate electrodes)

je suis charlie

 

[ViCH]

Nobody will allow me to do load test during plant production. Regarding load bank, - our generator 11kV, hand making load banks is simply not safe. Our engineers was trying to purchase load banks, but due to coronavirus all plans freeze.
Regarding blockage in intercooler. If clean air pass through compressor, how it can be clogged? And how it achieve 40% load, with blockage in I/C?
One more question, what temperatures should be on turbocharger surfaces of such big diesel engines?
Regarding pressures which should be on manifolds, - nothing in my manuals.. In FAT test reports also no any readings on that.

Viktor
Electrical Technician II

 

[TugboatEng]

Intercoolers have fins that make very small air passages. Couple that with 400°F+ air leaving the turbochargers, oil mist, and dirt from the air and you have a recipe for clogged intercoolers. High efficiency air filters will prevent this.

 

[catserveng]

So you've provided a good piece of info, so at some point earlier in the unit's life it made 2MW, then it would still carry load up to 1.6-1.8MW, now as time goes on you have problems at lower loads. In between this you run the unit at no load. This type of problem is not typical for a controller related issue. This type of worsening condition is usually mechanical in nature

I think you need to stop worrying about the "wastegate", engine and controls are still configured they way they were when the engine would make 2MW, right? If it was a problem it would have been there from early on.

As for the turbo and aftercooler, running a large turbo (actually any turbo) for extended periods at no load can result in oil leakage past the compressor and turbine seals, causing oil vapor to migrate to the exhaust and air inlet systems. You have large aftercooler cores on each side of the engine, as oil film builds up on the air side surfaces, it captures and holds all the small fine particles that got past the air cleaners, adding restriction. It doesn't take a completely plugged aftercooler core to start making your engine not perform, a partially restricted core will reduce air flow at higher loads, the more it restricts the less load you will be able to make. I'm not saying this is the only possible problem, but based on what info you have provided so far I'd say it needs to be checked.

The fact you cannot test the engine with load is probably the root cause of your problem. I have just been thru a similar issue at a government run medical facility, they have not been properly load testing their 2.5MW emergency generator because of cost, so mostly they run just start tests and for the last few years do a site load test once a year, but each year they were not able to carry as much load as the year before, so got to a point where the unit wouldn't carry more than 1MW. Everyone started pointing fingers, guy in charge of maintenance retired just before this got really serious and seems for the last few years has been getting a bonus for saving money on maintenance. After a bunch of finger pointing and repairs done that didn't go anywhere, I was asked to help evaluate the unit. We got a load bank on site, found a number of minor issue but two main factors for the continuing loss of power output was partially plugged intercooler core (what the manufacturer of that engine called it) and the critical grade exhaust silencer badly plugged and internally collapsed. Then unit ran fine up to about 800kW during our initial test, then started to surge, found the intercooler restriction was at 7 PSIG and the exhaust backpressure reading broke the digital manometer, a pressure gauge was installed and we had 8PSIG of backpressure on a unit designed for a MAX backpressure of 25 inches of water.

In you case I think two things need to happen, you need a way to properly test with a known controllable load like a load bank or run loads in your facility in a way that you can control the loads, and yes, that means production will be affected. Next someone who has a proper level of expertise needs to troubleshoot the problem in a methodical manner with the right diagnostic equipment and information about expected parameters and tolerances from the engine manufacturer.

So far you seem to have struggled getting thru what you could on this problem, fully understand you may not have the expertise you need to get to the bottom of this, but you have certainly done a good job with what you have to work with getting this far, now time for the equipment owners to pony up and get it fixed right, and in the process let you hang around and get some training and troubleshooting experience.

Hope that helps, MikeL

 

[ViCH]

Well, thanks for good words and advices, and sharing of your experience. Now I get point with intercooler. I think, if its partially clogged, I still may catch up higher pressure between compressor output and intercooler, compair to manifold MAP. Plug is there, gauge I will find.
Regarding owners and authorised troubleshooters, its very complicated issue. OEM vendor of this package is Intergen, Italy. As I understand, my company already do not have contract with them, and all service and repair support making by contractors from asian contries. This guys are not belong to GE or any known famous diesel engine manufactures, and even they have a lot of experiences, their logic of troubleshooting make me crazy.
Once, during turnaround activities night shift found some diesel leak from one of cylinder head. Engine was still running without alarm, and leak extingush itself. But after several hours our lube oil level start increasing. Coolant level maintain. After discussion with bosses, we stop engine with clear understanding that fuel found pass to lube oil. Service team was available in camps (they come to do some service on cylinder valves and injectors), so we call them. First what they said- fuel do not have any pass to lube oil, and ignore info about diesel temporary leak.
You will also become crazy, when know what they did:
1) They said our lube oil bad condition, its foaming and thats why level raising.
2) They drain lube oil
3) They top up new lube oil
4) They run engine.

Of course, lube oil increase again. They stop engine, and said that maybe its lube oil filter, or heat exchanger problem. When I ask, how can be 80% of lube oil become 100% due to dirty filter, they said "old oil could not drain".. They check and clean filter. It was dirty a little. Then they ask to open PTW to service heat exchanger. At that moment I exploded on them, and call my bosses. He ask them to check cylinder which was leak.. And they found broken rocker arm... They found "how fuel can mix with lube oil". After this, I start to study all other things, which is not related to electrical site. BTW, this problem was solved, by replacing cylinder head, we found spare on stock.

Regarging topic subject, - once I install gauges and test engine one more time, i will share results.

Viktor
Electrical Technician II

 

[ViCH]

Exhaust system is another area you should check for blockage. A pressure gauge at the turbine outlet should read less than 2 psi under load. The pressure before the turbine should be similar to the intake manifold pressure.

Unfortunately I did not find any plugs there to install pressure gauge...

Viktor
Electrical Technician II

 

[Lou Scannon]

Unfortunately I did not find any plugs there to install pressure gauge...

Then it would be a good idea to add a boss for a gauge. If the metal is thick enough, you can simply drill and tap for a suitable fitting. If metal is thin, find a welder that can drill a hole and weld in a boss for your pressure tap.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

 

[TugboatEng]

You can see a clogged intercooler. It should be readily accessible by removing an intake duct or using a borescope.

 

[ViCH]

Borescope can be used without removing of turbocharger?
If I want to remove intake duct to intercooler, should I drain coolant first?

Viktor
Electrical Technician II

 

[ViCH]

hemi, idea is good, thanks. But not in my company. Here I have to raise request for Management of Change to do such modifications.

Viktor
Electrical Technician II

 

[TugboatEng]

In the pictures you provided there is a duct from the turbocharger that makes a 90 degree turn and then enters the intercooler. If you could remove that elbow you would be able to view the intercooler and inspect it for clogging.

No you don't have to drain engine coolant tomopen ducts and inspect the intercooler.

Edit: looking more closely, it appears the duct is part of the compressor housing so removal of the entire turbocharger would be required.

 

[EdStainless]

Had an old salvaged turbo charged engine once that idled great but would not rev, found that the hot side of the turbo was spinning
free on the shaft and not driving the compressor. Don't overlook stupid simple stuff.
Does anyone remember the last time that the intercooler was cleaned? If not have them clean it.
The combination of slight restrictions at both inlet and outlet (exhaust filters) could easily cause your issues.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy

 

[ViCH]

Your turbocharger was multi-spool? Or your shaft was broken?
Another thing - could black smoke waste our turbine waste? If for example, intercooler is clean, then can be turbine dirty vanes be guilty? Several years ago we got problem with fuel injectors, and engine was running several days with excessive smoke.

Viktor
Electrical Technician II

 

[catserveng]

Short answer to your question is yes. That turbo likely has an axial flow turbine wheel, if you have slobber or poor combustion, the spaces in between the vanes can pack up with debris, and then it cokes up on the wheel. The turbo usually doesn't last too long after that starts to happen. One of the reasons I asked you to measure axial and radial runout of turbo, if that is a potential problem then you may catch it before a catastrophic failure occurs, otherwise if you just it progress you end up with a large bill for a major turbo overhaul or replacement.

Looked at the pictures again after Tug's comment, looks like there is a spool piece between the compressor housing and the inlet of the aftercooler. So it looks like just the end bells of the aftercooler can be removed and the core inspected. I'd likely just drop the inlet spool pieces and see if they show signs of oil.

Also, on the picture showing the inlet manifold on the left bank, there is a small pipe attached to the turbo compressor outlet elbow, what does that pipe connect too?

You also mentioned a crankcase fumes disposal system, with part of it attached to the exhaust, can you provide some more details on that? Crankcase fumes disposal system that regurgitate crankcase fumes into the engine, either the intake or exhaust, coupled with extended no or low load runtimes pretty much always lead to problems, at least in my experience.

MikeL.

 

[ViCH]

Ohh, that small pipe is actuation line to valve for coalescer filter outlet. This is a part of crancase ventilation system. I did not find details in manual, but in theory once compressor increase outlet pressure, it must open valve from coalescer filter to exhaust line. Vacuum from exaust should suck air from crankcase through coalescer. Coalescer will stop oil fumes, accumulate it and pass it down through drain line. Near intercooler at right side, you can see small drum, that is coalescer filter.
Regarding intercooler inspection, prior to do that, I want to test run with pressure gauge installed on compressor outlet first. Wednesday I will update results.

Viktor
Electrical Technician II

 

[ViCH]

One more finding (or maybe its normal) - when I removed plug from intake air manifold for pressure gauge installation, I have noticed that end of plug is dirty with soot. Today I decide to recheck - open manifold cover and found soot is everywhere inside, and even collected a small hall of soot nearby cover. Same time, using lighting torch, I noticed that output of intercooler looks like clean (no soot on surface). I thought - maybe soot blocked MAP sensor on other side, and remove cover with MAP/MAT sensors as well. It was dirty, but not clogged. we cleaned soot from surfaces and from sensors, and closed covers back.
BTW, we installed pressure gauge on intercooler inlet. And I found plug on exhaust output, once I find 100mBar gauge, I'll install it there.
So question to experienced mechanical staff: is that soot OK inside intake manifold?

Viktor
Electrical Technician II

 

[catserveng]

Without knowing full history of your engine and its operation, I'd say that looks excessive, inlet systems are supposed to be clean, chunks of soot and carbon material can migrate to the cylinders and cause issues. And all that material has to come from somewhere.

On the aftercooler, looking at the outlet side is not a very good indicator of what is condition is, even just looking at the inlet side doesn't always give you a good idea, most plugging occurs within the core as the compressor outlet air starts to cool. Taking off each end bell and looking thru the core with a strong light is probably the best solution.

MikeL.

 

[ViCH]

Couldnt it come from combustion of cylinders? If we dont have positive pressure during no-load tests, but we doing it weekly.. We do not have load tests, but we have annual turnaround activities, where engine runs for 2-3 week with 40-45% load.
History.. Few days run with cracked injectors long time ago, few days with broken rocker arm and pushrods on one cylinder 2 years ago. Filters replaced, tappet clearance calibrated. Readings for lube oil and coolant acceptable.

Viktor
Electrical Technician II

 

[miningman]

To the OP. please don't take my post as personal criticism, merely a suggestion on how to move this issue forward. Your posts todate strongly suggest you have one or two serious mechanical deficiencies with this gen set. It is clearly installed at a serious sized industrial facility. You have admitted that mechanical issues are completely outside your area of expertise. Your geographical location seems to be in an area without strong mechanical support.


IMO, you need to advise your management that this standby unit cannot be relied upon to provide power when needed. They can evaluate if the financial consequences are a risk they are prepared to take. Then contact a facility in europe that has the expertise to come in , diagnose the problems and make the necessary repairs.

I can already hear the howls of protest as to how expensive this will be. Thats why management has to make the call as to the costs of losing all power at some point in the future.

 

[TugboatEng]

Did anybody identify the cause of injector failure? What fuel is this running on? Do you have any way of managing any water that's in the fuel? The failed fuel injectors as well as the broken rocker arm (if it's a unit injector) may be symptoms of the water in fuel. Have you inspected the cylinders with the broken components with a borescope? Failed injectors can do a lot of damage to a power assembly.