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Re: G3516 exhaust temperatures

Thanks for the explanation.
I just hope there won't be more damage, as my client is not ready to give up the usage of the equipment for further examination and repair.
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Re: G3516 exhaust temperatures

The zero cylinder pressure reading when you perform a cylinder pressure test would indicate that those low pressure cylinders have bad exhaust valves allowing compression leakage during the pressure test.  During the engine running this leakage would allow combustion gases to leak into the exhaust stream more than the other cylinders elevating the exhaust temperatures.  It looks like the engine is close to having a valve breakage failure on those cylinders with the zero pressure reading if you continue to run the engine.  I would suggest that those cylinder heads be removed and inspected immediately before the valves break and cause serious damage to the piston and maybe the turbocharger.  I think you will find that the valves are damaged (what we call guttered) causing the high temperature issue.

 

Best Regards,

Al Hunt

Visitor

Re: G3516 exhaust temperatures

I worked on a G3516B genset in Nigeria. My client could not provide the recent gas composition for necessary AFR and tunning, and some of the cylinders are experiencing high exhaust temperature up to 1292F. After compression test, all the cylinders with high exhaust temperature are having zero psi as against average of 270psi on other cylinders.
Please what is the correlation between high exhaust temperature and zero cylinder compression pressure?
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Re: G3516 exhaust temperatures

Okay, let's see how that works out.  Since I don't perform the method 19 calculation, would you mind sending me your worksheet and notes?  use this email address; hunt_al@cat.com.

 

I have been using Cat's numbers and have never seen them cause an issue by not meeting a permit requirement level.  However, I will say that I don't get involved in the paperwork that a customer with an emission permit has to complete and submit.  So that is an area that I have no experience in.  Thanks.

 

Best Regards,

Al Hunt

Contributor

Re: G3516 exhaust temperatures

I will start with my newly certified analyzer, calibrate it, and compare the actual output with my readings and make sure the panel indicates the reading on my analyzer +/- 20 ppm and go from there.  I go off method 19 for calculations which has exhaust flow rate calculations that are not sanctioned by the EPA according to them.

 

https://www.epa.gov/sites/production/files/2016-08/documents/method19_faq.pdf

 

On CAT engines I go by manifold pressure for load and compare that to the fuel consuption chart according to GERP to derive the BSFC.

Darrel Fischer
Field Service Technician
Natural Gas Compression and Production
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Re: G3516 exhaust temperatures

I'm not sure that I have an answer for your question.

Cat has had a rating for the earlier G3516 with AFR at nominal 1.5 g NOx. We have used 240 ppm for the NOx value for this G3516 engine emission rating.  When the NSPS rule went into effect in 2007, the language said that the emissions could not exceed 2 g NOx; Cat set the target for the G3516 A3 at 240 ppm or a nominal 1.5 g NOx target when the G3516 A3 changed from the O2 sensor to the NOx sensor.  For the older G3516 which were a nominal 2 g NOx, we use 310 ppm for measuring the NOx in these earlier engines.

I don't know what equation you are using but 240 ppm calculates to the nominal 1.5 g NOx, not 0.67  NOx.  I would say that something is not right with the formula you are using and I would say that something is wrong with the engine adjustments, the NOx sensor calibration, or the emission analyzer or maybe partly all three have some issues.  I don't have enough information to evaluate your question but I will continue to discuss with you.  Maybe we can resolve the discrepancies.

 

Best Regards,

Al Hunt

Contributor

Re: G3516 exhaust temperatures

I have not had a problem with emissions, mechanical failure, or temperature issues with the 160 ppm setting.  I use GERP to assign my nox setting.  What I don't understand is the fact that I have a unit set at 240 nox but the output is coming in at 177.8.  Could that be a calibration issue?  According to my calculations this converts to .67g when I have a 2g limit.  Your thoughts?

Darrel Fischer
Field Service Technician
Natural Gas Compression and Production
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Re: G3516 exhaust temperatures

Darrel,

I have had some customers want to deviate from the target NOx but I don't really understand why. 

1. The target NOx is less than the NTE maximum NOx level.  For a G3516B rated at 1 g NOx, the target is 140 ppm.  The limit value is 156 ppm for 1 g NOx.  So if you are setting the target in the configuration screen to 160, the engine is nearly always going to be exceeding the rated emissions value of 1 g NOx.

2.  In addition, setting the target emissions to 160 ppm is richening up the air fuel ratio.  This moves the combustion closer to the detonation threshold, especially as the load nears rated.  Also, a richer air fuel ratio tends to elevate the combustion and exhaust temperatures.

3.  By setting the target to 160 ppm, the engine is going to operate closer to the edge of the software mapping.  This could cause some instability in operation if conditions move out of the mapping operating boundaries.

 

So I would not deviate from the target NOx shown in GERP for the various engine rating emissions.  This target gives a margin below the NOx limit to allow for variables in the engine adjustments and emission measuring equipment to keep the engine runnin below the NOx limit for permit compliance.

 

Best Regards,

Al Hunt

Contributor

Re: G3516 exhaust temperatures

I have never been alarmed about 1150 *F cylinder temps but the glowing draws concern.  I would check the input.

 

Al, I have been setting my 1g units to 160 ppm NOx. Your thoughts?  Igeneraly set the timing in the 22-30 area depending on the fuel supplied.

Darrel Fischer
Field Service Technician
Natural Gas Compression and Production
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Re: G3516 exhaust temperatures

Is this a G3516B or another model?  Stating the model is important when posting questions.

Now if this is a G3516B, an exhaust port temperature of 1140 F is not too hot.  This is in the range of what we normally see for this model engine when tuned properly running loaded.

It is important to remember that having a good current fuel sample analysis so that correct values for BTU, specific gravity, and specific heat can be entered into the configuration screen.  Further, it is important to use this analysis and methane number calculation to determine the methane number.  Use the methane number (MN) with the specific engine you have to determine the desired ignition timing to be entered into the configuration screen.  Additionally, for the G3516B you must enter the correct desired NOx into the configuration screen; 60 ppm for a 0.5 g NOx engine and 140 for a 1.0 g NOx engine.  And finally, you must use a calibrated exhaust analyzer to know for sure what the NOx is coming out of the exhaust to calibrate the NOx sensor so that the ECM can maintain an accurate air/fuel ratio for correct emissions.

 

If you have more questions, please don't hesitate to ask.  Be sure to include all the information that you can with your question so that we can give the most accurate answer possible.  Thanks.

Best Regards,

Al Hunt